CC2 Input Coupler Introduction, Installation, & Processing Tim Koeth November 16 th, 2005

Input Coupler Delivers power that develops gradient Allows D-Q’ing of cavities to match beam loading. Wave guide TE 01 to coaxial TEM mode

Typical Input Coupler

Input Coupler

Input Coupler Installation Cavity is assembled in Class 10 CR with 80K window and cold bellows. Cavity is shipped and installed with this portion installed. Note protective cover with RF test port.

Input Coupler Installation After the cavity was installed in the cryo vessel, we installed the rest of the input coupler.

Input Coupler Installation After the vacuum portion was sealed up, a 150C bake performed to remove water. Ramp ~ 6 o C/hr Dwell 24 hrs at 150 o C P < 1e-5mbar

Input Coupler Installation Be certain to protect warm ceramic window during bake. Never place heat tape directly on ceramic !

Input Coupler Installation After bake out, finish Wave Guide Hat installation.

Input Coupler Processing PMT looking for sparking in vacuum portion TC thermometer IR thermometer for ceramic DC Bias Wave Guide from Klystron Coupling Adjust Dry N 2 (optional) Not shown: 3 e- pickups Signals monitored during processing: Photo Diode for Sparking in atm portion

PRESENT DESY S/ H WARE THRESHOLDS: ValueFS Conv. ValueSoftware ThresholdHardware Threshold e-5mA  10V0.5 ~ 1 V5 ~ 6 V PMT1 LUX  10 V1 ~ 3 V5 ~ 6 V P.D V Temp Cerm.70ºC90ºC In-Cplr Vac1~2E-7 mbar1E-5mbar The spark interlock is NOT reset! One must inspect the copper waveguide and warm ceramic window after such an event. Input Coupler Processing

PROCESS CONTROL LOGIC: SOFTWARE LOGIC: After each RF pulse, if e-, PMT, light, vacuum, temperature etc signals are higher than the threshold value the power is decreased by one step, if not then the power is increased by one step. HARDWARE LOGIC: In addition to the software limits used during processing, there are hardware interlocks with greater trip thresholds. The RF is shut off with the “fast switch” when the Hardware Threshold is exceeded. In the event of a Hardware trip: 1. Turn RF off 2. Wait three minutes 3. The conditioning program tries to reset the interlock 4. If reset is successful, RF power setting is set to the minimum (starting) value, and program does fast power increase (10 steps in 10 seconds) to about 90 to 95% of RF power at the event.

Input Coupler Processing WARM PROCESSING (allows pump to remove contaminants) DESY’s Warm Processing Recipe: Pulse length Pwr Rise/fall RateMax Power Dwell time 20μS1kW/min in 30 sec incrm.1 MW1 hour 50 μS 1kW/min in 30 sec incrm.1 MW1 hour 100 μS1kW/min in 30 sec incrm.1 MW1 hour 200 μS1kW/min in 30 sec incrm.1 MW1 hour 400 μS1kW/min in 30 sec incrm.1 MW1 hour 800 μS1kW/min in 30 sec incrm.500 kW1 hour 1300 μS1kW/min in 30 sec incrm.500 kW1 hour “At the end of the procedure we also do the power sweep for some 2..5 hrs.” – D. Kostine

Input Coupler Processing e- coupler vacuum e- pickup in cavity vacuum An example: Multipactoring in “cold” portion during processing of AC68 at DESY

Input Coupler Processing Vacuum RF Power Temp An example: Power sweep processing during cooldown of AC68 at DESY

Input Coupler Processing DESY’s Cold & On Resonance Recipe: Pulse length Pwr Rise/fall RateMax Power Max Pwr 20μSrectangular1kW/min (30Ssec)1 MW1 hour 50 μS rectangular1kW/min (30Ssec).1 MW1 hour 100 μS rectangular1kW/min (30Ssec).1 MW1 hour 200 μS rectangular1kW/min (30Ssec).1 MW1 hour 400 μS rectangular1kW/min (30Ssec).1 MW1 hour μS Flat-top1kW/min (30Ssec).1 MW1 hour μS Flat-top1kW/min (30Ssec).1 MW1 hour μS Flat-top1kW/min (30Ssec).1 MW1 hour μS Flat-top1kW/min (30Ssec).500kW1 hour μS Flat-top1kW/min (30Ssec).500kW1 hour One must calculate the Eacc for each pulse and set the maximum power accordingly (in our case maximum. Eacc is about 25MV/m at 500 μS rise-time and 3e6 coupler Q loaded ). “We do also the high power cavity processing, but it is not possible in Your case – one needs 1MW at 100, 200, 300 us pulses for that purpose and the HPP on the cavity is done for 100,200,300,400,...,1300us pulses up to cavity quench each time.” - D. Kostine “Cold” Input Coupler Processing (On Cavity Resonance)

Input Coupler Processing It is important to monitor the gradient as not to quench the cavity or exceed rad-safety x-ray limits.

Goals for Nov/Dec ‘05 Warm and Cold processing of the input coupler on CC2 at Meson. Processing done manually ! We have begun developing the needed systems automation of input coupler processing: AD, TD, & CD