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Channeling and materials issues in channeling collimation

Channeling and materials issues in channeling collimation. Dick Carrigan Fermilab Legnaro National Laboratory, Legnaro, Italy March 8, 2006. Channeling collimation related issues. Two stage collimation E853 extraction and collimation Tevatron crystal collimation Fliller-Still shoulder

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Channeling and materials issues in channeling collimation

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  1. Channeling and materials issues in channeling collimation Dick Carrigan Fermilab Legnaro National Laboratory, Legnaro, Italy March 8, 2006

  2. Channeling collimation related issues • Two stage collimation • E853 extraction and collimation • Tevatron crystal collimation • Fliller-Still shoulder • Does Tevatron crystal deflect, collimate? • Channeling information needed • Radiation damage • Exotic acceleration and radiation damage Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  3. Conventional two stage accelerator collimation Channeling collimation Two-Stage Collimation with Target and Crystal - Mokhov Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  4. E853 Crystal Extraction at the Tevatron E853 in the mid-nineties was the first step at Fermilab in the direction of investigating channeling collimation. Serpukhov was also investigating this subject (1998). see Carrigan, Mokhov, et al., Phys. Rev. ST Accel. Beams AB 1, 022801 (1998) http://prstab.aps.org/abstract/PRSTAB/v1/i2/e022801 Carrigan, Mokhov, et al., Phys. Rev. ST. Accel. Beams, AB 5, 043501 (2002) http://prst-ab.aps.org/abstract/PRSTAB/v5/i4/e043501 (see these for collaborators)

  5. At crystal Lambertson, crystal C0 at the time of E853 “Murphy geometry” U counters Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  6. First crystal extraction at the Tevatron C0 straight section June 6, 1995 (230 microrad scan, kick mode) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  7. Relative rate Xc (mm) Series of ~100 m step collimator retraction Beam halo effects and collimation Moving crystals or collimators gives information on halo retracting crystal 200 microns cut signal by 4. In 2 minutes recovered somewhat. moving in-initial spurt for several minutes followed by 1/e decays of 0.5 to 5 hours • Extraction rate depended on shadowing of crystal by collimator • 5 mm retraction to behind collimators precipitously cut rate • Characteristically the D0 proton loss rate rose by 5% to 20% as the collimators were opened.

  8. E853 Experience • Bad: • Interaction counters very sensitive to beam motion (Still-Shiltzev much better) • Beams in the 108 - 109 regime need special instrumentation • Beam halo behavior is often non-linear • Lattice location important (RHIC – difficult, Tevatron better but imperfect) Good: Crystal extraction works well, robust Extraction in diffusion modes means crystal collimation can work Multiple pass works, can take bigger goniometer steps Neutral: Large variety of time dependent behavior Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  9. FNAL PROPOSAL FOR CRYSTAL COLLIMATION Blm Detector T:LE033 LE03 pin L shaped tungsten E0 Pin diode ? Current collimation system in Tevatron is somewhat different compared to the one planned before Run-II. Based on detailed modeling, Carrigan, Drozhdin, Mokhov and Still, proposed to implement a bent crystal in the EØ straight section. Done in 2004-2005. Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  10. Beam Direction 5mm REPLACING PRIMARY COLLIMATOR WITH RHIC/SERPUKHOV O-SHAPED CRYSTAL AT 5 s 1. At Fermilab installed modified BNL assembly and crystal during Fall 2004 shutdown 2. Vertical assembly was found to have “fallen” during exercising horizontal motion: repaired in place in February 2005 3. Beam studies at 150 and 980 GeV in summer and fall of 2005 O-shaped 110 Si-crystal 5-mm L, 5 mm H, 1 mm V Overall length ~50 mm critical angle 5 micro rad bending angle 439 micro rad miscut angle 465 micro rad Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  11. Fliller-Still Effect: 980-GEV BEAM at E0 (5.5 σ fit) Oct. 6, 2005 Jan. 31, 2006 With E03H out, LE033C BLM is proportional to nuclear interact. rate in crystal Full arc coherent Channeling Peak width is 22±4 mrad (rms) 440 microrad Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  12. CRYSTAL COLLIMATOR SYSTEM Laser – angular measurement PIN Diode BLM E0 Scintillator Paddles 23.8 m BLM 31.542 m 14 mm crystal channeled beam Pin Diode E03H 2nd Collimator E03 Secondary Collimator E0 Crystal Collimator Assembly

  13. Possible explanations for whole bend effect Volume capture Volume reflection Miscut angle for crystal Something else What to call effect? • Whole arc channeling (gets at characteristic of process) • Volume reflection (probably correct) • Volume capture (probably wrong) • Vorobiev-Taratin effect (sort of predicted but does not include accelerator) • Fliller shoulder (yes, but Tevatron confirmation helped) • Fliller-Still shoulder (includes Tevatron confirmation) • L5 effect (silly but 42% of Fliller-Still is ls) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  14. MODELING AND INTERPREATION (5.5 σ fit) (Mokhov) Crystal community: enthusiasm about peak (channeling efficiency up to 95%) and argue about plateau nature (volume capture vs reflections) V. Biryukov with CATCH: Random MCS • Peak dip is 95% from random rate • Its width is 25-30 mrad, 5-6 critical angles: multipass multiturn effect • Plateau is about 50% from random • At peak: channeling efficiency 78%, nucl. int. 3%, apertures 19% • At random, nucl. int ~70%, apertures 30% • Plateau may be due to scattering on potentials of atomic planes (“reflections”) that is stronger than MCS, with overall “coherent” rms angle several times larger. This –along with limiting apertures – makes the plateau Plateau Channeling Yu. Ivanov: Peak: 2 to 3 passages of proton beam through the crystal Plateau: 6-9 passages

  15. Volume capture • “Volume capture” is the putative process whereby particles outside a channel in a bent crystal diffuse into the channel. It was first investigated at Gatchina by Samsonov, Sumbaev and their colleagues at 1 GeV. Volume capture should deflect in the direction of the bend. This diffusion process is an analog of dechanneling where the particles diffuse in to the channel. Process occurs over the whole arc of the bend. Deflections can range up to the whole arc of the bend. • In their book BCK (Crystal channeling …) give a formula (BCK 5.27) for the transition probability to diffuse into the channel as: where p is the momentum and R is the radius of curvature Thus as the energy goes up, volume channeling goes down. As R gets smaller (tighter bend) it also decreases. Biryukov, et al., have shown that this relation holds true for 70 GeV protons and is characteristically small compared to ordinary bent crystal channeling (Fig. 3.30 in BCK) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  16. Volume reflection • Volume reflection was discovered in simulations by Taratin and Vorobiev in the eighties [Phys. Lett A, 119, 425 (1987 for English language version]. In essence particles reflect off of planes when they are nearly parallel and are deflected on the order of a critical angle away from the bend. The process will occur over the whole arc of the bend. It can be cumulative for many passes. Since the expected deflection is O(θc) the deflection will go as 1/(pβ)½. R does not appear but θc for a bent crystal will be a function of R. As a result the effect will diminish more slowly than volume capture as the energy increases. This is why many expect the whole arc effect seen at RHIC and the Tevatron is due to volume reflection. Useful to understand p, R scaling since we are extrapolating to LHC Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  17. Potential picture for volume reflection, volume capture (Ivanov) Volume reflection (Taratin-Vorobiev) Particle bounces off plane at some place in passage through a curved crystal. Deflection order of ψc Volume capture (Sumbaev/PNPI) Particle scatters into channel with lower transverse energy and remains there. Continues to end of bend.

  18. Possible volume reflections in E853 at the Tevatron Normal extraction did not see whole arc effects. Needed kick almost whole bend for extraction. Interaction (U counter) often drifted, was disregarded. Figure is selected (bad science but also wide variety of running conditions). Note that more negative angle is convex side, the volume reflection side. Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  19. Summary of coherent bend effects Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  20. E03 COLLIMATOR SCAN FOR DIFFERENT CRYSTAL ANGLES (Mokhov) Channeled beam produces a shoulder 7 mm from the core The channeled beam should have been ~10.5 mm from the core. First data set suggested the channeled beam was hitting an aperture. But on 1/10/2006, after moving the crystal 10mm, new data proved there was no aperture limit. Scatter Channel Reflections Beam probe w/out crystal

  21. E03 data fitted and differentiated Puzzle Apparent deflected angle is 296 micro radians. Should be 440. But maybe appropriate beam center is not E03H = 0. Channeling peak is 50% of deflected beam. Remainder dechanneling? Sigma is twice critical angle, some due to beam divergence.

  22. COMPARING EFFECTS OF PROTON HALO LOSSES FOR BENT CRYSTAL AND TUNGSTEN TARGET (Mokhov) Crystal aligned at peak (118 mrad) CDF E03 BLM PIN Using the crystal, the secondary collimator E03 can remain further (1 mm or so) from the beam and achieve almosta factor of 2 better result in reduction of CDF losses a half a ring (2 miles) downstream! Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  23. INSTALLING NEW CRYSTAL IN TEVATRON • Problems with the current BNL/IHEP crystal: too long, too large bending angle, O-shaped, 60% of declared 0.44-mrad bending angle, crystal squeezed? • A new custom crystal was prepared and characterized at Protvino and Ferrara: 3-mm long, 150 mrad bending angle, strip, chemical etching. • It will replace the current one during the Tevatron long shutdown starting February 28. Considering better instrumentation. Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  24. Negative hadron and e+/e- channeling? • Could one collimate antiprotons at the Tevatron? • Could one collimate e+/e- at ILC? • In TOTEM, etc. at LHC could one deflect negative particles including leptons? e+/e- channeling • channeling radiation impact must be considered • crystal lengths must be short • not so much dependence on charge • little of no experimental information at high energy, particularly for bending Negative hadron bending Bak et al. did studies of negative particle axial deflection at 10 - 12 Gev with pions [S. Anderson et al., Nucl. Phys. B167, 1 (81), J. Bak, et al., Nucl Phys. A389, 533(82)] Schiott simulated their data in Carrigan and Ellison (Relativistic Channeling, NATO 165, Plenum (87)). Saw only small effects on order of critical angle. Taratin & Vorobiev, Phys. Lett. A119, 425 (1987) also discuss negative bending simulation.

  25. + - Negative hadron and e+/e- channeling -continued More recently Greenenko and Shul’ga [NIM B90, 179 (94)] studied negative deflection with a simulation program. For axial channeling at 400 GeV they saw deflection at the same scale as the Schiott simulation. Their distributions for 100 GeV hadrons bent in a 3 cm crystal are shown below. Note that the negative deflection is of the same order as the positive case but very diffuse. In thinking about the possibility of negative particle deflection in the early eighties I discounted it because I thought in terms of discrete angular deflections in the spirit of an external beam. The situation is different for collimation where the important thing is to give the particles a kick, any kick, provided it is more than the multiple scattering. Multi-pass channeling also helps. High energy may also help. We need more information on negative channeling, negative bending!

  26. Scale 1/16 in/div Some radiation damage experience • E853: 70 hours of halo on crystal, no effect • Baker et al NIMB90, 119 (1994) – 3*10^19 protons @ 28 GeV (BNL) or fluence of 4*10^20/cm^2. Channeling minimum yield went from 2.3% to 4.1%. Related to crystal disorder. From Dynamitron study with energy there was a suggestion • it may have been dislocations • This article also considers relative impacts of dislocations, point defects • CERN saw 25% degradation of bending efficiency for 2*10^20p/cm^2 • IHEP bent crystal with temperature to 150 degree, 1 W beam power Issues • temperature effects (see later slides) • controlling damages • material? • types of defects • extrapolation to 7 TeV

  27. Bad things happen to crystals break radiation damage bend relaxes… Bad things happen to collimators melt fuse strip diode electrode xtal diode electrode ground plane Self monitoring? radiation damage via depletion voltage, leakage current ala Si strip detectors bend via capacitance? continuity via plated on fuse surface? Self monitoring crystal? Exotic damage cases Some exotic acceleration schemes could vaporize crystal How would channeling behave then? 

  28. Visionary possibilities for acceleration Would like much higher accelerating gradients Two thoughts: • Lasers • R. Palmer, Particle Accelerators V11, 81 (1980). Recent progress Kimura et al. PRL 92, 054801 (2004). See also LEAP at Stanford (Colby) Plasmas Tajima and Dawson PRL 43, 267 (1979) E. Esarey, et al., IEEE Trans. On Plasma Sci, 24, 252 (1996). J. Dawson, Scientific American March, 1989 (p. 54) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  29. Plasma wake field acceleration G= 0.96(n0)½ (V/cm) n0 is electron density RF cavity 0.0005 GV/cm gaseous plasma 1 GV/cm Photo S. Carrigan Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  30. A wakefield accelerator - E157 at SLAC Head of beam generates plasma wakefield, tail is accelerated by 80 MeV. Also do e+ - E162. (E-164 later version , ne O(3*1015), 100 micron bunches - see 2003 Particle Acc. Conf, p. 1530) M. HoganPhys. Plasmas 7, 2241 (2000) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  31. Results from SLAC E-157 Acceleration Barov and Rosenzweig (UCLA) see similar results at Fermilab. 100 MeV/m using A0 14 MeV photoinjector. 6-8 nC, ne ~ 1014/cc. M. HoganPhys. Plasmas 7, 2241 (2000). See also Muggli, et al. PRL 93, 014802-1 (2004) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  32. Bob Hofstadter "The Atomic Accelerator" HEPL 560 (1968) • "To anyone who has carried out experiments with a large modern accelerator there always comes a moment when he wishes that a powerful spatial compression of his equipment could take place. If only the very large and massive pieces could fit in a small room!” Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  33. Hofstadter wanted a crystal accelerator! • A table top accelerator ("miniac") • The first solid state accelerator • use channeling for focus • maybe an after-burner scheme • excite atoms coherently with 1 keV-xray Get out 1 keV/Å in 1 cm would get 100 GeV Need an x-ray laser (1968) Problem-transit time Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  34. Plasma wake field acceleration – solid state G= 0.96(n0)½ (V/cm) n0 is electron density RF cavity 0.0005 GV/cm gaseous plasma 1 GV/cm solid state plasma 100 GV/cm Photo S. Carrigan Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  35. Livermore wedge + - + - + - Laser Debye Protons sheath Pseudo solid state accelerators • At least four groups see high energy ions, electrons from intense lasers hitting foils • Livermore PRL 85, 2945 (2000) • Michigan APL 78, 595 (2001) • Rutherford PRL 90, 064801 (2003) – discussion of mechanisms, target evolution • LULI PRL 85 1654 (2002) 3*1020 W/cm2, 1000 TW, 1013 proton beams with E to 58 MeV, electrons protons can be focused by curving target process: electrostatic fields produced by ponderomotively accelerated hot electrons act on protons from absorbed hydrocarbons rear side (downstream) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  36. Basic Crystal Accelerator Concept excite plasma wake field in solid with density a thousand times gas use channeling to reduce energy loss, focus, and maybe even cool Chen-Noble Tahoe (1996), p. 441 Positives very high power, femtosec lasers radiative damping (Huang, Ruth, Chen) Big problems! • blow away material • dechanneling Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  37. The Fermilab A0 photoinjector • built as Tesla injector prototype in the late 1990s by Helen Edwards’ group • essentially a gigantic phototube powered by a laser followed by a so-called 3.5 MeV warm RF gun and second stage of a Tesla superconducting nine-cell RF cavity • beam energy 14.4 MeV. • very large picosecond electron pulses of 10 nanocoulombs or 106 A/cm2 • So what did the Fermilab A0 photoinjector do? • studied channeling nearer extreme conditions needed for • a channeling accelerator • Could we make a crystal accelerator or do unique channeling studies? Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  38. electronic plasma decay via interband transitions lifetime: (plasma frequency)-O(fs) excitation of phonons in lattice crystal disorder, fracture, or vaporization lattice dissociation via plasmon absorption lifetime: (ion plasma frequency)-1 vaporization O(10-100 fs) hydrodynamic heating O(1-10 ps) [Livermore] Crystal survivability? Process • excite electronic plasma • tunnel ionization • partial or total lattice ionization Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  39. Andersen96 Dynamic channeling and temperature effects • Intense beam through crystal could blow away electrons in much less than a picosecond • Acts like a larger screening length

  40. Crystal destruction • ACCELERATION • G (gradient) proportional to (n0)1/2, P (power) prop to n0 • for G = 1 GeV/cm P = 105 J/cm3 • 1019 W/cm3 • for O(10 fs) @ 1 GeV/cm LASER 1011 W/gm Belotshitkii & Kumakhov (1979) or 106 a/cm2 for particle beam 1012 W/cm3 ns long pulses 1013 W/cm3 Chen-Noble (1987) fracture threshold O(0.1 ns) ref 16 Skin depth < 0.1 mm LATTICE IONIZED 1015-1016 W/cm2 Chen & Noble (1996)/laser PARTICLE BEAM 1011 A/cm2 Chen & Noble (1987) (crystal OK for 10 fs) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  41. Situation for Fermilab A0 photoinjector • A0 RF GUN FOR COMPARISON • I/cm2 = 10 nc/1 ps in 1 mm2 or 106 A/cm2 (OK driver @ 1GeV) • A0 LASER FOR COMPARISON • 10 W/cm3 slap ruptured (continuous, 1015W/cm3 for 10 fs) • 109 W/cm2 damage on lens • 1018 W/cm2 1 Joule on 10 μm spot in 1 ps (OK driver) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  42. Faraday cup Spectrometer magnet Fermilab A0 experiment Detector: calcium tungstate ICT goniometer S1 Detector 1 m ICT Ne = 5*1010 or 10 nC peak, ε typically 10 mm*mrad, 10 ps R. Carrigan, et al. Phys. Rev. A68, 062901 (2003) Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  43. Planar and axial scans random Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  44. Summary of high charge measurements conjectural σb is O(0.5 mm), length = > 7 ps (s) Peak n/cm2 is 1013 electrons/cm2 I/cm2 = 105 A/cm2 flat is not ruled out Fermilab Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  45. The Future Beyond the Fermilab A0 Experiment • get into 10 fs regime • ne 103 to 105 larger (small beam size important) • higher energy might be better for channeling, beam size • But new experimental geometry, channeling approaches needed Possibilities: SLAC E164 geometry for channeling radiation at 30 GeV Livermore Toronto – studying laser melting with sub picosec electron diffraction Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

  46. Summary • Tevatron crystal collimation has been a big success • puzzle concerning apparent deflection angle • improvements ahead! • Channeling • Fliller-Still shoulder is probably volume reflection • understand scaling with p, Θb? • Negative particles, leptons? • Radiation damage • extrapolation to 7 GeV, very intense beams Issues in channeling collimation Legnaro National Laboratory D. Carrigan http://imapserver1.fnal.gov/~carrigan/ March 8, 2006

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