This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Cardman, L.

Friesel, D.

Jones, B.

Lee, S.Y.

Li, D.

Minty, M.G.

Pei, A.

Sloan, T.

English

IUScholarWorks

8. A. J. Dragt, AIP Conf. Proc. Vol. 87 (1982). 
9. L. Michelotti, AIP Conf. Proc. Vol. 153, 236 (1987). 
10. G. Guignard, A general treatment of resonances in accelerators, CERN 78-11, 1978. 
11. Tracking codes, such as TEAPOT, RACETRACK, PATRICIA, and MARYLIE. 
12. M. Ball, D. D. Caussyn, T. Ellison, B. Hamilton, N. Yoder, this report. 
PRELIMINARY REPORT ON THE FEASIBILITY OF USING THE IUCF COOLER 
RING SYNCHROTRON AS AN ELECTRON STORAGE RING 
S.Y. Lee, D. Friesel, B. Jones, Derun Li, M. G. Minty, Alex Pei, T. Sloan 
Indiana University, Bloomington,  Indiana 474 08 
L. Cardman 
Universi ty  of Illinois, Urbana, Illinois 61 801 
The IUCF Cooler Ring is a proton storage synchrotron dedicated to nuclear and 
particle physics research. A number of important experiments have been performed in the 
Cooler Ring. In recent years, electron beams in storage rings have also been widely used 
as an alternative probe. Having both capabilities in the same laboratory will offer great 
diversity in the studies of fundamental physics. Thus the adaption of the IUCF Cooler 
Ring to an electron synchrotron may prove to be instrumental in nuclear and particle 
physics research. It may also be used as a synchrotron radiation light source. Synchrotron 
radiation laser light from electron storage rings has been widely used in the research of 
basic atomic and molecular physics, condensed matter physics, material science, biological 
sciences, chemical science, medical science and material processing. Such a capability 
might reach an even broader spectrum of users at the IUCF facility. It may also be a great 
facility for educational purposes. 
I. Introduction 
The IUCF Cooler Ring is a versatile storage synchrotron. Its capability of storing and 
cooling light ion beams is important in the study of the proton and nuclear substructures. 
Alternatively, using the electron as a probe to unravel the nature of nuclear structure has 
also met great success. Thus studying the electron storage capability in the IUCF Cooler 
may be an interesting and possibly rewarding venture. 
Besides the benefit of being used as a probe for nuclear and particle physics, an 
electron storage ring may also serve as a synchrotron radiation source. Given 1 GeV 
electron energy in the Cooler Ring, the critical wavelength would be in the X-ray range. 
The study of the interaction of X-rays with matter goes back to the beginning of the century 
and has resulted in an large number of important discoveries, e.g. the understanding of 
the structure of crystallography, the unravelling of the structure of the DNA, etc.. 
Traditionally, X-rays were generated in X-ray tubes, where the radiation was produced 
by the bremsstrahlung of electrons as they struck an anode. These processes are inefficient 
and most of the electron energy is converted into heat. The dissipation of the heat sets 
a practical limit on the X-ray intensity that can be produced from the X-ray tubes. The 
resultant spectrum consisted of a continuous background with lines superimposed at fixed 
energies. The angular distribution of the emitted photons was approximately isotropic. 
Photon polarization was only partial and was a function of the continuous part of the 
spectrum. 
More recently, X-rays have been successfully produced from the synchrotron radiation 
of electron beams. Synchrotron radiation from an electron storage ring can, in principle, 
produce any intensity either in a continuous spectrum or in sharp tunable lines. It has 
excellent directional properties, well defined polarization, and can also have a very fast time 
structure. The availability of very intense, tunable X-ray sources gives rise to a multitude 
of applications. An extremely wide spectrum of important problems, ranging from pure 
science research to the semiconductor device production, from the basics of catalysis and 
corrosion to the properties of metals and alloys, from the detailed structure of protein 
molecules to the preventive diagnostics of heart diseases, can be studied. 
We are interested in investigating the feasibility of using the IUCF Cooler Ring for 
electron or positron storage, to provide a suitable electron source for nuclear and particle 
physics and to produce high brightness synchrotron radiation. 
2. Possible characteristics of IUCF Cooler Ring for electron storage ring 
A. Emittance: 
The emittance of an electron storage ring depends on the lattice design. For the 
Cooler Ring, the emitt ance is given by 
Table 1. Properties of the electron beam in the Cooler Ring 
Syn. Rad. [keV/Turn] 0.058 
7, [set] 2.5 
7, [set] 1.99 
7, [set] 
E, [pm-rad] 
Unp/p 
01 [mm] 
~(Touschek)  [min.] 
where Cg = 3.84 x 10-13m, J, E 1 is the damping partition number, y N, 2000 at 1 GeV 
energy, p is the magnetic rigidity and the function, H ,  is given by H = y,q: + 2aXq,q', + 
PXr)L2. Based on the operational parameters of the Cooler Ring, i.e. Circumference = 
86.82 m, Bp = 3.6 Tm, B = 1.47 T,  v, = 3.78 , and v, = 4.85, properties of the electron 
beam can be obtained (see Table I) ,  where T,, T,, re are respectively the damping time of 
the electron beam, and eZ is the horizontal emittance. u-aP/P is the rms momentum spread 
of the beam, 0 1  is the rms bunch length and r is the Touschek life time corresponding to 
single Coulomb scattering loss. The vertical emittance depends on the coupling. Normally, 
the vertical emittance is about one hundredth of the horizontal emittance. In order to 
obtain good quantum lifetime, the required voltage is about 300 kV. The advantageous 
harmonic number is 144, which corresponds to 497.1733 MHz. 
B. Critical wave length: 
A synchrotron radiation light source is normally a synchrotron, which transforms 
the kinetic energy of a relativistic electron beam into electromagnetic radiation. The 
critical wavelength, X in Angstroms, of synchrotron radiation emitted from an electron 
in a bending magnet is determined by the magnetic field, B, and electron energy, E: 
x ( A ) = ~ ~ . ~ / B ( T ) / E ~  ( G ~ v ) ,  where the electron energy is determined by 
E(GeV) = 0.3B(T)p(m) = 1 GeV. Using the parameters of the IUCF Cooler Ring, we ob- 
tain the critical wavelength on the order 13 A, which is in the X-ray range. Shorter wave 
lengths may be obtained using insertion devices. 
C. Power, Rf considerations and Cooling requirement: 
The total power radiated in a storage ring of energy, E, and magnet bending radius, 
p,  and currents, I, is given by 
Thus the power loss per unit angle is given by p(W/rnrad) = 0.00578E4[GeV]I[mA], and 
the power loss per unit area in the dipole section will be 
where E ,  z e,/lOO. 
The total current and the lifetime available depends on the operational condition of 
the Cooler Ring. The damping time is given by 
The voltage requirement becomes then V > 2 x 36.3E4[GeV][kV], where the factor of 
2 arises from the fact that the stable phase angle is about 30". To achieve good quantum 
lifetime, V > 300 kV is needed. 
D. The harmonic number, h: 
Let assume that we have a 200 MeV electron source. The momentum rigidity is then 
B p  = 0.667 Tesla-meters. Thus the low field requirement is B=0.273 Tesla. The required 
frequency swing for the rf cavity is therefore w 3.3 x Since the revolution 
frequency is fo = 3.45291 MHz, the harmonic number must be larger than 44 to achieve a 
cavity length less than 1 meter. The rf frequency should be 350 MHz or 500 MHz, where 
commercial Klystrons are available. TRISTAN, DORIS, and CESR are using 500 MHz 
systems and the APS, PEP, LEP etc. use 350 MHz systems. 
3. Conclusion 
We have made some rough estimation of the possible performance of the electron 
beam storage in the present Cooler Ring operational condition. The result is encouraging. 
Although the emittance is not small, we shall study retuning the lattice to achieve a smaller 
emittance. Further work is needed in studying the injection schemes from various electron 
sources, vacuum chamber design, retuning of the lattice for better emitt ance, beam current 
limit ation due to coherent instabilities, et c. 


Preliminary Report on the Feasibility of Using the IUCF Cooler Ring Synchrotron as an Electron Storage Ring

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Preliminary Report on the Feasibility of Using the IUCF Cooler Ring Synchrotron as an Electron Storage Ring

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