ISAC target vacuum system

Abstract

The Isotope Separator and Accelerator (ISAC) facility at TRIUMF has been in full operation since 1999. The ISAC east and west targets use proton beam from the cyclotron to produce various radioactive isotopes, which are then ionized and extracted. The ions are then passed through the mass separator and selected ions are transferred to the low energy experiments or injected into a radio frequency quadrupole accelerator. The accompanying radioactive contamination from the production of radioactive ions requires a complex vacuum system. The main target vacuum space consists of two semiseparate (primary and secondary) volumes pumped by turbo-molecular pumps. The primary volume uses four pumps while the secondary volume uses two pumps. Two hermetic rotary vane pumps are used as backing pumps. The nominal vacuum in both volumes is about 1.33×10−4Pa(1.0×10−6Torr). The pressure is monitored by two cold cathode and two hot filament ion gauges. The cold cathode gauges are used to interlock the system, which is critical during the bake out of the target and beam production. The exhaust gas from the vacuum pumps can be radioactive. Three gas storage tanks (decay tanks) are used for temporary storage of the radioactive exhaust and its controlled release to the atmosphere. Gas-species insensitive membrane gauges are used for monitoring the pressure in the storage tanks. This article describes the details of the ISAC target vacuum system as well as some procedures related to the handling of the exhaust gas with traces of radioactive contamination produced by the targets.