Laser ion source and RFQ Linac for Direct injection scheme

摘要

Ion beams extracted from ion source usually are injected to accelerator through Low Energy Beam Transport (LEBT) under controlling beam divergence. But beam loss is the problem in the case of high intensity heavy ion beam due to its very strong space charge force. We proposed and are studying Direct injection scheme as a solution of this problem. In Direct injection scheme, laser ion source is directly connected to RFQ Linac. Therefore LEBT does not exist. The plasma with initial velocity generate by laser in laser ion source. And the plasma goes toward RFQ linac without extraction and then space charge force does not work. When plasma arrived at just before RFQ Linac accelerating region, ion beam is extracted from the plasma. 4mA of C/sup 4+/ beam was successfully accelerated by this scheme. We manufactured ion source test bench which composed by laser ion source, faraday cup and electrostatic analyzer. Charge distribution of beam current was measured by using CO/sub 2/ laser and Nd-YAG laser. And based on this, beam simulation at RFQ linac injection area was done. The result indicates that most of the extracted beam was lost by hitting RFQ vane. It is possible that more high intensity beam is accelerated by more better extraction system. Now we begin to design a 100mA class RFQ accelerator and a new extraction system.