| Paper | Title | Page |
|---|---|---|
| MOPS048 | Microbunching Instability Studies at SOLEIL | 709 |
|
||
| Microbunching instability arises in storage rings when the number of electrons in a bunch exceeds a threshold value. Its signature, i.e. a strong and irregular emission of Coherent Synchrotron Radiation (CSR) in the Terahertz (THz) domain, is studied at SOLEIL on the AILES infrared beamline, with the storage ring tuned in a low-alpha configuration (used to get shorter electron bunch). The comparison of this observed THz CSR with numerical simulations of the longitudinal electron bunch dynamics, permits to put in evidence that during the instability a modulation appears and drifts in the longitudinal profile of the electron bunch. The understanding of this instability is important as it limits some operation of the storage rings. Indeed the induced fluctuations prevent the use of THz on the far IR beamline at high current per bunch. And in normal alpha operation this instability may spoil the electron/laser interaction effects used to get femtosecond and/or coherent pulse in storage rings (with slicing, Coherent Harmonic Generation or EEHG schemes on storage ring). | ||
| TUPC069 | Bunch Length Measurements from the Incoherent Synchrotron Radiation Fluctuation at SOLEIL | 1159 |
|
||
|
Bunch length measurements can be made by analysing the pulse to pulse intensity fluctuation of the incoherent synchrotron radiation as it has been reported elsewhere*. Such a method has been tested at SOLEIL for picosecond bunch durations, at several wavelengths and bandwidths in the visible range, using an avalanche photodiode. Thanks to the low-alpha optics the lengths of 10 μA bunches as short as 3 ps have been measured in good agreement with the streak camera results. We first used the radiation from a bending magnet, and then from a HU640 undulator that enhances the photon flux. Moreover, taking advantage of using the radiation from an undulator, we show that the method can still be used when the number of spikes emitted by the electron bunch is reduced to a few hundreds. This could be of interest for bunch length measurements of X-ray SASE FELs. Furthermore, we intend to use a single crystal diamond detector in order to perform these measurements in the X-ray range.
* F. Sannibale et al., "Absolute bunch length measurements by incoherent radiation fluctuation analysis", PRST AB 12, 032801 (2009). |
||
| WEPC169 | BPM System Interlock for Machine Protection at SOLEIL | 2379 |
|
||
| SOLEIL, a third generation light source, has its Beam Position Monitors (BPM) processed by the LIBERA electronics built by Instrumentation Technologies. This electronics initiated and specified by SOLEIL features a fast hardware interlock output for machine protection. Although interlocks are available in both horizontal and vertical planes, it was initially thought that only the vertical interlocks would be useful. Actually, the high photon beam power densities (up to 1kW/mm2) generated by the in-vacuum undulators could damage vacuum chamber elements in case of corrector power supply failures in horizontal or vertical plane. Crotch absorbers, XBPMs and their upstream absorbers were designed on the basis that they will be protected with interlock thresholds not tighter than ±1mm. This approach was also applied for specifying the apertures of the XBPMs and of their upstream absorbers. More recently tracking simulation has shown that the crotch absorber apertures downstream the new canted undulators needed special attention. | ||
| THPC006 | Experiments to Measure Electron Beam Energy using Spin Depolarization Method on SOLEIL Storage Ring | 2915 |
|
||
| The electron beam energy on SOLEIL storage ring was successfully measured using spin depolarization method after several attempts over the past few years. The experimental results demonstrate that the effective polarization was 91.3%±3% and polarization time was 17±2.3 minutes as expected from the simulation using SLIM code. The beam was depolarized using an AC shaker and the depolarization was monitored using DCCT and beam loss monitors. The beam energy was measured with accuracy up to a few 10-5. | ||
| THPC007 | Laser Electron Interaction Simulation for the Femtosecond Bunch Slicing on SOLEIL Storage Ring | 2918 |
|
||
| The interaction of an electron bunch and a laser in a wiggler (modulator) to generate a femtosecond slice is simulated for the slicing project on SOLEIL storage ring, using a code based on Monte-Carlo method and GENESIS. The results from these two codes are consistent with the theoretical values. The maximum modulated energy of the electron bunch and the number of electrons above a certain limit are studied for different wiggler and laser parameters. The transport of the 6D distribution of the sliced bunch from the modulator to the radiators are simulated using AT (Accelerator Toolbox) and ELEGANT, with synchrotron radiation on and taking into account the collective effects of the sliced bunch core. | ||