Bunch Length Measurements at JLab FEL
The JLab FEL is routinely operated with sub-picosecond bunches. The short bunch length is important for high gain of the FEL. Coherent transition radiation has been used for the bunch length measurements for many years. This diagnostic can be used only in the pulsed beam mode. It is our goal to run FEL with CW beam and 74.85 MHz micropulse repetition rate. Hence it is very desirable to have the possibility of doing the bunch length measurements when running CW beam with any micropulse frequency. We use a Fourier transform infrared interferometer, which is essentially a Michelson interferometer, to measure the spectrum of the coherent synchrotron radiation generated in the last dipole of the magnetic bunch compressor upstream of the FEL wiggler. This noninvasive diagnostic provides the bunch length measurements for CW beam operation at any micropulse frequency. We also compare the measurements made with the help of the FTIR interferometer with the data obtained by the Martin-Puplett interferometer. Results of the two diagnostics are usually agree within 15%. Here we present a description of the experimental setup, data evaluation procedure and results of the beam measurements.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 921657
- Report Number(s):
- JLAB-ACT-06-543; DOE/ER/40150-4213; TRN: US0801667
- Journal Information:
- Proceedings of the International Free Electron Laser Conference, Conference: 28th International FEL Conference (FEL06), 27 Aug - 1 Sep 2006, Berlin, Germany, Berlin (Germany), 27 Aug - 1 Sep 2006; ISSN 2673-5474
- Publisher:
- JACoW
- Country of Publication:
- United States
- Language:
- English
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