Amorphous NEA Silicon Photocathodes-A Robust RF Gun Electron Source

Award Information
Agency: Department of Energy
Branch: N/A
Contract: DE-FG02-06ER84475
Agency Tracking Number: 80198S06-I
Amount: $650,000.00
Phase: Phase II
Program: SBIR
Awards Year: 2007
Solicitation Year: 2006
Solicitation Topic Code: 38
Solicitation Number: DE-FG01-05ER05-28
Small Business Information
Saxet Surface Science
3913 Todd Lane, Suite 303, Austin, TX, 78744
DUNS: 135251267
HUBZone Owned: N
Woman Owned: N
Socially and Economically Disadvantaged: N
Principal Investigator
 Gregory Mulhollan
 Dr
 (512) 462-3444
 see comments
Business Contact
 Gregory Mulhollan
Title: Dr
Phone: (512) 462-3444
Email: see comments
Research Institution
N/A
Abstract
Energy recovery linacs and other CW accelerators mandate the use of radio frequency (RF) photoinjectors to generate the low emittance, high current, high-peak-charge electrons used in collisions with hadron beams, and for electron cooling of hadron beams. However, RF guns using thermionic cathodes are not able to supply the high-phase-space densities required. Amorphous silicon shows great promise as a negative-electron-affinity (NEA), visible-wavelength photocathode suitable for RF gun systems. The advantages of amorphous silicon include a high degree of immunity to charged particle flux, low thermal emittance, bandgap tunability when grown as a germanium alloy, and low production cost. Phase I involved measurements on amorphous silicon to determine activation procedure, photoresponse, and neutral and charged particle interactions. Amorphous silicon surface preparation as well as in vacuo treatment was established to achieve negative electron affinity performance. Photoresponse was measured as a function of wavelength and lifetime. In Phase II, amorphous silicon photoemitter quality will be improved by using RF plasma-enhanced chemical vapor deposition (PECVD). Characteristics relevant to RF gun operation, including emission angle and current density, will be measured. Other features important for RF gun use, including substrate diffusion blocking, will be optimized. The increased quality will lead to improvements in electron diffusion length and thereby the yield. Commercial Applications and Other Benefits as described by the awardee: Amorphous, silicon-based RF photoinjectors should find use in energy recovery linacs, free electron lasers, and other applications that require the lowest possible source emittance. Reliable, low-cost, photocathode driven RF gun systems could become ready replacements for the diode and triode guns used on medical accelerators (typically S band 5-20 MeV) for the production of clinical photon beams and therapy electron beams.

* information listed above is at the time of submission.

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