Author: Zen, H.
Paper Title Page
MOPOJO18 Manipulation and Measurement of Polarization State for THz Coherent Undulator Radiation 69
 
  • S. Kashiwagi, H. Hama, F. Hinode, T. Muto, I. Nagasawa, K. Nanbu, H. Saito
    Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
  • A. Irizawa
    ISIR, Osaka, Japan
  • H. Zen
    Kyoto University, Kyoto, Japan
 
  We are de­vel­op­ing an ac­cel­er­a­tor-based ter­a­hertz source that can pro­duce ar­bi­trary po­lar­iza­tion states from lin­early po­lar­ized co­her­ent un­du­la­tor ra­di­a­tion (CUR). The po­lar­iza­tion ma­nip­u­la­tion of the CUR can be re­al­ized using the Mar­tin’Pu­plett in­ter­fer­om­e­ter em­ployed as an op­ti­cal phase shifter. This study also demon­strates a vari­able po­lar­iza­tion ma­nip­u­la­tor by using the ter­a­hertz CUR (THz-CUR) source based on an ex­tremely short elec­tron bunch at Re­search Cen­ter for Elec­tron Pho­ton Sci­ence (ELPH), To­hoku Uni­ver­sity. The hor­i­zon­tally po­lar­ized CUR with a fre­quency of 1.9 THz was ma­nip­u­lated into vari­able po­lar­iza­tion state, and Stokes pa­ra­me­ters were mea­sured to de­rive the de­gree of po­lar­iza­tion. Beam ex­per­i­men­tal re­sults will be pre­sented in this con­fer­ence.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-MOPOJO18  
About • Received ※ 09 September 2022 — Revised ※ 18 September 2022 — Accepted ※ 21 September 2022 — Issue date ※ 12 October 2022
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TH2AA01
High Extraction Efficiency Operation of Oscillator-Type Free Electron Laser Driven by a Normal Conducting Linac  
 
  • H. Zen
    Kyoto University, Kyoto, Japan
 
  Funding: MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118070271.
The high­est ex­trac­tion ef­fi­ciency (9.4%) of a Free Elec­tron Laser (FEL) os­cil­la­tor has been achieved at the mid-in­frared FEL fa­cil­ity of Kyoto Uni­ver­sity*. The FEL is dri­ven by a nor­mal con­duct­ing linac con­sist­ing of a thermionic/pho­to­cath­ode RF gun and a trav­el­ing wave ac­cel­er­a­tor tube. The dy­namic cav­ity de­syn­chro­niza­tion method**,*** was used to achieve the high ex­trac­tion ef­fi­ciency with a short macro-pulse du­ra­tion (7 mi­cro-s). Be­cause of the in­ter­ac­tion be­tween the elec­tron beam and FEL elec­tro­mag­netic field, a max­i­mum elec­tron en­ergy de­crease of 16% was ob­served. An FEL mi­cro-pulse en­ergy of ~100 mi­cro-J with the mi­cro-pulse du­ra­tion of 150 fs at the wave­length of 11 mi­cro-m was ob­served. The de­tailed struc­ture of the FEL mi­cro-pulse was mea­sured using a fringe re­solved au­to­cor­re­la­tion with a phase re­trieval al­go­rithm. As a re­sult, su­per­ra­di­ance ring­ing (or Burn­ham Chiao ring­ing), i.e. gen­er­a­tion of mul­ti­ple sub-pulses and 180-de­gree phase jumps be­tween those sub-pulses, was ex­per­i­men­tally ob­served for the first time in an FEL os­cil­la­tor.
*H. Zen et al., Applied Physics Express 13, 102007 (2020)
**R.J. Bakker et al., Physical Review E 48, R3256 (1993)
***H. Zen et al., Physical Review Accelerators and Beams 23, 070701 (2020)
 
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