OVERVIEW OF THE SHANGHAI SYNCHROTRON RADIATION

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OVERVIEW OF THE SHANGHAI SYNCHROTRON RADIATION
FACILITY PROJECT


S
enyu
Chen
,

Hongjie Xu and Zhentang Zhao

SSRF Project Team, Chinese Academy of Sciences, China


Abstract

The Shanghai

Synchrotron Radiation Facility (SSRF)
,

a third generation synchrotron light source
,

was proposed by the
Chinese Academy of Sciences and the Shanghai Municipal Government in 1995.
The
SSRF
has been designed
to produce
high brightness and flux X
-
ray in the photon energy region of 0.1

40 keV

and
cover much wider spectrum.
It consists of a
300MeV linac, a 3.5GeV booster, a 3.5GeV storage ring and
seven

beam lines and experimental stations.

The estimated cost
is around 150M USD and operation is expected to begin at the end of 2005.
The R&D of the SS
RF project began in early
1999 and will be completed in the next March according to the schedule. Up to now, m
ost of the 44 hardware items have
been completed or nearly completed and testing is being carried out
. We hope the SSRF project can get final appr
oval next
spring.

In this paper, the main parameters and features of the SSRF are presented.

1 INTRODUCTION

In order to meet the growing demand for synchrotron radiation application in China,
t
he construction of a
third generation synchrotron r
a
diation lig
ht source in China was proposed at the end of 1993
.

In April, 1995, the
Chinese Academy of Sciences (CAS) and the Shanghai Municipal Government (SMG) agreed in principle to
make joint efforts for a proposal to co
n
struct an advanced third generation synchro
tron r
a
diation light source in
Shanghai. The SMG promised to contribute one third or more of the total budget if the proposal is approved by
the State, and the CAS is respo
n
sible for the scientific and technical guarantee.

One year later, the draft of the
SSRF Conceptual D
e
sign Report (CDR) was basically completed, and the intern
a
tional review on the SSRF
CDR by the CAS and SMG has been successfully accomplished in September, 1996.
Later

the R&D of the
SSRF project was approved and the 80M Chinese Yuan budg
et for this R&D was allocated.
At the same time,

the leading group of the SSRF was set up by the CAS and the SMG with the president of the CAS as its head and
the executive mayor of the SMG and a vice minister of the Ministry of Science and Technology of
China as its
vi
ce

heads.
The R&D of the SSRF project began in early 1999 and will be completed in the next March
according to the schedule. Up to now, m
ost of the 44 hardware items have been completed or nearly completed
and testing is being carried out
.

I
n
last
July, the Science and Education Leading Group under the State Council
thought
that the time was not
ripe yet for final approval and requested to study further such questions as users, operating costs and
the
mechanism

for
laboratory management and s
o on.

In line with the above, the Project Management is now
concentrating its efforts on a) organizing a large
-
scale user meeting with an aim to attract
potential users
,

b)
estimat
ing

future
operation,

upgrade and

research
cost
,
c) exploring

future laborat
ory operation mechanism
. We
hope the SSRF project can get final approval next spring. We are
ready for construction.

2 DESIGN OVERVIEW

The purpose to construct the SSRF is to establish a multidiscipline frontier research center and a high
-
tech
R&D base in

order to offer attractive research opportunities for a wide variety of fields in China. The
requirements of the CAS and the SMG on the construction of the SSRF are as follows. (1) The performance of
the SSRF should be better than that of the present exist
ing third generation light sources at the same energy
region, and be at the forefront of its kind when it is completed at the beginning of the 21st century. (2) The
research lifetime must be longer than 20~30 years after its establishment. (3) And its budg
et should be around
120M USD. They are quite ambitious.

Since the largest part of user community in China works in the X
-
ray region of spectrum 4
-
40keV and the
second largest in the soft X
-
ray region of 0.1~4keV, the SSRF is designed to produce high bright
ness and flux
X
-
ray in the energy region of 0.1~40keV.

I
n the initial design [1] of the SSRF, the nominal energy of the SSRF storage ring is 2.2GeV, so actually the
SSRF would be a VUV and soft X
-
ray light source even its energy can be upgraded to 2.5GeV,
it cannot fully
meet the user demands. This is mainly due to the budget limitation. The emphasis of the former design is laid on
reaching low emittance, therefore the brightness of the SSRF would be higher than that of currently operating
VUV and soft X
-
ra
y third generation light sources. After examining other alternatives, the modified TBA lattice
structure with the emittance of 3~4nm
-
rad and the circumference of 345

m
eter

is chosen for the SSRF storage
ring. In order to provide the capability of the hard
X
-
ray with the energy extending to 60keV, several normal
bending magnets can be replaced by superconducting dipoles. Furthermore two super long straight sections of
18m are preserved for the potential use in the future.

Considering seriously the suggestio
ns [2] of the experts attending the 96’ International Review Meeting on
the Concept Design Report of the SSRF, and the sharp increase of the user demand for X
-
ray and hard X
-
ray, we
have modified the SSRF design goal to greatly increase the brightness of t
he energy spectrum in hard X
-
ray
region and make the SSRF cover much wider spectrum by increasing the design energy to 3.5GeV with adding a
little investment, so that the SSRF has a better cost
-
effectiveness. In the present design, we sacrifice the
perform
ance of the SSRF in VUV and soft X
-
ray region and give up the original goal of providing the brightest
beam in the photon energies below 3keV.

3 MACHINE FEATURES

The SSRF complex sketched in Fig.1 consists of three major parts, a full energy injector incl
uding a 300MeV
linac and a 3.5GeV booster as well as the corresponding beam transport lines, a 3.5GeV storage ring and the
synchrotron radiation experimental facilities.

The magnet lattice

of the storage ring
is composed of 20 double
-
bend achromat
(DBA)
ce
lls

with 396 meter
in circumference.
It provides
10
straight sections
of 7.24 meter and 10
straight sections

of 5.0 meter for the
inclusion of insertion devices
.

Each asymmetrical DBA cell contains 2 bending magnets, 10 focusing
quadrupoles.
The horizontal

beta functions in the middle of longer straight sections and shorter straight sections
are 12 meter and 0.8 meter, respectively. The storage ring tunes
Q
x
=22.19 and
Q
y
=8.23 have been chosen to
get

low emittance, to avoid the strong resonances in the worki
ng diagram, and to provide an efficient horizontal tune
for injection.
The resulting structure has a natural horizontal emittance

11.8nm

rad and the lattice functions
shown in Fig.2.


There are
7

families of sextupole, in which
three

of them located at
the achromatic arc are used to correct
chromaticities, and the other
four

families distributed in dispersion
-
free

region are used for harmonic correction
to improve the dynamic aperture as well as the energy acceptance. After tentative optimisation, the ho
rizontal
0
5
10
15
20
0
8
16
24
32


x


y
10

x
Lattice Functions
Path Length (m)
Fig.2 Lattice functions for one
DBA
cell

of storage ring

0.6
300 MeV Linac
DUV FEL
3.5 GeV Storage Ring
Beam Lines and
Experimental Stations
Booster
Fig.1 Layo
ut of the SSRF

and vertical dynamic apertures off momentum (

2
%) with multipole field errors at the injection point reach

17

mm and

1
0
mm respectively, as shown in Fig.3. And the energy acceptance of the ring is larger than
2
%.



Fig. 3 Dynamic aperture at the

ring
injection point

Besides, the effects of insertion devices, the closed orbit distortion and correction,

the orbit stability and fast
orbit feedback,
the beam instabilities and
l
ifetime, the injection and etc. have been preliminarily studied, they
also

meet the design requirement.
Moreover, t
he storage ring optics with non
-
zero dispersion in the straight
sections has been examined, giving a reduction factor of about 2 in the beam
natural
emittance. Now the lattice
optimisation of the storage ring is st
ill underway.

M
ain
parameters

of the storage ring
are as followings:

Energy

3.5 GeV

Circumference

3
96
m

Natural
h
orizontal
e
mittance (rms)

11.8 nm

rad

Beam Current (multi
-
bunch)

200
-
300 mA


(single bunch)

>5 mA

Number of cel
ls

20

Insertion
s
traight
s
ections

7.24m

10,

5.0m

10

Magnetic field , normal dipole

1.10
5

T

Number of quadrupoles

200

Max. gradient for quads

18.5 T/m

Number of
s
extupoles

140

Max. sextupole strength

500

T/m
2

Betatron tunes, Q
x
/Q
y

22.19
/
8.23

Natura
l Chromaticities

x
/

y

-
52.8/
-
24.3

Momentum compaction

6.9

10
-
4

Harmonic number

6
6
0

Radio Frequency

499.65 MHz

RF Voltage

4.0 MV

Energy Loss per Turn

1.256 MeV

Bunch Length (rms)

s

4.59 mm

Beam Lifetime

>
15

hrs


Fig.4 and Fig.5 show the brightness

and flux of the SSRF under the current existing insertion devices.
Comparing with the original design, after the modification, the high harmonics from undulators could provide X
-
ray beams of 7~20keV with a brightness of about 10
17

or higher, 3 or more ord
ers of magnitude higher than that
from the super
-
conducing bending magnet in the original SSRF design. This significant increase in hard X
-
ray
brightness is the most important feature of the SSRF. In addition, the larger emittance and the higher electron
energy will greatly increase the beam lifetime and also the dynamic aperture of the storage ring. Another
-30
-20
-10
0
10
20
30
0
3
6
9
12
15
dp/p=-2%
dp/p= 0%
dp/p=+2%
Tracking for 1000 Turns
Y (mm)
x (mm)
advantage of this design is that the 300MeV SSRF linac could be used meanwhile for the application research of
the DUV FEL (Deep Ultra Violet Free Ele
ctron Laser).

Experts of the review meeting on beamline design thought that by e
xploiting the
new
undulator technology
,
the
3.5 GeV SSRF can provide 5
-
20 keV X
-
ray beams with brightness approaching that provided by undulators
on the larger and more expens
ive 6
-
8 GeV third generation rings. In the 1
-
5 keV spectral range, radiation from
appropriately designed undulators on the SSRF will be arguably the most intense in the world

[3]
.

In order to
guarantee

that detail designs can meet the requirements
, twelve
SSRF accelerator scientists and
engineers were sent to attend the review meeting on the SSRF accelerator technical design
,

which

sponsored by
SLAC, LBNL and ANL with the participation of about 30 US scientists and engineers, was held at LBNL from
February
22 to 25, 2000.
















Fig. 4 Spectral Flux of SSRF
















Fig. 5 Spectral Brightness of SSRF

4 BEAM LINES AND EXPERIMENTAL STATIONS

It is
im
possible to predict precisely the scientific r
e
search which will be undertaken on SSRF.
In 1996,
b
ased
on an extensive investigation of the existing users and potential users of the SSRF and 61 proposals regarding
the designs of beam lines and experimental stations, we selected
15

beam lines as the candidates
and
only 5 to 7
(including 2 insertion dev
ices
)

for the first phase co
n
struction of the SSRF.

In December 1998, a SSRF Beamline CDR Review Meeting and a user

s meeting were held with an
attendance of 145 domestic users. From the 70 solicited proposals on the conceptual design of beamlines b
y

more
than 20 universities and research institutes, the following seven beamlines have been
selected

to be built at
the first phase of construction. These beamlines are



Biological Macromolecular Crystallography

ID Beam Line



High Resolution X
-
ray Diffraction and

Scattering BM Beam Line



X
-
ray Absorption Spectroscopy (XAS) ID Beam Line



Hard X
-
ray Micro
-
Focusing BM Beam Line

0.01
0.1
1
10
100
10
11
10
12
10
13
10
14
10
15
10
16
U34
W136
Bend
U28
U90
W75
Spectral Flux [Photons/(s-0.1%BW)]
Photon energy (keV)
0.01
0.1
1
10
100
10
12
10
14
10
16
10
18
10
20
Low-emittance mode with

=0.01
U34
W136
Bend
Normal mode with

=0.1
U28
U90
W75
Brightness [Photons/(s-mm
2
-mrad
2
-0.1%BW)]
Photon energy (keV)


Medical Research ID Beam Line



Soft X
-
ray Coherent Microscopy ID Beam Line



Lithographie
-
Galvanik
-
Abformung (LIGA) BM Beam Line

After the meetin
g we organized experts from Fudan, Qinghua, Zhejiang and Shanghai Universities, Beijing
Microelectronics Research Center, Xi

an Optical and Mechanical Research Institute of CAS to carry out joint
design of the beamlines. After that, 48 dome
s
tic users and e
xperts were invited in June to review the design. On
this basis, the
conceptual

designs of these beam lines have been reviewed last October in Shanghai by a
international
committee

with the participation of 18 experts from the USA, Japan, Germany, France,
Italy and
Britain, headed by Prof. H. Winick and Prof. D. Xian. The committee thought that t
he overall design as
presented appeared to be sound and at the cutting edge of synchrotron radiation development,
w
hen SSRF is
commissioned it will clearly have the

capability to perform experimentation at the forefront of science and
technology in the field of synchrotron radiation

[3]
.

5
SITE,
COST AND SCHEDULE

The SSRF Project Leading Group finally decided to select Zhangjiang High
-
tec Park as the construction sit
e
of the SSRF in 1999. Zhangjiang High
-
tec Park promised to contribute a place of about 200000 squ
a
re meters to
SSRF, the place is free and excludes in the total cost of the SSRF project in following paragraph.

B
as
ed

on

the information acquired from the de
tailed design and the R&D of the SSRF
,

e
stimated
total
cost of
the SSRF
including seven beamlines and experimental stations to be built for the first phase construction
is
around 1
50

M
illion
USD

(
1.2 Billion RMB,
the FY of 2000, excluding
personnel expendi
ture

).

To catch up with the development of synchrotron radiation application in the world, we shall strive to make
the SSRF one of the advanced third generation synchrotron radiation facilities that will be operated at the
beginning of the 21st century. T
he te
n
tative project schedule has been proposed under the i
m
portant prerequisite
that the whole SSRF project should be approved before the middle of 2001 by the Chinese government. The
proposed overall schedule of the SSRF project is to start the light sou
rce commissioning in 200
5

and to
open
it
for the users
one year later
.

6
R&D OF SSRF PROJECT

The Project Management has employed 144 staff members for R&D works during the period of last two
years
, most of whom
are young guys and
have master
degree
or doct
or degree.

The SSRF leading group approved 44 hardware items as
SSRF R&D
works within two years in 1998. Up to
now, m
ost of the
m
, except the RF cavity, have been completed or nearly completed. Acceptance test of all the
items was scheduled to finish next M
arch. Currently, testing is being carried out on the following items: storage
ring and booster dipoles, super high vacuum NEG pumps, booster and storage ring vacuum chamber (including
bellows and photon absorber), electron gun, BPM data collecting and proc
essing electronics, EPICS evaluation
system and IOC/DEVC prototype experimental system, prototype of storage ring and booster B power source,
storage ring sextupole switch power source
, storage ring magnet girder,
and the beamline experimental cooling
syst
em and
the prototype of LTP
have also been tested. Test shows that the super
-
high vacuum NEG pump
reached the value of 8x10
-
12

torr, the static vacuum of storage ring vacuum chamber reached 2x10
-
10

torr.

7 ACKNOWLEDGMENT

This work was supported by the Chin
ese Academy of Sciences and the Shanghai Municipal Government and
performed by the SSRF project team. Particularly our colleagues

in project team

have played an important role
in the design of the
machine and beam
-
lines
. We are also thankful to
all friends

from other exiting synchrotron
radiation facilities

in the world
for their important consultation, useful comments, helpful suggestions and
discussions on the review
s
of the SSRF

designs
.

REFERENCES

[1]

S. Y. Chen and H. J. Xu

Current Status of the Proposed
Shanghai Synchrotron Radiation Facility


Proc. Of APAC98 Tsukuba, (1998)

[2]

H. Winick, S. Fang, et al,

Report of the Review Committee on the Conceptual Design Report (CDR) of the Shanghai Synchrotron
Radiation Facility (SSRF)

, Shanghai, (1996)

[3]

H. Winick, D
. Xian, et al
“Report of the Review Committee

for the Conceptual Design of Beam Lines

at the

Shanghai Synchrotron
Radiation Facility (SSRF)”

Shanghai, (1999)