Sorgente di elettroni da GaAs

Un campione di GaAs fortemente drogato p, attivato in condizioni di affinita' elettronica negativa depositando cesio e ossigeno, costituisce una sorgente di elettroni con ottime qualita': alta intensita' di corrente, bassa dispersione energetica, profilo temporale e polarizzazione controllabili dalla radiazione laser stimolante. Con opportune tecniche di attivazione e di rigenerazione, si sono ottenute ottime prestazioni per le caratteristiche piu` probelmatiche di tali sorgenti: efficienze quantiche elevate (4 %lambda>514 nm), correnti estratte in continua (500-1000) microA per diverse centinaia di ore ed un'ottima ripetibilita' per diverse attivazioni e rigenerazioni sullo stesso campione

Study on Photosource for Electron Cooling Devices

An intense cw beam is produced by GaAs photoemission. Some high performances have been achieved . In particular, several weeks long lifetime has been achieved with an electron current as intense as 1 mA over a few mm^2 beam size

Long-lifetime high-intensity GaAs photosource

We used a GaAs crystal operating in a negative electron affinity mode to produce an intense continuous electron beam by photoemission. The major drawback of photoemission from GaAs, i.e., rapid current decay, was overcome without continuously supplying cesium. After a little initial decay, the current remained constant at 1 mA over a few mm2, with no degradation. Seasoning of the vacuum chamber played a fundamental role in achieving this performance

Rilassamento in fasci di elettroni

Sono stati condotti esperimenti rivolti ad indagare i meccanismi di interazione fra gli elettroni di un fascio. Si e' studiato in dettaglio l'effetto di un forte campo magnetico assiale sulla dispersione energetica (effetto Boersch). Anche la dipendenza della dispersione energetica longitudinale dal modo in cui e' impartita l'accelerazione, all'energia finale, e' stata oggetto di sperimentazione. In particolare, la scelta di un accelerazione molto lenta (adiabatica)

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

Surface analysis of a GaAs electron source using rutherford backscattering spectroscopy

We experimented with Rutherford backscattering spectroscopy to measure the amount of cesium on the surface of a GaAs photocathode activated in negative electron affinity (NEA) conditions. The surface analysis was performed both immediately after activation of the source in NEA condition and also some time after its total spoiling. Results showed that cesium did not desorb from the GaAs surface. With any further cesium feeding to reactivate the surface, the cesium accumulated on the surface until a saturation level was reached

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