Author: Mitsuda, C.
Paper Title Page
THPC028 A Proposal of Short X-ray Pulse Generation from Compressed Bunches by mm-wave iFEL in the SPring-8 Upgrade Plan 2969
 
  • M. Masaki, K. Fukami, C. Mitsuda, T. Watanabe
    JASRI/SPring-8, Hyogo-ken, Japan
  
  In the SPring-8 up­grade plan, short pulse op­tions are pre­pared for time-re­solved ex­per­i­ments of pi­co-sec­ond order with high rep­e­ti­tion rate. The best sce­nario is that se­lect­ed bunch­es have equi­lib­ri­um bunch length of 1 ps or less. A mm-wave stor­age-ring iFEL may be one pos­si­ble so­lu­tion for it. If res­o­nant wave­length of the FEL is a few mil­lime­ters, which is about ten times longer than typ­i­cal short bunch length of 0.3 mm cor­re­spond­ing to 1 ps, al­most all elec­trons of a bunch can be con­fined in one val­ley of pon­dero­mo­tive po­ten­tials formed by the FEL mech­a­nism. The sys­tem con­sists of a he­li­cal wig­gler with pe­ri­od length of sev­er­al me­ters and a mm-wave res­onator. Nu­mer­i­cal sim­u­la­tions with co­her­ent syn­chrotron ra­di­a­tion ef­fect at bunch charge of 479 pC show that an ul­tra-short in­jec­tion bunch is trapped in a mm-wave “buck­et” and kept short­er than 1 ps (r.m.s.) even after twice the lon­gi­tu­di­nal damp­ing time from the in­jec­tion. The ul­tra-short bunch­es need to be in­ject­ed from the XFEL linac. XFEL-to-Stor­age Ring beam trans­port line is de­signed to sup­press dis­per­sions which cause bunch length­en­ing. Track­ing cal­cu­la­tions show promis­ing re­sults for bunch qual­i­ties at the trans­port line.  
 
THPC032 Current Status of SPring-8 Upgrade Plan 2981
 
  • T. Watanabe, T. Asaka, H. Dewa, H. Ego, T. Fujita, K. Fukami, M. Masaki, C. Mitsuda, A. Mochihashi, T. Nakamura, H. Ohkuma, Y. Okayasu, Y. Shimosaki, K. Soutome, M. Takao
    JASRI/SPring-8, Hyogo-ken, Japan
  • T. Tanaka
    RIKEN Spring-8 Harima, Hyogo, Japan
  
  The SPring-8 up­grade plan has been dis­cussed. The main goal is to re­place the stor­age ring in the ex­ist­ing tun­nel so that the re­sult­ing emit­tance will get as close to the diffrac­tion limit in hard x-ray re­gion as pos­si­ble. For 10 keV pho­tons, for in­stance, the diffrac­tion limit cor­re­sponds to the emit­tance of as small as 10 pm.​rad. For the chal­leng­ing goal, the new ring fea­tures a mul­ti-bend lat­tice with damp­ing wig­glers, which pre­sum­ably en­ables us to re­duce an emit­tance by two or­ders of mag­ni­tudes or more com­pared with the cur­rent dou­ble-bend lat­tice with­out damp­ing wig­glers. Up to now, a six-bend lat­tice has been main­ly stud­ied, which is sup­posed to gen­er­ate a nat­u­ral emit­tance of 60–70 pm.​rad for 6 GeV. In ad­di­tion, damp­ing wig­glers and cou­pling con­trol should as­sist to re­duce the emit­tance even more for ap­proach­ing the ul­ti­mate goal. The major mod­i­fi­ca­tion re­quires not only an ad­vanced lat­tice de­sign via ma­nip­u­la­tion of non-lin­ear beam dy­nam­ics but also ex­ten­sive tech­no­log­i­cal de­vel­op­ments in al­most every com­po­nent such as mag­nets, mon­i­tors, and RF sys­tems. The over­all re­view of the up­grade plan, in­clud­ing some de­tailed dis­cus­sions on the crit­i­cal is­sues, will be pre­sent­ed.  
 
THPC143 Beam-based Alignment for Injection Bump Magnets of the Storage Ring using Remote Tilt-control System 3221
 
  • K. Fukami, K. Kobayashi, C. Mitsuda, T. Nakamura, K. Soutome
    JASRI/SPring-8, Hyogo-ken, Japan
  
  Stored beam is os­cil­lat­ed in ver­ti­cal if the in­jec­tion-bump mag­nets have align­ment error in ro­ta­tion around the beam-ax­is (tilt). In ad­di­tion, even if the tilt is neg­li­gi­bly small, the beam out of the me­di­an plane is kicked in ver­ti­cal di­rec­tion. Also, there is a small long-term drift of the ver­ti­cal beam po­si­tions in the bump mag­nets, which caus­es the grad­u­al in­crease of the os­cil­la­tion. We have al­ready de­vel­oped a re­mote tilt-con­trol sys­tem to make a smooth re­align­ment*. To ob­serve the os­cil­la­tion, the beam po­si­tion was mea­sured bunch-by-bunch and turn-by-turn by using a bunch-by-bunch feed­back sys­tem** with high res­o­lu­tion strip-line type beam po­si­tion mon­i­tor. To ob­tain re­spons­es to the tilts of each mag­net, the os­cil­la­tions were mea­sured under the con­di­tion that the mag­nets were tilt­ed in­ten­tion­al­ly. Tilt er­rors were cal­cu­lat­ed with least-squares method using the re­spons­es. In order to con­firm the source of the resid­u­al os­cil­la­tion, a fre­quen­cy anal­y­sis was car­ried out with FFT method using the po­si­tion data from 1st to 128th turns. We suc­ceed­ed in sup­press­ing the ver­ti­cal os­cil­la­tion to sub-mi­crons order, the value of less than one tenth of the beam size.
* K. Fukami et al., Proc. of EPAC'08, p. 2172 (2008).
** T. Nakamura et al., Proc. of ICALEPCS'05, PO2.022-2 (2005). 		 
 
THPC144 The Construction Status of Beam Transport Line from XFEL-linac to SPring-8 Storage Ring 3224
 
  • C. Mitsuda, N. Azumi, T. Fujita, K. Fukami, H. Kimura, H. Ohkuma, M. Oishi, Y. Okayasu, M. Shoji, K. Tsumaki, T. Watanabe
    JASRI/SPring-8, Hyogo-ken, Japan
  • M. Hasegawa, Y. Maeda, T. Nakanishi, Y. Tukamoto, M. Yamashita
    SES, Hyogo-pref., Japan
  • N. Kumagai, S. Matsui
    RIKEN/SPring-8, Hyogo, Japan
  
  The beam trans­port line from XFEL-linac to SPring-8 stor­age ring is now under con­struc­tion to use the ultra short bunched elec­tron beam at the stor­age ring. The newly con­struct­ed line is about 300 m, which is just a half of the whole path from the XFEL linac to the stor­age ring. The beam ex­tract­ed from XFEL-linac is guid­ed to the beam trans­port tun­nel con­nect­ed to the match­ing sec­tion of boost­er syn­chrotron bend­ing by 55.2 de­grees hor­i­zon­tal­ly and by 10.0 de­grees ver­ti­cal­ly. A dou­ble-bend based lat­tice was adopt­ed to rea­son­ably sup­press emit­tance growth and bunch length­en­ing. Sup­pos­ing a bunch length and hor­i­zon­tal emit­tance at the exit of the XFEL-linac are es­ti­mat­ed about 100 fs and 0.04 nmrad re­spec­tive­ly, it is ex­pect­ed that the cur­rent beam emit­tance in stor­age ring is im­proved to about 0.4 nmrad and al­most same bunch length in­clud­ing co­her­ent syn­chrotron ra­di­a­tion ef­fect. In 2010, the con­struc­tion of ex­tract­ing part from XFEL-linac was com­plet­ed and we fin­ished the in­stal­la­tion and align­ment of main com­po­nents. The con­cep­tu­al de­sign and con­struc­tion sta­tus of trans­port line will be pre­sent­ed with the em­pha­sis on the de­tail mag­net de­sign and the fab­ri­ca­tion.