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.
X-band structure and its input/output power couplers.
First acceleration with the SwissFEL C-band module
First Electron Beam in the SwissFEL Facility
21st International Conference on Cyclotrons and their Applications
Proton Accelerator Operation Statistics 2015
GFA delivers the SwissFEL magnets on schedule
29.01.2016 The Paul Scherrer Institut is building an X-ray free electron laser (SwissFEL) providing a source of intense, ultra-short pulses of coherent radiation in the wavelength range of 0.1 nm to 0.7nm. For the hard X-ray beam line, the magnet section in GFA/ATK has the responsibility for the design, the procurement and the magnetic qualification of 267 electro-magnets of 22 different types. Several design studies were performed in an attempt to meet the required magnet specifications while optimizing construction and operation cost. Various types of dipole magnets (26 units in total) are used to bend the electron beam either horizontaly or vertically, whereas quadrupoles of 45 mm, 22 mm and 12 mm aperture (173 units), solenoids (10 units) and sextupoles (14 units) provide linear and non-linear focusing. Separate dipole correctors (44 units) complete the production. The majority of the magnets were manufactured in industry according to detailed magnet section specifications. A strict Quality Assurance strategy based on (1) the qualification of the manufacturing tools, (2) the monitoring of the critical steps in the assembly phase and (3) the application of the qualified procedures and full traceability was applied. A dedicated magnet measurement plan for the magnetic qualification, in house, of all the magnets at their operating conditions and within the required tolerances was implemented. It includes an accurate assessment of the field quality and the determination of the magnetic axis position. Dedicated measurements systems were used for this purpose: the field quality of the quadrupoles was measured with an accuracy of 0.1 % using two small aperture rotating coils, designed and produced by CERN following magnet section specifications, and a vibrating wire system was built in GFA/ATK to determine the magnetic axis position with an accuracy of 50 micro meters. Several developments on the magnet section Hall probes were also carried out for magnetic field mapping in small aperture magnets. All the magnets for the hard X-ray beam line were delivered on time and progressively installed. The developed equipment and the experience gained during the design, the fabrication and the series tests are a significant asset for the production of the magnetic elements for the Athos beam line and future PSI light sources.
Figure 1: 22 mm aperture quadrupoles with their integrated dipole corrector coils in the assembly area of ATK before the magnetic tests.
ETH-Medal 2015 for outstanding MSc thesis
17.04.2015 The detailed understanding of particle motion in the outer region (halo) of a bunched beam is of utmost importance for all existing and future high intensity hadron accelerators in view of minimizing particle losses and machine activation. Particle-core models separate the motion of halo particles from the core and treat them as test-particles. Therefore these reduced-order models are computationally inexpensive compared to full particle-in-cell simulations and can, to some extent, be derived analytically, thus giving insights into the non-linear mechanism of halo formation. These models have been successfully applied to linear accelerators, first by Gluckstern in 1994, for coasting round beams. The key point of Pirmin Berger's thesis is the extension of the model to ellipsoidal 3D bunched beams including dispersion, acceleration, and a self-consistent prediction of the core motion. A fully analytic model and a numerical model, the so-called extended particle-core model, have been derived. The new models were then applied to a simplified cyclotron but with parameters (e.g. tunes, energies) similar to the PSI Injector 2.
Figure 1: Phase-space after 40 turns. The numerical model (right) shown with characteristic phase-space points calculated with the analytic model (left).
A division of the phase space into four characteristic regions (A: unstable fix-point, B: inner separatrix, C: stable fix-point and D: outer separatrix) has been observed, as depicted in Figure 1. The purely analytic model (left of Fig. 1) compares, within limits, very well to the numerical model. We speculate that such reduced-order models may be the nucleus of future on-line models, accurately describing halo phenomena in high intensity hadron accelerators such as the Injector 2 and the PSI Ring cyclotron.
First beam from the SwissFEL electron gun
6.06.2014 The new 3 GHz photocathode gun will provide the electron bunches for SwissFEL and has recently been installed in the SwissFEL injector test facility. There, it replaced the CTF2-gun 5, borrowed from CERN. The new gun is capable now of operation with 100Hz repetition frequency and a higher field on cathode and improved field symmetry. After RF conditioning of about 4 days, the gun reached the nominal acceleration gradient of 100 MV/m at an input power of about 17 MW and pulse-width of 1 microsecond. The gun incorporates the same type of copper cathode plugs, as the CTF2-gun and accelerates the electrons in 3 cells up to a kinetic energy of 6.6 MeV. Each cell has a pick-up for amplitude and phase monitoring. The first measurements of the electron beam on the spectrometer arm confirm the expected kinetic energy. Next weeks of test injector operation will be dedicated to gun commissioning and more detailed beam quality measurements.
CTF-2 gun (left), new PSI Gun (middle) and Energy-spectrum of its first electron beam (right).
RF Pulse compressor for the SwissFEL
MEGAPIE samples delivered to partners for post irradiation investigation
24.05.2013 The MEGAWatt Pilot Experiment was operated for neutron generation with the PSI high intensity proton beam in 2006. The experiment utilized liquid target material, a lead bismuth eutectic. This marked a major milestone towards Accelerator Driven Systems (ADS), which are intended to be used for the incineration of nuclear waste. Now, after a 5 year long campaign at PSI and in ZWILAG, unique material samples from the irradiated target have been produced and distributed amongst the partners of this international initiative. The sample material – mostly structural material used for the construction of the target vessel – will, for the first time ever, allow scientists to investigate damage of these materials due to irradiation and liquid metal corrosion/erosion at the same time. On May 15th 2013 the last shipment of samples has left PSI towards Japan. With more than 800 material samples the post irradiation examination of MEGAPIE is the biggest effort of its kind. PSI scientists from NUM, GFA and NES were involved in the project.
Material samples from the beam entrance window