Dear colleagues,
Regarding the CLIC module installation, I would like to rise an issue that we could maybe discuss during our next CLIC Module Working Group Meeting: the operational temperature of the CLIC module.
Presently inside CLEX the thermalized water temperature is set around 30 0C with an accuracy of +/- 0.05 0C. This water temperature is the same for all the RF systems (LIL accelerating structures, PETS and ACS) excepted for the gun that has its own thermal station.
The CLIC module is said to have its operational point at 25 0C (why this difference with the PETS and the ACS installed in TBTS ?).
If confirmed the CLIC module should have its own water station and cannot be connected to the existing thermal water in CLEX. This solution will also allow more flexibility during the operations.
Now comes the issue of the selection of the water station. For tests in the workshop the nominal thermal load is applied on the module using heaters, this implies a water station with high cooling capabilities. Conversely in CLEX the Drive Beam repetition rate will never be greater than 5 Hz and probably will stay at 0.8 Hz (to be compared to 50 Hz for CLIC).
Consequently, not only the water station could have much lower cooling capabilities but it must be fitted with heating capabilities, that is not presently the case. In effect the module will not reach its RF tuning point (25 oC) in an ambient air temperature of 20 oC in CLEX without heating it using the water circuit.
We have to decide soon which solution to be adopted and the dimensions of the water station that impacts on the installation works foreseen in June (the water station could either be installed in the CLEX gallery or directly in the CLEX if too large).
Best regards
Wilfrid