Design, simulation and implementation of an efficient vacuum system and gas load calculations for a 6 MeV industrial LINAC

The design of vacuum system for a 6 MeV, commercial LINAC is presented. Unlike many commercial LINACs, the LINAC being developed has demountable electron gun, RF-waveguide and X-ray target assemblies. This design scheme is more efficient and economical. The LINAC has a total internal volume of 1.9 land surface area of ~3.2 × 103cm2, and is operated at Ultra High Vacuum. An iterative Simulation-Experimental approach is adopted to freeze a viable vacuum system for the LINAC. The vacuum simulations are performed in MOLFLOW+2.7.7, and the results are benchmarked experimentally. Due to compact geometry of the LINAC, reduced pumping speeds are experienced. The system was implemented using two 550 l/s commercially available turbo molecular pumps backed by rotary pumps, consuming ~2.4 kW. Particle dynamics simulations were performed using PARMELA 3. These simulations quantified the beam loss in the LINAC and predicted the sites of beam impingement. The system was experimentally verified for establishment of base pressure, activation of dispenser cathode, electron gun conditioning and the full power operation of LINAC at repetition rate of 50–110 Hz. Through all these regimes the vacuum system performed within permissible limits. The gas loads induced in the system were also evaluated using steady state and transient analysis. The pumping speed is optimized, and it is shown that base pressure of 1 × 10−9mbarcan be achieved at reduced pumping speed of ~100 l/s at the pumping ports. This reduced pumping speed also performed well for routine LINAC operation. Therefore, using benchmarked simulated results, an optimized and commercially economical vacuum system is proposed with reduced pumping speed of ~100 l/s consuming 6 times reduced power (0.4 kW) and ~40% reduced cost. •A cost effective and ecofriendly vacuum system designed for a 6 MeV industrial LINAC.•The LINAC has demountable electron gun, RF window and X-Ray target.•Simulations performed in MOLFLOW to calculate the pumping speeds and pressure profiles.•The simulated results are benchmarked experimentally.•The study is carried through establishment of base pressure-conditioning and full power operation of LINAC.•Based on simulation-experimental results an efficient pumping scheme is suggested.