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

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

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

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

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 θ o < 0.5 µrad

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

Such a crystal in H8 beam line

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

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 θ c /2=5 μrad Cut of horizontal coordinates allow to observe fraction 2 which should be deflected by θ c

Probability of nuclear interactions − atomic density For a substance with atomic density N and length L − P in = σ in NL For interaction of 400 GeV/c protons with Si nuclei in Glauber approach σ in = b Atomic density in Si − N=0.05× cm -3 with L = 2 mm → P in =0.506% Thermal vibration of atoms around the plane position gives the atomic distribution N(x) ~ exp(-x 2 /(2u 1 2 )), u 1 =0.075Å There are no atoms in the middle of channel At the plane position − N(0)=10 N am Interactions occur near the planes “nuclear corridor” width 6u 1 < 0.25 d p (110) Si channel width d p =1.92 Å

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

Study of R-dependence in volume reflection For ions with p z =120 GeV/c in (110) Si crystal of 2 mm long Parallel beamGaussian, θ cut =10 µrad Probability increase by 27% and 23% for R=40m

Study of angular dependence in a straight crystal For ions with p z =120 GeV/c in (110) Si crystal of 2 mm long Parallel beamGaussian, θ cut =10 µrad Probability increase by 36% and 25% for θ o ≈θ c

Experiment with 400 GeV/c protons at H8 (2009) Two 10×10 cm 2 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 Background F in (BG) was determined by measurements without crystal Interaction frequency F in =N 12 (A>A b )/N o Interaction probability – P in =(F in -F in (BG))/F 12 Coincidence frequency F 12 was determined by simulation

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

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 3 rd plane plot rate as a function of impact angle in X of incoming track on crystal surface - (goniometer angle + theta_in + torsion corrections) high stat run 630 Channeling Volume Reflection Amorphous Channeling Volume Reflection Amorphous scan run 629 background rate

PXR yield dependence on particle charge Crystal 2×2×0.5 mm 3 for particles with p z =400 GeV/c protons, γ=400 Pb ions, γ=158 X-angle width ± 50 mrad Y-angle width ± 100 mrad