1. 1 FJPPL optical cavity Compton collaboration Optical Stacking Cavity for ILC Compton e + source FJPPL2008@KEK 15/May/2008 Junji Urakawa (KEK)

2. 2 Today's Talk 1. Introduction 2. Goal of the R&D 3. R/D status in Japan 4. Future R&D 5. World-wide collaboration 6. Summary

3. 3 Two ways to get pol. e + (1) Helical Undurator (2) Laser Compton e - beam E >150 GeV Undulator L > 200 m Our Proposal

4. 4 325 MHz Laser Pulse Stacking Cavity Cavity Enhancement Factor = 1000 - 10 5 Laser-electron small crossing angle Laser bunches L cav = n  L cav = m L laser n, m : integer Reuse high power laser pulse by optical cavity.

5. 5 Goal of our R&D a) 1.7x10 12 photons x 2700 bunches/train /20% bandwidth during 100msec b) The efficiency of whole system highly depends on the optical cavity design. laser spot size is less than 10  m. collision angle is less than 8 degree. enhancement factor is more than 100000. c) 220mJ @1064nm in the cavity, 5 cavities d) 2.2  J @325MHz ---  1kW laser oscillator e) Fiber Amplifiers Assuming 2nC/bunch, 1psec bunch length of electron bunch and 1psec laser pulse width, 325MHz collision frequency.

6. 6 R/D Status in Japan Moderate Enhancement ~ 1000 Moderate spot size ~ 30 micron Simple cavity stucture with two mirrors Get experinence with 43MeV and 1.3GeV e- beam Laser Undulator Compact X-ray (LUCX) Project at KEK-ATF 43MeV Multi-bunch beam+ Super-Cavity = 33keV X-ray. Expected X-ray is generated.

7. 7 Laser Undulator Compact X-ray (LUCX) Project at KEK-ATF (Kyoto-Waseda-KEK) Multi-bunch photo-cathode RF Gun S-band Acc. Structure Storage Laser power 36kW, 7psec(FWHM), next step :1MW Beam size at CP 60  m in  Multi-bunch e- beam 300nC at gun 43MeV Multi-bunch beam+ Super-Cavity = 33keV X-ray. X-ray Detector At present, laser waist size is 30  m in  We should reduce both beam size at CP down to 30  m. 33keV X-ray generation based on inverse Compton scattering is started from May 2007 with Super-Cavity.

8. 8 e - beam laser beam pulse stacking cavity in vacuum chamber  -ray Generation with Laser Pulse Stacking Cavity (Hiroshima-Waseda-IHEP-KEK) 1.Achieve high enhancement & small spot size 2.Establish feedback technology 3.Achieve small crossing angle 4.Get experinence with e - beam We should detect 20  ’s/collision.

9. 9 Compact X-ray source is required from various fields. >Medical Diagnosis Angiography, Mammography … >Biological Sciences Soft X-ray microscopy … >Drag Manufacturing X-ray protein crystal structure analysis …Application 1. ~Compact X-ray Sources~ Our aim ~Medical Application~ Development of compact high brightness X-ray generator for K-edge digital subtraction angiography. Angiography is a procedure that enables blood vessels to be visualized using the absorption by Iodine at 33keV 2. High brightness  -ray beam Nondestructive assay of radio-nuclides in nuclear waste by nuclear resonance fluorescence : 10 10 photons/sec ・ keV for Interrogation of fissile material in cargoes and versatile method of nondestructive analysis of both radioactive and stable nuclides.

10. 10 Future R/D 1. Points for high enhancement factor 2. Points for small spot remove/suppress vibration establish feed-back technology 2  - L cav --> +0 good matching between laser and cavity Achieve both high enhancement(1000) & small spot (30  m) (less stabile) & (less stabile) (Mirror R = 99.7%-  R=99.9%-  R=99.99%-  R=99.999%?) Next step : from 1000 to 10000 or 100000 Next step : from 30  m to 10  m or 6  m

11. 11 3. Points of R/D (continued) Number of  -rays strongly depends on crossing angle Achieve smaller crossing angle 10W, 357MHz 0 2000 4000 6000 8000 0102030 crossing angle Counts/crossing --> Small crossing angle is preferable. --> constraint in chamber design ATF e - bunch length = 9 mm (rms) Ne = 1x10 10 /bunch (In the case of 1mm bunch length, this dependence is not strong.) Short bunch beam is preferable. Next step : from 12 degree to 8 degree or 5 degree.

12. 12 Mirror R (mm) rms laser spot size (micron) 25088 21135 210.530 210.120 210.0111 210.001 6 L R Laser stacking cavity with Two Spherical Mirrors Choice of R and spot size our choice for 1st prototype L = 420.00 mm concentric configuration R + R ~ L

13. 13 World-Wide-Web of Laser Compton Laser Compton ILC e+ CLIC e+ Optical Cavity High power laser e- source ILC, ERL Medical applications Industrial applications ERL 4 th Generation light source LW monitor  collider Polari- metry X-ray source Nuclear Assay Diagnostic

14. 14 Summary 2. Laser stacking cavity is a key. 3. In Japan, we are generating X-ray and  -ray by installing the stacking cavity in LUCX and ATF-DR. 4. In France, we are developing a very advanced cavity with 4 mirrors. In 2009, a 4 mirror cavity will be installed in ATF-DR for  -ray generation.-  next talk. 1. Compton e + source is an advanced alternative of ILC e + source 5. We have world-wide collaboration for Compton. Not only for ILC e + source. Also for many other applications.

15. 15 Extra Slides

16. 16 Expected Number of  -rays at ATF Number of  -rays/bunch Electron :Ne = 2x10 10 (single bunch operation) Laser : 10 W (28 nJ/bunch) Optical Cavity: Enhancement = 1000 Ng =2500/bunch X-ing angle = 5 deg N  =1300/bunch X-ing angle = 10 deg N  = 900/bunch X-ing angle = 15 deg Number of  -rays/second Electron :Ne =2x10 10 (multi-bunch and multi-train operation) Electron 20 bunches/train, 3 trains/ring Laser : 10 W (28 nJ/bunch) Optical Cavity: Enhancement = 1000 Ng = 3.4x10 11 /sec X-ing angle = 5 deg N  = 1.7x10 11 /sec X-ing angle = 10 deg N  = 1.1x10 11 /sec X-ing angle = 15 deg

17. 17

18. 18 What we want ILC YAG case (Snowmass 2005) Now on Going at KEK-ATF Achieved in 2004 (Takezawa(Kyoto U) et al) at KEK-ATF Electron Energy (GeV)1.3 Ne/bunch6.2E102.0E101.0E10 Electron repetition rate (MHz)325357 Hor. Beam size (rms,us)2579 Ver. Beam size (rms,us)566 Bunch length (rms,mm)599 Laser type (wavelength)YAG(1064nm) Laser frequency (MHz)325357714 Laser radius (rms, um)529125 Laser pulse width (rms,mm)0.9 Laser pulse power /cavity 750  J x 1000 28nJ(10W) x 10001nJ(0.3W) x 65 Number of laser cavities3011 Crossing angle (degree)81290 by H. Sato (Posipol 2006) Cavity History in Japan

19. 19 Compton for " 2 x 6 km DR " : no simulation yet

20. 20 Collaborating Institutes: BINP, CERN, DESY, Hiroshima, IHEP, IPN, KEK, Kyoto, LAL, NIRS, NSC-KIPT, SHI, Waseda, BNL, and ANL Sakae Araki, Yasuo Higashi, Yousuke Honda, Masao Kuriki, Toshiyuki Okugi, Tsunehiko Omori, Takashi Taniguchi, Nobuhiro Terunuma, Junji Urakawa, X. Artru, M. Chevallier, V. Strakhovenko, Eugene Bulyak, Peter Gladkikh, Klaus Meonig, Robert Chehab, Alessandro Variola, Fabian Zomer, Alessandro Vivoli, Richard Cizeron, Frank Zimmermann, Kazuyuki Sakaue, Tachishige Hirose, Masakazu Washio, Noboru Sasao, Hirokazu Yokoyama, Masafumi Fukuda, Koichiro Hirano, Mikio Takano, Tohru Takahashi, Hirotaka Shimizu, Shuhei Miyoshi, Akira Tsunemi, Li XaioPing, Pei Guoxi, Jie Gao, V. Yakinenko, Igo Pogorelsky, Wai Gai, and Wanming Liu PosiPol Collaboration World-wide Collaboration POSIPOL 2007 LAL-Orsay, France 23-25 May POSIPOL 2006 CERN April 2006 http://posipol2006.web.cern.ch/Posipol2006/ http://events.lal.in2p3.fr/conferences/Posipol07 /