Amberg, M.

Barth, W.

Busch, M.

Mickat, S.

Podlech, H.

Ratzinger, U.

GSI Repository

Progress of the 325 MHz sc CH Cavity ∗M. Busch†1, H. Podlech1, U. Ratzinger1, W. Barth2,3, S. Mickat2,3, and M. Amberg1,31Institut fu¨r Angewandte Physik, Goethe Universita¨t, Frankfurt; 2GSI, Darmstadt; 3HIM, MainzAbstractAt the Institute for Applied Physics (IAP), FrankfurtUniversity, a superconducting 325 MHz CH-Cavity hasbeen designed and built. The 7-cell cavity features a ge-ometrical β of 0.16, corresponding to a beam energy of11.4 AMeV. The design gradient is 5 MV/m. Main novelfeatures of this resonator are a compact design, low peakfields, easy surface processing and power coupling. Fur-thermore a new tuning system based on bellow tuners in-side the resonator will control the frequency during opera-tion. The progress in processing the cavity as well as tunerdrive measurements are presented.Progess and SetbacksAfter successful measurements [1] at Frankfurt the cav-ity was sent back to Research Instruments for final process-ing steps. Buffered Chemical Polishing and High PressureRinsing (s. fig. 1) have been performed.Figure 1: Set-up for BCP (left), Mounting for HPR (right).Afterwards a helium leak was found in the area of thepick-up pipe socket which led to a reaming of the pick-uppipe (s. fig.2). The subsequent reparation steps have beenperformed and the processing steps can be repeated.Figure 2: Helium leak at the pick-up pipe (left), Reamedpick-up pipe (right).∗Work supported by GSI, BMBF Contr. No. 06FY7102,FAIR@GSI PSP code:6-6-7-05† busch@iap.uni-frankfurt.deTuner MeasurementsThe new dynamic frequency tuner for sc CH-Cavitiesconsisting of a stepper motor and a fast piezo actuator pro-vides slow and fast tuning by pushing/ pulling capacitiveacting dynamic bellow tuners, which are welded on thegirders inside the cavity. The slow tuner must be able to de-flect the bellow tuner around +/- 1 mm, which correspondsto a tuning range of several hundred kHz to compensate fre-quency changes due to evacuation and cavity cool down.Additionaly, fast piezo actuators react on frequency vari-ations in the range of several hundred Hz caused by dy-namic effects like Lorentz-Force detuning or microphon-ics. A prototype of this frequency tuning system was builtat the workshop of the IAP. First measurements at room-temperature have been performed.Figure 3: First tuner measurement results at room temper-ature.Figure 4: Mounting of the fast tuner system on the heliumvessel (left). Main components of the tuner system (right).References[1] M. Busch, F. Dziuba, H. Podlech, U. Ratzinger, M.Amberg,”Cold Measurements on the 325 MHz CH Cavity”, SRF2013, Paris, France.FG-UNILAC-16 GSI SCIENTIFIC REPORT 2013312 doi:10.15120/GR-2014-1-FG-UNILAC-16

Progress of the 325 MHz sc CH Cavity

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Progress of the 325 MHz sc CH Cavity

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