PNPI Gatchina Crystal Farm

1. PNPI Gatchina Crystal Farm Yuri M. Ivanov, PNPI

2. Milestones 1985 – by initiative of A.I.Smirnov and O.I.Sumbaev the crystal-optics fabrication at PNPI was organized by outstanding engineer Yu. P. Platonov (worked under D. D. Maksutov who founded large astronomic optics production in USSR). 1985-90 – design and fabrication of elastic quasimosaicity quartz crystals and bending devices for 5 meter crystal diffraction spectrometer to study exotic atom X-rays. Precise measurements of K- and Σ- masses at IHEP. 1991-96 – design and fabrication of silicon crystals to focus particle beams (invented by A.I.Smirnov). Experiments with focusing crystals at IHEP. 1997-2005 – design and fabrication of silicon O-crystals for charged particle beam multi-turn extraction and collimation. Experiments with O-crystals at IHEP, BNL, FNAL. 2000-2006 – design and fabrication of elastic quasimosaicity silicon crystals. Experiments with X-rays at PNPI and with 70 GeV protons at IHEP. Observation of volume reflection effect. CERN, 9-10 March 2006

3. Samples of precise crystal diffraction units for X-rays Quartz plate sizes 1x120x120 mm3 Bending radius 5 meters Elastic quasimosaicity 3”-20” (15-100 μrad) 3 units made CERN, 9-10 March 2006

4. Focusing crystals for charged particle beams A.I.Smirnov 1987 Experiment PNPI-IHEP 1991 F2 = 4r2 – R2 F - focal distance R - bending radius of the crystal r - radius of the exit crystal face CERN, 9-10 March 2006

5. Deflection and transformation of divergent beams Experiment IHEP-PNPI 1995 Possibility to form secondary particle beams with focusing crystals CERN, 9-10 March 2006

6. Samples of focusing crystals About 10 crystals made CERN, 9-10 March 2006

7. Multi-turn extraction of proton beam with short bent crystals • Bent crystal to deflect beam into septum aperture • Magnet system to extract beam IHEP-PNPI 1998 CERN, 9-10 March 2006

8. O-crystal design Typicaldimensions: 5 x 5 x 50 mm3 CERN, 9-10 March 2006

9. Samples of O-crystals prepared at PNPI in 1998 Typical interference pattern from a bent face of the O-crystal CERN, 9-10 March 2006

10. O-crystals prepared at PNPI in 1999 for experiment at RHIC BNL Slide taken from report to EPAC02 (Paris, France) on Crystal Collimation at RHIC CERN, 9-10 March 2006

11. O-crystals prepared at PNPI in 2003-2004 for using in IHEP ring 20 crystals made CERN, 9-10 March 2006

12. Main results with O-crystals at IHEP • Length along beam > 3 mm • Extraction efficiency < 70% • Intensity of extracted beam < 2 x 1012 • Radiation hardness ~ 1020 • Still working with efficiency ~ 40% CERN, 9-10 March 2006

13. New approach – to use Sumbaev (elastic quasimosaicity) effect • Studied by O.I.Sumbaev in 1957 • Resulted in broadening of gamma-ray diffraction peaks from bent quartz plates • Caused by bending of the reflecting atomic planes (initially flat and normal to large faces of plate) due to crystal anisotropy • Depends on choice of crystallographic plane and orientation angle of plate cutting relative to a normal to the chosen crystallographic plane Figure from article: O.I.Sumbaev, Reflection of gamma-rays from bent quartz plates, Sov. JETP 32(1957)1276 CERN, 9-10 March 2006

14. Idea • Detailed description of deformed crystal plate done by V.M.Samsonov in 1975 • Resulted in predictions of elastic quasimosaic effect for some other quartz and silicon plate orientations • Large elastic quasimosaicity for (011) plane of silicon predicted • Zero result in first experiment in 1999 • New calculations: (111) plane, not (011) Figure from article: V.M.Samsonov and E.G.Lapin, On some possibilities and pequliarities of a curved crystal use in crystal diffraction instruments, 1980 CERN, 9-10 March 2006

15. Crystal design CERN, 9-10 March 2006

16. Bendingof Si(111) planes in dependence on cut angleφ Dq= 2k9 T, where T – thickness of plate k9 – deformation coefficient For bending radius R = 1 m (relationship from: V.M.Samsonov and E.G.Lapin, Preprint LIYaF-578, 1980 ) CERN, 9-10 March 2006

17. Cut  = 0 for Si(111) planes Yu.M.Ivanov, A.A.Petrunin, and V.V.Skorobogatov, JETP Lett. 81(2005)99 CERN, 9-10 March 2006

18. (1 1 1) j ° = 0 (1 1 1) j = 30 ° <1 1 1> <0 0 1> (1 1 1) (1 1 0) Different cuttings of Si plate Cutting with quasimosaicity Cutting without quasimosaicity Oriented ingot CERN, 9-10 March 2006

19. Production of elastic quasimosaicity crystals at PNPI in 2002-2005 2002 – 4 crystals (0.4 mm, 0.7 mm) 2 for studies of elastic quasimosaicity effect with X-rays 1 for channeling studies with external 70 GeV p-beam 1 for collimation studies in U-70 ring 2003 – 3 crystals (0.3 mm, 2.7 mm) 3 for collimation studies in U-70 ring 2004 – 1 crystal (2.7 mm) 1 for high intensity beam extraction (4x1012) 2005 – 1 crystal (0.4 mm) – not used 1 for reflection/channeling studies with external p-beam CERN, 9-10 March 2006

20. Crystal design for experiment at SPS 30 60 Crystal plate sizes 1x30x55 50 CERN, 9-10 March 2006

21. Oriented piece of silicon ingot prepared CERN, 9-10 March 2006

22. Billet for plates cut from oriented piece CERN, 9-10 March 2006

23. Grinding and polishing of (111) faces of billet completed CERN, 9-10 March 2006

24. Measurement of (111) orientation with respect to face using double crystal diffraction scheme for X-rays and optical autocollimation Miscut angle ~4” (20 μrad) CERN, 9-10 March 2006

25. Face flatness check: ~0.2 μm CERN, 9-10 March 2006

26. Face non-parallelism check: ~3” CERN, 9-10 March 2006

27. Rocking curve measurement: width ~10”, polishing should be continued CERN, 9-10 March 2006

28. Further steps • To complete polishing of (111) billet faces • To measure widths of rocking curve from (111) faces of billet. • To cut billet for plates. • To grind and to polish large faces of plates providing necessary orientation of crystallographic axes. • To bend plates providing 100 μrad bending angle for (111) planes. • To investigate bent crystals with X-rays. • To complete first crystal in April, second one – in May CERN, 9-10 March 2006