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During operation, the LHC high power RF equipment such as klystrons, circulators, waveguides and couplers have to be protected from damage caused by electromagnetic discharges. Once ignited, these arcs grow over the full height of the waveguide and travel towards the RF source. The burning plasma can cause serious damage to the metal surfaces or ferrite materials. The "crowbar" protection system consists of an arc current detector coupled with a fast high voltage switch in order to rapidly discharge the main high voltage components such as cables and capacitors and to shut down the high voltage source. The existing protection system, which uses a thyratron for grounding the high voltage circuit, has been installed in the LHC about 20 years ago. The problem of "faulty shots" appears due to the higher energy of LHC compared to LEP, which may lead to unnecessary stops of the LHC due to the crowbar system. This paper presents two approaches under consideration to improve the thyratron’s performance and to use a solid state thyristor in high energy environment. The main objectives will be dissipate as little energy as possible in the arc and avoid "faulty shots".
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