CC2 Input CouplerIntroduction,Installation,

& Processing

Tim Koeth

November 16th, 2005

Input Coupler• Delivers power that develops gradient

extL QQQ

111

0

• Allows D-Q’ing of cavities to match beam loading.

Wave guide TE01 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 InstallationAfter the vacuum portion was

sealed up, a 150C bake performed to remove water.

Ramp ~ 6oC/hrDwell 24 hrs at 150oCP < 1e-5mbar

Input Coupler Installation

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

Input Coupler InstallationAfter 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 N2 (optional)

Not shown: 3 e- pickups

Signals monitored during processing:

Photo Diode forSparking in atmportion

• PRESENT DESY S/ H WARE THRESHOLDS:

Value FS Conv. Value Software Threshold Hardware Threshold

e- 5mA 10V 0.5 ~ 1 V 5 ~ 6 V

PMT 1 LUX 10 V 1 ~ 3 V 5 ~ 6 V

P.D. ------ ----- 0.2 V

Temp Cerm. 70ºC 90ºC

In-Cplr Vac 1~2E-7 mbar 1E-5mbar

The spark interlock is NOT reset! One must inspect the copper waveguide and warm ceramic window after such an event.

Input Coupler Processing

Input Coupler ProcessingPROCESS 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 off2. 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 Rate Max Power Dwell time

20μS 1kW/min in 30 sec incrm. 1 MW 1 hour50 μS 1kW/min in 30 sec incrm. 1 MW 1 hour100 μS 1kW/min in 30 sec incrm. 1 MW 1 hour200 μS 1kW/min in 30 sec incrm. 1 MW 1 hour400 μS 1kW/min in 30 sec incrm. 1 MW 1 hour800 μS 1kW/min in 30 sec incrm. 500 kW 1 hour1300 μS 1kW/min in 30 sec incrm. 500 kW 1 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

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 Rate Max Power Dwell @ Max Pwr20μS rectangular1kW/min (30Ssec) 1 MW 1 hour50 μS rectangular1kW/min (30Ssec). 1 MW 1 hour100 μS rectangular 1kW/min (30Ssec). 1 MW 1 hour200 μS rectangular1kW/min (30Ssec). 1 MW 1 hour400 μS rectangular1kW/min (30Ssec). 1 MW 1 hour500+100 μS Flat-top 1kW/min (30Ssec). 1 MW 1 hour500+200 μS Flat-top 1kW/min (30Ssec). 1 MW 1 hour500+400 μS Flat-top 1kW/min (30Ssec). 1 MW 1 hour500+600 μS Flat-top 1kW/min (30Ssec). 500kW 1 hour500+800 μS Flat-top 1kW/min (30Ssec). 500kW 1 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 ProcessingIt 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