Personal summary of work carried out at Daresbury Laboratory: ILC/CLIC, NLS, ALICE and ITER

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Nov 15, 2013 (3 years and 11 months ago)

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Personal summary of work carried
out at
Daresbury

Laboratory:
ILC/CLIC, NLS, ALICE and ITER

Luis Fernandez
-
Hernando

STFC/ASTeC Daresbury Lab



ILC and CLIC collimation:



Wakefields test beam



Thermo
-
mechanical studies



ILC positron target



Radiation/dose studies



Thermo
-
mechanical studies



New Light Source beam dump



ALICE



RF instability problem



BLM



ITER Central Interlock System



Summary

ILC and CLIC collimation design

ILC 0.5 TeV


30 km

ILC 1 TeV


50 km

CLIC 3 TeV: 48 km

CLIC 0.5 TeV: 13 km


J.L. Fernandez
-
Hernando

The collimator mission is to clean the beam halo from e
-

or e+ off orbit which could damage the
equipment and mainly to stop the photons generated during the bending of the beam towards the
Interaction Point. These photons, if not removed, would generate a noise background that would
not allow the detectors to work properly.

The spoiler serves as protection for the main collimator body as it will disperse the beam, reducing
the beam energy density by multiple Coulomb scattering, in case of a direct bunch hit avoiding
severe radiation damage.


CLIC

ILC

Energy

1500

GeV

250/500
GeV

Bunches it has to resist

312

2/1

Particles

per bunch

3.72E9

2E10

σ
x

in

the spoiler position

796

µm

111
µm

σ
y

in

the spoiler position

21.9
µm

9
µm

ILC and CLIC spoilers


J.L. Fernandez
-
Hernando




Long, shallow tapers to reduce short range transverse wakes


High conductivity surface coatings


Robust material for actual beam spoiling


Long path length for errant beams striking spoilers (
Large
c
0

materials
(beryllium…, graphite, ...)


Consider range of constructions, study relative
resiliance

to damage (melting,
fracture, stress)




Starting point

ILC and CLIC spoilers


J.L. Fernandez
-
Hernando

Beam Parameters at SLAC ESA and ILC

Parameter

SLAC ESA

ILC
-
500

Repetition Rate

10 Hz

5 Hz

Energy

28.5 GeV

250 GeV

Bunch Charge

2.0 x 10
10

2.0 x 10
10

Bunch Length

300
m
m

300
m
m

Energy Spread

0.2%

0.1%

Bunches per train

1 (2*)

2820

Microbunch spacing

-

(20
-
400ns*)

337 ns

*possible, using undamped beam

ILC and CLIC spoilers


Wakefields test beam


J.L. Fernandez
-
Hernando

T480

“wakefield box”


ESA beamline

ILC and CLIC spoilers


Wakefields test beam


J.L. Fernandez
-
Hernando

BPM

BPM

BPM

BPM

A run with the beam going through the middle of the collimator (or without the collimator) is used as
reference for the next run where the collimator will be moved vertically. This run also serves to calculate the
resolution of each BPM.

BPM

BPM

BPM

BPM

The analysis will do a linear fit to the upstream and downstream BPM data separately, per each pulse
(bunch) . For this fit the data is weighted using the resolution measured for each BPM.

The slopes of each linear fit are subtracted obtaining a deflection angle. This angle is transformed into V/pC
units using the charge reading and the energy of the beam.

All the reconstructed kicks are averaged per each of the different collimator positions and a cubic, or linear
fit of the form:

y’ = A
3
∙y
3

+ A
1
∙y + A
0
or
y’ =

A
1
∙y + A
0
(only to collimator positions from
-
0.6 mm to 0.6 mm)

is done to the result. The error in the kick reconstruction at each collimator position weights the different
points for the fit.

The kick factor is defined as the linear term of the fit (
A
1
)
.

ILC and CLIC spoilers


Wakefields test beam


J.L. Fernandez
-
Hernando


J.L. Fernandez
-
Hernando

0
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Collimator number
Kick factor [V/pC/mm]
Experimental data
GdfidL 500 microns
GdfidL 1 mm
ILC and CLIC spoilers


Wakefields test beam


J.L. Fernandez
-
Hernando

1
±

0.1 V/pC/mm

1
±

0.2 V/pC/mm

1.4
±

0.3 V/pC/mm

1.7
±

0.1 V/pC/mm

1.9
±

0.2 V/pC/mm

1.7
±

0.1 V/pC/mm

2.6
±

0.1 V/pC/mm

ILC and CLIC spoilers


Wakefields test beam

Flexural Section (
wakefield

taper)

Peripheral cooling
sufficient? Angle varies from 0 at max aperture
opening to
90mrad ~5
o

(full included angle (or
±
20mrad about axis)



Precision encoded actuators

with bi directional repeatability
to <10
m
m (<5
m
m possible?).
Note with 10
m
m over 300mm
span, 0.03mrad angle control is
possible on pitch of collimator
surfaces


Vented Side
Grill

for
Wakefield
continuity and
pumping

Vessel (wire seal
UHV compatible)

EntranceTransition Flare

From 20mm diameter to
30(h)x40(w)mm rectangular
section.

Spoiler Block

21mm width Ti

Inclined Wakefield Collimator Block

Bulk Material


Be, semi
-
transparent to 500GeV electrons. Converging
in 2 steps of opening angle 65mrad (3.7
o
) & 40mrad (2.3
o
) nearer the
spoiler block (note: opening angle =
±

32.5mrad &
±
20mrad about
central axis respectively) then diverges at same angular rate
downstream of the spoiler block


EPAC08, WEPP168

ILC and CLIC spoilers

Energy

spoilers

Energy

1500

GeV

Bunches it has to resist

312

Particles

per bunch

3.72E9

σ
x

in

the spoiler
position

779.6

µm

σ
y

in

the spoiler
position

21.9
µm

Material

length
needed to spoil
beam

0.05 Xo


J.L. Fernandez
-
Hernando

Resulting stress (using FLUKA and ANSYS)
right after a CLIC bunch train has hit the
spoiler at 0.2 mm from its bottom (or 4.29
mm from its top). Being the normal orbit of
the beam at 8 mm from the bottom of the
spoiler (3.51 from the top) that represents a
deviation from normal orbit of
10
σ
x
.

950MPa, and tensile, which is way
above tensile strength limit.


J.L. Fernandez
-
Hernando

The top value of stress is ~340MPa and compressive. Meaning that
there will not be fracture

but
there will be a permanent deformation
, and in this case it is a vertical deformation of 5 µm,
which represents
a 0.1% of the half gap
. Can we live with that?

But… is a deviation of 10 sigmas even possible?


I have also calculated the stresses when the bunch train hits 0.2mm from the top instead of 4.29
mm (or 4.29 mm from the bottom instead of 0.2). Which means a deviation of “just”
4.75
σ
x
.

ILC and CLIC spoilers

Silicon carbide (SiC) foam

Material

Radiation length

Xo [cm]

Copper

1.44

Ti alloy

3.56

Beryllium

35.3

SiC

(solid)

8.1

SiC

(foam

8%)

337

SiC is a material with good
thermomechanical properties. Used
for LHC collimation phase 2, in F1
brakes, and aerospace applications.


It can be used as core material for
CLIC spoilers, coated with metal
(Be, Cu...)

Very long radiation length of
the foam at 8% of nominal
density allows for low energy
deposition of the particle
beam.

ILC and CLIC spoilers


J.L. Fernandez
-
Hernando

Pros and cons for using SiC foam as core material in CLIC
energy spoilers covered by 0.05Xo (in the z direction) of
beryllium:


Pros:




It will not matter the depth the beam hits as it will always see 0.05Xo of
beryllium (the contribution of the SiC foam can be negligible).




Save some beryllium.


Cons:




The junction of two different materials is a complicate thing, mechanically
speaking. The different thermal properties can lead to dislocation or fracture
of the junction when the bunch train hits. A single material spoiler is more
“whole” in that aspect.

ILC and CLIC spoilers


J.L. Fernandez
-
Hernando

ILC positron target studies


J.L. Fernandez
-
Hernando

Right after 8 hours
irradiation (no
cooling time)

Dose rate [pSv/s]

1 hour cooling time

Simulated a photon irradiation of 8 hours, bunches of 2E10 photons separated 300 ns.
(6.67E16 photons/second)

This edge is due to the
steel vacuum vessel the
target is in

ILC positron target


Radiation and thermal effects


J.L. Fernandez
-
Hernando


J.L. Fernandez
-
Hernando


J.L. Fernandez
-
Hernando

NLS beam dump

2.25 GeV e
-


2E9 e
-

per bunch

1 MHz frequency

meaning 450 kW in total

A high repetition rate coherent FEL, a new class of machine which
produces fully controlled X
-
ray pulses.


J.L. Fernandez
-
Hernando

14 cm
7 cm
200 cm
1
0 cm
Copper
backstop
Graphite dump core
Radial copper shell
Water cooling
r
z
Energy density deposition given by FLUKA for a 2 mm radial
beam size NLS beam into 200 cm of graphite and 10 cm of
copper. Results are normalised per primary particle.

Graphite

Copper

Density

[g/cm
3
]

1.71

8.96

Critical

energy

E
C

[MeV]

84.25

20.17

Radiation

Length

X
0

[cm]

25.1

1.44

Molière

radius

R
M

[cm]


7

1.6

Melting

Temp

T
melt

[

C]

3800

1083

Operating

Temp

T
op

[

C]

500
-
600

<200

Static

stress

limit

[MPa]

100
-
250 at compression

>40 at tension

σ
0.2
≈150
-
400
(plasticity limit)

Cyclic

stress

limit

[MPa]

60 at compression

30 at tension

60
-
100

NLS beam dump design


J.L. Fernandez
-
Hernando

0.00E+00
5.00E+05
1.00E+06
1.50E+06
2.00E+06
2.50E+06
3.00E+06
0
2
4
6
8
10
12
14
16
Equivalent stress
Peaks of stress
quadratic fit
Stress [Pa]

Time [seconds]

Equivalent stress (σ
eq
) in the initial sweep spot
position in the graphite core and a quadratic fit done
to its peaks of stress showing how the stress
stabilizes after a period of ~13 seconds at a value
nearing 3 MPa

Temperatures achieved in the section of the dump
where the electromagnetic shower generated by
the beam is at maximum intensity

NLS stress studies


Steady and transient states

Steady state
calculation of the
temperatures, in
degrees C,
achieved in the
impacting surface
of the 200 cm
graphite/Cu beam
dump using a
beam sweep
radius of 9 cm
with 12 spots


J.L. Fernandez
-
Hernando

NLS beam lines, experimental areas and beam dump


J.L. Fernandez
-
Hernando

ALICE

Nominal bunch charge on ALICE is 80pC.


The bunches are produced in trains lasting from ~10ns to 100ms and the train repetition frequency
can vary from 1 to 20Hz.


Within the train, the bunches are separated by 12.3ns that corresponds to the laser pulse repetition
frequency of 81.25MHz
.

Booster

Compressor

IR
-
FEL

Photoinjector
Laser

High brightness
electron source

Linac

Arc

FEL

Acceleration

LINAC

Deceleration

ALICE : Design, commissioning and running

ALICE


Accelerators and Lasers In Combined Experiments

350 keV

8.35 MeV

35 MeV

EMMA


The first non scaling FFAG

A FFAG (Fixed Field Alternating Gradient) is
a type of accelerator in which the magnetic
field in the bending magnets is constant
during acceleration. This means the particle
beam will move radially outwards as its
momentum increases.


A linear non
-
scaling FFAG is one in which a
quantity known as the betatron tune is
allowed to vary unchecked. In a
conventional synchrotron such a variation
would result in loss of the beam. However,
in EMMA the beam will cross these
resonances so rapidly that their effect
should not be seen.


EMMA (Electron Machine for Many
Applications) accelerates electrons from 10
to 20 MeV.


J.L. Fernandez
-
Hernando

ALICE commissioning and Beam Loss Monitoring system

My

tasks
:



Characterise

the

BLM

system
.

Design

and

carry

out

experiments
.

Analyse

the

signal

of

the

ionisation

chambers

and

of

the

BPMs

to

extract

a

charge

measurement

that

can

be

correlated

with

the

monitor

readings
.


Investigate

the

possible

sources

of

RF

phase

instability
.


Operate

the

machine

both

for

experiments

I

am

responsible

and

other

experiments

related

to

ALICE
.

0
100
200
300
400
500
600
0
50
100
150
200
250
300
350
BC1 crest
LC1 crest
BC1crest v LC1 crest THz
BC1 crest v LC1 crest FEL
BC1 crest v LC1 crest EMMA
BC1 crest v LC1 crest Unknown
0
100
200
300
400
500
600
0
50
100
150
200
250
300
350
BC1 crest
LC1 crest
BC1crest v LC1 crest THz
BC1 crest v LC1 crest FEL
BC1 crest v LC1 crest EMMA
BC1 crest v LC1 crest Unknown
My

tasks
:



Characterise

the

BLM

system
.

Design

and

carry

out

experiments
.

Analyse

the

signal

of

the

ionisation

chambers

and

of

the

BPMs

to

extract

a

charge

measurement

that

can

be

correlated

with

the

monitor

readings
.


Investigate

the

possible

sources

of

RF

phase

instability
.


Operate

the

machine

both

for

experiments

I

am

responsible

and

other

experiments

related

to

ALICE
.

ALICE commissioning and Beam Loss Monitoring system

ALICE commissioning and Beam Loss Monitoring system

My

tasks
:



Characterise

the

BLM

system
.

Design

and

carry

out

experiments
.

Analyse

the

signal

of

the

ionisation

chambers

and

of

the

BPMs

to

extract

a

charge

measurement

that

can

be

correlated

with

the

monitor

readings
.


Investigate

the

possible

sources

of

RF

phase

instability
.


Operate

the

machine

both

for

experiments

I

am

responsible

and

other

experiments

related

to

ALICE
.

Example of the signals on a BLM sensor for different
dipole currents. The base plateau moves away from zero
and needs to be subtracted from the top signal plateau
in order to get the real reading value.

To test and characterise the BLM sensors in ALICE a
test was done using BLM4 (in ST1), BLM5 (in ARC1)
and BLM6 in ST2). Varying the currents on DIP
-
03 of
ST1 and DIP
-
01, DIP
-
02 and DIP
-
03 of ARC1.

The beam loss induced radiation is
detected by a series of long ionization
chambers (LIC) distributed around the
machine. These chambers consist of an
air
-
filled coaxial cable (Andrew HJ4
-
50, 50
Ω) with a 1 kV potential to attract the
ionised gas particles forming a current
flow. This current, although very small, can
be measured to give an indication of beam
loss.

Linearity check on the BLM response


Several measurements were taken for
BLM
4 whilst
maintaining the current setting for
ST1 DIP
-
03 at 20 A
.
The train length was then incremented from 1 µs to
10 µs to vary the charge the
BLM

sensor would see.

Example of a test on the ARC
-
01 BLM sensor.
Analysis of the signal for different DIP
-
01 currents


When we vary the current in DIP
-
01 we have a high
increase of signal which decreases as we move away
from nominal. This is due to the beam hitting less
beam pipe and less accelerator components such as
quadrupoles, sextupoles, screen vacuum vessels, etc.
In the lower end of dipole current settings we start to
see an increment of BLM signal, which is probably due
to backscattering off the lead shielding surrounding
the external face of this bending section
.


J.L. Fernandez
-
Hernando

ITER Central Interlock System


J.L. Fernandez
-
Hernando

Follow

up

and

manage

ITER

contracts

with

different

companies

and

institutes

(CERN,

Create,

Procon)

for

the

creation

of

a

Central

Interlock

System

and

Quench

Loop

prototypes
.

Design,

prepare

and

carry

out

tests

of

the

different

prototype

systems
.

Investigate

the

functions

to

be

implemented

into

the

Interlock

system

to

ensure

machine

safety
.

PIS
PBS
-
11
/
41
Simplified
Plant Simulator
CIS
PIS
PBS
-
34
PIS
PBS
-
31
PBS
-
34
PBS
-
31
PBS
-
26
Digital signal
Analog signal
ICS
prototype
PIS
PBS
-
26
PBS
-
11
PBS
-
41
Redundant

PLC

system

s

are

used

for

the

Central

Interlock

System

(CIS)

and

the

Plant

Interlock

System

(PIS)

For

the

prototype

two

Plant

Interlock

Systems

will

be

used

(Vacuum

and

Cryo)

.

Each

of

them

communicates

with

a

single

CIS
.

ITER Central Interlock System


Machine protection


J.L. Fernandez
-
Hernando

ET200M

SM 331

8AI

2xSM
321
32DI

Quench Detection System
Fast Discharge Unit
1
Fast Discharge Unit
9
Power Converter
QL
-
TF
1
QL
-
TF
2
QL
-
TF
3
Switch closed
:
No quench
Switch open
:
Quench detected
Switch closed
:
Operation ok
Switch open
:
Spurious opening
Switch closed
:
Operation ok
Switch open
:
Spurious opening
Switch closed
:
Operation ok
Switch open
:
Discharge request
3TK
-
2841 S
-
RELAY

T

T

T

PROFIBUS DP

CPU414
-
2DP

CPU414
-
2DP

PROFIBUS DP network for
redundant link (via CP
-
343
-
5
module one at each CPU)

IM 153
-
2

3xSM
322
16DO
relay

ITER


Quench Loop prototype

The

Quench

Loop

main

target

is

to

protect

the

ITER

superconducting

(sc)

magnet

system

composed

of

a

total

number

of

48

magnets
:

18

Toroidal

Field

magnets,

6

Poloidal

Field

magnets,

6

Central

Solenoid

magnets

and

18

Correction

Coil

magnets
.

In

order

to

assure

magnet

protection

throughout

the

different

operational

phases,

several

actors

are

required
:

the

quench

detection

system

which

mission

consists

of

detecting

any

imminent

quench

in

one

of

the

sc

coils,

the

fast

discharge

units

(FDUs)

to

extract

the

energy

stored

in

the

magnets,

power

converters

that

feed

the

magnets

with

current,

and

finally

the

central

interlock

system

for

magnet

protection

based

on

PLC

(Programmable

Logic

Controller)

technology
.

The

quench

detectors,

the

FDUs

and

power

converters

can

open

the

Quench

Loop

if

they

detect

a

fault

or

see

the

status

of

the

Quench

Loop

and

act

accordingly
.

ITER Central Interlock System



Quench Loop Prototype

Thank you for your attention