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Yoskowitz, J. T.

Publications and source records attributed to Yoskowitz, J. T..

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

New Results at JLab Describing Operating Lifetime of GaAs Photo-guns

Po­lar­ized elec­trons from GaAs pho­to­cath­odes have been key to some of the high­est-im­pact re­sults of the Jef­fer­son Lab sci­ence pro­gram over the past 30 years. Dur­ing this time, var­i­ous stud­ies have given in­sight into im­prov­ing the op­er­a­tional life­time of these pho­to­cath­odes in DC high-volt­age photo-guns while using lasers with spa­tial Gauss­ian pro­files of typ­i­cally 0.5 mm to 1 mm FWHM, cath­ode volt­ages of 100 kV to 130 kV, and a wide range of beam cur­rents up to mul­ti­ple mA. In this con­tri­bu­tion, we show re­cent ex­per­i­men­tal data from a 100 kV to 180 kV setup and de­scribe our progress at pre­dict­ing the life­time based on the cal­cu­la­ble dy­nam­ics of ion­ized gas mol­e­cules in­side the gun. These new ex­per­i­men­tal stud­ies at Jef­fer­son Lab are specif­i­cally aimed at ex­plor­ing the ion dam­age of higher-volt­age guns being built for in­jec­tors.

Bruker, M. W.↗
DOE OSTI2022

New Results at JLab Describing Operating Lifetime of GaAs Photo-guns

Po­lar­ized elec­trons from GaAs pho­to­cath­odes have been key to some of the high­est-im­pact re­sults of the Jef­fer­son Lab sci­ence pro­gram over the past 30 years. Dur­ing this time, var­i­ous stud­ies have given in­sight into im­prov­ing the op­er­a­tional life­time of these pho­to­cath­odes in DC high-volt­age photo-guns while using lasers with spa­tial Gauss­ian pro­files of typ­i­cally 0.5 mm to 1 mm FWHM, cath­ode volt­ages of 100 kV to 130 kV, and a wide range of beam cur­rents up to mul­ti­ple mA. In this con­tri­bu­tion, we show re­cent ex­per­i­men­tal data from a 100 kV to 180 kV setup and de­scribe our progress at pre­dict­ing the life­time based on the cal­cu­la­ble dy­nam­ics of ion­ized gas mol­e­cules in­side the gun. These new ex­per­i­men­tal stud­ies at Jef­fer­son Lab are specif­i­cally aimed at ex­plor­ing the ion dam­age of higher-volt­age guns being built for in­jec­tors.

Bruker, M. W.↗
DOE OSTI2021

Improving the Operational Lifetime of the CEBAF Photo-Gun by Anode Biasing

The operating lifetime of GaAs-based photocathodes in DC high voltage electron photo-guns is dominated by the ionization rate of residual beamline gas molecules. In this work, experiments were performed to quantify the improvement in photocathode charge lifetime by biasing the photo-gun anode with a positive voltage, which repels ions generated downstream of the anode. The photo-cathode charge lifetime improved by almost a factor of two when the anode was biased compared to the usual grounded configuration. Simulations were performed using the particle tracking code General Particle Tracer (GPT) with a new custom element. The simulation results showed that both the number and energy of ions play a role in the pattern of QE degradation. The experiment results and conclusions supported by GPT simulations will be presented.

Yoskowitz, J. T.↗
DOE OSTI2021

Simulating Electron Impact Ionization using a General Particle Tracer (GPT) Custom Element

A new C++ custom element has been developed with the framework of General Particle Tracer (GPT) to simulate electron impact ionization of residual gas molecules. The custom element uses Monte-Carlo routines to determine both the ion production rate and the secondary electron kinetic energy based on user-defined gas densities and theoretical values for the ionization cross section and the secondary electron differential cross section. It then uses relativistic kinematics to track the secondary electron, the scattered electron, and the newly formed ion after ionization. The ion production rate and the secondary electron energy distribution determined by the custom element have been benchmarked against theoretical calculations and against simulations made using the simulation package IBSimu. While the custom element was originally built for particle accelerator simulations, it is readily extensible to other applications. The custom element will be described in detail and examples of applications at the Thomas Jefferson National Accelerator Facility will be presented for ion production in a DC high voltage photo-gun.

Yoskowitz, J. T.↗