Scientific Highlights from the Department "Large Research Facilities" (GFA)

GFA Scientific Highlights

X-band prototype structure

08.11.2016 Radio-frequency structures at X-band frequencies (~ 12 GHZ) are being considered for applications in compact Free Electron Lasers, medical linacs, a future linear collider (CLIC project) and as a diagnostic for measuring ultra-short (femtosecond) electron pulses in FELs. A first prototype of such a structure has been built at PSI employing the realization procedures that have been developed for the C-Band (6 GHz) structures of the SwissFEL linac. The structure was designed in the framework of a collaboration between CERN and the Large Research Facilities Division (GFA) of PSI with the financial support of the SNF (grant 20FL20_147463). The individual cells were precision machined by the company “VDL Enabling Technologies Group Switzerland AG” and the structure brazed by the mechanical engineering department (AMI) at PSI. In the near future, it will be tested at high power on a test bench at CERN.

First acceleration with the SwissFEL C-band module

13.09.2016 On Thursday 08/09/2016, the first C-band module boosted an electron beam from 150MeV to 390 MeV. This is the first beam acceleration test of a C-band module in PSI and is an important milestone for the project, since the main accelerator consists of 26 C-band modules of the same kind. In the module, the RF pulse is first generated by a pulsed modulator- klystron amplifier, placed in the technical gallery, and is guided to the pulse compressor (BOC), where it is compressed by a factor four and split to the four accelerating cavities in the beam tunnel. The 104 accelerating cavities are two meters long and have been developed at PSI, produced together with the VDL Enabling Technologies Group Switzerland AG. The 26 BOCs have been developed and fully produced at PSI. An outstanding feature of the SwissFEL C-band module is that for the first time, accelerating structures and pulse compressors have been produced on frequency, i.e. without any tuning of the frequency. During the acceleration test, the module was operating at the nominal RF power setting of 36 MW and 3 microseconds pulse at 5.712GHz and a repetition rate of 10Hz. The measured beam energy gain was 240 MeV, with excellent agreement with the expected value of 233 MeV. The installation of the C-band modules has been completed with the mounting of the last unit on Tuesday 13/09/2016.

First Electron Beam in the SwissFEL Facility

24.08.2016 On August, 24th 2016, the electron gun accelerated the first photo-electrons in SwissFEL up to the energy of 7 MeV, initiating the beam commissioning phase of the new SwissFEL facility. After several days of RF conditioning, the gun reached the nominal acceleration gradient of 100MV/m at an input power of 17MW with a pulse-width of 1 micro second at an operating frequency of at 2998.8 MHz. This gun has previously already been commissioned in the SwissFEL Test Facility from June until October 2014 and then relocated to the new SwissFEL facility in the forest of Würenlingen. During this period, several upgrades to the system have been carried out; The klystron and pulsed high power modulator systems have been relocated and equipped with new, improved high voltage connectors, a rectifier unit, suitable to allow 100 Hz stable operation, and a new isolation oil purification system. The RF-system has also been equipped with a new interlock system to ensure safe operation. Additionally, a new optical based reference signal system provides ultra-low phase jitter rf signals in the few femto seconds range which guarantees, together with a new sophisticated low level RF system, stable operation and synchronization with all other subsystems. The low level RF system is well integrated into the EPICS control system and delivers detailed beam synchronous data for every RF pulse.