1. Experiments on beam deflection by crystals Masataka IINUMA Department of Quantum Matter Graduate School of Advanced Sciences of Matter Hiroshima University

2. V. Biryukov (a), Yu. Chesnokov (a), I. Endo (b), M. Iinuma (b), H. Kuroiwa (c), T. Ohnishi (c), S. Sawada (d), S. Strokov (b), T. Takahashi (b), K. Ueda (b) (a): IHEP-Protovino (b): Hiroshima University, ADSM (c): Hiroshima University, VBL (d): KEK Collaborators

3. 3 Recent activities – proton beam – 12 GeV proton beam : beam separation bent Si crystal ( length:10 mm, angle:32.6 mrad ) bent crystallographic plane : (111) plane Experiments at proton synchrotron facility in KEK ( KEK-PS ) Scope : Application to J-PARC Beam separation in the slow extraction line Crystal collimation in the future

4. 4 Recent activities – electron beam – 150 MeV electron beam : beam deflection straight Si crystal ( thickness : 16  m ) crystal axis tilted to the beam axis Experiments at electron beam facility in Hiroshima University Scope Understanding of basic properties on the electron beam deflection Application to a beam collimation in ILC

5. 5 Experiment at KEK-PS 12 GeV Proton Synchrotron East counter hall EP2 line Experiments in EP2 line North counter hall

6. 6 Experiment for beam separation Fluorescence plate (10 x 10 cm) Fluorescence plate (10 x 10 cm) CsI plate (5 x 2.5 cm) Goniometer Bent crystal Main beam Deflected beam Top view Crystal Deflection angle Deflection angle 12 GeV protons  

7. 7 Typical images Deflected beam CsI plate Primary beam raw image image after background subtraction fluorescence plate

8. 8 Results – intensity dependence – Angle between crystal and beam axis (  ) intensity of deflected beam primary beam 10 12 pps mrad  pps

9. 9 Dependence on beam divergence 5 mrad 1 mrad 0.5 mrad 0.3 mrad Smulation by using CATCH code

10. 10 Results – intensity dependence – angle between crystal and beam axis (  ) intensity of deflected beam primary beam 10 12 pps mrad  pps beam divergence : 0.6 mrad – simulation ( CATCH code ) – experiment

11. 11 Estimation of crystal efficiency N deflected = Crystal Efficiency x Angle Efficiency x N incident protons upon the crystal. N deflected = Crystal Efficiency x Angle Efficiency x N incident protons upon the crystal. ratio of number of incident protons within Lindhard angle to number of total incident protons 0.3% of Intensity ( 10 12 ) N incident upon the crystal = 3x10 9 Crystal Efficiency 23%

12. 12 Summary on proton experiment We demonstrated the beam separation of 12 GeV proton beam with the bent crystal. Experimental results are quantitatively understood. The  2 analysis gives the beam divergence of 0.6 mrad. By using the obtained beam divergence and data, the crystal efficiency of 23 % was obtained.

13. 13 Experiment with 150 MeV electrons REFER (Relativistic Electron Facility for Education and Research) ring at Hiroshima University

14. 14 REFER (Relativistic Electron Facility for Education and Research) 150-MeV electron beam injection line beam extraction line QM3 magnet ( control beam divergence ) beam intensity: 1x10 4 s -1 REFER ring @ Hiroshima University Setup area

15. 15 Fiber Optics plate with a Scintillator (FOS plate) Experiment for beam deflection Straight Si crystal thickness: 16  m beam profile 150-MeV electron beam    direction of axis direction of axis e–e– 2.3 m Observation of a beam profile at the FOS plate in each combination of  and  angles Linhard angle : 0.7 mrad

16. 16 Vertical beam divergence: 3.0 mrad  =0 mrad Results (1) crystal angle  deflection angle beam divergence > 0.7 mrad ( Lindhard angle ) ( mrad )

17. 17 Vertical beam divergence: 3.8 mrad  = 0 mrad Results (2) Vertical beam divergence: 5.2 mrad  = 0 mrad crystal angle , (mrad) deflection angle, (mrad) crystal angle , (mrad) The maximum deflection angle depends on the beam divergence.

18. 18 Deflection vs. beam divergence Derivation of  by fitting the plot with 1 st derivative of Gaussian function Larger beam divergence  Smaller deflection beam divergence normalized deflection magnitude  ( mrad )

19. 19 Simulation : Comparison with Experiment Beam divergence: 5.2 mrad Beam divergence: 3.0 mrad crystal angle , (mrad) deflection angle, (mrad) crystal angle , (mrad) Rough behavior : Agreements with experimental results Details : Discrepancy between simulation and data Simulation includes only dynamics under the string potential.

20. 20 Summary on electron experiments The results showed clear evidence of ability to use crystals for handling 150 MeV electrons under the following condition. Beam divergence > 0.7 mrad ( Linhard angle ) The deflection magnitude depends on the beam divergence. Larger beam divergence smaller deflection On rough behavior, the simple simulation agrees with the data. On details, there are discrepancies between the simulation and the data.

21. 21 Future prospect For application to J-PARC Studies for the beam separation in the slow extraction Learn practical know-how from Tevatron and LHC for the crystal collimation in future Understanding of electron beam deflection aiming at the future application of a beam collimation in ILC Investigation on basic properties under the condition beam divergence < Lindhard angle Planning next deflection experiment at KEK-ATF ultra-low emittance, small beam size …

22. 22 Beam separation in J-PARC 50 GeV proton beam : intensity of 10 14 protons per second smaller beam profile smaller beam profile (few mm 2 ) and emittance (few mm 2 ) and emittance compared with the conventional compared with the conventional separation systems separation systems smaller beam losses smaller beam losses

23. 23 Deflection experiment at ATF Beam energy : 1.28GeV Intensity : 1x10 10 /bunch Beam divergence < Lindhard angle Effect of multiple scattering with 1.28GeV beam smaller than that with 150 MeV beam Low Emittance X: 1x10 -9 rad m Y: 1x10 -11 rad m Characteristic of electron beam multiple scattering ( 1.28 GeV ) : 0.14 mrad 16  m straight Si crystal Lindhard angle ( axis ) : 0.24 mrad beam divergence ( x ) : 0.1 mrad ( 10  m size ) ( y ) : 0.001 mrad ( 10  m size ) We can see the deflection effect more clearly.

24. 24 test for deflection ATF2 beam line Layout at KEK-ATF

25. 25 Proposed setup at KEK-ATF Taking account of radiation safety regulation Vacuum condition : pressure less than 10 -7 Torr small amount of material in the beam similar situation in ATF2 beam line

26. 26 Conclusion We performed two kinds of experiments. Proton beam separation with the bent crystal for 12 GeV beam Electron beam deflection with the straight crystal for 150 MeV beam under the condition; beam divergence > Lindhard angle Study for beam separation in the slow extraction line in J-PARC : the crystal collimation in future Deflection experiment at KEK-ATF for understanding basic properties. These results can be linked to a feasibility test for the crystal collimation in ILC in future.

27. 27 Backup slides

28. 28 Trajectory of the 150-MeV electrons inside of the Si crystal Simulation: trajectory Initial position : X=-2.5 Å,Y=-2.5 Å Initial position : X=0 Å,Y=-2.5 Å axes X direction = 0.095 mrad Y direction = 0.09 mrad X direction = 0.1 mrad Y direction = 0.01 mrad

29. 29 QM3: 2.0 A,  = 0,  = -1.5 mrad Beam divergence: 3.0 mrad QM3: 2.6 A,  = 0,  = -1.5 mrad Beam divergence: 5.2 mrad Beam profiles at FOS position

30. 30 vacuum: 1.0x10 -5 torr extraction line QM3 QM3: quadruple magnet thickness of crystal: 16  m Setup change of beam divergence at the crystal position FOS plate

31. 31 Si crystal Goniometer Beam IIT & CCD FOS plate +mirror Photos

32. 32 REFER ring Creation of the system to extract 150-MeV electron beam Replace aluminium energy degrader by the crystal will reduce energy losses and increase the intensity of extracted beam.

33. 33 String potential Lindhard continuum axial potential a – Thomas-Fermi radius Z 1 e – charge of incident particle Z 2 – atomic number of crystal material C – Lindhard constant ( )  – distance from axis d – lattice constant Lindhard angle ( critical angle ) Transverse energy of particles < Potential depth at a 5.4 3 Å

34. 34 Beam size, divergence mm АА

35. 35

36. 36 Extraction line QM3 magnet injection line extraction line Experimental setup

37. 37 Data Acquisition system The procedure of grabbing pictures and movement of two goniometers was synchronized with the beam gate. Pictures were taken only when electron beam hit the FOS plate.

38. 38 Simulation (1) Beam divergence: 5.2 mrad Beam divergence: 3.0 mrad Larger beam divergence  Smaller deflection crystal angle , (mrad) deflection angle, (mrad) crystal angle , (mrad)

39. 39 Application to collimation - ILC (International Linear Collider) - Creation of system to remove beam tails Spoiler – copper 8.6 mm thick (0.6 X 0 ) X 0 : Radiation length Absorber – copper 4.3 m thick (30 X 0 ) proposed by A. I. Drozhdin Bent crystal – silicon 2 mm thick(0.02 X 0 ) Deflection efficiency of 250-GeV positrons with the 2 mm Si crystal bent at 0.1 mrad is 80% Deflected beam tail can be localized and is not scattered anywhere.

40. 40 For practical realization Many issues on electron beam deflection by crystals are unclear. For example How is an efficiency of deflection? How is a maximum angle for being trapped in the potential ? How is a length of crystal ? ( How is dechanneling length ? ) Necessity of basic studies on electron beam deflection by crystal

41. 41 Deflection by BENT crystal ( thick crystal ) Deflection by BENT crystal ( thick crystal ) deflection angle Thick crystal : Disadvantage for low energy beam due to large influence of multiple scattering Electron beam deflection Deflection by STRAIGHT crystal ( thin crystal ) Deflection by STRAIGHT crystal ( thin crystal ) deflection angle Thin crystal : possible for low energy beam ( ex. 150 MeV electron beam )

42. 42 Lindhard critical angle for axis of Si crystal: 0.7 mrad Beam divergence > Lindhard angle vertical horizontal Beam divergence at crystal position Beam divergence as a function of QM3 current current of QM3 magnet, (A) beam divergence, (mrad)

43. 43 Vertical beam divergence: 3.0 mrad ( QM3: 2.0 A ) projection Beam center Weighted mean in 2  region Analysis of images vertical projection, (mm) Fitting with double Gaussian

44. 44 Lindhard string continuous potential Conditions for simulation Simulation ( axial channeling ) a – Thomas-Fermi radius  – distance from axis d – lattice constant, it is 5.43 A for Si Z 1 e – charge of incident particle Z 2 – atomic number, 14 for Si C – Lindhard constant ( ) 4 th order of Runge-Kutta method primitive simulation - without consideration of single and multiple scattering, channeling radiation and crystal imperfection Incident angles of particles limited to the twice of Energy of electrons: 150 MeV Thickness of the crystal: 16  m

45. 45 Searching of  minimum Beam divergence found to be 0.6 mrad, and the normalization for deflected beam intensity 1/0.93 Beam divergence found to be 0.6 mrad, and the normalization for deflected beam intensity 1/0.93 beam divergence, (mrad) n – number of data p – number of adjustable parameters (=2) y i exp – i-th experimental vaue y i sim – data from the simulation  i = 1/  i 2 – weight of each experimental point, where  i is a standard deviation normalization factor for d.b. intensity

46. 46 Physics process electron beam scattering with uniform transverse momentum in initial condition deflection angle crystal axis  transverse momentum in initial condition Width of profile broadening due to a helical motion Deflection angle smaller angle than crystal angle No effects for a bent crystal ? straight crystal

47. 47 Crystal and proton beam Material: Silicon Size: 3 x 0.3 x 10 mm Bending angle: ~ 32.6 mrad Plane: (111) Lindhard angle:0.051 mrad Parameters of crystal bending angle, 32.6 mrad Energy: 12 GeV Intensity: 10 12 protons/spill Size: 15 x 12 mm Divergence: < 5 mrad 15mm 12mm Parameters of the proton beam