Conductance calculation and vacuum system design for twin source experiments

The TWIN (Two driver based Indigenously built Negative ion source) source provides a bridge between the operational single driver based negative ion source test facility, ROBIN in IPR and an ITER-type multi driver based ion source. The source is designed to be operated in CW mode with 180kW, 1MHz, 5s ON/600s OFF duty cycle and also in 5Hz modulation mode with 3s ON/20s OFF duty cycle for 3 such cycle. TWIN source comprises of ion source sub-assembly (consist of driver and plasma box) and extraction system sub-assembly. TWIN source experiments has been planned for two modes of operation i.e. Air mode and Vacuum mode. First phase will be air mode operation where ion source will be kept at atmospheric condition and extraction system will be inside vacuum enclosure. Second phase will be vacuum mode operation where both ion source and extraction system will be placed inside vacuum chamber. Current configuration of vacuum chamber facilitate the easy transformation of air mode to vacuum mode of operation without disturbing assembled configuration of ion source with vessel. Vacuum vessel is consist of two parts i.e accelerator vacuum box (vessel-1) and driver vacuum box (vessel-2). Vessel-1 needs to be pumped to pressure of less than 10^-05 mbar whereas vessel-2 needs to be pumped to a pressure of less than 10^-03 mbar. For this purpose TMP is connected to accelerator vacuum box (vessel-1). For the medium vacuum pumping of vessel-2 a conductance path has been provided between vessel-1 and vessel-2 via DN 100 port. Both part of vacuum vessel would be pumped with separate rotary pumps for rough pumping