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

A storage ring for crystalline beam studies

The possibility of generating crystallized ion beams, i.e. beams whose particles are located at fixed positions, has always excited the interest of most people working on particle accelerators. The reason of this interest has many aspects: knowledge either of a completely new research field or of some of the applicative potentialities, connected with crystalline beams, would justify a careful investigation of this subject. After the successful exploitation of electron cooling in several heavy ion storage rings the possibility of generating crystalline ion beams became more realistic. New cooling methods, like laser cooling, give a further opportunity to reach an ultracold system of particles necessary for the state transition to the crystalline configuration. The conceptual design of a low-energy heavy-ion storage ring, called CRYSTAL, proposed for the experimental demonstration of crystalline beams at Legnaro Laboratories is presented. The physics of crystalline beams as well as the main criteria to design a storage ring suitable to crystallize ion beams are discussed. The effects of instabilities for space charge dominated beams, shear forces in dipole magnets and lattice periodicity breaking are also discussed in detail