Conveners
Polarized Sources
- Matthew Poelker (Jefferson Lab)
Polarized Sources
- Matthew Poelker (Jefferson Lab)
Photocathodes based on GaAs can be used in photo-electron sources to supply spin-polarized, high-current electron beams for various applications. An activation, adding a thin surface layer, is needed to achieve negative electron affinity (NEA) for such cathodes. Typically, Cs is used in combination with an oxidant. Previous studies have suggested that the addition of Li to this process can...
GaAs-based DC high voltage photo-guns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed high average current facilities that must operate at tens of milliamperes or more. Specifically, the operating lifetime is dominated by ion back-bombardment of the photocathode from...
GaAs photocathodes provide a source of highly polarized electron beams. To ensure reliable operation for high current applications it is necessary to increase charge lifetime. To improve the local vacuum condition around the cathode the use of a cryogenic sub-volume is proposed. It is expected that the cryogenic adsorption of reactive residual-gas molecules yield an enhanced lifetime of the...
In order to facilitate Real Compton scattering studies off of nucleons a novel, high intensity, compact photon source (CPS) was developed for Halls A and/or C at Jefferson Lab. This source will provide a factor of 30 figure of merit improvement over existing technology. While developed for use in nuclear/particle physics experiments, the CPS design can be adapted to other fields. The source...
We have previously developed a concept for a polarized 3He ion source based on the existing Electron Beam Ionization Source (EBIS) at Brookhaven National Laboratory (BNL). Successful tests of polarizing 3He in a high magnetic field have led to the development of the Extended EBIS upgrade. The spin-rotator and 3He++ beam polarimetry development is also in progress in collaboration with MIT.
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Polarized light ion beams are essential to the physics program for a future electron-ion collider (EIC), and polarized deuterons have been identified as essential tools to probe the sea quark and gluon distributions in studies of hadronization. Polarized deuterons form an especially unique system for study by providing a combination of quark and nuclear physics, and thus can yield new insights...
GaAs-based photocathodes are widely used to produce highly spin polarized electron beams at high currents. Spin polarized photoelectrons can escape into vacuum only when GaAs surface is activated to Negative Electron Affinity (NEA). The NEA surface is notorious for extreme vacuum sensitivity, and this results in rapid QE degradation. We activated GaAs samples by unconventional methods using...
