Development of cathode conditioning bench for LaB6 cathode

A 20 MeV microtron is used at Raja Ramanna Centre for Advanced Technology as injector to 700 MeV booster synchrotron. The microtron uses an LaB6 cathode as electron emitter. It has been observed that required level of electron emission as well as vacuum level in microtron can be quickly achieved, if the cathode is conditioned prior to installation in the microtron. An improved cathode conditioning test setup has been developed in Raja Ramanna Centre for Advanced Technology for conditioning of LaB6 cathode. Before assembling the LaB6 cathode in microtron, it is necessary to degas it properly by slowly heating it to a temperature of approximately 1500℃ in a vacuum better than 1x10-6 mbar. The degassing ensures better beam stability and avoids gas loading in microtron chamber during operation and thus reduces the chances of electrical breakdown. The cathode is heated with a regulated DC supply which provides constant 30A current. Power supply, vacuum controller and pyrometer for temperature measurement have been interfaced with PC on a LabVIEW based platform. Measurements of various test parameters are logged onto memory. The assembly, housing of the cathode, has been designed to provide more strength and better vacuum. Vacuum interlock has been implemented in software module to protect the cathode coming in contact with air. Interlock signal trips the power supply and automatically closes a gate valve to maintain vacuum within acceptable limit. This paper presents test setup design and automation works that has been carried out for efficient degassing. (author)