Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
* S. Di Mitri, Phys. Rev. Special Topics Accel. Beams, 17, 074401 (2014).
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
* S. Di Mitri, M. Cornacchia, Phys. Reports, 539 (2014) 1~48.
** S. Di Mitri, Photonics, 2 (2015) 317~341
JAEA, Ibaraki-ken, Japan
Future ERL light sources and high repetition rate X-ray FELs require high-brightness and high-current electron guns. A DC photoemission gun is one of the most promising candidates for such guns, because a record high current of 65 mA and generation of high brightness beam with 90% normalized emittances of 0.3 mm-mrad with bunch charge of 77 pC were recently demonstrated at the Cornell photoinjector with a 350 kV photoemission gun [1,2]. Further increase of the gun high voltage is desirable to reduce space charge induced emittance growth especially for high bunch charge application such as X-ray FEL. Employment of a segmented insulator is a key to reach higher voltage [3]. This technique led to generation of 500 keV beam from the JAEA gun with 160mm acceleration gap [4], conditioning voltage more than 500 kV at the Cornell gun with gap < 50 mm [5], and demonstration of 500 kV holding for 10 hours at the KEK gun with 70 mm gap [6]. In this talk, we present recent experimental results of high brightness DC guns and discuss highlights and limitations in FEL applications.
[1] Dunham, APL 102, 034105.
[2] Gulliford, PRSTAB 16, 073401.
[3] Nagai, RSI 81, 033304.
[4] Nishimori, APL 102, 234103.
[5] Maxson, RSI 85, 093306.
[6] Yamamoto, private communication.
DLS, Oxfordshire, United Kingdom
JAI, Oxford, United Kingdom
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
[1] N.M. Kroll, P.L. Morton, M.N. Rosenbluth, J. Quantum Electronics 17, 8 (1981).
Chiang Mai University, Chiang Mai, Thailand
Linac based terahertz (THz) source at the Plasma and Beam Physics (PBP) Research Facility, Chiang Mai University, consists of a thermionic RF electron gun, an alpha magnet for magnetic bunch compressor, a travelling wave S-band accelerating structure for post acceleration, and various beam diagnostic instruments. The PBP-CMU linac can produce relativistic femtosecond electron bunches, which are used to generate coherent THz radiation via transition radiation technique. To increase the radiation intensity, an electromagnetic undulator will be added in the beam transport line. The designed electromagnetic undulator has 40.5 periods with a period length of 56 mm and a pole gap of 15 mm. Numerical calculation result shows that the brightness of the undulator radiation, which is produced from electron bunches with an energy of 10 MeV, a peak current of 300 A, and an effective bunch length of 120 fs, is about 10 thousand times higher than the brightness of the transition radiation. This study investigates the dependence of the electron beam energy, electron bunch charge, and electron bunch length on the coherent undulator radiation by using the PARMELA code. The numerical simulation and procedure to generate the undulator radiation in the terahertz regime by using femtosecond electron bunches produced at the PBP research facility is reported and discussed in this contribution.
The authors would like to acknowledge the financial support to participate this conference by the Department of Physics and Material Science and the Graduate School, Chiang Mai University.