Non-destructive singlepass monitor of longitudinal charge distribution in an ultrarelativistic electron bunch

We present here the first experimental test of a singlepass non-destructive method of monitoring of longitudinal charge distribution in an intensive relativistic electron bunch. This method is based on the scanning of a thin electron beam within the energy range 20-100 keV in the electromagnetic field of an intensive relativistic bunch

Performace of a radio-frequency-based strak camera

We have experimented with a streak camera based on radio-frequency detection of the electron beam. The time-resolution was measured to lie in the sub-ps domain. The method allowed considerable simplification of triggering, weaker dependence on space-charge within the electron beam, high modularity, and ease of implementation. We discuss experimental results and future prospects

Setting up and time-resolution measurement of a radio-frequency-based streak camera

We have experimented with a radio-frequency-based streak camera. The basic idea behind the method consists of magnetic deflection of the electron beam imparted by a radio-frequency cavity. All the components of the camera were tested and the time resolution was measured to lie within the sub-ps domain. Further advantages of the method are simplification of triggering, weaker dependence on space-charge effect within the electron beam, high modularity, and ease of implementation

"Hollow" cathode gun for electron cooling purpose

Characteristics of an electron beam, generated by a "hollow" cathode gun in a cusp magnetic field are investigated. Measurements are carried out on a prototype designed in the framework of CRYSTAL Storage Ring Project. Main criteria required to reach a beam quality useful for cooling purpose are established

First experimental observation of an electron beam with a plasma parameter greater than one

An electron beam generated by a GaAs photocathode, activated in negative electron affinity conditions, was studied under two different accelerating regimes. The energy spread of the beam, after an adiabatic acceleration is lower than after a fast acceleration. For the first time a longitudinal plasma parameter greater than one has been obtained for an electron beam

Relaxations in electron beams and adiabatic acceleration

In order to produce electron beams with the minimum possible energy spread we have investigated the possibility of replacing the usual thermocathodes with a photoemissive source such as GaAs. A comparison carried out between these two sources indicated the latter as the best device to obtain a very-low-energy spread. Beam relaxation after emission also leads to an increase in the energy spread. Therefore an experimental study on the nature of relaxations occurring in electron beams, yielded both by a thermocathode and by a photocathode, has been performed. More specifically, we investigated the possibility of reducing the transverse-longitudinal and the longitudinal-longitudinal relaxations. With this aim, the features of adiabatic acceleration, which damp the pure longitudinal relaxation, have been examined. The experience gained during the measurement cycle demonstrated that an adiabatic structure, accelerating electrons emitted by a GaAs photocathode, leads to the best performances

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

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

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

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