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Possible measurements with crystals in NA -------------------------------------------- PowerPoint Presentation
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Possible measurements with crystals in NA --------------------------------------------

Possible measurements with crystals in NA --------------------------------------------

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Possible measurements with crystals in NA --------------------------------------------

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  1. Possible measurements with crystals in NA -------------------------------------------- 1. Test of single crystals for the SPS and LHC beam collimation 2. Test of multi-strip crystals for the SPS beam scraping --------------------- 3. Study of short crystals – crystal mirror and scatterer 4. Study of nuclear interaction probability in crystals 5. Measurements of PXR yield dependence on particle charge with protons and Pb ions

  2. Test of single crystals for the SPS and LHC -------------------------------------------- 1. Test and correction of the crystal bend angle and torsion It should be ≤ 1 µrad/mm a) Crystals with different lengths for the SPS b) Crystals for the LHC (3-4 mm, 50 µrad) 2. Crystals with decreased dechanneling a) Crystals with a slot near its entrance (idea of Tikhomirov) b) Crystals with decreasing curvature produced by IHEP

  3. Test of multi-strip crystals for the SPS beam scraping -------------------------------------------- Scraping of the SPS beam halo 7 σ → 3σ Change of beam envelope direction (α/β)× 4σ≈80 µrad Test of deflection angle and acceptance for multi-reflections Optimal radius for VR is about 10 Rc for 450 GeV/c – about 7 m Volume reflection angle θvr≈ 11 µrad For parallel sequence of crystals Angular acceptance = bend angle α - N×θvr With N=10 and α=200 µrad and L=1 mm Possible parameters: Acceptance = 100 µrad Deflection = 100 µrad

  4. Studies with thin crystals λ/2- reflection ----------------------------------------- For 400 GeV/c with the crystal length λ/2=28 µm orientation angle θc/2=5 µrad Angular cut ± 1 µrad Angular cut ± 4 µrad

  5. Studies with thin crystals λ/4– potential scattering ---------------------------------------------- For parallel beam of 400 GeV/c protons L=14 µm L=16 µm Multiple scattering angle θo < 0.5 µrad

  6. Studies with thin crystals ---------------------------- Use of thin central area of a straight crystal 400 µm 29 or 15 µm Proton beam

  7. Such a crystal in H8 beam line ---------------------------------------------

  8. Some sign of the mirror effect in run 2012 --------------------------------------------- It is difficult to find the crystal orientation Step of angular scan should be ≤ 5 µrad with high statistic to apply the angular cut

  9. Bent crystal with λ/2 bump at its entrance --------------------------------------------- Crystal alignment is realized by the deflection observation for channeled fraction 1 Then the crystal orientation is changed by θc/2=5 μrad Cut of horizontal coordinates allow to observe fraction 2 which should be deflected by θc

  10. Probability of nuclear interactions − atomic density ------------------------------------------------- For a substance with atomic density N and length L − Pin=σinNL For interaction of 400 GeV/c protons with Si nuclei in Glauber approach σin = 0.506 b Atomic density in Si − N=0.05×10-24 cm-3 with L = 2 mm → Pin=0.506% Thermal vibration of atoms around the plane position gives the atomic distribution N(x) ~ exp(-x2/(2u12)), u1=0.075Å There are no atoms in the middle of channel At the plane position − N(0)=10 Nam Interactions occur near the planes “nuclear corridor” width 6u1< 0.25 dp (110) Si channel width dp=1.92 Å

  11. Atomic density along trajectories − channeling and volume reflection -------------------------------------------------------------------- Potential averaged along the planes governs particle trajectories Averaged density is larger than Nam when transverse energy Ex is close to Uo for channeled particles with large amplitudes and for above-barrier particles At VR in bent crystals near tangency point averaged density N > Nam (27%)

  12. Study of R-dependence in volume reflection ---------------------------------------------- For ions with pz=120 GeV/c in (110) Si crystal of 2 mm long Parallel beam Gaussian, θcut=10 µrad Probability increase by 27% and 23% for R=40m

  13. Study of angular dependence in a straight crystal ---------------------------------------------- For ions with pz=120 GeV/c in (110) Si crystal of 2 mm long Parallel beam Gaussian, θcut=10 µrad Probability increase by 36% and 25% for θo≈θc

  14. Experiment with 400 GeV/c protons at H8 (2009) ------------------------------------------------------------ Two 10×10 cm2 scintillation detectors − 60 cm behind the crystal Trigger – scintillation detector upstream The events registered for incoming tracks passed through the crystal with coincidence in both detectors Interaction frequency Fin=N12(A>Ab)/No Background Fin(BG) was determined by measurements without crystal Interaction probability – Pin=(Fin-Fin(BG))/F12 Coincidence frequency F12 was determined by simulation

  15. Use of tracking system to register inelastic events in crystal ------------------------------------------------------------ The events registered for incoming tracks passed through the crystal with more than 2 hits in plane 3 Background due to around-beam particles arriving in-time with primaries may be reduced using veto counter after plane 2 suggestion of Mark

  16. n>1 event rates during angular scans (629) and high stat runs (630) • choosing events with (n>1) hits on both X&Y sensors in 3rd plane • plot rate as a function of impact angle in X of incoming track on crystal surface • - (goniometer angle + theta_in + torsion corrections) scan run 629 high stat run 630 background rate Volume Reflection Volume Reflection Amorphous Channeling Amorphous Channeling

  17. PXR yield dependence on particle charge ----------------------------------------------- for particles with pz=400 GeV/c Pb ions, γ=158 protons, γ=400 Crystal 2×2×0.5 mm3 X-angle width ± 50 mrad Y-angle width ± 100 mrad