• H. Zen
  UVSOR, Okazaki
• M. A. Bakr, K. Higashimura, T. Kii, R. Kinjo, K. Masuda, K. Nagasaki, H. Ohgaki
  Kyoto IAE, Kyoto
• H. Zen
  Sokendai - Okazaki, Okazaki, Aichi

Thermion­ic RF guns are com­pact, eco­nom­i­cal and high bright­ness elec­tron sources. How­ev­er, when the guns are used for a driv­er linac of os­cil­la­tor-type Free Elec­tron Lasers (FELs), which re­quires mod­er­ate bunch charge (sev­er­al tens pi­co-coulomb) and long macro-pulse du­ra­tion (sev­er­al mi­cro-sec­onds), the guns have been suf­fered from the back-bom­bard­ment ef­fect*. The ef­fect in­duces beam cur­rent in­cre­ment in a macro-pulse. And con­se­quent­ly the cur­rent in­cre­ment leads to decre­ment of beam en­er­gy dur­ing a macro-pulse and sig­nif­i­cant­ly lim­its the beam macro-pulse du­ra­tion after some bend­ing mag­nets. Our group found a new en­er­gy com­pen­sa­tion scheme called as cav­i­ty de­tun­ing** and the method was in­tro­duced to com­pen­sate the beam en­er­gy decre­ment in the thermion­ic RF gun used for KU-FEL***. In this pre­sen­ta­tion, we will in­tro­duce the prin­ci­ple of the method and ex­per­i­men­tal re­sults. De­tailed anal­y­sis of the method will be also pre­sent­ed.

* C.B. McKee et al., NIM, A296, pp. 716-719, 1990.
** H. Zen et al., IEEE Trans. of Nucl. Sci., vol. 56, No. 3, pp. 1487-1491
*** T. Yamazaki et al., Proc. of 23rd FEL Conf., pp. II-13-14, 2002.

• M. A. Bakr, Y.W. Choi, T. Kii, R. Kinjo, K. Masuda, H. Ohgaki, T. Sonobe, M. Takasaki, S. Ueda, K. Yoshida
  Kyoto IAE, Kyoto
• H. Zen
  UVSOR, Okazaki

RF gun has been cho­sen as in­jec­tor for Kyoto Uni­ver­si­ty free elec­tron laser be­cause it can po­ten­tial­ly pro­duce an elec­tron beam with high en­er­gy, small emit­tance, more­over in­ex­pen­sive and com­pact con­fig­u­ra­tion in com­par­i­son with other in­jec­tors. As for the RF gun cath­ode, thermion­ic cath­ode is sim­pler, eas­i­er to treat and re­li­able than pho­to­cath­ode. On the other hand, back­bom­bard­ment elec­trons make cath­ode sur­face tem­per­a­ture and cur­rent den­si­ty in­crease with­in the macropulse, as a re­sult, beam en­er­gy and macropulse du­ra­tion de­crease, which means, it is dif­fi­cult to gen­er­ate sta­ble FEL. The heat­ing prop­er­ty of cath­ode not only de­pends on phys­i­cal prop­er­ties of the cath­ode ma­te­ri­al such as work func­tion, but also back­bom­bard­ment elec­trons en­er­gy. We in­ves­ti­gat­ed the heat­ing prop­er­ty of six hex­a­boride ma­te­ri­als against the back­bom­bard­ing elec­trons by nu­mer­i­cal cal­cu­la­tion of the range and stop­ping power. In this in­ves­ti­ga­tion, the emis­sion prop­er­ty of the cath­ode was also taken into ac­count, since high elec­tron emis­sion is re­quired for gen­er­a­tion of high bright­ness elec­tron beam. The re­sults will be dis­cussed.

• T. Kii, M. A. Bakr, Y.W. Choi, R. Kinjo, K. Masuda, H. Ohgaki, T. Sonobe, M. Takasaki, S. Ueda, K. Yoshida
  Kyoto IAE, Kyoto

A mid-in­frared free elec­tron laser (MIR FEL) fa­cil­i­ty has been con­struct­ed for the basic re­search on en­er­gy ma­te­ri­als in the In­sti­tute of Ad­vanced En­er­gy, Kyoto Uni­ver­si­ty. The MIR FEL sat­u­ra­tion at 13.2 μm was ob­served in May 2008, and the con­struc­tion of the FEL de­liv­ery sys­tem from ac­cel­er­a­tor room to the op­ti­cal di­ag­nos­tic sta­tion and ex­per­i­men­tal sta­tions has been fin­ished in Dec. 2009. In the con­fer­ence, op­ti­cal prop­er­ties of the MIR FEL and re­search pro­gram using MIR-FEL will be in­tro­duced.

• R. Kinjo, M. A. Bakr, Y.W. Choi, T. Kii, K. Masuda, K. Nagasaki, H. Ohgaki, T. Sonobe, M. Takasaki, K. Yoshida
  Kyoto IAE, Kyoto

Aim­ing at re­al­iz­ing a short pe­ri­od un­du­la­tor with strong mag­net­ic field, we have pro­posed a Bulk HTSC (high tem­per­a­ture su­per­con­duc­tor) Stag­gered Array Un­du­la­tor which con­sists of bulk high tem­per­a­ture su­per­con­duc­tor mag­nets with a stag­gered array con­fig­u­ra­tion. The ex­per­i­ment with the pro­to­type un­du­la­tor at 77 K shows this con­fig­u­ra­tion can be ap­pli­ca­ble to real un­du­la­tor. We also es­ti­mat­ed the mag­net­ic per­for­mance of real de­vice by cal­cu­la­tions with a loop cur­rent model based on Bean model of su­per­con­duc­tor. Al­though end field ter­mi­na­tion is re­quired for prac­ti­cal use, tra­di­tion­al meth­ods are not ap­pli­ca­ble for the bulk HTSCs. We found that the end field ter­mi­na­tion can be re­al­ized by con­trol­ling the shape and size of bulk HTSCs at the end sec­tion by nu­mer­i­cal cal­cu­la­tion using the loop cur­rent model. In the con­fer­ence, the cal­cu­la­tion and ex­per­i­men­tal re­sult of end field ter­mi­na­tion will be pre­sent­ed.