Dielectric Strength Test Status B. Freemire IIT HPRF/Vacuum Meeting September 9, 2015
Dielectric Strength Test Goal Determine the dielectric strength of each of the four purity (96, 98.5, 99.5 & 99.8%) ● samples of alumina Ramp up E-field slowly – May require some conditioning, as per past experience ● Induce breakdown in the cavity and then back off in E-field until sparking stops – Use nitrogen to ease the safety requirements and compare measurements ● with past results Run at Station 2 to minimize conflict with MICE or MC programs ● Repeat at different gas pressures – 9/9/15 B. Freemire - HPRF/Vacuum Meeting 2
Operational Pressure Range Using existing spacers: ● Pressure range for donuts: – 99.5%: 31.2 – 87.4 atm ● 98.5%: 48.4 – 98 atm (safety) ● 96%: 62.6 – 98 atm (safety) ● Pressure points: – 99.8%: 35, 50, 75, 85 ● 99.5%: 35, 50, 75, 85 ● 98.5%: 50, 75, 85, 98 ● *96%: 65, 75, 85, 98 ● 9/9/15 B. Freemire - HPRF/Vacuum Meeting 3
Run Plan 1) Pressurize the cavity with 50 atm N 2 2) Tune klystron at low power 3) Ramp up E-field in 1.0 MV/m steps 4) Wait 5-8 minutes at each step 1) Record 2 RF pulses 2) If no sparks observed, move on 3) If few sparks observed, wait longer 4) If many sparks observed, decrease E-field 5) ~2 hours to reach 14 MV/m 5) Once E-field limit reached, collect 5,000 pulses 1) Record every 500 pulses 2) ~2.75 hours at 0.5 Hz 6) Repeat at three other pressures, then return to 50 atm 9/9/15 B. Freemire - HPRF/Vacuum Meeting 4
Timeframe I would like to complete 2 gas pressures per day ● 5 pressures / 2 per day = 2.5 days required per donut ● 2.5 days per donut x 4 donuts = 10 days of data taking ● 1 day setup per donut x 3 donuts = 3 days setup ● 10 days data + 3 days setup = 13 days ● Wait time and # of RF pulses may be affected by heating of cavity ● Four thermocouples installed on HPRF cavity – Pressure window, coupler waveguide, end plate, cavity equator ● Monitor pressure gauges during running – ACNET parameters: – Pressure – E:C8GLP1 & E:C8GLP2 ● Temperature – E:C2TC45-48 ● 9/9/15 B. Freemire - HPRF/Vacuum Meeting 5
Accomplished Pressure test passed as of September 1 st ● Awaiting safety paperwork to be processed – Operational pressure relief valve installed ● Full bottle of N 2 ready ● Purchase order for dry air completed – RF calibration complete ● 1 MV/m on axis = 1.75 MV/m on donut = 4.052 kW – Magnetic probe: -32.0 dB, electric probe: -34.4 dB – Q 0 = 8,875 – Cavity connected to waveguide and waveguide pressurized ● Thermocouples reinstalled ● (Most) Signal cables connected ● 9/9/15 B. Freemire - HPRF/Vacuum Meeting 6
To Be Done Check for leaks in new pressure relief valve ● Connect optical fibers to cavity and PMT box ● Connect signal cables to PMTs ● Power PMTs ● RF switch moved to position for Station 2 ● Verify DAQ configuration ● Order new gaskets ● Awaiting new drawings from Terry when he returns on Monday – Thicker radial diamond structure – 9/9/15 B. Freemire - HPRF/Vacuum Meeting 7
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