BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
25 years ago, Brookhaven Accelerator Test Facility (ATF), sponsored by the U.S. Department of Energy's (DOE's) Office of High-Energy Physics (HEP), pioneered a concept of a proposal-driven user facility for advanced accelerator research using lasers and electron beams. Since then, the ATF became an internationally recognized destination for researchers to benefit from free access to unique equipment not affordable otherwise to individual institutions and businesses. We will show by examples how collaborative user research achieves high productivity when supported by the ATF's capabilities. Researchers from academia, industry and national laboratories coming to ATF successfully investigate wide range of topics. Recently endorsed as an Office of Science National User Facility and a flagship in Accelerator Stewardship, ATF continues broadening its user community. DOE is now planning a considerable expansion of the ATF's capabilities via simultaneously upgrading the parameters of the e-beam and laser.
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
SBU, Stony Brook, New York, USA
We present simulations of a semiconductor beam detector using the code VSIM. The 3D simulations involve the movement and scattering of electrons and holes in the semiconductor, voltages which may be applied to external contacts, and self-consistent electrostatic fields inside the device. Electrons may experience a Schottky barrier when attempting to move from the semiconductor into a metal contact. The strong field near the contact, due to trapped electrons, can result in hole injection into the semiconductor due to transmission of electrons from the valence band of the semiconductor into the metal contact. Injected holes are transported in the applied field leading to current through the detector. We compare our simulation results with experimental results from a prototype diamond X-ray detector.
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
LBNL, Berkeley, California, USA
Developments in materials design and synthesis have resulted in photocathodes that can have a high quantum efficiency (QE), operate at visible wavelengths, and are robust enough to operate in high electric field gradient photoguns, for application to free electron lasers and in dynamic electron microscopy and diffraction. However, synthesis often results in roughness, ranging from the nano to the microscale. The effect of this roughness in a high gradient accelerator is to produce a small transverse accelerating gradient, which therefore results in emittance growth. Although analytical formulations of the effects of roughness have been developed, a full theoretical model and experimental verification are lacking, and our work aims to bridge this gap. We report results on electron emission modeling and 3D simulations from photocathodes with controlled surface roughness similar to grated surfaces that have been fabricated by nanolithography. The simulations include both charge carrier dynamics in the photocathode material and a general electron emission modeling that includes field enhancement effects at rough surfaces. The models are being implemented in the VSim code.