SESAME Publications 
SESAME, a 2.5 GeV Synchrotron Light Source for
the Middle East Region
D.Einfeld1, R.H.Sarraf2, M.Attal3, K.Tavakoli3,
H.Hashemi4, H.Hassanzadegan4,
E. Al-Dmour1, B.Kalantari5, A.Aladwan5, H.Tarawneh5, S.Varnasery7
Abstract
Developed under the auspices of UNESCO, SESAME (Synchrotron light for
Experimental Science and Application in the Middle East) will be a major
international research center in the Middle East and Mediterranean region where
most of the applications require hard x-rays up to 20 KeV photons. At the 6th
of January 2003 the official foundation of SESAME as well as the ground
breaking for the building took place. The accelerator SESAME is based upon the
synchrotron light source BESSY I, which was, with the operation of BESSY II,
devoted to SESAME. The original plan was to upgrade BESSY I to an energy of 1
GeV and use super conducting wigglers to reach 20 keV photons. According to the
present design SESAME will be a 2.5GeV 3rd Generation light source with an
emittance of 24.6 nm.rad and up to 13 places for the installation of insertion
devices with an average length of 3.1 meters. The circumference of the machine
will be 124.8 m. As injector the 800 MeV Booster Synchrotron of BESSY I will be
used with minor changes. At SESAME around 39.7% of the circumference can be
used for the installation of insertion devices. At the beginning of operation 6
beam lines should be installed.
INTRODUCTION
According to the workshops held in the Middle East Region the scientific case
for SESAME includes structural molecular biology, molecular environmental
science, surface and interface science, micro mechanical devices, x-ray
imaging, archaeological microanalysis, material characterization, and medical
applications. Most of this applications require hard x-rays up to 20 KeV
photons. Within the "Green Book"-design [1] this 20 KeV can be reached by
upgrading BESSY I from 0.8 to 1 GeV and use 7.5 T super conducting wigglers. In
order to increase the number of hard X-ray beam lines it was decided to upgrade
the SESAME to 2.0 GeV and to optimize the design for a higher brilliance with a
larger number of straight sections (White Book) [2]. According to the "1st User
Workshop of SESAMA" in Amman, October 2002, it should be possible to reach the
selenium K-edge with in-vacuum undulators. This is only possible by increasing
the energy to 2.5 GeV. The proposed upgrade to this energy is presented in this
paper.
The machine functions of one unit cell are given in figure 1.
and the main parameters of the ring are summarized in table 1. For operational
purposes it must be possible to change the vertical tuning. For SESAME the
gradient in the bending magnets must be varied by 6% in order to change
the tune by 0.5. Using pole-face windings that will be introduced into
the bending magnets will do this. To reach a sufficient dynamic aperture and an
energy acceptance of 4%, chromatic and harmonic sextupoles have to be used. The
arrangements of the magnets within one cell are given in figure 2 and the
magnets with the quadrupoles and sextupoles are located around it. The average
length of the straight sections is 3.1 meters. It is foreseen to extract two
beam lines (6° & 14.5°) from each bending magnet in addition to one
zero-degree line which comes from upstream insertion device. The layout of the
whole storage ring with the 800 MeV BESSY I booster synchrotron is shown in
figure 3.
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NEW LATTICE
For the new lattice a so called "TME-Optic" [3] was chosen, which gives the
smallest emittance and it should give the highest percentage of the
circumference, dedicated to the installation of the insertion devices. The
basic elements of the lattice are a combined function bending magnets, with a
set of quadrupoles and sextupoles on each side. The combined bending magnets
perform the deflection and the focusing in the vertical direction, the
quadrupoles make only the horizontal focusing.
Figure 1: Optical functions of SESAME lattice, The green
line represents dispersion, the pink circles represent the BPMs, while the
correctors will be inside the sextupoles.
Table 1: Main parameters of the new SESAME upgrade
| Parameters |
Values |
| E (GeV), No. of BMs |
2.5 , 16 |
| C (m), ه(Str.Sec.) / C |
124.8 , 39.7% |
| ex (nm.rad) |
24.6 |
| Qx , Qz |
7.217 , 5.192 |
| zx , xz |
- 13.1 , - 13.8 |
| bx , bz , hx (m) |
11.12, 1.89, 0.453 (8 sec.)
10.9, 1.73, 0.534 (other 8 sec.)
|
| B0 (T) ,n (strength) |
1.4 , 12.9 (k = -0.3636 m-2) |
| No., Gr. of Quads |
32 (2 families) 19 T/m |
| No., Gr. of Sext. |
64 , 116 T/m2 |
| No. of Str. Sec. |
16 ( 8 x 3 m + 8 x 3.19 m ) |
layout of the whole storage ring is given in figure 3. It should be noted here
that the above optics is the original one from paper [2] and it could be
changed a bit to get the optimum optics for high brilliance due to different
insertion devices number and types according to the requirements of the users.
LAYOUT OF THE MACHINE
The layout of one cell is given in figure 2. The main elements are the 22.5
degrees vertical focusing bending
Figure 4: Brilliance of the synchrotron radiation emitted from the
stored beam in the bending, wigglers and undulators. |
Figure 2: Arrangements of magnets within one unit cell
of the storage ring SESAME.
Storage Ring SESAME
Energy: 2.5 GeV
Circumference: 124.8 m
Emittance: 24.6 nm.rad
No. of Straights: 16
Figure 3: Layout of the 2.5 GeV storage ring of SESAME
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COMPONENTS OF THE MACHINE
The original BESSY I injector will be used with some modifications. Instead of
the 10 Hz white circuits, 1 to 3 Hz fast power supplies will be used. Hence all
power supplies have to be replaced. With this transaction the current for all
power supplies will be increased in order to upgrade the energy of the injector
from 0.8 to 1 GeV. At this energy the flux in the bendings is 1.25 T. Perhaps
in a later stage the 20 MeV Microtron as pre-injector will be replaced by a 50
MeV linac or racetrack microtron. According to the upgrading of 2.5 GeV, the
bending magnets with a flux of 1.4 Tesla and a gradient of 3 T/m must be new.
This is also true for the quadrupoles and sextupoles. With the changes of the
circumference from 64 to 124.8 m the vacuum system must be new. It will be an
antechamber system like SLS or the CLS. All photons will be stopped at lump
absorbers. Overall a pumping speed of 32000 L/s will be installed in order to
get after one year of operation an average pressure of 1 nTorr. The RF-system
will be build up in steps too, which are determined by the donations of other
laboratories. DESY will donate to the project some 250 kW klystrons and ELETTRA
a cavity and the low level electronics. The layout of the RF-system will be the
same as for ANKA. All the power supplies for the project will be build in a
collaboration between SESAME and the Yerevan Physics Institute (Yerphi). The
intention is to use the higher power parts of the old power supplies and
replace the electronics. For the control system we expect some donations from
the Swiss Light Source. The concept is based upon EPICS but for graphical user
interface we take the ANKA approach. The same control system will be used for
both, the machine and the beam lines. The whole diagnostics system for the
SESAME storage ring will be new.
BRILLIANCE OF RADIATION
The brilliance of the emitted radiation of a 400 mA stored beam from the
different sources are presented in figure 4. For the bending magnet it is given
for the energies 1.0, 1.5, 2.0, and 2.50 GeV. For the wigglers with the maximum
flux density of 2.0 T (W100), 2.5 T (W120) and 3.5 T(W80). For the undulators
with the period length of 40 mm (U40), 25 mm (U25) and 14 mm (U14). U25 is an
in-vacuum undulator and U14 is an super conducting mini undulator.
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the contribution of Gustav Adolf Voss
(DESY), Mark Plesko (JSI), Amor Nadji (LURE), Lothar Schulz (SLS) and Ernst
Weihreter (BESSY). Many thanks to all the colleagues at the different host
laboratories [ANKA, DESY, MAXLAB, LURE, SLS, DARESBURY, ELLETRA].
REFERENCES - Green Book, Conceptual Design Report for SESAME, OCT 99, BESSY,
Berlin.
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Whitw Book, Conceptual Design for the Upgrading of SESAME to 2 GeV,
UNESCO-Office, Amman, July 2002
-
A. ROPERT, Lattices and Emittances, CAS, 1996, CERN 98-04.
-
First operation of the Swiss Light Source, EPAC02, 3-7 June 2002, Paris.
-
Gradient Dipole Magnets for the Canadian light Source, EPAC02, 3-7 June 2002,
Paris.
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1 UNESCO office Amman, Jordan. 2 Al-Balqua Applied University, Alt-Salt,
Jordan. 3 LURE, Orsay, France. 4 DESY Hamburg, Germany. 5 Swiss Light Source,
Villingen, Switzerland. 6 MAX-Lab, University Lund, Lund, Sweden. . 7 Daresbury
Laboratory, Daresbury, United Kingdom.
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Host Institute
