1. Update on PETS experiments (Igor for the CLIC collaboration)
and PETS development (Alessandro)

2. PETSing at SLAC
June 08.
…We have made some breakdown statistics, looking at Dark current to determine the rate. It was about 24/hour at about 120 MW at the full (266 ns) pulse length. However, I found that the PETS are very hot (to the touch) I thing about 70 C, this causes vacuum to go up and then a breakdown! Sami Tantawi
Cooling blocks for the PETS coupler were fabricated at CERN and send to SLAC on June 22.
June 24.
We have been doing systematic studies on the PETS for breakdown rates at 110, then 120 MW levels after putting a very big fan on it. This has been going on all of the last two weeks. The initial result is that of about 2 /hour at 110MW, and again I believe only limited by accumulating vacuum Sami Tantawi
Coming soon:
I have made a decision to remove the PETS to get the C10. If every thing goes well, we will finish this experiment in three weeks or so, bring back the PETS with cooling blocks and run statistics on it again Sami Tantawi

3. PETS Power History for week of June 15-19 2009
31/6hrs
June 24.
The last week of data shows running at around 125MW average. The integrated breakdown rate for the week data was 2.15 breakdowns/hour for 52 hours of operation (2x10-5/pulse/m). There are higher peak power values on the plot which are due to the SLED system being out of tune.
Jim Lewandowski
21/13hrs
3/5.5hrs
34/13.5hrs
18/7hrs
5/7hrs
130 MW
103 MW
133 ns
266 ns
Example of the pulses envelopes in ASTA
“short”
“long”
power
BDR

4. Following Alexej “theory”, at any conditioning state of the structure the following statement can be applied:
AT 135 MW
Sc (MW/m2)
Here Sc is a combined surface RF power density (the ratio was derived/fitted from experiments).
The equation tells that there is a strong (the only?) correlation between parameters included.
week of June
CLIC working point
BDR=10-7/m, 135 MW, 180 ns (flat)
SLAC PETS
266 ns
I have used Jim’s graphs and data to plot the PETS Ap history in ASTA. One may see/speculate that the PETS was improving the performance, especially when we compare the first and the last day, and it reached ~85% of the CLIC working point. It should be noted that T18 have reached AP ~ 58 (about 3 times higher than the PETS made recently).
Just as an example/expectation; if the measured BDR stays ~ 2/hour, but the power arrives at 160 MW and 266 ns, then this point will be the CLIC one.

5. PETS processing in ASTA (full story)
133 ns
266 ns
CLIC target
266 ns
RF/vacuum screens installed
Waiting for cooling blocks

6. The first beam in TBTS (30.06.09)
PETSing at CERN
The first beam in TBTS ( )
3 consequent pulses

7. Present on/off scheme with a choke based tunable reflector
Rf network for the choke testing with the klystron
Drawbacks:
The proof of operational principle needs to be done at a high power. The results be will not available before the next year and success is not guaranteed.
The system quite bulky (many elements) and thus expensive.
about 0.5 kg has to be moved, can we do it fast?

8. We just need a compact, tunable high power reflector!
Step#1 : 3 port waveguide junction (T-splitter) ON
OFF
Short circuit moved by λ/4
Short circuit

9. Step#2 : Compact, contact free high power movable short circuit
Compact H10□-> H20 □ ->H GHz mode convertor (original idea by S. Kazakov, KEK)
E-field
H-field
H01
H20□
H10□
CERN version
KEK version

10. Step#3 : Tunable reflector RF network
OFF ON
phase

11. Step#4 : Et voilà – reflector integrated with PETS coupler; CLIC choice.
Version#1 (horizontal)
Version#2 (vertical) ON
OFF

12. Early (2009) ON/OFF tests in TBTS, proposal.
Current TBTS PETS layout with external re-circulation
- The layout with internal re-circulation will allow for the feasibility demonstration of the PETS on/off operation as foreseen in CLIC.
It can also be operated in amplification mode (as we do it now).
Hardware: the moveable short circuits need to be build (we already have T-splitters)
ph. shifter
attenuator
PETS
Modified TBTS PETS layout with internal re-circulation
Tunable reflector
(aka attenuator)
Tunable short circuit
(aka ph. shifter)