1. Status of crystal undulator experiment at IHEP Yu.A.Chesnokov for the collaboration of Institute for High Energy Physics, Protvino, Russia INFN - Laboratori Nazionali di Frascati, Italy Department of Physics and INFN, Ferrara, Italy St. Petersburg Institute for Nuclear Physics, Russia Aarhus University, Denmark

2. At present to researches in biology, medicine, material and many other areas of science and engineering intensive x-ray beams are applied. Conventional way for production of such beams (with the energy of few KeV and higher) is the use of special magnets – undulators in accelerators [1]. The energy of photons generated in undulator is proportional to a square of the gamma-factor of a particle and is reverse proportional to a period of an undulator (about several centimeters in usual electromagnetic undulator). Thus way at energy of a beam in accelerator about 1 GeV photons are produced with the energy of about 1 KeV. To increase the energy of photon beams is very important for several applications. The idea of creation of undulators on the basis of crystals, in which an intensive periodic electrical field is created by nature, was actively discussed in the last quarter of a century [2-9].

3. Idea of CU: to bent crystal like a snake

4. 1.Beam Line, v. 32, no. 1 (2002). 2.V.V. Kaplin, S.V. Plotnikov, and S.A. Vorobiev, Zh. Tekh. Fiz. 50, 1079-1081 (1980). 3.V.G. Baryshevsky, I.Ya. Dubovskaya, and A.O. Grubich, Phys. Lett., 77A, 61-64 (1980). 4.H. Ikezi, Y.R. Lin-Liu, and T. Ohkawa, Phys. Rev., B30, 1567-1568 (1984). 5.S.A. Bogacz and J.B. Ketterson, J. Appl. Phys. 60, 177-188 (1986). S.A. Bogacz, Particle Accelerators, 42 (1993) 181. 6.G.B. Dedkov, Phys.Stat.Sol.,(b)184, 535-542 (1994). 7.A.V. Korol, A.V. Solovev, and W. Greiner, Intern. Journal of Mod. Phys., 8, 49-100 (1999) 8.U. Mikkelsen and E. Uggerhoj, Nucl. Instr. and Meth., B160, 435- 439 (2000). 9.R.O. Avakian, K.T. Avetyan, K.A. Ispirian and E.G. Melikyan. Nucl. Instr. and Meth., A492, 11-13 (2002).

5. S. Bellucci et al., Phys. Rev. Lett. 90 (2003) 034801. S. Bellucci et al., Phys. Rev. ST AB 7 (2004) 023501. A.Afonin et al NIMB-2005 V.Baranov et al JETP Letters (2005) 562

6. Origins for our approach to CU at IHEP The micro- photography of crystal end face with scratches (left) and image of the deflected by this crystal 70 GeV proton beam at distance of 1 m (right).

7. Angular distortion of crystal planes near a surface scratch

8. Scheme of realised crystalline undulator.

9. IHEP workshop: rough scratching by a diamond cutter. SEM image of one of our Si crystal undulators, showing 50 micron grooves on the undulator surface, spaced by 200 micron.

10. IHEP workshop: rough scratching by a diamond cutter. Side view of the sample: micromachining produces periodical deformations that propagate in the bulk of the crystal.

11. Ferrara group technology A special diamond blade scratched one or two faces of silicon plate. The scratches on crystal surface cause a deformation of the crystallographic planes. Potential interest to realize an undulator for positrons with submillimeter spasing

12. The CU samples were tested first by X ray at PNPI

13. Angle of reflection from unscratched surface of CU with 0.5 mm period

14. CU sample A sample of CU mounted in a holder (the holder can give compensation for global bending)

15. Scheme of extraction of circulating high-energy proton beam with bent undulator-type crystal.

16. Deflected beam profile and efficiency of extraction versus crystal orientation angle.

17. Scheme of CU radiation experiment at IHEP

18. In experiment as this detector were used two calorimeters (not simultaneously): on the basis of crystals of YAlO3 and BGO. Yttrium detector was adapted for registration of photons in the field of 60 KeV up to 2 MeV energy. The BGO detector could register photons with energies from 2 MeV to few GeV.

19. The vacuum box with CU and cleaning magnet (IHEP setup)

20. The photon spectrometer (1) and scintillator trigger (2) mounted on mechanical drivers.

21. Data acquisition system

22. The specific character of this radiation experiment is included in unusual geometry of the source. It has the small sizes in transversal direction ( ~0.3 mm ) and significant extent along the beam, few mm, as it is required about ten undulator periods with 0.5 mm step and 100 Å amplitude. Earlier the experiments on radiation from crystals were carried out with short targets, less than 1 mm.

23. Therefore the first problem consists in identification of a source, as only the small fraction of beam particles cross a crystal (~1/500). We used thin scintillator S1, 500 microns in width as a trigger, and remotely moved a crystal across a beam, therefore have easily found out the source of radiation. Orientation curve that is dependence of a signal on crystal alignment, shown on fig. 3, proves, that the source of radiation is exactly crystal.

24. The number of registered photons versus orientation of a crystal. Ten bins correspond to 1 microradian angle.

25. . The gamma spectrum in oriented (white dots), disoriented crystal(black dots) and background without crystal( square points) measured by BGO detector.

26. The second feature, connected with large extent of crystal, resulted in multiple production of photons, deforming measured spectra. At the energy of positrons 10 GeV the average number of irradiated in crystal photons is about 5, appreciably exceeding by 1 (so called multiplicity factor), thus way most part of undulator events are accomplished by few another photons and registered with distortions.

27. . Spectra of irradiated power from oriented (white dots) and disoriented crystal (black dots) measured by yttrium detector. Two right bins show up 2 MeV signals (oriented/disoriented case) and these bins are decreased 50 times in scale.

28. Selection of events with small energy transfer

29. Observation of undulator effect

30. Comparison with theory

32. Future plans: modernization of the setup: installation of gamma-collimator, application of new-type calorimeters, testing of 3 undulator samples with an account of theoretical recommendations

33. New proposal for collaboration: creation of Multilayered crystal mirror for steering of TeV-energy particle beams.

34. A.M.Taratin and S.A.Vorobiev, Phys.Lett. A119 (1987) 425 and A.M.Taratin and S.A.Vorobiev, NIM in PR B26 (1987) 512 Reflected Channeled d U Mini workshop on crystal channeling (December 2005) Prediction of beam reflection in bent crystal

35. A.M.Taratin and S.A.Vorobiev, Sov. Journal of Technical Physics, v.55, p.1598, 1985 (in Russian) Mini workshop on crystal channeling (December 2005) O.I.Sumbaev, The theory of volume capture by a curved crystal in the channeling regime, Preprint LIYaF-1201, 1986 (in Russian) Prediction of beam reflection in bent crystal

36. Scheme of experiment crystal extraction at IHEP with 70 GeV protons Crystal 1 Magnets Crystal 2 Emulsion 1 S1 S2 S3 Background Channeled_1 30 m 35 m 4.6 m Collimator 1.3 m Emulsion 2 Channeled_2 70 GeV p-beam 5 m R=3 m Mini workshop on crystal channeling (December 2005)

37. Exposure of emulsions 1 and 2 made at IHEP in 2002 Mini workshop on crystal channeling (December 2005)

38. Interpretation of the IHEP results Mini workshop on crystal channeling (December 2005)

39. 1 TeV Channeling at the Tevatron, October 5, 2005 Not volume capture, but volume reflection ! Mini workshop on crystal channeling (December 2005) The observed tail beside the channeling peak is most likely induced by beam reflection into the crystal itself

40. Creation of multilayered crystal mirror

41. Scattering and reflection in 1mm long silicon bent crystal Accelerator Energy 70 GeV U-70 450 GeV SPS 1 TeV Tevatron 7 TeV LHC Reflection 2  c, µrad 5020125 Scattering 1500/p, µrad 203.51.50.2 Scattering and reflection in serial of 10 silicon bent crystals Accelerator energy 70 GeV U-70 450 GeV SPS 1 TeV Tevatron 7 TeV LHC Reflection 10×2  c, µrad 50020012050 Scattering √10×1500/p, µrad 651150.6

42. CU sample A sample of CU mounted in a holder (the holder can give compensation for global bending)

43. Different multilayered strips.