TY - JOUR
T1 - Simple one dimensional simulation of a laser photoemitted electron bunch
AU - Sapir, B.
AU - Shuker, R.
AU - Hazak, G.
AU - Levin, L. A.
N1 - Funding Information:
Efficient transfer of beam energy into a radiative field of free electron lasers, synchrotron sources, and powerful microwave tubes require electron beams of very high brightness. Pulsed electron beam production by the irradiation of a pulsed laser on a photocathode has been demonstrated experimentally \[1-4\]. It has become increasingly important to investigate the nature of the space charge effect on the electron beam. Two and three dimensional codes have been constructed for sophisticated microwave device simulations \[5-7\]. In this paper we report the results of a simplified one dimensional simulation of photoelectrons in the diode region, We use the particle in cell method and calculate particle trajectories. In spite of the fact that physical experiments are at least two dimensional, our simplified model enables a thorough investigation of the time evolution of the photocurrent pulse and an instructive demonstration of the space charge effects on pulse dynamics. Relativistic effects in this one dimensional study exhibit distinct features. The behavior of the system can be qualified into one of two distinct regimes by considering the relations between two parameters. The first is the transit time % of a particle under the * This work is supported in parti by a grant from the Israeli ministery of Science and Technology (MOST).
PY - 1993/7/1
Y1 - 1993/7/1
N2 - The dynamics of a photoemitted charged pulse in a one dimensional photocathode is investigated. At a very short pulse duration, on the order of a few picoseconds, short with respect to the transit time, interesting features are revealed. After a transient period, the charged pulse spreads and becomes uniformly distributed. The pulse spreads approximately to the extent of the transit time in the gap. This behavior is the result of the self-action electric field and depends on the total charge emitted under the laser power, on the pulse length and on the electric field. A one dimensional simulation and an analytic model describe the pulse propagation and are in excellent agreement. At high acceleration fields, in the relativistic regime, different time evolutions result. In the present simulation we make the simplified assumption that the relativistic effect only changes the electron mass. The result is that the self-field is overcome by the relativistic dynamics, and the electron pulse steepens.
AB - The dynamics of a photoemitted charged pulse in a one dimensional photocathode is investigated. At a very short pulse duration, on the order of a few picoseconds, short with respect to the transit time, interesting features are revealed. After a transient period, the charged pulse spreads and becomes uniformly distributed. The pulse spreads approximately to the extent of the transit time in the gap. This behavior is the result of the self-action electric field and depends on the total charge emitted under the laser power, on the pulse length and on the electric field. A one dimensional simulation and an analytic model describe the pulse propagation and are in excellent agreement. At high acceleration fields, in the relativistic regime, different time evolutions result. In the present simulation we make the simplified assumption that the relativistic effect only changes the electron mass. The result is that the self-field is overcome by the relativistic dynamics, and the electron pulse steepens.
UR - http://www.scopus.com/inward/record.url?scp=0027627189&partnerID=8YFLogxK
U2 - 10.1016/0168-9002(93)90065-P
DO - 10.1016/0168-9002(93)90065-P
M3 - Article
AN - SCOPUS:0027627189
SN - 0168-9002
VL - 331
SP - 314
EP - 317
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
IS - 1-3
ER -