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| TH5RFP042 | Bunch Length Monitoring at the A0 Photoinjector Using a Quasi-Optical Schottky Detector | 3543 |
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Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-07CH11359. Noninvasive bunch duration monitoring has a crucial importance for modern accelerators intended for short wavelength FEL’s, colliders and in some beam dynamics experiments. Monitoring of the bunch compression in the Emittance Exchange Experiment at the A0 Photoinjector was done using a parametric presentation of the bunch duration via Coherent Synchrotron Radiation (CSR) emitted in a dipole magnet and measured with a wide-band quasi-optical Schottky Barrier Detector (SBD). The monitoring resulted in a mapping of the quadrupole parameters allowing a determination of the region of highest compression of the bunch in the sub-picosecond range. The obtained data were compared with those measured using the streak camera. A description of the technique and the results of simulations and measurements are presented and discussed in this report. |
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| TH5RFP043 | Mitigation of COTR due to the Microbunching Instability in Compressed Electron Beams | 3546 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. The challenge of mitigating the strong enhancements of the optical transition radiation (OTR) signal observed after bunch compression in the Advanced Photon Source (APS) linac chicane and at the Linac Coherent Light Source (LCLS) has recently been addressed. We have demonstrated a technique to mitigate the intensity of the coherent OTR (COTR) relative to the OTR signals on the APS beams at 325 MeV. Since the previously reported spectral content of the COTR at LCLS after the first compression stage is similar, the concepts should also apply to LCLS. We utilized the stronger violet content at 400 nm of the OTR compared to the observed gain factors of the COTR in the blue to NIR regime. We also demonstrated the use of an LSO:Ce scintillator that emits violet light to support lower-charge imaging. Spectral-dependence measurements of the COTR were done initially at the 325-MeV station using a series of band pass filters inserted before the CCD camera, but recent tests with an Oriel spectrometer with ICCD readout have extended those studies and confirmed the concepts. These techniques are complementary to the proposed use of a laser heater to mitigate the microbunching itself at LCLS. |
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| TH6REP016 | Analysis of Contribution from Edge Radiation to Optical Diffraction Radiation | 3984 |
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Funding: DOE Contract DE-AC05-060R23177 China Scholarship Council Beam size measurement with near-field optical diffraction radiation (ODR) has been carried out successfully at CEBAF. The ODR station is installed on the Hall-A beam line after eight bending magnets. The ODR images were affected by an unexpected radiation. Some calculations for analyzing the source of the radiation will be presented. Furthermore, two schemes will be proposed to alleviate the contamination. |
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| TH6REP090 | Laser Timing Jitter Measurements Using a Dual-Sweep Streak Camera at the A0 Photoinjector | 4171 |
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Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. Excellent phase stability of the drive laser is a critical performance specification of photoinjectors such as Fermilab’s A0 photoinjector (A0PI). Previous efforts based on the measurement of the power spectrum of the signal of a fast photodiode illuminated by the mode locked infra-red laser pulse component indicated a phase jitter of less than 1.4 ps (technique limited). A recently procured dual-sweep plugin unit and existing Hamamatsu C5680 streak camera were used to study the phase stability of the UV laser pulse component. Initial measurements with the synchroscan vertical sweep unit locked to 81.25 MHz showed that the phase slew through the micropulse train and the phase jitter micropulse to micropulse were two key aspects that could be evaluated. The phase slew was much less than 100 fs per micropulse, and the total phase jitter (camera, trigger, and laser) was approximately 300 fs RMS for measurements of 20-micropulse trains. Data on the macropulse phase stability were also obtained. A possible upgrade to achieve better phase stability will be also discussed. |
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| FR5PFP020 | Emittance Exchange at the Fermilab A0 Photoinjector | 4350 |
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A transverse to longitudinal emittance exchange experiment is installed at the Fermilab A0 Photoinjector. We report on the completed measurement of emittance exchange transport matrix as well as the ongoing program to directly measure the emittance exchange. Both the transverse and longitudinal input beam parameters are being explored in order to achieve direct emittance exchange with minimal dilution effects |