Misura del tempo di risposta del GaAs come fotoemettitore

E' stato allestito un apparato sperimentale per la misura del tempo di risposta del GaAs come fotoemettitore, in condizioni di affinita' elettronica negatva. I risultati mostrano un tempo di risposta inferiore a 60 ps (rms), molto piu' rapido di quanto previsto da calcoli basati sull'equazione di diffusione. Questa evidenza sperimentale suggerisce che un fotocatodo di GaAs possa essere installato in un cannone a radiofrequenza con frequenze fino a 800 MHz circa, e lascia intravedere buone opportunita' anche per frequenze maggiori

Device For Electron Bunch Length Measurement In the Picosecond Region

We designed, created, and tested a device for measuring electron bunch length in the picosecond region. The basic idea behind the method is a circular scanning of the electron bunch in the rotating magnetic field of a TM110 rf cavity. As a result, the longitudinal position of the electrons is transformed into an angular position in a plane orthogonal to the axis. The resolution limit of the instrument is 4 ps (rms)

High performances from a GaAs photoemitter

This paper aims at collecting the experimental results we have obtained ahout a GaAs photocathode, activated in negative affinity condition by depositing a thin layer of caesium and oxygen al its surface

The GaAs electron source: simulations and experiments

In this paper we calculate electron emission from GaAs photocathodes using the Monte Carlo technique. Typical data of energy spread of the electron beam are presented. For photoenergy ranging from 1.6 to 2.1 eV, the calculated longitudinal and transverse energy spreads are 14.4–78 and 4–14.7 meV respectively. Temporal response measurement of GaAsphotocathodes has been performed. The preliminary results show that the temporal response is faster than 200 ps

Low energy intense electron beams with extra-low energy spread

Maximum achievable intensity for lowenergyelectronbeams is a feature that is not very often compatible with lowenergyspread. We show that a proper choice of the source and the acceleration optics allows one to match them together. In this scheme, a GaAs photocathode excited by a single-mode infrared laser and adiabatic acceleration in fully magnetised optics enables the production of a low-energy-spreadelectronbeam with relatively high intensity. The technological problems associated with the method are discussed together with its limitations

The production of short intensive bunches from GaAs photocathode

The installation for length measurements of the electron bunches emitted from GaAs photocathode is constructed. Two methods of bunch length measurements are suggested and applied. The bunch length is calculated on the basis of experimental data. The experimental results are analyzed and compared with results of computer simulations

Measurements of the longitudinal coupling impedences using short electron bunch

The longitudinal coupling impedance in modern storage rings has to be limited to ensure beam stability. To de- termine the real part of the narrow band impedance we suggest to measure the loss factor of the resonant modes using short electron bunch passing through the tested el- ement. This method is also suitable for the measurement of the longitudinal impedances for nonrelativistic particles, that is important for some modern projects of ion storage rings designed to achieve ordered structure in the ion beam. The desired value of relativistic parameter gamma can be chosen by adjusting energy of the electron bunch. The impedance of the fundamental mode of the wall current monitor was measured using 60 ps electron bunch from photogun. The dependence of impedance on beam energy is measured in the range 25-50 kV . Comparison of experimental data with computer simulation is done

Very-high-resolution energy analyser for electron beams

The authors designed an energy analyser for electron beams which exploits the retarding potential method over a small portion of the beam when all relaxations in the beam have occurred. This permits great improvement of energy resolution with respect to standard devices. The resolution depends on beam energy and is in the range 5-7 meV. The authors applied the energy analyser to determine the temperature dependence of the energy spread for electron beams emitted from GaAs

Investigation On Relaxations In Electron-beams

The achievement of high density very-low energy spread electron beams requires a deep knowledge of this topic. For this purpose longitudinal and transverse beam relaxations are studied for two different sources, a thermo- and a photocathode. As a result a plasma parameter greater than 1 has been measured, that may potentially increase the efficiency of the electron cooling techniqu

Experimental study of the response time of GaAs as a photoemitter

An experimental investigation was carried out to measure the response time of GaAs in negative electron affinity conditions as a photoemitter. During the experiment, the photocathode was excited by a short-pulse (38 ps rms) frequency-doubled Nd:YLF laser. Results show that the rms response time of GaAs is shorter than 40 ps