Minutes RF structure meeting 02.11.2007

F. Gerigk, G. Michele, M. Pasini, S. Ramberger, C. Rossi, M. Vretenar, R. Wegner

news & facts:

DTL cold model

• the measurements seem to show a stem mode below the TM01 mode, Nader should check the field maps of this mode and then test if it is really a stem mode. This can be done by disturbing the mode in an area where it has high field (e.g. by putting a metal block inside the tank) or by suppressing the mode (e.g. by using some copper foil in an area where it prevents the stem mode but does not disturb the TM01 mode).
• Rolf has prepared one antenna and one loop for the first measurements and it was suggested to prepare another loop,
• TE modes should disappear if the exiting and the measuring loops are close to the end walls, this way it would be easier to concentrate on the TM modes,
• before detailed measurements on the modes are done the tuning should be verified by looking at the field levels of the TM01 mode with the bead-pull measurement,
• the bead-pull system should be ready by next week,

DTL hot model

• discussed outside the meeting: there should be a short hot model (power limit 50 kW), which can be built in Saudi Arabia. This model can be used to test: i) PMQs in vacuum, ii) a possible alignment system for the drift tube stems. Possibilities will be discussed with P. Bourquin and Y. Cuvet. (Action on Nader to determine the number of cells for a 50 kW model)

PIMS:

• a simple heating simulation conducted by M. Timmins shows that stainless steel is not a good choice for the PIMS operating with SPL duty cycle. The simulation assumed a constant temperature of 22 deg in the cooling channels (infinite water flow), no heat transfer by radiation, and an averaged heat load on the side walls (which means that the heating around the coupling holes is not calculated correctly). For a copper cavity we get 27 deg on the noses, while for a stainless steel cavity we get 167 deg (!).
• it was suggested to use a CW amplifier with around 1 kW to simulate the heating of a PIMS structure during Linac4 operation. This can be done in air, so that one can do a bead-pull measurement. This test should rule out any stability concerns due to uneven heating for Linac4 operation. For SPL operation one can only estimate because this kind of test will be limited to around 6 kW before we have break down in air. Same test can be done on the CCDTL. (action on Frank to see if we have such an amplifier)

CCDTL tests:

• Rolf and Matteo will measure if there is a different field level in two cavities for different duty cycles. The procedure should be to start a the lowest possible duty cycle, to measure in both tanks, to change the probes with detectors, and to repeat the measurement. Then to go to the Linac4 duty cycle and the SPL duty cycle.

decisions taken:

• use copper for the PIMS,

new actions

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minutes by Frank Gerigk

-- FrankGerigk - 02 Nov 2007