Performance Degradation and Performance Recovery in c ERL
- Slides: 8
Performance Degradation and Performance Recovery in c. ERL Injector Cryomodule Eiji Kako (KEK, Japan)
c. ERL Injector Section Gate valve 2 K Cold Box X-ray detector Collimator 500 k. V DC Gun Buncher Cavity Faraday cup Lower Center Upper Screen monitor No. 1 Faraday cup No. 3 Screen monitor Injector Cryomodule No. 2 Merger Section Ion pump Specification 7. 0 MV/m x 3 cavity Total Vacc : 5 MV
History of cool-down cycles Year Assembly of Injector Cryomodule 1 st cool-down 2 nd cool-down 3 rd cool-down 4 th cool-down 5 th cool-down 6 th cool-down 7 th cool-down 8 th cool-down 9 th cool-down 10 th cool-down 2012 2013 2014 2015 2016 4 6 9 Low RF power tests of Injector Cryomodule 1 High RF power tests of Injector Cryomodule 4 Beam commissioning 5 7 of Injector section at 5 Me. V 11 1 High RF power tests of Main Linac Cryomodule Beam commissioning of Main Linac section 3 Beam commissioning of Re-circular ring 4 6 Beam operation at 20 Me. V, ~10 m. A 1 4 Beam operation at 20 Me. V, ~100 m. A LCS experiments 5 6 Beam operation at 20 Me. V, ~1 m. A 1 3
Severe increase of x-ray radiation level > 100 m. Sv/h Jump Quench #1 Cavity #2 Cavity #3 Cavity Total : 5 MV (Ave. 7. 0 MV/m)
Performance degradation in long term beam operation for 3 years Eacc = 7. 0 MV/m individual cavity Observations Degradation firstly initiated in #3 cavity close to merger section. Then, contamination area seems to have gradually extended toward #2 cavity and #1 cavity. Qo values in #3 cavity dramatically degraded after June 11 th , together with heavy x-ray radiation. Field emitted electrons, which run away from #3 cavity, were accelerated by #2 and #3 cavities. These electrons went toward upper stream and collided with cathode surface of DC-gun.
Pulsed RF conditioning for performance recovery CW 30 k. W Klystron CW 300 k. W Klystron QL interlock < 0. 8 x QL(normal)
Performance recovery by pulsed RF conditioning
Questions ? ? How do you clean warm components? l l l l Gate valves Ion pump Beam position monitor Screen monitor Faraday cup Collimator Beam pipes (Charge-up of insulator) Where dust particles come from?
