%ACultrera, L.%ACultrera, L. [Brookhaven National Laboratory, Upton, New York 11973, USA]%ARocco, E.%ARocco, E. [College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12203, USA]%AShahedipour-Sandvik, F.%AShahedipour-Sandvik, F. [College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12203, USA]%ABell, L.%ABell, L. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA]%ABae, J.%ABae, J. [CLASSE, Cornell University, Ithaca, New York 14853, USA]%ABazarov, I. [CLASSE, Cornell University, Ithaca, New York 14853, USA]%ABazarov, I.%ASaha, P. [Department of Physics, Arizona State University, Tempe, Arizona 85287, USA]%ASaha, P.%AKarkare, S.%AKarkare, S. [Department of Physics, Arizona State University, Tempe, Arizona 85287, USA]%AArjunan, A.%AArjunan, A. [Structured Material Industries Inc., Piscataway, New Jersey 08854, USA]%BJournal Name: Journal of Applied Physics; Journal Volume: 131; Journal Issue: 12; Related Information: CHORUS Timestamp: 2023-08-09 19:20:57 %D2022%IAmerican Institute of Physics %JJournal Name: Journal of Applied Physics; Journal Volume: 131; Journal Issue: 12; Related Information: CHORUS Timestamp: 2023-08-09 19:20:57 %K %MOSTI ID: 10364227 %PMedium: X %TPhotoemission characterization of N-polar III-nitride photocathodes as candidate bright electron beam sources for accelerator applications %X

We report on the growth and characterization of a new class of photocathode structures for use as electron sources to produce high brightness electron beams for accelerator applications. The sources are realized using III-nitride materials and are designed to leverage the strong polarization field, which is characteristic of this class of materials when grown in their wurtzite crystal structure, to produce a negative electron affinity condition without the use of Cs, possibly allowing these materials to be operated in radio frequency guns. A Quantum Efficiency (QE) of about 1×10−3 and an emitted electrons’ Mean Transverse Energy (MTE) of about 100 meV are measured at a wavelength of 265 nm. In a vacuum level of 3×10−10 Torr, the QE does not decrease after more than 24 h of continuous operation. The lowest MTE of about 50 meV is measured at 300 nm along with a QE of 1.5×10−5. Surface characterizations reveal a possible contribution to the MTE from surface morphology, calling for more detailed studies.

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