Summary of Polarized e-/e+ Source Presentations Page: 4 of 4
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One of the more disturbing measurements reported by Poelker shows that the cw
current is not linear with laser power despite the fact that this power is orders of
magnitude lower than that required to reach the surface charge limit for pulsed
systems. This indicates that the SCL may have a serious effect on the operation of
future high-current cw sources as well as possibly the ILC source.
OTHER
GaAs polarized electron sources for accelerators are very expensive and require a
permanent highly-trained staff to operate. Y. Niu (HKUST) described a simpler field-
emission source of polarized electrons (Pe-25%) that utilizes an Fe film on a single-
crystal W(100) tip10. Beams stable for several days have been demonstrated. R&D
continues.
Finally there were 2 talks on polarized positron sources for the ILC. The baseline
design generates polarized gammas from an unpolarized high-energy electron beam
that passes though a long helical undulator. Compton backscattering from a relatively
low-energy electron beam is an alternative scheme, but requires a very powerful laser.
P. Schuler (DESY) described the recently completed proof-of-principle experiment at
SLAC (E166) that uses the first approach". M. Kuriki (KEK) described advances with
the Compton approach2. Both approaches generate the polarized positrons by passing
the polarized gammas through a thin conversion target.
REFERENCES
1. C. Sinclair, Polarized Electron Sources, this workshop.
2. Yu. A. Mamaev, Record Values of Electron Beam Polarization and Quantum Efficiency for Semiconductor
Photocathodes, this workshop.
3. L. G. Gerchikov, Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice
with Distributed Bragg Reflector, this workshop.
4. A. Brachmann, Polarized Electron Source for the ILC, this workshop.
5. M. Yamamoto, Development of High-Performance Polarized e- Source at Nagoya University, this workshop.
6. J. Kewisch, The Polarized SRF Gun Experiment, this workshop.
7. M. Poelker, High Intensity Polarized Electron Sources, this workshop.
8. J. Grames, A Biased Anode to Suppress Ion Back Bombardment in a DC High Voltage GaAs
Photocathode Gun, this workshop.
9. E. Tsentalovich, Polarized Source for eRHIC, this workshop.
10.Y. Niu, Spin-Polarized Electrons from Fe Films Coated Single Crystal W(100) Tips by Field Emission, this
workshop.
11.P. Schuler, The E166 Experiment: Undulator-Based Production of Polarized Positrons, this
workshop.
12.M. Kuriki, ILC Polarized Positron Source Based on Laser Compton Scattering, this workshop.4
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Clendenin, J. E. Summary of Polarized e-/e+ Source Presentations, article, November 28, 2007; [Menlo Park, California]. (https://digital.library.unt.edu/ark:/67531/metadc897502/m1/4/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.