quasimosaic crystals
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Quasimosaic crystals. Yu.M.Ivanov. Elastic quasimosaic (Sumbaev) effect. Studied by Sumbaev in 1957 Resulted in broadening of gamma-ray diffraction peaks from bent quartz plates - PowerPoint PPT PresentationTRANSCRIPT
Quasimosaic crystals
Yu.M.Ivanov
Elastic quasimosaic (Sumbaev) effect
• Studied by Sumbaev in 1957
• Resulted in broadening of gamma-ray diffraction peaks from bent quartz plates
• Caused by bending of the reflecting atomic planes (initially flat and normal to large faces of plate) due to crystal anisotropy
• Depends on choice of
crystallographic plane and orientation angle of plate cutting relative to a normal to the chosen crystallographic plane
Figure from article: O.I.Sumbaev, Reflection of gamma-rays from bent quartz plates, Sov. JETP 32(1957)1276
Quasimosaic effect in silicon
• Calculations of deformed crystal plate done by V.M.Samsonov (Preprint No. 278, LIYaF AN SSSR, 1976).
– Resulted in predictions of elastic quasimosaic effect for some other quartz and silicon plate orientations
– Large elastic quasimosaicity for (011) plane of silicon predicted
• Zero result in the first experiments in 1999
• New calculations using Samsonov approach and new measurements:
- (111) plane, not (011) - published in JETP Letters 81, 99, 2005
Figure from article: V.M.Samsonov and E.G.Lapin, On some possibilities and pequliarities of a curved crystal use in crystal diffraction instruments, Preprint No. 587, LIYaF AN SSSR, 1980
Elastic quasimosaic in dependence on cut angle for Si
(111) plane
T – thickness of plate
k9 – deformation coefficient
= 2k9 T , where
Plate bending radius R = 1 m
( formula taken from V.M.Samsonov, E.G.Lapin, Preprint No. 587, LIYaF AN SSSR, 1980 )
Silicon cuts
Cut without quasimosaic
Cut with quasimosaic
Oriented ingot
φ
Rocking curves for Si plate with quasimosaic
before and after bending.
Quasimosaic effect in Si with X-rays
Rocking curves for Si plate without
quasimosaic before and after bending.
Shape of bent Si plate with elastic quasimosaic
Bending device
First quasimosaic silicon crystal prepared in 2002 for channeling experiment with 70 GeV protons
Layout of experiment at IHEP in April, 2002
Crystal 1Magnets
Crystal 2
Emulsion 1
S1
S2 S3
Background
Channeled_1
30 m
35 m 4.6 m
Collimator
1.3 m
Emulsion 2
Channeled_2
70 GeVp-beam
5 m
R=3 m
Profile of 70 GeV proton beam passed through the crystal measured with emulsion: superposition of channeling and volume reflection effects
Explanation of the observed picture on emulsions
Proton trajectories crossing the crystal and emulsions in horizontal plane (top view)
Samples 0.3 mm and 2.7 mm with ~0.4 mrad bending angle
Sample 10 mm with ~100 μrad bending angle
Crystals for experiment on extraction of high entensive proton
beam at IHEP
Plane (111)
Length along beam 2.65 mm
Bending angle 400 μrad
Crystal station at IHEP ring
Crystal mounted on station
Result
Beam in the U-70 ring 5.5∙1012 p
Intensity of extracted beam 4.0∙1012 p
Efficiency 70%
Experiment on observation of volume reflection effect with 1 GeV protons
at PNPI, Gatchina
Beam divergence ~ 160 μrad
Beam size ~ 0.8 mm
Critical angle for channeling ~ 170 μrad
Crystal length along beam ~ 30 μm
Bend angle of (111) planes ~ 380 μrad
One of unsuccessful attempts to bend a 30 μm crystal on 20 mm
radius
Bent crystals in bending devices
Check of crystal shape with laser
~1
m
Measurement of bending angle with X-rays
Collimator
Crystal mounted on goniometer
Horizontal profiles of the p-beam vs. crystal angle measured with
PPC
p-beam
reflection
channeling
p-beamCry
sta
l an
gle
, ste
p 6
2.5
μra
d
Channel number, step 200m
Channeling experiment with 400 GeV protons
H8 beam line
FAR_DETECTOR areaCRYSTAL area
QM2
QM2
2 4 6 8 10 120
50
100
150
200
250
300
350
400
Position, mm
Cry
stal
ang
le, m
krad
Crystal QM2
QM2
Channeling angle (68.2 0.4) μrad
Volume reflection deflection (12.7 0.6) μrad
Volume capture ε (1.8 0.7) %
QM1
QM1
2 4 6 8 10 120
20
40
60
80
100
120
140
160
180
200
Position, mm
Cry
stal
ang
le, m
krad
Crystal QM1
QM1
Channeling angle (77.0 0.4) μrad
Volume reflection deflection (11.6 0.8) μrad
Volume capture ε (2.6 0.8) %
QM2+QM1
QM2+QM1
2 4 6 8 10 120
50
100
150
Position, mm
Cry
stal
ang
le, m
krad
Crystal QM1-QM2
QM2+QM1
Channeling angle
Volume reflection deflection (23.4 0.7) μrad
Volume capture ε (5 1) %
QM3
QM3
2 4 6 8 10 120
20
40
60
80
100
120
140
160
180
Position, mm
Cry
stal
ang
le, m
krad
Crystal QM3
QM3
Channeling angle (72.7 0.8) μrad
Volume reflection deflection (11.9 0.7) μrad
Volume capture ε (5 1) %
QM4
QM4
2 4 6 8 10 120
20
40
60
80
100
120
140
160
180
Position, mm
Cry
stal
ang
le, m
krad
Crystal QM4
QM4
Channeling angle (120.0 0.4) μrad
Volume reflection deflection (12.7 0.5) μrad
Volume capture ε (4.4 0.7) %
Design: sequence of quasimosaic crystals cut from a
single initial plate
p
1 Si plate 0.3 x 30 x 60 mm3
12 Si plates 0.3 x 8 x 14 mm3
Check of plate wedging with optical goniometer
Prototype assembly from 5 plates
0
1000
2000
3000
4000
5000
6000
7000
14,85 14,90 14,95 15,00 15,05 15,10 15,15 15,20 15,25
Check with narrow X-ray beam
ΔN
Δθ≈0.017x ΔN μrad
Δθ < 40 μrad
X, mm
N,
coun
ts
ΔX
N1
N2
Δθ
ΔN=N2-N1
ΔX
Need to provide or to compensate plate wedging
Realization with evaporation technique
Al-layer of 0.14 μm thickness
Δθ = 0.14 μm / 12 mm = 12 μrad
Further steps
• to improve prototype assemly for experimental run in May’07 at CERN
• to prepare larger plates and assemble them for experiments at CERN and IHEP in the Fall’07