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CRYSTAL COLLIMATION EXPERIMENT AT THE TEVATRON

Accelerator Advisory Committee. Fermilab. CRYSTAL COLLIMATION EXPERIMENT AT THE TEVATRON. Nikolai Mokhov Fermilab. Accelerator Advisory Committee Fermilab, Batavia, IL August 8-10, 2007. OUTLINE. Introduction Crystal Channeling and Collimation Studies at Tevatron

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CRYSTAL COLLIMATION EXPERIMENT AT THE TEVATRON

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  1. Accelerator Advisory Committee Fermilab CRYSTAL COLLIMATION EXPERIMENTAT THE TEVATRON Nikolai Mokhov Fermilab Accelerator Advisory Committee Fermilab, Batavia, IL August 8-10, 2007

  2. OUTLINE • Introduction • Crystal Channeling and Collimation • Studies at Tevatron • Bent Crystal Collaboration: • Towards Crystal Collimation at LHC • Proposal for Experiment at Tevatron • Tevatron Study Plan • Contributions, Matching Efforts, LARP Support • Summary Crystal Collimation Experiment - N.V. Mokhov

  3. INRODUCTION (1) • Bent-crystal technique is well established for extraction of high energy hadron and heavy-ion beams from accelerators. Such an extraction was successfully demonstrated for up to 900 GeV beams at JINR, IHEP, CERN and Fermilab, and measurements confirmed its high efficiency predicted in simulations. • The promise of bent crystal channeling technique for beam halo collimation at high-energy colliders was recognized at the SSC in 1991. A bent crystal, serving as a primary element, should coherently bend halo particles onto a secondary collimator. First successful measurements were performed at IHEP in 1998 for 1 to 70 GeV protons. • Based on realistic modeling (1999, 2003), it was proposed to implement a bent crystal into the Tevatron collimation system. First measurements (2005) were quite encouraging. Crystal Collimation Experiment - N.V. Mokhov

  4. INTRODUCTION (2) We propose a 2-year LARP project directed towards high-performance crystal-based collimation at the LHC, Phase-II, utilizing unique possibilities provided at the Tevatron at the end of the experimental collider run (from now to 2009). LARP and International Bent Crystal Collaboration are supportive and enthusiastic about these vital accelerator studies using the Tevatron and CERN SPS beams. Crystal Collimation Experiment - N.V. Mokhov

  5. CRYSTAL CHANNELING • Channeling/Dechanneling • Critical angle c = (2U/pv)1/2 • Bending: Ueff = U(x) – pvkx, k=1/R • Dechanneling due to MCS & bending --> LD= 0.9m x p (TeV/c) --> LB = LD (1-F/3)2, F=3k/kc, kc~Z2/pv (well ‘disappears’) Channeling probability Extremely high interplanar electric fields from screened nuclei (a few GV/cm) allow to bend and focus (cylindrically-shaped crystal exit) high-energy beams with very short crystals. Interplanar spacing ~ 2Å. It was shown at CERN and IHEP that crystals are heat- and radiation-resistant. Deflection efficiency deteriorates at about 6%/1020 p/cm2 rate Crystal Collimation Experiment - N.V. Mokhov

  6. Two-Stage Collimation with Target and Crystal Courtesy R. Assmann Crystal Collimation Experiment - N.V. Mokhov

  7. 1 to 70 GeV Crystal Collimation at IHEP (1998) Also crystal extraction, focusing, characterization, radiation damage and heating Crystal Collimation Experiment - N.V. Mokhov

  8. Crystal Collimation at RHIC (2003) • Measured bent crystal channeling • for gold ions was 26% • Crystal channeling worked as • expected once lattice functions and • halo distribution were understood • Collimation was unsuccessful because lattice was not optimal in • area of collimator and IP (high • angular spread at crystal, phase • advances): crystal caused increased • background in experiment Crystal Collimation Experiment - N.V. Mokhov

  9. BENT CRYSTAL FOR TEVATRON COLLIMATION • Biryukov, Drozhdin, Mokhov (PAC99) have shown – and later calculations (2003) confirmed - that implementation of a silicon bent crystal instead of amorphous primary collimators (targets), can improve the Tevatron collimation efficiency – defined then as a reduction of beam loss in CDF - by a factor of: • 2 with one (horizontal) target replaced, and with contribution from beam-gas scattering unsuppressed • 3 with one (horizontal) target replaced, and with contribution from beam-gas scattering suppressed • up to a factor of 4 to 6 for the 2-plane collimation. Crystal Collimation Experiment - N.V. Mokhov

  10. Collimator Scattered trajectories Target @ ~5s Collimator @~6s WHERE TO INSTALL CRYSTAL Install Crystal Collimator at E0 to replace a Tungsten Target and utilize the rest of the collimator 2 stage System. Proton Set 1 D49 Tar, E03 & F172 2nd Proton Set 2 D171Tar, D173 & A0 Pbar Set 1 F49 Tar, F48 & D172 Pbar Set 2 F173 Tar, F171 & E02 Crystal Collimation Experiment - N.V. Mokhov

  11. Beam Direction 5mm REPLACING PRIMARY COLLIMATOR WITH CRYSTAL AT 5 s The primary H-collimator (D49 tungsten L-shaped target) is before the dog-leg at bH=96 m, D=2.3 m. The crystal is in the dog-leg at bH=73 m, D=2.5 m, about the same phase advance wrt secondary collimators. Channeled and scattered protons on E0 secondary collimator 1. 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, 1mm V critical angle 5 mrad bending angle 439 mrad miscut angle 465 mrad Crystal Collimation Experiment - N.V. Mokhov

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

  13. 980-GEV BEAM CHANNELING: DATA vs THEORY Oct. 6, 2005 By Dean Still Jan. 31, 2006 With E03H out, LE033C BLM is proportional to nuclear interact. rate in crystal Channeled beam “peak” width is 22±4 mrad (rms) Crystal Collimation Experiment - N.V. Mokhov

  14. COMPARING EFFECTS OF PROTON HALO LOSSES FOR BENT CRYSTAL AND TUNGSTEN TARGET Crystal aligned at peak (118 mrad) CDF E03 BLM PIN • Using the crystal: • The secondary collimator can remain further (1 mm or so) from the beam thus reducing impedance. • Almost a factor of 2 better reduction of CDF losses achieved a half a ring (2 miles) downstream (in agreement with modeling) !!! Crystal Collimation Experiment - N.V. Mokhov

  15. VOLUME REFLECTION This work at RHIC/FNAL uncovered the importance of the long neglected coherent crystal effect predicted at Tomsk two decades ago, volume reflection. • Contrary to channeling, which is extremely sensitive to beam-crystal alignment (10-urad level in Tevatron), VR is a much higher acceptance effect: promising as a collimation tool for TeV beams as well as for Recycler (Project X) and a muon collider! • The IHEP/PNPI/RHIC/FNAL investigation has helped to spark interest in the volume reflection process including a fast track investigation in the H8 400-GeV p beam at the CERN SPS in the fall of 2006 (W. Scandale et al.). That precision investigation has produced a spectacular confirmation of volume reflection (97% efficiency) and also developed tools to characterize crystals that could potentially serve as LHC collimators. Crystal Collimation Experiment - N.V. Mokhov

  16. CRYSTAL COLLIMATION COLLABORATION • Encouraged by these results and recent crystal developments, and aiming at a high-performance collimation vital for the LHC, crystal collimation collaboration was formed in December 2005: • Better crystals characterized mechanically, optically and with beams • Beam tests at the SPS extracted beams (~400 GeV) • Support crystal collimation expt at Tevatron to guarantee its success • Crystal collimation experiment at SPS (?) • A consensus on the Tevatron experiment was reached: • The old crystal needs to be replaced with the optimal characterized one with a bending angle of about 0.15 mrad. • Dedicated beam diagnostics must be implemented to see the deflected beam (phosphorous screen, crawling wire, etc.), in addition to excellent global beam instrumentation in Tevatron. • The characterization and knowledge of the additional crystal parameters (miscut angle, surface perfection) are vital for success of the studies. The crystal preparation, etching, characterization and beam tests will be done for INFN and INTAS money. Crystal Collimation Experiment - N.V. Mokhov

  17. INSTALLING NEW CRYSTAL IN TEVATRON • Questions with the BNL/IHEP crystal: too long? too large bending angle? Expect two-fold improvement with O-shaped strip. • A custom crystal was prepared and characterized at Protvino and Ferrara: 3-mm L, 1-mm W, 150 mrad bend. angle, strip, chemical etching. • It replaced the old one during the 2006 Tevatron long shutdown. Crystal Collimation Experiment - N.V. Mokhov

  18. TESTS AT TEVATRON IN 2007 (1) Goal for studies in the Tevatron by the Collaboration was to use end of stores (EOS) to compare the proton halo reduction at the  CDF for existing 2-stage collimation with  the D49 tungsten target and the bent crystal (BC-strip): 1) Use EOS to compare W target and BC-strip with losses CDF on C:LOSTP and diamond detectors by using collimators E03H and F172H to remove channeled beam.  All other collimators are pulled out (with exception of A48V used for kicker prefire protection).  This may take multiple EOS to determine angle and details for channeling. 2) Use a dedicated proton only store (4-8 hours) at 980 GeV and repeat item (1) for channeled beam. 3) Use a dedicated proton only store(4-8 hours) at 980 GeV and repeat item (1) for volume-reflected beam.  Use E02H and find out if volume reflected beam ends up at F17. Crystal Collimation Experiment - N.V. Mokhov

  19. TESTS AT TEVATRON IN 2007 (2) In Jan-Feb 2007 in EOS studies, the entire angular range has been scanned at 2 urad steps and have found NO channeling. It was then found that there was a problem with the alignment of the crystal.  It was misaligned by ~14mrad.   The crystal was realigned and scans continued on May 25, 2007: The data looked like channeling was demonstrated with new crystal. But the size of the volume reflected region should be proportional to the bend angle of the crystal (150urad).  The data showed ~ 320urad which is too big. Therefore, an additional period on July 9 was requested to produce a finer 1-urad scan of this region. However, channeling could not be observed,  not clear why. 320 urad 150 urad May 26, 2007 by Dean Still Crystal Collimation Experiment - N.V. Mokhov

  20. PROPOSAL FOR EXPERIMENT AT TEVATRON Aiming at the high-performance collimation vital for the LHC, considering a unique possibility provided by the Tevatron collider (before its shutdown for collider physics in 2009), and having already established fruitful collaborative efforts on crystal characterization, tests and use for collimation, We propose a LARP Crystal Collimation Project to conduct crucial studies in the time frame required by the LHC plans. Crystal Collimation Experiment - N.V. Mokhov

  21. TEVATRON MEASUREMENT GOALS • Channeled beam* • Volume-reflected beam* • Beam loss and radiation levels downstream of the crystal setup • Beam loss rate in the B0 (CDF beam-halo monitors) for 1- and 2-plane collimation • Possible deformation of the crystal or crystal holder during a vacuum baking process. • Attempt to study crystal damage: shock and integrated dose. • (*) Add dedicated beam diagnostics • Quantitative measure of collimation efficiency improvement is reduction of (3) – primary LHC concern – and (4). • We are going to simulate the deflected beam loss in the Tevatron and LHC (in collaboration with IHEP and CERN colleagues). Consistency with the current secondary collimator and absorber layout is of a concern here: need simulations and optimizations. Crystal Collimation Experiment - N.V. Mokhov

  22. TASKS-2007 (TeV study time: 1 shift = 8 hrs) • Demonstrate channeling with the existing strip crystal or with the ST4 crystal that was characterized in the September 2006 H8 experiment at CERN (by IHEP, CERN & INFN, arrived at Fermilab in March 07). • Confirm the 2005-2006 result that crystal channeling and volume reflections can improve the Tevatron collimation system efficiency. • Perform detailed simulations of collimation system performance with a single strip crystal in the realistic Tevatron lattice for both channeled and volume-reflected beams. • Work out a plan on beam diagnostics improvement and specify new goniometer for 2009 beam studies. Crystal Collimation Experiment - N.V. Mokhov

  23. TASKS-2008 (TeV study time: 1.5 shifts = 12 hrs) • Build improved beam diagnostics system and new Ferrara goniometer. • Develop new strip and multistrip crystals. • Complete EOS and proton-only store angular scans with the crystal chosen in 2007. • Perform detailed simulations for a complete two-plane crystal-based Tevatron collimation system. • Try to perform tests to provide information about the possible deformation of the crystal or crystal holder during a vacuum baking process (up to 200 degrees). • Investigate a possibility for a crystal damage experiment where crystals and instrumentation for assessing dose rates could be placed in the Fermilab beams. Once enough beam is integrated on one crystal, it should be moved back to CERN for H8 beam line characterization. Crystal Collimation Experiment - N.V. Mokhov

  24. GOAL-2009 • Demonstrate efficiency of a well-prepared bent crystal collimation system for 2 planes with channeled and volume-reflected 1-TeV beams at least for two crystal types (single and multi-layer) in comparison with tungsten target results. Crystal Collimation Experiment - N.V. Mokhov

  25. TASKS-2009 (TeV study time: 6 shifts = 48 hrs) • Install New Hardware: • Remove E01 collimator to replace with vertical crystal assembly • Crystal, goniometer, instrumentation tunnel installation • 2. 150-GeV Beam Tests (1.25 shifts): • Test BLM response, inchworm and channel the beam • Debug all motion control and instrumentation • 3. 980-GeV End-of-Store Beam Studies (4.75 shifts): • Find and characterize channeling (V-plane) • Collimate channeled beam (V, H) • Collimate volume-reflected beam (V, H) • Attempt full channeled collimation (V&H) • Attempt full volume-reflected collimation (V&H) • Repeat with another crystal type Crystal Collimation Experiment - N.V. Mokhov

  26. COLLABORATION CONTRIBUTIONS • CERN: Experiments at H-8 beamline, manpower, beam characterization of “TeV” crystals to guarantee success at Tevatron • INFN: manpower, crystal preparation, etching, mechanical and optical characterization, goniometer (100 keuro) • IHEP: manpower, crystal preparation, etching, characterization; simulations, new crystal technologies • PNPI, JINR: manpower, theory, simulations, beam diagnostics, DAQ, new crystal technologies • KEK: manpower, beam diagnostics • Fermilab*: crystal and other hardware implementation in the Tevatron, • EOS beam time, beam diagnostics, DAQ, simulations, deformation/damage tests • SLAC*, BNL*: manpower, beam diagnostics, deformation and damage tests • (*) As a part of the LARP project Crystal Collimation Experiment - N.V. Mokhov

  27. CERN SUPPORT TO THIS PROPOSAL • Ralph Assmann: "In view of the possible limitations for conventional collimation like implemented for the LHC start-up, CERN is presently investigating possible paths to enhancing the efficiency of the LHC cleaning systems. The use of crystals has been proposed as one possibility for improving collimation. However, a clear demonstration of improved collimation efficiency in an existing storage ring is still missing. • The CERN collimation team therefore fully supports the proposed experimental investigation at the Tevatron. The support will include advice on important experimental observables, participation to beam tests and help for analysis of recorded data. It is our hope and expectation that Tevatron beam tests on crystal collimation provide conclusive data and directly relevant input for decisions on a possible upgrade path for LHC collimation." Crystal Collimation Experiment - N.V. Mokhov

  28. CERN CONTRIBUTION • The experiment H8RD22 approved for 3 runs and a total of 7 weeks in 07 is the biggest part of the effort of CERN. The PhD student of Ralph Assmann is the other strong contribution. Ralph, his student Valentina Previtali and Stefano Redaelli agreed to participate to the FNAL experiment. Walter Scandale and his colleagues are already doing amazing job. Crystal Collimation Experiment - N.V. Mokhov

  29. UNIVERSITY OF FERRARA CONTRIBUTION Ferrara is ready to take the responsibility and the charge of building the goniometer and eventually incorporating the most appropriate crystal. The financial load is estimated to about 100 keuro. Ferrara's officials are asking Walter Scandale to act as the contact-man both towards Fermilab and CERN. Their wish is to proceed in collaboration with IHEP, if possible, also to use the frame of the existing INTAS program. However this is to be clarified at a later stage once the goals will be clear. This is a good news but it requires some additional discussions and work to clarify the deliverables and the time-table. Crystal Collimation Experiment - N.V. Mokhov

  30. IHEP: MULTI-LAYER VR & MULTI-STRIP DEVICE Protvino-Ferrara IHEP offers: 1. Detailed simulations of multi-VR crystal systems for collimation in the Tevatron and LHC. 2. Manufacturing new multi-layer VR crystals, their tests at IHEP and testing at the Tevatron. 3. Push-pull goniometers. 4. CsI scintillator on the collimator. Crystal Collimation Experiment - N.V. Mokhov

  31. IHEP GONIOMETER DESIGN Crystal Collimation Experiment - N.V. Mokhov

  32. DELIVERABLES • Conclusive data and directly relevant input for decisions on a possible upgrade path for LHC collimation: improved collimation efficiency and reduced irradiation of downstream components in a quantitative agreement with corresponding calculations, and quantitative answers to the questions on damage limits and sensitivity analyses. • 2. Crystal technology, process (channeling or volume reflection), hardware (goniometer etc.) & instrumentation most suitable for 2-plane collimation of LHC beams, transferred to CERN. Crystal Collimation Experiment - N.V. Mokhov

  33. LARP SUPPORT This proposal was presented to the LARP Collaboration meeting in April 2007 and was very welcomed at the meeting. It was noted that the timing is right and critical (next year start would be too late). The proposal was supported by the LARP Accelerator System management, DOE Review and approved by the LARP Executive Committee. The FY08 budget request is $0.22M, while for FY09 it is $0.13M. Crystal Collimation Experiment - N.V. Mokhov

  34. SUMMARY • Demonstration of crystal-based collimation by utilizing unique possibilities provided at the Tevatron at the end of the experimental collider run opens doors to: • Possible upgrade path for the LHC collimation system: • enhanced performance • reduced impedance • heavy-ion beam halo cleaning • Possible complementary collimation systems: • Fermilab Recycler in Project X • ILC Beam Delivery System • Muon Collider With all of the above, we are now seeking for the AAC support of this proposal. Crystal Collimation Experiment - N.V. Mokhov

  35. Appendix 1: LHC Phase-II Information Required • Crystals are an interesting advanced technology for Phase 2 of LHC collimation. To evaluate their benefits in detail the following information is required: • Crystal parameters for the highest efficiency for channeling and volume reflection at both injection (450 GeV) and top (7 TeV) proton energies. • Probability spectrum of proton deflections at 0.45 to 7 TeV for all physics processes down to a 10-5 level. • Damage limit of crystals for instantaneous shock beam impact at ~15 MJ/mm2. • Damage limit of crystals for an integrated dose at ~5×1016 p/year at 7 TeV. • Handling of crystals during normal operation at high-power impact. • Number, opening (impedance) and locations of absorbers for extracted and scattered beam. • Sensitivity to beam angle and angular spread in the TeV region. • Requirements for alignment and operational set-up (tolerances, time). Crystal Collimation Experiment - N.V. Mokhov

  36. Appendix 2: Ralph Assmann Comments (04/20/07) (1) • “I would see the following critical components to prove the potential of crystal collimation which was unsuccessfully tried at RHIC: • High energy, low diffusion stored beam to have impacts with small impact parameters (micron-range). Multi-turn collimation is really an edge effect-channeling experiments that hit crystals in the middle are in a very different regime. Fulfilled at TEVATRON and RHIC. • Crystal must have minimized amorphous layer facing the beam and small surface roughness to handle small impacts. Fulfilled at TEVATRON. • For comparison of efficiency a traditional two-stage cleaning system is required. Fulfilled at TEVATRON and RHIC. • Crystals must be complemented by secondary collimators at reasonable phases to catch and absorb the extracted halo. Fulfilled at TEVATRON. • Losses with/without crystals must be measured in critical locations, including the SC magnets directly downstream of the cleaning system (LHC is expected to be limited there and not in the experimental detectors). Some improvement in monitoring is required at TEVATRON in the section after the cleaning section. Crystal Collimation Experiment - N.V. Mokhov

  37. Appendix 2: Ralph Assmann Comments (04/20/07) (2) So there are a number of reasons why TEVATRON could give better results than RHIC. Once the predicted improvement in cleaning efficiency is proven for the first time (what is the prediction?) then crystal-enhanced collimation would in my view move beyond its status of a conceptual idea. There would still be many technical challenges need to be addressed for an LHC implementation but it is a big difference whether we would consider crystal collimation as a technique with proven feasibility or not. TEVATRON is a good opportunity to make progress now. Collimation experiments in the SPS seem very unlikely to me (absence of good two stage cleaning) and crystal tests in the LHC could not be concluded before 2009 or 2010, likely too late to include crystals into the decisions for the LHC collimation upgrade. Crystal collimation is a good example where the US has experimental possibilities that we presently do not have at CERN. Ralph P.S. A thought on the impact on collimator R&D: In my opinion crystals will never replace collimators but complement them and enhance the overall system performance. This means that crystal collimation also requires powerful collimators. R&D on advanced collimators is very important in any case and cannot be compromised. In the end it might be a combination of several improvements that allow us to reach our goals (like often)...” Crystal Collimation Experiment - N.V. Mokhov

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