FZJ, Jülich
TU Darmstadt, Darmstadt
Since many years, sc cavities have been designed and tested in Juelich: The 5-cell elliptical prototype cavity for the ESS was measured in a horizontal cryostat. A vertical test cryostat was installed to characterise the Halve Wave Resonators (HWRs) for the COSY linac project and several spoke-type cavities. During the measurements of the 352 MHz, tripple-spoke cavity (designed and built within the Hippi collaboration) a 2K operation was established using some refurbished pumps from the University of Wuppertal. First experiences with the 2 K operation, sometimes hindered by thermo-acoustic oscillations and the final results of the 352 MHz spoke-cavity will be presented. Furthermore we will report on the cryomodule performance, build for the Half Wave Resonators. Currently one prototype cavity was completed with a titanium helium cover and installed into the cryostat. The whole system with one cavity is now ready for first RF test.
TU Darmstadt, Darmstadt
During the last two years, the S-DALINAC operation suffered severely from cold leaks. These leakages were hard to localize and vanished sometimes without any obvious reason or showed up again depending on the thermo-cycle. Finally, the gaskets, sealing the cavity against the helium reservoir, were found to be the reason for this behaviour. We will report on the findings itself, the systematic becoming obvious and the solution chosen to ensure tightness in the future. Moreover, we will give a status report on two ongoing projects in Darmstadt. First the injector upgrade where a new cryo-module is built, housing two cavities and improved power couplers and secondly the cavity performance improvement by heat treatment at 850 C in an UHV oven.
TU Darmstadt, Darmstadt
FZJ, Jülich
The low level RF system for the S-DALINAC was developed 20 years ago and is still in operation. The RF-board converts the 3 GHz signals down to the baseband while the IF-board houses the special analogue control algorithm to control the 20-cell cavities. Both modules were redesigned, built and tested. The modulator and demodulator on the RF-board can be easily changed. Thus cavities operating at frequencies other than the S-DALINAC 3 GHz can be controlled with only minor modifications. A 6 GHz version, needed for a harmonic bunching system at the S-DALINAC and a 324 MHz solution to be used on a room temperature cavity at GSI will be presented. The IF-board is now based on a FPGA. In a first step the old control algorithm was successfully implemented in the FPGA and was already used together with the new RF-board as 1 to 1 copy of the old control system with some improvements. First results gained during the operation on a superconducting cavity will be presented. The flexibility of the FPGA allows now the implementation of optimized new algorithm.