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

Abstract

Sodium potassium antimonide photocathodes with Quantum Efficiency (QE) in the range of few percent have been grown, and their photoemission properties are measured. We report the intrinsic emittance and response time of electron bunches extracted from this material. It is possible to recover the QE of an overheated cathode by simple potassium addition, and the cathode is rugged enough to deliver tens of mA of average current with no or minimal degradation.

Kinetics of alkali-based photocathode degradation

“…7,10,12 Many authors quote 1/e lifetimes without determining whether the degradation curve is exponential. 8,11,12,15 Some attempts have been made to introduce a more practical and universal metric for the lifetime by integrating pressure over time to obtain exposure expressed in Langmuir units. 6,10,11 Only one study conducted for (NEA) GaAs photocathodes provides reliable data that correlates QE with the time and the pressure of individual gases.…”

Development of a Multialkali Photocathode Dc Gun for a Smith-Purcell Terahertz Free-Electron Laser

“…The 1/e lifetime of a GaAs photocathode during 52 mA beam generation is a few hours, while that of a CsK 2 Sb photocathode during 60 mA beam generation is Particles 2018, 1 167 30 h [8]. Electron beam generation with currents of up to 75 mA was demonstrated at the Cornell photoinjector with an alkali antimonide photocathode, and the charge lifetime was measured as greater than 15 kC [9]. In addition, a low-emittance electron beam for high-repetition-rate X-ray FEL has been demonstrated with an alkali antimonide photocathode [10].…”

Synchrotron x-ray study of a low roughness and high efficiency K2CsSb photocathode during film growth

“…Especially, the bialkali photocathode, K 2 CsSb, exhibits QE over 5% in the green light range, several orders of magnitude higher than that of a metal photocathode (typical QE ~ 10 −5 ) [1,13]. Test results of K 2 CsSb photocathodes under laser illumination show a low emittance of 0.37 µm mm −1 rms −1 at 543 nm and a reasonable life time of over 20 h even with relatively high residual water contamination [14].…”

“…Among various photocathode materials, alkali antimonides, such as K 3 Sb, Cs 3 Sb, K 2 CsSb and Na 2 KSb, have great promise in the application of future light sources because of their high QE, fast response time and low thermal emittance [11][12][13][14][15]. Especially, the bialkali photocathode, K 2 CsSb, exhibits QE over 5% in the green light range, several orders of magnitude higher than that of a metal photocathode (typical QE ~ 10 −5 ) [1,13].…”