Siddharth Karkare

Record high-average current from a high-brightness photoinjector

High-power, high-brightness electron beams are of interest for many applications, especially as drivers for free electron lasers and energy recovery linac light sources. For these particular applications, photoemission injectors are used in most cases, and the initial beam brightness from the injector sets a limit on the quality of the light generated at the end of the accelerator. At Cornell University, we have built such a high-power injector using a DC photoemission gun followed by a superconducting accelerating module. Recent results will be presented demonstrating record setting performance up to 65 mA average current with beam energies of 4–5 MeV.

Monte Carlo charge transport and photoemission from negative electron affinity GaAs photocathodes

High quantum yield, low transverse energy spread, and prompt response time make GaAs activated to negative electron affinity an ideal candidate for a photocathode in high brightness photoinjectors. Even after decades of investigation, the exact mechanism of electron emission from GaAs is not well understood. Here, photoemission from such photocathodes is modeled using detailed Monte Carlo electron transport simulations. Simulations show a quantitative agreement with the experimental results for quantum efficiency, energy distributions of emitted electrons, and response time without the assumption of any ad hoc parameters. This agreement between simulation and experiment sheds light on the mechanism of electron emission and provides an opportunity to design novel semiconductor photocathodes with optimized performance.

Effect of nanoscale surface roughness on transverse energy spread from GaAs photocathodes

High quantum yield, low transverse energy spread, and prompt response time make GaAs activated to negative electron affinity an ideal candidate for a photocathode in high brightness photoinjectors. Even after decades of investigation, the exact mechanism of electron emission from GaAs is not well understood. We show that a nanoscale surface roughness can affect the transverse electron spread from GaAs by nearly an order of magnitude and explain the seemingly controversial experimental results obtained so far. This model can also explain the measured dependence of transverse energy spread on the wavelength of incident light.

Thermal emittance measurements of a cesium potassium antimonide photocathode

Thermal emittance measurements of a CsK2Sb photocathode at several laser wavelengths are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. The thermal emittance is 0.56±0.03 mm mrad/mm(rms) at 532 nm wavelength. The results are compared with a simple photoemission model and found to be in a good agreement.

Cold electron beams from cryocooled, alkali antimonide photocathodes

In this paper we report on the generation of cold electron beams using a

Thermal emittance and response time of a cesium antimonide photocathode

{\mathrm{Cs}}_{3}\mathrm{Sb}

Growth and characterization of rugged sodium potassium antimonide photocathodes for high brilliance photoinjector

photocathode grown by codeposition of Sb and Cs. By cooling the photocathode to 90 K we demonstrate a significant reduction in the mean transverse energy validating the long-standing speculation that the lattice temperature contributes to limiting the mean transverse energy or intrinsic emittance near the photoemission threshold, opening new frontiers in generating ultrabright beams. At 90 K, we achieve a record low intrinsic emittance of

Thermal limit to the intrinsic emittance from metal photocathodes

0.2\text{ }\text{ }\ensuremath{\mu}\mathrm{m}

Photocathode behavior during high current running in the Cornell energy recovery linac photoinjector

(rms) per mm of laser spot diameter from an ultrafast (subpicosecond) photocathode with quantum efficiency greater than

Review and demonstration of ultra-low-emittance photocathode measurements

7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}