• T. Fujita, H. Hanaki, T. Nakazato
  JASRI/SPring-8, Hyogo-ken
• K. Akai, K. Ebihara, T. Furuya, K. Hara, T. Honma, K. Hosoyama, A. Kabe, Y. Kojima, S. Mitsunobu, Y. Morita, H. Nakai, K. Nakanishi, M. Ono, Y. Yamamoto
  KEK, Ibaraki
• M. Matsuoka, K. Sennyu, T. Yanagisawa
  MHI, Tokyo
• M. Monde
  Mitsubishi Heavy Industries Ltd. (MHI), Takasago

We have been de­vel­op­ing a sys­tem to gen­er­ate a short pulse X-ray using crab cav­i­ties at SPring-8 Stor­age Ring. The ring holds 30-m long straight sec­tions and the ver­ti­cal beam size at the cen­ter of the straight sec­tions is 6.5 mi­crom­e­ters in stan­dard de­vi­a­tion. If we in­stall four su­per­con­duct­ing crab cav­i­ties and a mi­ni-pole un­du­la­tor in one of the straight sec­tions, we can con­vert the time dis­tri­bu­tion of the elec­tron bunch into the spa­tial dis­tri­bu­tion. After slic­ing the emit­ted pho­tons with ver­ti­cal slits, we can ob­tain a sub-pi­cosec­ond X-ray pulse. In this scheme, the max­i­mum rep­e­ti­tion rate of the short pulse X-ray is the same as the ac­cel­er­a­tion fre­quen­cy of the ring (508MHz) and user ex­per­i­ments at other beam-lines are not dis­turbed by this short pulse gen­er­a­tion. We are plan­ning to in­stall KEKB type crab cav­i­ties as ver­ti­cal de­flec­tors. Phase fluc­tu­a­tion among crab cav­i­ties must be re­duced less than 14 mdeg in order to avoid resid­u­al de­flec­tion in the ver­ti­cal di­rec­tion. In this paper, we re­port an overview of the short pulse gen­er­a­tion scheme and top­ics of hard­ware de­vel­op­ment for sta­bi­liza­tion of the RF phase fluc­tu­a­tion.

Slides

• H. Tomizawa, H. Dewa, H. Hanaki, S. Matsubara, A. Mizuno, T. Taniuchi, K. Yanagida
  JASRI/SPring-8, Hyogo-ken
• T. Ishikawa, N. Kumagai
  RIKEN/SPring-8, Hyogo
• K. Lee, A. Maekawa, M. Uesaka
  The University of Tokyo, Nuclear Professional School, Ibaraki-ken

We are de­vel­op­ing a sin­gle-shot and non-de­struc­tive 3D bunch charge dis­tri­bu­tion (BCD) mon­i­tor based on Elec­tro-Op­ti­cal (EO) sam­pling with a man­ner of spec­tral de­cod­ing for XFEL/SPring-8. For fine beam tun­ing, 3D-BCD is often re­quired to mea­sure in re­al-time. The main func­tion of this bunch mon­i­tor can be di­vid­ed into lon­gi­tu­di­nal and trans­verse de­tec­tion. For the trans­verse de­tec­tion, eight EO-crys­tals sur­round the beam axis az­imuthal­ly, and a lin­ear-chirped probe laser pulse with a hol­low shape pass­es thor­ough the crys­tal. The po­lar­iza­tion axis of the probe laser should be ra­di­al­ly dis­tribut­ed as well as the Coulomb field of the elec­tron bunch­es. Since the sig­nal in­ten­si­ty en­cod­ed at each crys­tal de­pends on the strength of the Coulomb field at each point, we can de­tect the trans­verse BCD. In the lon­gi­tu­di­nal de­tec­tion, we uti­lize a broad­band square spec­trum (> 400 nm at 800 nm of a cen­tral wave­length) so that the tem­po­ral res­o­lu­tion is < 30 fs if the pulse width of probe laser is 500 fs. In order to achieve 30-fs tem­po­ral res­o­lu­tion, we use an or­gan­ic EO ma­te­ri­al, DAST crys­tal, which is trans­par­ent up to 30 THz. We re­port the first ex­per­i­men­tal re­sults of this 3D-BCD mon­i­tor.

• H. Hanaki, T. Asaka, H. Ego, H. Kimura, T. Kobayashi, S. Suzuki, M. Yamaga
  JASRI/SPring-8, Hyogo-ken
• T. Fukui, T. Inagaki, N. Kumagai, Y. Otake, T. Shintake, K. Togawa
  RIKEN/SPring-8, Hyogo

The in­jec­tor of the 8 GeV linac gen­er­ates an elec­tron beam of 1 nC, ac­cel­er­ates it up to 30 MeV, and com­press­es its bunch length down to 20 ps. Even slight RF in­sta­bil­i­ty in its mul­ti-stage bunch­ing sec­tion fluc­tu­ates the bunch width and the peak cur­rent of an elec­tron beam and it ac­cord­ing­ly re­sults in un­sta­ble laser os­cil­la­tion in the un­du­la­tor sec­tion. The ac­cept­able in­sta­bil­i­ties of the RF fields in the cav­i­ties, which per­mit 10% rms vari­a­tion of the peak beam cur­rent, are only about 0.01% rms in am­pli­tude and 120 fs rms in phase ac­cord­ing to beam sim­u­la­tion. The long-term RF vari­a­tions can be com­pen­sat­ed by feed­back con­trol of the RF am­pli­tude and phase, the short-term or pulse-to-pulse vari­a­tions, how­ev­er, have to be re­duced as much as pos­si­ble by im­prov­ing RF equip­ment such as am­pli­fiers. Thus we have care­ful­ly de­signed and man­u­fac­tured the RF cav­i­ties, am­pli­fiers and con­trol sys­tems, giv­ing the high­est pri­or­i­ty to the sta­bi­liza­tion of the short-term vari­a­tions. Com­po­nents of the in­jec­tor will be com­plet­ed by the end of the April 2010, and the in­jec­tor will be per­fect­ed in the sum­mer 2010. We will pre­sent the per­for­mance of the com­plet­ed de­vices in the con­fer­ence.

• T. Asaka, H. Ego, H. Hanaki, T. Kobayashi, S. Suzuki
  JASRI/SPring-8, Hyogo-ken
• T. Inagaki, Y. Otake, K. Togawa
  RIKEN/SPring-8, Hyogo

XFEL/SPring-8 is under con­struc­tion, which is aim­ing at gen­er­at­ing co­her­ent, high bril­liance, ul­tra-short fem­to-sec­ond X-ray pulse at wave­length of 1Å or short­er. The in­jec­tor con­sists of a 500kV thermion­ic gun (CeB6), a beam de­flect­ing sys­tem, mul­ti-stage RF struc­tures and ten mag­net­ic lens­es. The mul­ti-stage RF struc­tures (238MHz, 476MHz, 1428MHz) are used for bunch­ing and ac­cel­er­at­ing the beam grad­u­al­ly to main­tain the ini­tial beam emit­tance. In ad­di­tion, in order to re­al­ize lin­eariz­ing the en­er­gy chirp of the beam bunch at three mag­net­ic bunch com­pres­sion sys­tems after the in­jec­tor sys­tem, we pre­pared extra RF struc­tures of 1428MHz and 5712MHz. It is im­por­tant to sta­bi­lize the gap volt­age of those RF struc­tures be­cause the in­ten­si­ty of X-ray pulse is more sen­si­tive for a slight vari­a­tion of the RF sys­tem in the in­jec­tor. We de­vel­oped some sta­ble am­pli­fiers for those RF struc­tures, and con­firmed the am­pli­tude and phase sta­bil­i­ty of an RF sig­nal out­putted from the am­pli­fiers. The mea­sure­ment re­sults achieved near­ly the re­quire­ment of de­sign pa­ram­e­ters. In this paper, we de­scribe the de­vel­op­ment sta­tus and the achieved per­for­mances of RF equip­ment of the in­jec­tor sec­tion.

• S. Sakanaka, M. Akemoto, T. Aoto, D.A. Arakawa, S. Asaoka, A. Enomoto, S. Fukuda, K. Furukawa, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, H. Honma, T. Honma, K. Hosoyama, M. Isawa, E. Kako, T. Kasuga, H. Katagiri, H. Kawata, Y. Kobayashi, Y. Kojima, T. Matsumoto, H. Matsushita, S. Michizono, T.M. Mitsuhashi, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, E. Nakamura, K. Nakanishi, K. Nakao, T. Nogami, S. Noguchi, S. Nozawa, T. Obina, S. Ohsawa, T. Ozaki, C.O. Pak, H. Sakai, H. Sasaki, Y. Sato, K. Satoh, M. Satoh, T. Shidara, M. Shimada, T. Shioya, T. Shishido, T. Suwada, M. Tadano, T. Takahashi, R. Takai, T. Takenaka, Y. Tanimoto, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, K. Watanabe, M. Yamamoto, S. Yamamoto, Y. Yamamoto, Y. Yano, M. Yoshida
  KEK, Ibaraki
• M. Adachi, M. Katoh, H. Zen
  UVSOR, Okazaki
• R. Hajima, R. Nagai, N. Nishimori, M. Sawamura
  JAEA/ERL, Ibaraki
• H. Hanaki
  JASRI/SPring-8, Hyogo-ken
• H. Iijima, M. Kuriki
  HU/AdSM, Higashi-Hiroshima
• I. Ito, H. Kudoh, N. Nakamura, S. Shibuya, K. Shinoe, H. Takaki
  ISSP/SRL, Chiba
• H. Kurisu
  Yamaguchi University, Ube-Shi
• M. Kuwahara, T. Nakanishi, S. Okumi
  Nagoya University, Nagoya
• S. Matsuba
  Hiroshima University, Graduate School of Science, Higashi-Hiroshima
• T. Muto
  Tohoku University, School of Scinece, Sendai
• K. Torizuka, D. Yoshitomi
  AIST, Tsukuba

Fu­ture syn­chrotron light source using a 5-GeV-class en­er­gy re­cov­ery linac (ERL) is under pro­pos­al by our Japanese col­lab­o­ra­tion team, and we are con­duct­ing ac­tive R&D ef­forts for that. We are de­vel­op­ing su­per-bril­liant DC pho­to­cath­ode guns, two types of cry­omod­ules for both in­jec­tor and main su­per­con­duct­ing linacs, 1.3 GHz high CW-pow­er rf sources, and other im­por­tant com­po­nents. We are also con­struct­ing a com­pact ERL for demon­strat­ing the re­cir­cu­la­tion of low-emit­tance, high-cur­rent beams using those key com­po­nents. We pre­sent our re­cent progress in this pro­ject.

• J. Watanabe, S. Kimura, K. Sato
  Toshiba, Yokohama
• T. Asaka, H. Ego, H. Hanaki
  JASRI/SPring-8, Hyogo-ken

TOSHI­BA is man­u­fac­tur­ing the L-band ac­cel­er­a­tion sys­tem for the SPring-8 Joint Pro­ject for XFEL. We have de­vel­oped a new type duct-shaped SiC dummy load for its power dis­tri­bu­tion sys­tem. The load ter­mi­nates a WR650 waveg­uide and can ab­sorb the max­i­mum mean power of 10kW. In order to re­duce VSWR less than 1.1 in the fre­quen­cy range of 1.428GHz, we shaped the SiC ab­sorber into a 35cm long ta­pered cylin­der and mount­ed match­ing stubs in the waveg­uide near the inlet of the load. The SiC ab­sorber was fit into a cylin­dri­cal cop­per with ef­fi­cient wa­ter-cool­ing chan­nels. The de­sign and man­u­fac­ture and the low-pow­er tests of our orig­i­nal dummy load are de­scribed in this paper.

• H. Tomizawa, H. Dewa, H. Hanaki, A. Mizuno, T. Taniuchi
  JASRI/SPring-8, Hyogo-ken

We have de­vel­oped a laser-in­duced Schot­tky-ef­fect-gat­ed pho­to­cath­ode gun since 2006. This new type of gun uti­lizes a laser's co­heren­cy to re­al­ize a com­pact laser source using Z-po­lar­iza­tion of the IR laser on the cath­ode. This Z-po­lar­iza­tion scheme re­duces the laser pulse en­er­gy by re­duc­ing the cath­ode work func­tion due to Schot­tky ef­fect. Be­fore this epoch-mak­ing scheme, pho­to­cath­ode guns had never uti­lized laser's co­heren­cy. A hol­low laser in­ci­dence is ap­plied with a hol­low con­vex lens that is fo­cused after pass­ing the beam through a ra­di­al po­lar­iz­er. Ac­cord­ing to our cal­cu­la­tions (con­vex lens: NA=0.15), a Z-field of 1 GV/m needs 1.26 MW at peak power for the fun­da­men­tal wave­length (792 nm) and 0.316 MW for the SHG (396 nm). There­fore, we ex­pect that this laser-in­duced Schot­tky emis­sion re­quires just a com­pact fem­tosec­ond laser os­cil­la­tor as a laser source. Be­sides, a dichro­mat­ic laser scheme (pho­to-ex­cit­ing: 780 nm; gat­ing: 30 um) should be ap­plied to po­lar­ized elec­tron sources for In­ter­na­tion­al Lin­ear Col­lid­er (ILC). We re­port the first fea­si­bil­i­ty study of this laser-in­duced Schot­tky-ef­fect on sev­er­al metal pho­to­cath­odes by com­par­ing ra­di­al and az­imuthal po­lar­iza­tions.