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MOPA44 |
Coherent Optical Transition Radiation at the SwissFEL Injector Test Facility | |
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| SwissFEL uses magnetic dispersive sections for bunch compression, which may cause micro-bunching within the electron bunch. Studies of Coherent Optical Transition Radiation (COTR) allow us to see whether or not such bunching is present. We present pilot results of COTR experiments carried out at the SwissFEL Injector Test Facility. Optical transition radiation is generated at an aluminium-coated silicon wafer that can be inserted into the beam. This can either be imaged to a CCD camera, or focused into a spectrometer with a spectral range from 200 nm to 925 nm. The compression of the electron bunches was varied, and data was recorded at different bunch lengths. Spectral data shows a clear gain of the signal and a shift towards the infrared for a stronger compression of the bunches. Results indicate that the spectrum fluctuates at maximum compression. This is consistent with fluctuations observed in COTR images. | ||
| MOPB82 | Bunch-Compressor Transverse Profile Monitors of the SwissFEL Injector Test Facility | 1 |
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| The 250 MeV SwissFEL Injector Test Facility (SITF) is the test bed of the future 5.7 GeV SwissFEL linac that will drive a coherent FEL light source in the wavelength range 7-0.7 and 0.7-0.1 nm. Aim of the SITF is to demonstrate the technical feasibility of producing and measuring 10 or 200pC electron bunches with normalized emittance down to 0.25 μm. A further goal is to demonstrate that the electron beam quality is preserved in the acceleration process, in the X-Band linearizer and the magnetic compression from about 10 ps down to 200 fs. The SITF movable magnetic bunch-compressor is equipped with several CCD/CMOS cameras for monitoring the beam transverse profile and determining the beam energy spread: a Ce:YAG screen and an OTR screen camera at the mid-point of the bunch compressor and a SR camera imaging in the visible the Synchrotron Radiation emitted by the electron beam crossing the third dipole. Results on the commissioning of such instrumentations, in particular in the low charge limit, and measurements of the beam energy spread vs. the compression factor will be presented. | ||
TUPB80 |
Transverse Profile Monitor for SwissFEL | |
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| In future free electron lasers, electron and photon beam sizes range between 10 um and a few millimeters. For an initial set up of the accelerator, to confirm target parameters for optics and emittance, and to optimize the FEL for different user requests, the transverse profile of these beams has to be determined. A monitor based on a scintillating crystal as well as optical transition radiation (for the electron beam) has been designed for the SwissFEL project. It features a projected pixel size of 7 micrometers, a good resolution over a field of view of 6 mm x 15 mm, a good sensitivity (as required for the low-charge mode of SwissFEL) and a 100 Hz image readout. To test the monitor, it has been installed at the SwissFEL Injector Test Facility, where electron bunches between 10 and 200 pC can be generated. In conjunction with a transverse deflecting cavity, the profile monitor has been used to measure the time-resolved slice emittance of these bunches. | ||