GOVERNING COUNCIL Dr. Anil Kakodkar Chairman

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1







GOVERNING COUNCIL


Dr. Anil Kakodkar Chairman


Prof. V.S.Ramamurthy Member


Dr. S. S. Kapoor Member


Dr. Bikash C Sinha Member


Shri P. D. Kar
andikar Member


Ms. Sudha Bhave Member


Prof. G. S. Agarwal Member


Shri.Arvind N. Lalbhai Member


Shri V. M. Vora Member


Prof.P.K.Kaw Member




Shri M. A. Shah Non
-
Member Secretary




2












COVER STORY













INSTITUTE FOR PLASMA RESEARCH


On the west bank of the river Sabarmati, a few kil
ometers upstream from the Gandhi Ashram, a small
number of low buildings are grouped together on a little hillock rising among the ravines and low
grazing land. The pastoral setting and the quiet surroundings belie the high tech character of th
e place
where a group of scientists are engaged in one of the most exciting and challenging tasks of this
century
-

controlling nuclear fusion. The idea that energy can be obtained by fusing nuclei of light

elements to produce heavi
er elements has been known for a long time. It is also a process that
continually occurs in the Sun where the fusion of hydrogen is the principle source of its energy. But
the real challenge lies in trying to create this form of energy on ear
th by recreating the conditions of the
Sun in the laboratory. The pursuit of this goal has been a worldwide effort over the last forty years. The
Institute for Plasma Research, located in village Bhat
-

a few kilometers outside Ahmedabad, is a rece
nt
entrant in this endeavour and is the prime expression of India's commitment to this futuristic energy
source.


The Institute has a broad charter of objectives to carry out experimental and theoretical research in
plasma sciences with empha
sis on the physics of magnetically confined plasmas and certain aspects of
nonlinear phenomena. The Institute also has a mandate to stimulate plasma research and development
activities in the Universities and the industrial sector. It is also expec
ted to contribute in the training of
plasma physicists and technologists in the country. Since its inception the Institute has pursued these
goals in an active manner and made some effective contributions. The Institute in its second pha
se of
experimental activity has embarked on an ambitious project of building the first Indian Steady State
Superconducting (SST1) Tokamak.










3














EXECUTIVE SUMMARY



The Institute is pursuing several facets of plasma research and technology d
evelopment. Work on fusion
plasmas is being conducted on tokamak ADITYA. Some novel features of tokamak edge turbulence
relevant to transport of matter and heat across field lines were studied during the year; it was shown that for
short scales, turbulence

exhibits features of scale invariant Levy statistics. This may have relevance to
observations of bursty transport from tokamaks. Experiments with many new diagnostics and RF heating

systems have also been initiated on ADITYA during the year. Many of these

are preparing the ground work
for SST 1 experiments. Fabrication of SST
-
1 subsystems is now approaching conclusion. The prototype for
the 1/8
th

sector of vessel and cryostat has been completed by BHEL, Trichy. It has been delivered to IPR
and is being use
d for a number of in
-
house tests. The liquid Helium plant has been fabricated, tested and
delivered. It is getting ready for

erection, commissioning and testing. The subsystem for AC power
distribution systems is in an advanced state of completion. Many of

the superconducting coils for SST
-

1
have been wound

and delivered to IPR. The coming 2 years should see the completion of all SST
subsystems, their erection and early commissioning tests of the device. Fundamental plasma experiments
with dusty plasmas ha
ve led to exciting new results on the first demonstration of transverse shear modes in
3
-
d fluid like dusty plasmas. Novel methods of current drive in a basic toroidal experiment using whistler
modes have also led to unexpectedly efficient current generati
on.




P.K. KAW

DIRECTOR



4







ANNUAL REPORT


April 1, 2000 to March 31, 2001


The institute was established as a
n autonomous institution in 1986. The major objectives of the institute
have been to carry out experimental and theoretical research in plasma physics with emphasis on the physics
of magnetically confined hot plasmas and non
-
linear plasma phenomena.


1 S
CIENTIFIC AND TECHNICAL PROGRAMMES


Scientific programme of the institute is aimed at generating expertise in high temperature magnetically
confined plasma experiments. High temperature plasma environment is mandatory to achieve fusion
reaction. Activities

in the institute, therefore, relates to study of equilibrium and stability of high
temperature plasmas and upgradation of their parameters. At the same time basic experiments and
experiments related to immediate plasma technology dissemination to industry

forms an integral part of the
programme.



The programme can broadly be categorised in to three activities: a) studies on high temperature
magnetically confined plasmas, b) basic experiments in plasma physics including Free electron laser, dusty
plasmas
and other nonlinear phenomena, c) industrial plasma processing and application.


The major experimental work on high temperature magnetically confined plasmas is being conducted in
tokamak ADITYA. Main aim of this activity is to reliably operate a tokamak
at high temperature and high
plasma current. The plasma is formed by an electrical breakdown in an ultra high vacuum toroidal vessel
and a current is inductively driven in the plasma. As the plasma temperature rises the efficiency to heat the
plasma drops.

To further raise the temperature of the plasma to fusion grade, one has to use auxiliary
heating schemes. During experimentation at high temperatures, it is also required to diagnose the plasma
with various sophisticated diagnostic tools. Work on these ar
eas is being perused in these areas.


During the course of the year few new diagnostics, namely, Thomson scattering for temperature
measurement, ECE diagnostic for temperature profile measurement, soft X
-
ray camera and laser blow
-
off
diagnostic systems hav
e been commissioned on ADITYA. At the same time a high power electron cyclotron
resonance frequency system at 28 GHz has been successfully commissioned on ADITYA. The will be used
during initial break down of the plasma as well heating at a later date.


A
new experiment (SST
-
1) in the field of steady state operation of tokamaks is the other main experimental
effort in the institute. This project is focussed to address physics and technology issues related to steady
state tokamaks and so called advanced toka
mak configurations. In this experiments many conventional
questions in tokamak physics will be addressed in the steady state scenario. Some of these questions will be
in the areas of energy, particle and impurity confinement during steady state operation.
Plasma disruptions
and vertical displacement episodes will also be studied. Non
-
inductive current drive would sustain the
plasma current during steady state. Different aspects of current drive will also be studied. Since we will
have long duration plasma,
lot of heat will be

removed by components near the edge of the plasma. Various
aspects of these problems are being studied during the fabrication and integration of SST
-
1.


Proto type fabrication for most of the subsystems have been concluded and based on

the results final
fabrication of many components of the subsystems for SST
-
1 have concluded. They are being tested before
integration. The proto
-
type of the vacuum vessl


cryostat has been installed at the laboratory. All invessel

5

components would be qua
lified for their vacuum compatibility in it. Some of the magnetic field coils have
been received at site after successful predespatch tests. Liquid helium plant is being erected and
commissioned at site. Many of the components for the RF heating and NBI sy
stems have been received at
site. Final tests are being performed before integration and commissioning. Diagnostic systems, control and
data acquisition systems are being prepared.


Basic experiments have always formed a major part of our research efforts.

Various new and ongoing basic
experiments are being carried out in the institute. Plasmas in these experiments are relatively cooler, rarer
and less complicated. Hence, they can be easily and thoroughly diagnosed. They relate to understanding of
various f
acets of plasma which is otherwise difficult to study in bigger experiments. Stability and
equilibrium of toroidal plasma in presence of radio frequency waves and new current drive mechanism with
these waves are being continued. Issues related to excitati
on, propagation and linear, nonlinear interaction
of whistler and helicon waves are being studied in a large volume plasma device. Free electron laser
experiment is being continued. Many aspects of dusty plasma are being experimentally studied.


Equilibriu
m and non
-
equilibrium plasma properties can be exploited for commercial uses. In the areas of
plasma processing and application, the engineering and technological experties of the institute are exploited
to generate advanced material processing technologie
s. Development programmes are selected on the basis
of the need expressed by industries. A multi
-
disciplinary team of physicists, engineers and material
scientists has been nucleated. They cover activities like liasion with industries, consultancy and tec
hnology
transfer to industries. Commercial prototype of medical waste plasma pyrolysis system, plasma nitriding
system installation at IGCAR, experimentation on plasma nitriding of titanium and SiOx like coating using
constricted anode plasma source, suppl
y of PSII system to IIT Kharagpur are some of the major activities
concluded by this group.


Activities performed during the year in these areas are described in some detail in the following sections of
this report.


1.1 ADITYA TOKAMAK


1.1.1

THE DEVICE


ADITY
A, a medium size Tokamak, is being operated for over a decade. It is regularly being operated with
the transformer
-
converter power system. ~100 msec 80
-

100 kA plasma discharges at toroidal field of 8.0
kG are being regularly studied. During this period

experiments on edge plasma fluctuations, turbulence and
other related works have been conducted. Standard diagnostics have been employed during these
measurements. The accompanying figure gives a view of ADITYA with the auxiliary heating systems
attached

to it.






Present View of ADITYA Tokamak


6


ADITYA has been upgraded. Upgradation has been in different fronts. Vacuum system has been upgraded
interms of more cleaning

facilities. Some more diagnostics have been integrated and made on
-
line. Some
are in the design/fabrication phase. To increase the plasma energy content during the discharge, auxiliary
heating systems have been integrated. A 20


40 MHz, 200 KW Ion Cyclot
ron Resonance Heating (ICRH)
system has been integrated to ADITYA vacuum vessel. A 28 GHz, 200 KW gyrotron based electron
cyclotron resonance heating (ECRH) system has been successfully commissioned on ADITYA tokamak.


Vacuum System


Main objective is to
maintain good vacuum and wall conditioning and reduce impurity level in ADITYA
Tokamak.


Lithium Surface Conditioning and Limiter Biasing Experiments have been conducted. An experiment on
Molecular Beam Injection in ADITYA has also been proposed and woul
d be carried out in future.
Following other experiments have been initiated in ADITYA, edge profile measurement, lithium oven
diagnostics, etc., in which ADITYA vacuum group has been involved. Efforts have been made to have pre
ionisation to assist plasma
break down.


During the year, complex installations of mirror box of ECRH system, movable limiter, Langmuir probes
etc. have been carried out.


A new power supply with controls for Electron Cyclotron Resonance (ECR) discharge cleaning has been
designed, p
rocured, tested and installed. ECR and/or PDC discharge cleaning is routinely carried out for
few hours to 24 hours in shifts, as and when required. Experiments have been carried out to optimise ECR
parameters.


Molecular beam injection system has been ins
talled on ADITYA for efficient gas feeding. Experiments
would be performed using this system to study its efficiency on ADITYA.


To improve performance of ADITYA vacuum system, a control system has been designed. Experiments
have been carried out to st
udy contamination due to exposure to atmosphere. While leak testing, the gate
valve on Laser blow off system was found to be leaking. It was opened and repaired in situ.


Surface analysis of coatings on various samples has been carried out at FCIPT. Aditya

poloidal limiter has
been exposed to more than 10,000 discharges. Therefore the tiles will be replaced with new graphite tiles
which have been baked upto 1000
o

C for 24 hours in the vacuum oven, commissioned recently and have
been kept ready for replaceme
nt during the next opening.


Like earlier times, leak testing

of various diagnostics systems

with

helium

leak detector and Ultra High
Vacuum testing with UHV test
-
stand

have been carried out as and when required.


EXPERIMENTAL RESULTS


Lithium Surfac
e Conditioning Experiment



An experiment in ADITYA with in
-
situ lithium conditioning to study effect of lithium conditioning on
ADITYA discharges has been performed. The aim of lithium conditioning is to reduce hydrogen recycling,
impurity influx and to
improve plasma parameters viz.. plasma density, temperature, confinement time and
MHD activities. Lithium conditioning has been done by evaporation of lithium in ADITYA vacuum vessel
during discharge cleaning. Partial pressures of lithium and oxygen are mo
nitored with Quadrupole Mass
Analyser. An increase in partial pressure of lithium (100 %) has been observed whereas for oxygen, it is
reduced to 50 %. The density achieved is 1 x 10
13

/cc. It had a flat top for 30 millisecond. Sawtooth

7

activity is su
ppressed. Presence of lithium is also monitored by spectroscopy. It observed an increase in H
-
alpha (instead of reduction) and reduction in hard X
-

rays. The plasma parameters thus are improved.


Experiments to study lithium coating on vacuum vessel wall

have been initiated. Solid lithium target probes
have been prepared. These probes are introduced in a UHV system and lithium coating experiments have
been performed successfully. More experiments would be performed to study the effect of lithium coating.

Lithium coating on limiter is also proposed in ADITYA.


Limiter Biasing Experiment


The ADITYA limiter consists of 16 segments of graphite tiles and thus provides an opportunity to study the
role of biasing with a set of biasing in different configuratio
n. One of the limiter tiles is biased up to

500 V
with respect to the vessel. When the limiter current drawn exceeds 300 A various diagnostic signals
indicate an improvement of particle/energy confinement. H


radiation as well as floating potential
fluct
uation (monitored by Langmuir probes) shows significant reduction. The amplitude of floating
potential reduced by 80 % at all frequencies. Before biasing the limiter frequency spectrum of the
fluctuation shows a peak at 10
-
15 KHz, which disappeares during
biasing. Signals from the central detector
of the soft X
-
ray camera indicate a rise in temperature by 50
-
100 eV within 3
-
4 ms of the

application of the
bias. A sharp decrease up to 50 % in

H


radiation has been observed.


Turbulence Studies


The understan
ding of fluctuation driven anomalous transport of particle and heat is still of paramount
interest in modern fusion devices. The apparent lack of any characteristic time and length scales in the edge
plasma fluctuations has prompted a search for scale inva
riant properties. To that end, the floating potential
fluctuations in the Scrape
-
off layer plasma of ohmically heated ADITYA tokamak have been analyzed. It is
observed that the probability distribution function of a sum of
n
random fluctuations converge t
o a Lévy
distribution for
n

< 40 whereas for larger
n
, the distribution converges to a Gaussian. The Lévy and the
Gaussian processes are paradigms of super diffusive and diffusive transport processes respectively. Thus
our observation indicates that the
transport of small scale fluctuations takes place by convection, whereas
large scales follow the diffusive law.


1.1.2 DIAGNOSTICS


New diagnostic systems include Thomson scattering, Lithium beam, ECE, Bolometer, Soft X
-
ray etc.
Polarimetry is being des
igned and fabricated to be tested on ADITYA and finally used in SST
-
1. Some of
these systems are described below.


THOMSON SCATTERING SYSTEM


The aim is to provide electron temperature

and density measurements of ADITYA plasma on
shot to shot basis. The s
ystem is capable of measure electron temperature (T
e
=20 eV
-

500 eV)
and electron density (n
e
= 5.0x10
12

-
10
13

cm
-
3
) profiles of ADITYA plasma (from z = +22 cm. to
-
14cm) with a spatial resolution of 1cm and temporal resolution of 50 nsec. The system is ba
sed
on a Ruby Laser ( 10J, 20 nsec) that enters the plasma through an extended

bottom vertical
port and exits through a top vertical port



The 90
0

scattered photons are collected through a radial port using a f/5 optical system ( a set of different
lens systems) collected scattered spectrum is dispersed using a grating spectrometer( 1200 grooves/mm,

8

resolution 8A
0

, focal length 1m) and exit of spectrometer is coupled with a fiber bundle to detectors( 10
channels, PMT of RCA make).







ADIYTA Thomson scattering Signal in presence of plasma




Electron temperature measurement during a typical plasma shot



9

The output signals from PMT are amplified and digitized using CAMAC modules and the data is
acquired
and analyzed using a PC located at the laser control room.


Wavelength and spectral calibrations of spectrometer, PMTs are done regularly using the standard W
-
lamp
source and LED. System calibration is done by Rayleigh scattering for stray light m
easurements at various
pressures by filling the vessel with N
2

.


SPECTROSCOPY


The existing spectroscopic diagnostic channels on ADITYA are utilised for various experiments (Limiter
Biasing, Lithium injection) on the tokamak , to monitor any changes
in impurity emission and Zeff due to
these perturbations to the discharges .


Two additional channels of spectroscopic diagnostics are added to the ADITYA tokamak. These view,
respectively, the inboard and outboard limiters In future attempts would be ma
de to identify the
inward/outward movements of the plasma during a discharge by the relative amount of radiation emanating
from the respective surfaces.


The Normal Incidence VUV spectrometer has been fitted with the ICCD camera. This enables us to acquir
e
multiple spectra (every 10 millisecond) of a selected spectral region (120 Angstroms wide) during a single
ADITYA discharge. The survey spectra thus recorded show the presence of highly ionized impurity
species, C V & O VII, being the highest ioni
zation states observed to date. Also, numerous lines of
medium
-

Z impurities like Fe, Si etc have been definitively identified in these spectra (see figure).




ECE DIAGNOSTICS


Electron Cyclotron Emission (ECE) diagnostic provides very useful measu
rements of electron temperature
and its radial profile. An eight channel E
-
Band Super Heterodyne Radiometer (SHR) is used to measure
ECE on ADITYA tokamak. The temporal and the spatial resolutions of the SHR are ~10

s and ~ 4 mm
respectively. Measurem
ents have been done with different toroidal magnetic fields ranging from 0.75 T to 1
T. Initially only the optically thin, third harmonic was measured with toroidal magnetic field 0.75 T.
Typical signal for such condition on all the eight channels are sho
wn figure 5.


With the help of density measurement by interferometer and reflectivity estimation from the measurement
of temperature with soft x
-
ray diagnostic, efforts are being made to find out the radial profile of electron
temperature.



10






Eight channel ECE radiometer signal for toroidal field of 0.75 T.



1.1.3. RADIO FREQUENCY HEATING ON ADITYA


ION CYCLOTRON RESONANCE HEATING (ICRH) SYSTEM



Auxiliary heating at ion cyclotron frequency range has been planned and with this in

mind a 20


40 MHz,
200 KW system has been integrated and commissioned. Flexibility in frequency and minimum power have
been arrived at from the existing ADITYA parameters such as ambient toroidal field, energy confinement
time during ohmic heating etc.


It operates independently during tests and acts with a master trigger from the ADITYA control system
during operation.



Regular rf shots with the 20 kW stage of the generator are being generated on the dummy

load in the absence of ADITYA operation to he
lp in optimizing operating parameters. Antenna position
inside the vacuum vessel is shown in the picture below.



11




RF power coupled to the plasma has been optimized at 25.5 MHz. This is done off
-
line based on the signal
o
btained from the directional coupler positioned at the load end and the signals from the twenty probes to
measure the VSWR placed also in the load end of the transmission line. The antenna current is also
measured. Electric and the magnetic field component
s are measured from the local diagnostics positioned
near the antenna.



Along with regular operation, final stage of the ADITYA system (200 kW) is being integrated. The final RF
testing of the 200 kW stage with all the required controls and HVPS has
been initiated. During the first
phase of testing, inadequacy in the amplification factor of the output circuit of the amplifier has been
measured. Based on the data the output as well as the input circuits have been modified. Renewed
integration and testi
ng has started.


Successful operation at 30 MHz has been achieved with the modified circuits. With an input power of 1200
W, an output of 40 KW has been achieved. At present this output has been optimised at other frequencies as
well. Power is limited to t
his value due to the available dummy load at 50 KW. The system is being
prepared to be integrated to the main 1.5 MW dummy load through a SPDT switch. This would enable us to
go to high power and operation on ADITYA.


ICRF breakdown of initial plasma and
wall conditioning in a steady state tokamak would be prefered to the
conventional schemes due to the fact that the same heating system could be used at full toroidal magnetic
field between successive shots. Therefore, besides heating, the same system is
being used to experiment on
plasma breakdown and preionization to help ohmic break down. Keeping in view the need for such a
scheme on SST
-
1, experiments are underway to study plasma breakdown at different values of toroidal
magnetic field at different pre
ssures. RF wall conditioning would start soon.


LOWER HYBRID CURRENT DRIVE (LHCD) SYSTEM


A LHCD system for Aditya machine is being fabricated. The system would be introduced through one of
the pumping ports. To maintain the pumping speed, a line has been

designed and fabricated. The system
would consist of eight wave guide and would deliver about 120 kW of rf power to the plasma at 3.7 GHz.
Transmission from the RF laboratory would be transmitted through commercially available rectangular
channels, having

inner dimensions close to that of WR284 wave guide. The line is under fabrication. The
antenna has been fabricated and is being tested for ADITYA vacuum environment compatibility.


The 8 channel LHCD system for ADITYA is being erected. Minor modifications

required in one of the
pumping line of ADITYA to accommodate the launching system has been designed and being fabricated.
This system would act as a test bed for the current drive scheme in SST
-
1. The vacuum window is being
prepared in collaboration with
LPSC, Bangalore on titanium frame. In the meantime Titanium to SS 304
welding has been done successfully in the group. The transmission line from the RF laboratory to ADITYA
hall has been installed.


ELECTRON CYCLOTRON RESONANCE FREQUENCY (ECRF) SYSTEM


12


Th
e paramerter space of operation of ADITYA is affected by the stray magnetic fields. Electron cyclotron
resonance breakdown for preionization and startup has been incorporated recently on ADITYA. For this
purpose, an Electron Cyclotron Resonance Heating (E
CRH) system has been installed and commissioned
for operation on tokamak Aditya. The system would serve dual purpose of electron heating during a normal
discharge and initial breakdown to help increase the operational window. The 200 KW gyrotron, VGA
-
2000A
19, operating at a frequency of 28

0.1GHz is first commissioned into a dummy load for pulsed
operation. The output power in TE
-
02 mode is measured by various techniques. Paper burn pattern is
measured at the tube output to confirm the mode structure.


A M
atching Optics Unit is used to convert the TE
-
02 mode to a HE
-
11 mode which is then transmitted
through a ~10 mt long transmission line. The total attenuation of the transmission line is measured to be
less than 1.1dB. Paper burn patterns at various locati
ons of the transmission line confirm the mode
structure.

The gyrotron operation is remotely controlled using the data acquisition and control (DAC) system.


The system has been commissioned in two stages. First the gyrotron output power has been measured
in a
dummy load. Then the out put power is converted to HE11 mode before transmitting through the line
components, vacuum window to the BLS.


Initially the tube is conditioned by applying high voltage for short durations. Gradually, the pulse length is
in
creased, the beam voltage is raised to

50 kV and the ion pump current is not allowed to exceed 20

A
during this process.


Figure 14 shows the output power as a function of beam voltage and beam current. Due to stiffness of the
potential divider anode vo
ltage did not increase beyond 23 kV and hence operation is restricted to

48 kV
beam voltage with pulse width slowly increased to 300 msec due to restriction of water flow in the dummy
load to 45 lpm.


The maximum measured output power for a period of 300

ms pulse length, is ~ 90 KW at a cathode
voltage of
-
48 kV and ~6.5 A beam current. Burn pattern of the


Microwave output power as a function of beam voltage and beam current (at
-
42 kVDC of Beam Voltage).


microwave output power confirms the f
actory result of a 93% pure TE02 mode.





13




(i)





(ii)




(iii











(iv)


(v)



Burn patterns at various locations : I) gyrotron output, ii) 1
st

mirror of MOU, iii) 2
nd

mirror of MOU, iv)
polariser output, v) transmission line output.


Then the HE
-
1
1 gaussian beam is transmitted through the over moded corrugated wave guide, mitre bend,
polariser and a boron nitride barrier window to fall on the beam launching system. Attenuation of less than
1.1 db is ensured in the transmission line.


The above figu
re shows the burn patterns at different locations of the transmission line. The transmission
line terminates in a barrier window connected to the beam launching system housed in UHV box and
connected to ADITYA tokamak.

The Beam Launching System (BLS) cons
ists of two matellic mirrors to steer and focus the beam at centre of
the vessel to initiate the breakdown.. BLS has been designed and fabricated indigenously. It has been
coupled to Aditya vacuum system and the vacuum compatibility has been established be
fore microwave
power is introduced.


The gaussian beam entering the BLS is focussed at the minor axis. The tokamak gas feed controls the

background pressure. Spectroscopic diagnostics and Langmuir Probes positioned at plasma edge measures

various quantit
ies during breakdown of the gas. The pressure and the magnetic field are varied to study the
plasma breakdown. A plasma density of ~ 5 x 10
11

per cc is obtained.


1.2. STEADY STATE SUPERCONDUCTING TOKAMAK (SST1) EXPERIMENT



SST1 is a large as
pect ratio (ratio of the major radius to the minor radius of the plasma) tokamak
configured to run a double/single null, elongated, triangular plasma, with a pulse duration of 1000 sec.



SST1 is being fabricated with a major radius of 1.1

meters with a plasma minor radius of 20 cm. The
maximum toroidal field of 3 Tesla would be produced at the plasma centre. A plasma current of 200
KAmp is envisaged. Provisions are being kept to drive a much higher current to operate with a low safet
y
factor of around 3 which otherwise would be in the range of 5.0
-

7.0. To accommodate larger plasma
current the plasma would be shaped with the help of a set of poloidal magnetic field coils placed at

appropriate positions around the p
lasma. The plasma elongation would be varied between 1.7 and 1.9
while the triangularity would be varied between 0.4
-

0.7.


14


The status description of the sub systems of SST
-
1 are given below.


1.2.1. SST
-
1 VACUUM GROUP


Fabrication of different subsy
stems of SST
-
1 machine shell is being continued at M/S. Bharat Heavy
Electricals Limited (BHEL), Trichy. These subsystems include vacuum vessel, cryostat, liquid nitrogen
panels, cold mass support structure and machine support structure. Major achievement

of this year is the
completion of fabrication and testing of SST
-
1 Prototype Vacuum Vessel and Cryostat at BHEL. Prototype
is toroidally 1/8
th

of SST
-
1 and all other dimensions are same as SST
-
1 main vacuum vessel. It is fabricated
from the same material

(SS 304 L) of SST
-
1 vacuum vessel. Development of this prototype has brought out
many issues related to fabrication of SST
-
1 vacuum vessel and cryostat. A large number of special tools,
fixtures, jigs and processes were developed to resolve these problems

and for successful fabrication of
Prototype. Also, with fabrication of Prototype, processes and facilities for electropolishing and ultrasonic
cleaning of different components of non
-
uniform shapes and with surface area varying from few cm
2

to m
2

have bee
n established. Due to the limitation of power supply, various combinations of current density and
process time have been worked out to achieve required surface finish of large size components with
electropolishing process. Similarly ultrasonic cleaning pro
cedure with limited numbers of immersable
transducers and power supply has been worked out for different components of varying size and shapes.
Large amount of TIG welding of SS 304 L is required in fabrication of vacuum vessel and cryostat. With
the devel
opment of prototype TIG welding, procedure for main system has been established. Most
importantly, the fabrication of Prototype vessel has built up confidence in the engineering design and
fabrication feasibility of main vacuum vessel and cryostat of SST
-
1. Also, the development of Prototype
vacuum vessel and cryostat of SST
-
1 has generated immense confidence in different teams of BHEL
working on fabrication of SST
-
1 main system.


Prototype vacuum vessel has been designed, fabricated and tested as per Ult
ra High Vacuum (UHV)
standards while cryostat as per High Vacuum (HV) standards.






Assembly of Prototype vacuum vessel and cryostat in progress


15

Prototype vacuum vessel has been baked to 200


C
-

250


C by passing hot air (inlet temperature 310


C,
3.5

bar(g) pressure) through U
-
channels welded on inner surface of vacuum vessel, which is exposed to
UHV during testing at BHEL. Unique baking scheme for SST
-
1 vacuum vessel with hot nitrogen gas and
interface of high temperature / high pressure gas flow in

UHV environment of vessel has been thoroughly
tested on the prototype chamber. The measured temperature profile of vessel surface matches with
calculated values within acceptable limits. Set up used for UHV testing of Prototype at BHEL, Trichy is
shown in

the figure. Figure shows two out of four turbomolecular pumps used for vessel pumping, diffusion
pump used for cryostat pumping and hot nitrogen gas system.



UHV testing of SST
-
1 Prototype vacuum vessel and cryostat at BHEL, Trichy



A large number of w
ork centers has been opened up by BHEL. Machining and rolling in D
-
shape vessel
sectors and inter connecting rings are in progress. Other components of main system, like radial ports,
vertical ports, baking channels, cryostat plates, and flanges etc.; are

at different machining stages. Very
strong and active interaction between different teams working at IPR, BHEL Trichy and other work centers
has been established to control the quality of the product within acceptable time limits.


Fabrication of support

structure of SST
-
1 has been started at BHEL, Trichy.


Test liquid nitrogen cooled (LN2) panels have been fabricated at BHEL, Trichy and tested at IPR by
passing liquid nitrogen through cooling tubes. It is observed during testing that the temperature dis
tribution
on these test panels is not acceptable. Development of new brazing process is under progress at IPR as well
as at BHEL.


Fabrication of UHV pumping lines for SST
-
1 vacuum vessel and cryostat has been started at M/S BOCI,
Kolkata. First stage mac
hining of all big size flanges (500 mm diameter and about 200 numbers) has been
completed and other components are at different stages of machining and fabrication. Delivery of first batch
of five numbers of pumping lines is expected by end of September 20
01. All sixteen pumping lines will be
delivered to IPR by December 2001. Final UHV testing of these pumping lines will be carried out at IPR.


16


Design of support structure for all pumping lines is completed and the Contract for this work will be
awarded bef
ore October, 2001.


SST
-
1 vacuum vessel will be baked to 525 K by passing hot nitrogen gas through the baking U

channels
welded on inner surface of vessel. All Plasma Facing Components will either be baked by thermal radiation
from hot vessel or by passin
g hot nitrogen gas through their cooling tubes. There will be a common nitrogen
gas heating system both for vacuum vessel and Plasma facing components.



Gas feed system has to cater the need to supply fuel (hydrogen) gas for different operating condition
s like
pre
-
fill, plasma density built up and control, wall conditioning, special needs of different plasma diagnostics
etc. A programmable gas feed system is under design and gas feed testing system is expected to be ready by
December 2001. Time response a
nd gas feed rate will be analyzed for different gas feed valves and their
attachments on SST
-
1 using this testing system. Also, SST
-
1 Prototype will be used to study rate of pressure
rise, pressure distribution etc.


Facility to measure gas load from diff
erent type of samples has been set up in SST
-
1 vacuum laboratory
and being used regularly for materials to be used in SST
-
1. Pressure difference across aperture of known
conductance is measured with gas load in this system. Since, the accuracy of gas load
measurement depends
on accuracy of pressure measurement in this system, vacuum gauges need to be calibrated regularly. Facility
for the calibration of vacuum gauges using spinning rotor gauge also has been set
-
up.


Experiments on wall conditioning and bo
ronization are being carried out using boronized graphite felt and
hydrogen glow discharge plasma. Interestingly it is observed that thin boron film is deposited on floating
sample placed in glow discharge plasma. It is also planned to use carborane materi
al for boronization with
helium/hydrogen glow discharge plasma. Figure

4 shows experimental set up used for this study.


1.2.2.

SST
-
1 MAGNET GROUP


Manufacturing of the SST
-
1 magnet system consisting of both superconducting and resistive magnets
further got a b
oost during 2000
-
2001. During this period, all the superconducting poloidal field magnets (9
in number), ohmic central solenoid (one) and the TR
-
2 magnets (two) have been successfully manufactured.
These magnets have qualified all the recommended electrica
l, hydraulic and insulation tests during and after
winding at the manufacturer’s (Bharat Heavy Electricals Limited) site before dispatch to IPR. The winding
related technologies for non
-
circular SST
-
1 TF magnets, vacuum pressure impregnation of large vol
ume
magnets and the consolidation of the TF winding pack process and technologies have been established and
realized during 2000
-
01. As a result of these efforts, two 1 : 1 prototype TF double pancakes have been
successfully manufactured, spring
-
back corre
cted and impregnated during this period. The final profile of
the prototype double pancakes could match with those of the prototype TF casing. In the meanwhile all the
machining processes and process technologies appropriate for the manufacturing of the ac
tual TF cases
have been established through the successful manufacturing of a 1 : 1 prototype casing.


A new novel insulation system suitable for cryogenic applications has been developed jointly by IPR and
BHEL, Bhopal during 2000
-
01. This insulation sy
stem known as BHELMAT
-
G has been qualified for
electrical, mechanical and thermal shocks which are typically expected in severe normal and off normal
scenarios of the SST
-
1 superconducting magnets and is at par with other available cryogenic insulation
sys
tems. Consequently, this insulation system has been used in all the SST
-
1 superconducting PF magnets
as well as, being applied in the ongoing TF magnets. This insulation system is also suitable for vacuum
pressure impregnation in large volume large size ma
gnets.


High current feedthroughs for the SST
-
1 in
-
vessel PF
-
6 and vertical Feedback coils have been designed and
tried out at IPR. As a part of the developmental effort first piece of such a feedthrough has been tested

17

successfully at IPR. Necessary ceram
ic components for these feedthroughs are currently being procured.
Winding and consolidation related activities of the SST
-
1 in
-
vessel magnets are currently underway.


The control system of the SST
-
1 superconducting and resistive magnets have been consoli
dated during
2000
-
01. Hardware related to the quench detection and protection of the superconducting magnets,
protection and regulation concerning the resistive magnets are being procured. Some of the procured
components have also been successfully tested.

A full fledged control system is expected to be ready by the
end of 2001
-
02.


As a part of the in
-
house developmental R and D efforts, the overlap joints involving the full scale SST
-
1
CICC has been planned to be experimentally validated in 2001
-
02.


A

picture of D
-
shaped TF double pancake

1.2.
3 FIRST WALL GROUP

The engineering design of all the first
-
wall components of SST
-
1 has been completed and engineering
drawings prepared. After techno
-
commercial evaluation of the quotations that were received, t
he contract
for fabrication of the first wall components, namely, divertors, passive stabilizers, baffles and auxiliary
baffles and their respective supports has been awarded.

The progress of the fabrication of the limiters and NBI shine through is being

monitored. Most of the work
related to SS components for the limiter system has been completed. The process to regain the strength of
the copper alloys after a braze cycle has been a concern. The recent trials on samples by the fabricator
indicate that th
e acceptable strength can be regained through suitable cold working. With this process, we
believe, that brazing of the SS cooling tubes to the copper alloy back plates with compatible filler materials
and a suitable braze cycle can be taken up on the actu
al jobs.

Thermal hydraulic calculations for baking and cooling of the first
-
wall have been completed. The baking
calculations under different conditions, namely, vacuum vessel baking and first wall baking have been used

18

to generate specifications for a Ni
trogen gas based heating system. In
-
vessel and ex
-
vessel cooling tube
layout for the first
-
wall and instrumentation in these distribution lines is being finalized.


Temperature measurement of the first
-
wall components during plasma operation and baking is
very
important not only to the safety of these components but also to understand if there is any asymmetric heat
loading due to plasma. These measurements can supplement the other diagnostics and may be used for
better control of the plasma. A large number

of thermocouples will be incorporated in the first
-
wall to
measure the temperature at the inside of the graphite tiles. Details of their locations, type of thermocouples
to be used, vacuum feedthroughs etc. are being worked out.


1.2.4 CRYOGENICS GROUP



The Liquid helium plant has been assembled and partly tested at the works of M/s Air Liquide, France
under observation of I.P.R. representative. All the components of the cold box, ON
-
line purifier, Oil
removal system and main compressors have been indivi
dually tested and integrated with the main system.
The attached picture shows the completed cold box, purifier and main compressor system. All the tests have
been successfully performed. The individual logic sequences of the control system of the liquid he
lium plant

have been checked at the works of M/s Schnider, France.


The LN
2

transfer lines, sub
-
cooler Dewar and Quality Meters along with the control system and
instrumentation have been manufactured by M/s B.O.C. (I) Limited in collaboration with M/s Spe
cial Pipe
System, The Netherlands. The vacuum test, helium leak test and net evaporation rate (NER) test have been
carried out on the transfer lines as well as on the sub
-
cooler Dewar. The vacuum hold test has been found
satisfactory. The helium leak rate
has been found to be 3 X 10

9

mbar
-
lt/sec. Two sections of the LN
2

transfer lines (3 m each) with one elbow and one vacuum barrier have been assembled and tested as per
QAP under supervision of I.P.R. representative in order to verify the design conditions
. The overall NER
has been found to be 0.1 l/hr/m (4 Watts per meter). The head load due to various components has been
found. The phase separator has been tested under pneumatic pressure of 10 bar with Argon gas. All the
control function with the logic se
quences and MIMICS have been checked along with the PLC. All the
components have been supplied to I.P.R. after completion of the pre dispatch inspection.


Two nos. of Multi
-
layered high pressure (150 bar) storage tanks manufactured by M/s B.H.P.V. have bee
n
successfully commissioned at IPR. Four medium pressure storage tanks (16 bar) have been manufactured by
M/s Patel Air Temp Pvt. Ltd., Ahmedabad. These tanks are presently under acceptance test at the works.
The inter
-
connecting pipe work between differen
t sub
-
systems of the Liquid Helium plant has been
awarded to M/s B. O. C. (I) limited, Calcutta. The inter
-
connecting pipe work is presently under progress.


The Integrated Flow distribution and control system (IFDC) of the SCMS has been defined along wit
h the
detailed valve scheme. The contract for execution of the job is awarded to M/s B. O. C. (I) Limited. In
order to get a flow control over all the coils, flow control valves has been incorporated at the outlet of the
TF coils and casing. Two separate l
ines have been branched off from the main supply line with control
valve to feed the bus
-
bars with super critical helium. All the instrumentation and control system for the
IFDC has been identified.



The major interface of electrical as well as cryogen h
as also been defined for the magnet system.
Accordingly the 20 nos. of current leads have been arranged in a chamber. The super
-
conducting bus bars
will be connected between the bottom of the current leads and the magnet system. The bus
-
bar design has
been

finalized considering all the operating scenarios. Engineering design has been completed for the
current feeder system which include the current lead assembly chamber along with LN
2

shield and LHe/SHe
header, return header etc., three nos. of super conduc
ting bus duct (two for PF coils and one for TF coil),
joint box. All the instrumentation and control system have been defined for this system. Detailed analysis

19

has been carried out in order to optimize the vacuum pump

requirement for the current
feeder sy
stem
and accordingly the vacuum pumps have been defined.


As a confidence building measure, the cryogenic group has also designed and indigeneously fabricated one
LN
2

transfer line and verified the design parameters by performing tests. The Multi layered i
nsulated
transfer line have been designed for a flow rate of 120 l/h with expected heat load of 1.5 W/m and pressure
drop of 20 mbar per meter for two phase flow. The bayonet coupling has been designed for a heat load of 2
-
3 W. The performance test has be
en conducted on this transfer line with LN
2

at 80 K. The test results have
confirmed that the developed transfer line has pressure drop of 15 mbar/m with heat load of 4 W. In order
to establish the pressure drop in the bus bar, the pressure drop experime
nt has been conducted with single
phase nitrogen vapour at 300K on the actual CICC using fliud simulation technique by varying the mass
flow rate. The obtained results have been extrapolated for super critical helium at 4.0 bar @ 4.5K. The
results obtained

have confirmed that the pressure drop for the flow condition of bus bar (supercritical
helium @ 4.0 bar, 4.5 K, 1.2 g/s) is 4 mbar per meter. The cryogenic group has also successfully developed
the vacuum/electrical interface for the bus bar at cryogenic
temperature. The performance test has been
conducted for vacuum compatibility, thermal shock test at 80K and break down voltage test up to 5 kV. The
cryogenic group also conducted experiments on the LN
2

panels of the SST
-
1 cryostat for temperature
distrib
ution in order to establish the fabrication procedure and to obtain the optimized design. Many
experiments at low temperature are presently

underway.



20









Views of Cold Box of Helium Plant under fabrication.


1.2.5. PHYSICS
-
MODELING



21

Tokamak plasm
a evolution and control simulation:



Simulations of SST1 plasma discharge evolution with Lower Hybrid Current Drive have been carried with
the code TSC+LSC. The simulations include shaping of the superconducting PF coil and copper VF coil
currents for th
e initial circular plasma evolution where the superconducting coils cannot be switched on due
to fast plasma current ramp. The vertical field in this period is provided by the copper VF coil, which
however cannot be operated continuously due to heating. O
nly after the plasma current reaches about 100
kA (in ~ 100 msec), the superconducting coil currents are slowly ramped up and the VF coil current ramped
down, with simultaneous current control transferred from Ohmic to LHCD. The position control code RZIP

version 4 for SST1 has been implemented in which the control matrices are more symmetric to avoid
hysteresis problems.


MHD Equilibrium and Stability Interface between Equilibrium code and the Stability code (ERATO) is
completed. Now stability of equilibr
ia like SST
-
1(Shaped plasma), ADITYA(circular plasma) and
STSS(TF coil is replaced by plasma shell current) can be analysed with ERATO.


High
-
beta, high q, low aspect ratio tokamak equilibria have been studied analytically and the existence of
hole type s
olution for beta more than critical value is demonstrated. Using Solovev's analytical approach, a
relationship has been established between various compact equilibria(e.g. Spherical Tokamak(ST), Field
Reversed Configuration (FRC), Spheromak, Spherical To
kamak surrounded by Spheromak shell and FRC
surrounded by ST). With this study, the relevant parameters to have "hole" type equilibrium in TS
-
3/TS
-
4
experiment have been identified.




A one
-
D stability code for arbitrary q and pressure profile and circula
r tokamak equilibria has been written
and tested with published results. This has been used to study the stability of Spherical Tokamak
surrounded

by Spheromak Shell equilibria for large aspect ratio.


Magnetic Error Fields:


The SST
-
1 tokamak subsystems a
re going to use Mild
-
Steel (MS) as a part of support structure in certain
areas around the main SST
-
1 machine. The MS material gets magnetized and produces certain error

magnetic fields which need to be estimated and corrected if necessary. The error field
s are also produced by
the misalignment of various coils. Fields due to magnetization of MS rods which are to be used in the SST
-
1 base and in support structure of some of its subsystems have been found to be well below the threshold for
causing MHD insta
bilities in the proposed configuration (where almost all the MS material is more than 4
meters away from the machine center). Although the field from these kind of material may be small, that
from the misalignment of coils is not. Therefore a set of 12 co
rrection loops (with "picture
-
frame"
geometry) has been proposed for SST1. This consists of 4 loops each on the top, bottom and radially
outboard side of the tokamak, to be mounted on the outer side of the cryostat.



22


The nonlocal diffusion equation with
a model of thermal diffusivity as proposed by Taylor et al. (Taylor,
Connor and Helander, Physics of Plasmas Vol. 5 (1998) 3065) has been used to explain fast response of the
tokamak temperature profile to externally imposed transients.


1.2.6.Data Acquis
ition




23

SST
-
1 Data Acquisition Group is engaged in designing a High speed loss less data acquisition system for
diagnostics of SST
-
1.


In pursuance of continuous acquisition and to achieve self reliance in the area of CAMAC based data
acquisition, effo
rt are being put for developing CAMAC digitiser modules supporting continuous
acquisition.


In case of multi channel CAMAC module a four
-
channel CAMAC module supporting 1MHz sampling rate
per channel has been designed and developed. It supports all three
modes of operations, namely, continuous
acquisition, single shot and on fly monitoring mode. The second prototype in the same category has been
designed to improve the data transfer performance on the CAMAC back plane. The PCB has been
procured and wired
for testing.


A very versatile general purpose CAMAC digitizer development board has been designed.

This will allow
one to implement any prototype CAMAC development work. It is capable to decode all CAMAC functions,
addresses, handles FIFOs, RAM up to 256
Kbytes and TTL ckts to implement any kind of prototype
circuitry. It also includes the FPGA socket and programming chips to interface with on board ADC, RAM,
FIFO and CAMAC lines.


A Device driver for data transfer from CAMAC to host PC has been developed
for WindowsNT. It
supports programmed I/O mode and DMA transfer mode. A library of CAMAC callable routines has been
developed which can be called from VC++ programming environment.

As a requirement of continuous data acquisition of various diagnostics a

PXI based data acquisition system
has been evaluated. The system is provided by National Instruments for the demonstration purpose. The
configuration of the system is as follows.


Data Acquisition Module with 16 channels, 12 Bit ADC, supporting maximum o
f 1.2 Msamaples/sec.
2 channels DAC, 2 channels of counter/timers and 8 Lines of Digital I/O. Such three modules comprising

of 48 channels of analogue In, 6 channels of analogue out, 24 I/O and 6 counter timers have been tested for
continuous ac
quisition.

These three modules are in 3U PXI chassis containing


a PXI controller to connect
it to host PC.
The link

between the Host and controller is fiber optic supporting data transfer rate of 1 G
Bits/sec.

The system supports multiple chassis and a ma
ximum distance of 200 Meters. Some proto
-
type
programs for single shot, multiple trigger and continuous acquisition have already been developed.

In case of continuous acquisition it acquires data from 48 channel @ 10KHz sampling rate and pushes all
the 4
8 data channels on network as well as writes to the hard disk simultaneously. A client utility also has
been developed to view the data from any network node. It generates a data file of about 1Gbyte over a
period of 1000sec
.


1.2.7 RADIO FREQUENCY HEATING

AND CURRENT DRIVE


ION CYCLOTRON RESONANCE HEATING (ICRH) SYSTEM


Ion cyclotron heating is chosen to heat the plasma to 1.0 KeV, during pulse length of 1000 s. A
1.5 MW ICRF system would operate at different frequencies between 20
-
92 MHz for different
h
eating scenarios at 1.5 T and at 3.0 T operation.


Order for the fabrication of the 1.5 MW stage amplifier has been finalised. The dummy load for this
amplifier has been erected. Testing of the same has been initiated with the available power. Fabricatio
n of
low power stages of the source at 20.0 to 91.2 MHz that would be used in SST
-
1 has been continued.
Fabrication of the amplifiers up to 20 kW and 47.6 MHz has been completed. Tests are under progress.


All the components for the transmission line have

been finalised. Orders for the fabrication


24

of these components as per IPR design at various industries have been finalised. A prototype liquid stub has
been made and rf characteristic of the same has been studied. High power tests of the same would be
in
itiated soon. Interfaces and mechanical supports required for integrating the lines to SST
-
1 have been
designed and orders for fabrication are being finalized. Antennae and invessel support structure have been
designed and orders for fabrication are being

finalised.



Cooling water distribution system along with instrumentation for the complete system has been finalised
and given to the cooling group for execution. The channels required for the entire ICRH system control
monitoring and data acquisition ha
ve been finalised and different activities for realization have started.
Support structure for different components have been finalised for order.


LOWER HYBRID CURRENT DRIVE (LHCD) SYSTEM


LHCD system would be used as the prime method of steady state pla
sma current in a circular as
well as an elongated plasma. The system has been optimised for efficient current drive for 1.5 T
and 3.0 T operation, for different plasma elongation

and triangularity for plasma inductance
value
of 0.75 to 1.4.


Prototypes de
veloped for various components have been tested for mechanical compatibility and their rf
characteristics at low power. The same have been assembled and tested for high power tests on the klystron
based test system. In the meantime some of the high power
components have been received after factory
tested and have been tested at IPR for high power. Duplication of some of the power supplies for the second
klystron have completed and are being tested for integration. One of the major achievement has been to
d
evelop high power dummy load at 3.7 GHz. They have been successfully tested at 60 KW power level. E,
H plane bends, narrow wave guides and many other components have been developed and final order has
been placed for use on SST
-
1.


Support structure for th
e LHCD system to be used on SST
-
1 has been ordered for fabrication and
commissioning. Cooling water distribution system has been finalised. Hard X
-
ray diagnostics system has
been finalised. The support structure requirement has been passed through the draw
ing committee and the
procurement procedure has been initiated.


In the meantime all the channels for the DAC system has been finalisedVME based software development
for the data acquisition and control system have been initiated. The required hardware is
being procured. for
the same. Many of the front end electronics have been modified after hot test on the test system
.


ELECTRON CYCLOTRON RESONANCE FREQUENCY (ECRF) SYSTEM


Based on the comments of Engineering Design Report (EDR) for a 82.6 GHz system, mi
nor
modifications in some auxiliary power supplies have been incorporated. The final order for the
gyrotron along with the transmission line has been placed after extensive technical and
commercial discussions. Support structure for the transmission line h
as been designed and order
for its fabrication has been placed. Cooling water distribution system has been finalised and
details have been given to the cooling group. Total number of channels in the DAC system has
been finalised. Auxiliary power supplies f
or the system have been designed and fabricated.
Testing for some of the unit would commence soon. The beam launching systems have been
engineered and the order has been placed for fabrication. Acceptance test procedure for the
gyrotron and the transmissio
n line has been finalised. The special flanges required for integration
of the beam launching systems have been designed and indent has been raised.


1.2.8 DIAGNOSTICS



25

SPECTROSCOPY


Two spectrometers
-

a 1m multi
-
track visible wavelength spectrometer and

a 0.3 m grazing incidence
spectrometer
-

would constitute the basic spectroscopic diagnostics on the SST
-
1 tokamak in the very first
phase. Quotations had been invited for these. At present the details of the performance tests to be
conducted prior to t
he acceptance of the two spectrometers are being worked out with the respective
suppliers.


The facility for polishing and connectorising optical fibers to be used for transporting light from the
tokamak to the detectors has been set up. A sample piece (
10 m, 1 mm core silica/silica optical fiber) made
thereby is being used satisfactorily in our laboratory . Quotations received for a bulk order for the silica
core
-
silica cladding fibers ( samples of which have been satisfactorily tested earlier) are

being processed.


A laboratory test of a prototype of the electronics to be used with photodetectors has been completed. It
is being used on the ADITYA tokamak at low frequency band widths (<10KHz). The necessary
modifications are being incorpor
ated. It has been proposed to have a few channels (of H
-
alpha and CIII
line detectors) with high speed detection to track fast plasma events and the requirements for suitable
high frequency (~100 kHz) low noise electronics are being worked out.


So
lid metal mirrors of different materials have been considered for in
-
vessel use to view the Divertor
region of the SST
-
1 tokamak, taking into account out gassing rate, achievable

reflectivity and robustness
against sputtering in a plasma. Two sample piec
es (Stainless steel and Molybdenum) have been procured
for testing for any warping or changes in reflectivity during baking and evacuation cycles in the tokamak.


It has been proposed to have an optical system to image the SST
-
1 plasma and the plasma faci
ng surfaces.
This would consist of coherent optical fiber bundles, image quality lenses and electronic cameras. The
details of the components of this system have been worked out taking into account the expected brightness,
proximity and the required sp
atial and temporal resolution. Discussions are on with the suppliers of
cameras on the issue of adequately fast transfer of image data from camera for storage and display.


1.3 BASIC EXPERIMENTS


1.3.1. RF PRODUCED TOROIDAL PLASMA


In the radio fre
quency laboratory of the institute, a toroidal radio frequency plasma device (TRFPD) has
been set up to study the basic aspects of RF produced plasmas in curved geometry of the torus. This
toroidal plasma device is made of stainless steel with major radiu
s 30 cm and minor radius 10.5 cm.

A pulsed toroidal magnetic field with the peak magnitude of 600 Gauss is produced for approximately 100
ms duration. On this device, 100 W of CW RF power is available in the frequency range of 1
-
9 MHz. In the
high RF powe
r experiments, a pulsed RF generator with 2 kW of peak RF power, in the frequency

range of 1
-
20 MHz is used. In the present studies on this device, bounded whistler wave is excited to
produce the plasma. This wave is toroidal counter part of well known he
licon waves in thin cylindrical

geometry. This wave possesses unique feature of strong poloidal mode coupling, introduced due to
inhomogeneity in the ambient magnetic field and toroidal curvature. Parallel wavelength of the excited
wave is also comparable

to the system dimensions. Therefore, this system acts like a plasma filled toroidal
resonant cavity. For a typical case of poloidal mode number one and toroidal mode number three, field
pattern of this wave in the poloidal cross section is displayed in th
e following figure.




26

Typical field pattern of toroidal bounded whistler wave in the poloidal plane of the torus. Here 'r' is minor
radius and 'theta' is poloidal angle.


Apart from, producing the plasma with peak electron density of 10
12

per cc and 18
eV electron
temperature, present studies on this wave have explored a new method of current drive in the plasma along
toroidal direction. Approximately 1 kA of plasma current has been observed with 1 kW of RF power.

27

Further studies on this device are ai
med towards better understanding of underlying physical mechanism
responsible for observed plasma currents and their implications in tokamak plasma research.


1.3.2. FREE ELECTRON LASER EXPERIMENT


The new 50
-
period electromagnetic wiggler with off
-
axis f
ield has been assembled and integrated into the
FEL system. The preliminary electron beam propagation studies conducted during this period using this
wiggler showed marked improvement in beam propagation as compared to the earlier 20 period wiggler
mainly
due to the off
-
axis configuration of the wiggler field.


Experiments to study FEL emission are currently underway.


Development of an
in
-
situ

field mapping device based on the pulsed
-
wire technique is currently being
carried out. This technique is current
ly being tested and optimized on the 15
-
period permanent magnet
wiggler. Also, a magnet based electron beam energy analyzer is also being fabricated for more accurate
energy measurements of the e
-
beam.


1.3.3. EXPERIMENT ON DELAY COUPLED OSCILLATOR


Expe
rimental observations of time delay induced amplitude death in a pair of coupled nonlinear electronic
circuits that are individually capable of exhibiting limit cycle oscillations are described. In particular, the
existence of multiply connected
death isla
nds

in the parameter space of the coupling strength and the time
delay parameter for coupled identical oscillators is established. The existence of such regions was predicted
earlier on theoretical grounds in [Phys. Rev. Lett. 80 (1998) 5109; Physica 129D
, 15 (1999)]. The
experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations
with increased time delay and the onset of both in
-
phase and anti
-
phase collective oscillations. in our
experiment. Some theoretic
al understanding of these results as well as their practical implications for
physical and biological systems are discussed.


1.3.4. BASIC EXPERIMENTS IN SPECTROSCOPY


The Spectroscopy group is also continuing its laboratory experiments on the expansion o
f spark and
exploding wire discharges and developing expertise in spectroscopic diagnostics of high resolution for
such plasmas of short duration and small spatial extent .


Comparison of the expansion of a spark channel on a polymeric surface wit
h that of a freely expanding
spark had revealed a faster expansion along the surface and a reduced expansion away from the surface i.e.
the plasma tends to remain close to the surface. This has been found , on the basis of spectroscopic data
acquired duri
ng this experiment, to be due to the rapid heating of the top layers of the surface (within a few
hundred nanoseconds of the initiation of breakdown) and the further discharge current channel being
governed by the ionization of the molecules emanating f
rom the surface.


Experiments on the plasma produced in an exploding wire have been initiated. The rupture of the wire and
the development of the plasma have been recorded by fast imaging of the exploding wire and monitoring
the current and voltage across

the plasma channel. Preliminary results indicate the formation of a high
density (inferred from highly broadened spectral lines) and low temperatures (0.2
-

0.5 ev) plasma .


1.3.5 RELATION BETWEEN ELECTRONIC STRUCTURE AND ELASTIC PROPERTIES


In order

to relate the elastic properties with electronic structure, TiNi has been studied, a shape memory

alloy which undergoes a martensite transition at T
m

= 333 K. As a function of temperature, we observe

changes only in the Ti 2p core levels and not in the N
i 2p core levels, and confirms the stability of the Ni

derived states across the transition.



28

1.3.6 LOW Tc SUPERCONDUCTING METALS AND CHARGE ORDERING SYSTEMS
EXHIBITING SUPERCONDUCTIVITY



The work has been conducted in collaboration with Prof. S. Shin of

University of Tokyo. The work on Pb

and Nb is a study of the one
-
electron removal spectrum of low
-

Tc superconductors using temperature

dependent (5.3 K to 12 K) ultrahigh resolution photoemission spectroscopy. This constitutes the first study

of the chan
ges in the density of states using photoemission spectroscopy across the transition and

establishes the strong coupling nature of the transition.



1.3.7 CHARGE ORDERING SYSTEMS


The effects of the co
-
existence of charge
-
order and supercond
uctivity on the electronic structure in 3

dimensional non
-
magnetic Ba
1
-
x
K
x
BiO
3
system is investigated. A pseudogap in the normal state single

particle density of states, associated with the breathing
-
mode phonon energy scale, has been identified.


1.3.8 EL
ECTRONIC STRUCTURE OF SmS


This work has been conducted in collaboration with Prof. T. Takahashi of Tohoku University, Japan. SmS
exhibits a well
-
known pressure induced semiconductor
-
metal transition. The ambient pressure phase as a
function of temperat
ure to look for a precursor effect to the pressure induced transition has been
investigated. The results indicate that SmS is best described as a low carrier density Kondo lattice system.


1.3.9 TRANSVERSE SHEAR WAVES IN STRONGLY COUPLED DUSTY PLASMAS


Exp
erimental observations of transverse shear waves in a tree
-
dimensional dusty plasma that is in
the strongly coupled fluid regime has been reported. These spontaneous oscillations occur when
the ambient neutral pressure is reduced below a threshold value an
d measured propagation
characteristics of these waves are found to be in good agreement with theoretical predictions.


1.4. OTHER ACTIVITIES


FCIPT Report

1.4.1 COMMERCIAL PROTOTYPE OF MEDICAL WASTE PLASMA PYROLYSIS
SYSTEM


Based on the extended operatio
n and field trials of the technology demonstration prototype, a
compact and user friendly plasma pyrolysis system has been designed and fabricated. The proto
-
type system is ready for the demonstration of the technology with actual hospital waste. Its
schem
atic diagram is shown in the figure. Following features are incorporated in the system.




Waste feed mechanism with inert gas lock to prevent puffing



Arrangement for the removal of solid residuals



Positioning of plasma torch for efficient heat transfer



Sh
ielding of plasma torch after shutdown



Controlled injection of sub
-
stoichiometric air during pyrolysis



Metal shell in the primary chamber for proper heat distribution



Low impedance for pyrolysis product gas flow



Compact system



29

Primary and secondary chamb
ers, scrubber and induced draft fan all are mounted on a common
movable platform of size 5’x 8’. The double port feeding mechanism is easy to operate, leak
proof and is charged with inert gas to prevent air venting into the hot zone. Fish mouth door has
be
en provided with a cover of heat resistant material, which do not allow heat to enter the
hopper. The primary chamber is aligned in such a way that waste material falls into the hot zone
of the plasma arc. In addition, auxiliary cooling of anode with air
has been incorporated in the
plasma torch. In the secondary chamber, the burner is mounted vertically which enables easy
flow of the product gas into the combustion chamber ensuring extended flame length.


Many trial experiments have been conducted to che
ck the performance and user friendliness of
the system. Typical gaseous products formed in the pyrolysis chamber are rich in hydrogen and
carbon monoxide with some lower hydrocarbons such as methane, propane etc. The total
quantity of H
2

and CO in the gase
ous mixture is more than 49% by volume thus provide an
option to recover energy. These gases burn in the combustion chamber and release CO
2

and
water vapour. When the selected material contain some poly vinyl chloride it produces a small
quantity of HCl,
which is scrubbed off by alkaline solution in the scrubber. This system is being
shifted to Gujarat Cancer Research Institute (GCRI), Ahmedabad for a second round of field
trials with actual medical waste.


Plasma Pyrolysis System


ENERGY RECOVERY

FROM PYROLYSIS


Plasma Pyrolysis of hospital waste material under optimised conditions can provide a large
quantity of CO and H
2

gases as by
-
products. The electrical energy through plasma is consumed
in melting of plastics, bond dissociation and endother
mic reactions. Recovery of these gases will
improve the economics of the plasma waste treatment process.




30

A research project sponsored by Johnson & Johnson, USA to investigate energy recovery from
pyrolysis has been initiated. The first part of the projec
t will be directed towards optimising the
pyrolysis process to increase the combustible gas content and will employ gas chromatograph
mass spectrometer and FT
-
IR Spectrometer as diagnostics. In the second part of the project,
studies will be focused on ene
rgy recovery. Atmospheric pressure nonequilibrium plasma
techniques will be applied for plasmachemical reforming of the product gas.


A versatile basic research system has been conceptualised and the engineering of various
subsystems is in progress


BOOT
STRAP PLASMA PYROLYSIS SYSTEM


In the bootstrap system, a more rational use of the heat generated by the combustion of the
pyrolysis product gases will be exploited. Enclosing the primary chamber within the combustion
chamber (Figure 4) will achieve this.
The heat energy released during the combustion of
pyrolysed gases will be utilized for heating the primary chamber. This will improve the energy
economics of the pyrolysis technology. A prototype system has bee built and tested.


1.4.2 PLASMA NITRIDING SYS
TEM INSTALLED AT IGCAR


FCIPT has successfully installed and commissioned a plasma nitriding system at the Indira
Gandhi Centre for Atomic Research, Kalpakkam. IGCAR scientists plan to use the plasma
nitriding system for developing the nitriding process fo
r fast breeder reactor components.


The pulsed power supply along with control and process instrumentation has been supplied by
FCIPT. The vacuum and pumping system have been designed by FCIPT and engineered and
commissioned by Vacuum Techniques, Bangalore
. This vacuum system is the first indigenously
built externally heated hot wall chamber for plasma nitriding. This design provides unique
advantages of clean vacuum and uniform heating of workload for plasma nitriding. The pulsed
power supply and computer

based control system has been integrated with vacuum system at
Kalpakkam by FCIPT. The pulsed power supply is rated for peak current of 20 amperes with
variable frequency and duty cycle.


BASIC STUDIES ON PLASMA NITRIDED AISI 420


Plasma nitrided AISI 42
0 steel have been analysed by glancing angle XRD (phases formed on the modified
surface), SEM (microstructural changes in the nitrided region) , XPS and AES (amount of nitrogen
concentration on the surface and in the modified zone). A correlation of these
results is made to the change
in hardness values measured from the surface towards to the core.






31


Untreated





Plasma Nitrided AISI 420





Glancing Incidence X
-
Ray Diffraction Patterns of untreated and

plasma nitrided AISI 420


While the GIXRD pattern for the untreated sample shows the

-
Fe peak, the treated surface
shows additional peaks, which are assigned to hexagonal

-
Fe
3
N. The presence of a single phase
of

-
Fe
3
N only on the surface can be attribu
ted to the carbon intake from the material. SEM
micrograph also shows up to 2
-
5 microns a different microstructure from that of the diffusion
zone. Since GIXRD penetrates a few microns from the surface, the diffractogram results are
consistent with the mic
rostructure.


Fe 2p X
-
ray photoemission spectra as shown in the figure have been obtained from the modified
surfaces using monochromatic AlK


photons. The Fe 2p spectrum of the modified surface show
single peaks of Fe 2p
3/2

and Fe 2p
1/2

featuring at 707 eV

and 719 eV due to spin
-
orbit splitting.
The binding energies and the asymmetric spectral shape are quite like that of metallic Fe,
indicating that the processing has not resulted in oxidation of the surface. Oxidation results in a
large chemical shift and

satellite structure in Fe2p spectrum, which is not observed here. More
significantly, the N 1s spectrum with a binding energy of 397 eV is also a single peak typical of a
metal nitride. Using single asymmetric Voigt functions for the Fe 2p
3/2

and 2 p
1/2


peaks as well
as for the N 1s spectrum, the good fits obtained confirm that the nitride is formed on the surface.




X
-
Ray Photoemission Spectrum Indicating Fe2p Core Level














-
Fe

Fe
3
N

Fe
3
N

Fe
3
N


-
Fe

Intensity (a.u)

Intensity (a.u)


2


in degrees

2


in degrees


705
710
715
720
725
730
XPS Fe 2p
Intensity
Binding Energy (eV)

32






To investigate the CrN content on the surfac
e, the Cr 2p core level spectra has been measured
using monochromatic AlK


photons. The spectra indicate CrN formation, since negligible O or
C has been measured on the surface. The total intensity of the peaks at higher binding energy
amounted to a maximu
m of 34% of the total Cr content present in the surface, indicating that less
than 4% of the 12% Cr present in the surface has been transformed into a nitride.


The relative atomic concentrations on the same sample cut in cross
-
section has been measured
u
sing small spot electron induced AES to study the constituent elements over the case depth, to
relate to the microhardness. Microhardness has shown a direct correlation with the nitride phase
formation. The microhardness is maximum to a depth of ~60 micron
s, at which depth the
nitrogen concentration reduces very sharply. The reduced N content results in a marked reduction
in surface hardness, and the hardness values reaches that of the base material by about 80

90
microns.


HIGH QUALITY SILICON OXYNITRIDE
FILMS FOR ELECTRONIC AND OPTICAL
APPLICATIONS



SiO
x
N
y

films have been grown by Plasma
-
enhanced chemical vapour deposition (PECVD) on
single crystal Si (100) wafers using an organic precursor, Hexamethyl
-
Disilazane (HMDSN).
Using the Lucovsky
-
Phillips cri
terion of bond co
-
ordination constraints, high
-
quality thin (~20
angstroms) and thick (up to 2700 angstroms) films have been grown which are Carbon free (<1.0
% ) as characterised by X
-
ray photoemission spectroscopy(XPS) and Auger electron
spectroscopy(AES
) depth profiles. XPS of the Si 2p, O 1s and N 1s core
-
levels is used to
conclusively identify oxy
-
nitride bonding in the films in good agreement with films grown using
silane as a source of Silicon. Valence band XPS confirms the changes associated with th
e band
gap reduction in SiO
x
N
y

compared to SiO
2
. The deposition rate determined from AES depth
profiles has enabled accurate thickness control (
+

15 angstroms). In addition, knowing the
chemical composition

(SiO
1.6
+
0.1
N
0.3
+
0.05
), and hence the refractive i
ndex, we have succeeded in
growing

/4 films with a specific colour, spanning the visible spectrum.


AEROSOL GENERATOR


The simulation of core disruptive accident is essential for understanding the behavior of the
aerosol inside and outside a nuclear reac
tor. The dynamics of aerosol viz., release and transport,
properties of the aerosol etc. are essential for the simulation. Experimental validation of the
computer predictions is essential to improve the reliability. The aerosol formation in the core
disrup
tive accidents is essentially considered to be condensation of the vapors.


The steep temperature gradient and high quenching rates of the thermal plasma are utilized for
generation sub
-
micron sized aerosol powder. Additional advantages include: (I) plas
ma based
aerosol generator can provide intense aerosol flux, (ii) it can be used to produce aerosol of
metals, ceramics and composites and (iii) the aerosol generation rate and size can be controlled

33

by operating parameters. The typical aerosol generation

rate in nuclear accidents is few gm/m
3

and the generation rate is few gm/sec.


A joint experiment between Health and Safety division of Indira Gandhi Centre for Atomic
Research (IGCAR) and FCIPT to evaluate the suitability of plasma torch aerosol generat
ion was
undertaken. The results of the experiment indicated that aerosol of desired characteristics can be
generated. A magnetically rotated non
-
transferred arc plasma torch has been designed, fabricated
and tested up to 25 kW. Thyristor based arc power su
pply with arc initiator has been built and
tested up to 25 kW of continuos operation. It has been provided with water (temperature and
flow), gas and other interlocks. The accessories viz., wire feeder and powder feeder operation
can be operated in manual

mode or timer mode. The arc rotation can be varied during the
operation. The complete system consisting of arc power supply, plasma torch, wire feeder,
powder feeder have been integrated and tested.


The results of the sampling measurement suggest that
the peak of the particle size distribution
occur at 1

m. Electron micrograph of the particles collected in the Andersen sampler is shown
in the figure. The particles are found to be highly agglomerated clusters of very fine primary
particles. Further an
alysis also indicates presence of individual rectangular particles likely to be
unreacted particles of Mg powder.


The X
-
ray diffraction of the powder collected in the chamber shows formation of magnesium
oxide.
P
eaks corresponding to magnesium are not o
bserved. These experimental results
demonstrate the feasibility of aerosol generation using thermal plasma.




Electron micrograph (Magnification 36000 X) showing agglomerated clusters of very fine
primary particles


1.4.3. SURFACE CHARACTERISATION LABORA
TORY


Surface characterisation facilities are used for internal work as well as external work on
commercial basis for a wide spectrum of fields and applications. The highlights of the main