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

5. Measurements of PXR yield dependence on particle chargewith protons and Pb ions

4. Study of nuclear interaction probability in crystals

3. Study of short crystals – crystal mirror and scatterer

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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

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 Rc

for 450 GeV/c – about 7 m

For parallel sequence of crystalsAngular acceptance = bend angle α - N×θvr

Volume reflection angle θvr ≈ 11 µrad

With N=10 and α=200 µrad and L=1 mm

Acceptance = 100 µradDeflection = 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 θc/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 angleθo < 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 2012---------------------------------------------

It is difficult to find the crystal orientation

Step of angular scan should be ≤ 5 µradwith 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 θc/2=5 μradCut of horizontal coordinates allow to observe fraction 2

which should be deflected by θc

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/(2u1

2)), 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

Atomic density along trajectories − channeling and volume reflection--------------------------------------------------------------------

Potential averaged along the planes governs particle trajectoriesAveraged 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 tangencypoint averaged density N > Nam (27%)

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

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

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

Background Fin(BG) was determined by measurementswithout crystal

Interaction frequency Fin=N12(A>Ab)/No

Interaction probability – Pin=(Fin-Fin(BG))/F12

Coincidence frequency F12 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 primariesmay 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 3rd 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

Chan

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Chan

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scan run 629

background rate

PXR yield dependence on particle charge-----------------------------------------------

Crystal 2×2×0.5 mm3

for particles with pz=400 GeV/c

protons, γ=400 Pb ions, γ=158

X-angle width ± 50 mrad

Y-angle width ± 100 mrad