Computational Tool for Modeling and Design of Rugged GaAs- based Polarized Electron Sources

Award Information
Agency: Department of Energy
Branch: N/A
Contract: DE-SC0019585
Agency Tracking Number: 242349
Amount: $156,497.00
Phase: Phase I
Program: SBIR
Solicitation Topic Code: 30d
Solicitation Number: DE-FOA-0001940
Solicitation Year: 2019
Award Year: 2019
Award Start Date (Proposal Award Date): 2019-02-19
Award End Date (Contract End Date): 2019-11-18
Small Business Information
5621 Arapahoe Ave, Suite A, Boulder, CO, 80303-1379
DUNS: 806486692
HUBZone Owned: N
Woman Owned: N
Socially and Economically Disadvantaged: N
Principal Investigator
 Dimitre Dimitrov
 (303) 443-2657
Business Contact
 Laurence Nelson
Phone: (720) 974-1856
Research Institution
High-current, high-brightness, spin-polarized electron beams are required for next generation electron-ion colliders (EIC). Proposed cathode designs are based on negative electron affinity (NEA) GaAs. A major limitation of these cathodes is their operational lifetime due to their susceptibility to damages in electron guns. Recent experiments done in Cornell University have demonstrated that a NEA GaAs photocathode can be activated with a protective Cs2Te cap layer leading to a factor of 5 lifetime improvement due to the resistance of Cs2Te to poor vacuum and chemical poisoning. The optimum design parameters for a NEA GaAs photocathode with a protective layer are still to be determined, however, there are no available codes to efficiently explore the large number of possible material design choices. We propose to address this problem by developing software to model both charge and spin transport together with transmission of electrons across cap layer-vacuum interfaces to enable simulations for investigation and design of rugged GaAs-based photocathodes. Our overall approach is to design and implement software for high-fidelity, three-dimensional, modeling of photo-excited polarized electrons in GaAs with a protective cap layer, Monte Carlo charge and spin transport across a GaAs-layer-vacuum system, and emission into vacuum with realistic surface potentials. Simulation results from the implemented models will be verified against existing theoretical results and validated against experimental data on NEA GaAs photocathodes with protective layers. We will design software to model electron spin dynamics in simulation subregions with different material properties. Then, we will implement prototype code for modeling of spin and charge transport together with electron emission. We will run simulations to test the prototyped models for spin transport across different material layers and emission of spin-polarized electrons. The implementation will be fully three-dimensional and tested using parameters derived from Cornell University experiments.

* Information listed above is at the time of submission. *

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