Crystal collimation at CERN

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Nov 15, 2013 (3 years and 11 months ago)

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Crystal collimation at CERN
Alexei Sytov,Victor Tikhomirov
Belarusian State University,
Institute for Nuclear Problems
Minsk, Republic of Belarus
Gomel July 29, 2013
Recent progress
in crystal application
for beam handling
at CERNand FNAL
Outline
Crystallcollimation idea
UA9 collimation experiment and the role of crystal
miscut
Multiple Volume Reflection effectand its amplification
by channeling effect
Channeling capture increase by the crystal cut and its
application to beam transfer at FNAL
An idea of crystal accelerator
Conclusions
-8-4048
-8
-4
0
4
8
y/
σ
y
x/σx
However luminosity increase will
intensify the beam haloformation
Halo sources:

beam physics and operational instabilities
–intra beam scattering
–scattering with residual gas
–synchrotron radiation
–collective instabilities

Collimationis used to scrape the halo
How it must look at the LHC
crystal
Proton
absorption
Crystals improve collimation efficiency
Crystalsare used in either channeling
orvolume reflectionregimes
Newest results
on crystal assisted
collimation
by Alexei Sytov
with Alexei Sytov
INP, BSU, FNAL, CERN
Deflection particles by bent crystal at 7 TeV
ChannelingVR
Dechanneling+
amorphous
Nuclear scattering
Comparison with CERN simulations I
The difference is considerable!
Exit through
crystal lateral surface + VR
Channeling
Dechanneling+ amorphousNuclear scattering
Ionization losses for 7 TeV
Comparison with CERN simulations II
The difference is essential !!!
It looks like
presently used
CERN and FNAL
simulation tools can be
considerably improved
First experiment on crystal assisted collimation at CERN
Background reduction dependence
on crystal collimator orientation
channeling
VR
Unexpectedly low collimation efficiency of channeling
“Miscut
problem”
“незамеченное”проявлениемиската
z
θ s
θ c
θ m
ϕ
δ
0
z
e
l
Δ
z
x
x
c
Δ
x
s
(0)
θ
x
e
θ s
θ, μ
m
rad
δ, Α
o
13579
0
50
100
150
200
250
300
Effective crystal pass vsmuscutangle and diffusion step in UA9
UA9 experiment was conducted in the most unfavorablesituation!
-300-200-1000100200300
0
2
4
6
8
θ m,
μrad
P
r
,10
-3
Small miscutangle can drastically improve the situation
-1000010002000
0
20
40
60
80
N
am
/N
r
(
θ
inc
=0,
θ
mc
)
θ
mc
, μrad
120 GeV 6.67m 1mm
-200-1000100200
20
40
60
80
θmc, μrad
N
am
/N
r
(
θ
inc
=0,
θ
mc
)
The difficulties of the UA9 experiment interpretation
are explainedin great extend by a miscutrole
Nuclear reaction rate suppression degree
vscrystal orientation
Is crystal
collimator
miscutso
important for
the LHC?
0.00.20.4
0
2
4
SPS
<|θ|>,
μrad
(1/N)dN/d
θ
,1/
μ
rad
0.00.51.01.52.0
0.0
0.5
1.0
LHC
(1/N)dN/d
θ
,1/
μ
rad
<|θ|>,
μrad
Proton distributions in incidence angle
in UA9 experiment and in the LHC
0.00.20.4
0
2
4
SPS
<|θ|>,
μrad
(1/N)dN/d
θ
,1/
μ
rad
0.00.51.01.52.0
0.0
0.5
1.0
LHC
(1/N)dN/d
θ
,1/
μ
rad
<|θ|>,
μrad
Proton distributions in incidence angle
in UA9 experiment and in the LHC
1000-fold difference!
10-4
10-2
100
0.01
0.1
1
10
100
<
Δ
>,
μ
m
δ
,
μm
UA9
LHC
”Miscutproblem”is not essential for the LHC,
on the opposite to UA9 experiment
Crystal
collimator
miscutis
not important
for the LHC!
Outline
Crystallcollimation idea
UA9 collimation experiment and the role of crystal
miscut
Multiple Volume Reflection effectand its amplification
by channeling effect
Channeling capture increase by the crystal cut and its
application to beam transfer at FNAL
An idea of crystal acceleration
Conclusions
Volume Reflection prediction
A.M.Taratinand .A.Vorobiev
Phys. Lett. A119 (1987) 425, NIM B26 (1987) 512
Large acceptance however
small deflection
Comovingreference frame
rYz
rotates with the normal bent
axisdirection when a particle moves through the crystal.
Horizon projections of the angles of reflectionfrom different skew planes
sum upgiving rise to the MVROC effectwhile the vertical angles of reflection
from symmetric skewplanes, like (-101) and (0-11), mutually compensate
.
Reflection from different crystal planes
increases VR angle about 5times
Reflection angles from planes of
one crystal vsbending radius
37
37
First MVROC observation
W. Scandale et al, PLB 682(2009)274
MVROC indeed increases reflection angle 5 times
MVR
is better suited
to remove the “large angle”
halo fraction than channeling
Main effects of beam losses at the LHC*
Main effects of beam losses at the LHC*
Effect
Beam life time, h
Inelastic scattering in IP
108
108
70
41
Elastic scattering in IP
310
197
Diffractive scattering in IP
539
Inelastic scattering on residual gas
129
101
Elastic scattering on residual gas
459
*
*M. Lamont, LHC Project Note
375
Beam profile and angular divergence
for channeling
Beam profile at large σdue to
elastic nuclear scattering on the
residual gas
Average angular divergence vsimpact
parameter for different beam edges
Channeling zone
Conclusion:
The angular divergence is much larger
than the critical angle of capture in the
channeling regime. So, the channeling
effect is not applicable for the LHC case.
-2002040
0.00
0.03
0.06
0.09

drastic MVR angular divergion increase by channeling


(1/N) dN/d
θ
y
,
μ
rad
-1
θ
x, μrad
δθ
X = 3.56 --> 13.5 μ
rad
-20-1001020304050
-40
-30
-20
-10
0
10
20
30


MVR + Channeling
θ
y
,
m
rad
θx, mrad
-20-1001020304050
-40
-30
-20
-10
0
10
20
30


nearly pure MVR

θ
y
,
m
rad
θx, mrad
-20-1001020304050
-40
-30
-20
-10
0
10
20
30


MVR + Planar Channeling vs Axial Channeling
θ
y
,
m
rad
θx, mrad
Comparison Axial Channeling
-2002040
0.00
0.02
0.04
0.06
2

(1/N) dN/d
θ
y
,
m
rad
-1
θx, μrad

7 TeV p MVR and Axial Channeling in SI
lcr=5mm,
δθX0=4μrad
MRV R=70m,
θx,y=30,17.3
μrad
AxCh R=700m,
θx/y=0μrad
δθX=13.5/3.71
X
Comparison with Axial Channeling
Outline
Crystallcollimation idea
UA9 collimation experiment and the role of crystal
miscut
Multiple Volume Reflection effectand its amplification
by channeling effect
Channeling capture increase by the crystal cut and its
application to beam transfer at FNAL
An idea of crystal acceleration
Conclusions
Fermilab
Fermilab
, Accelerator Physics Center (APC)
, Accelerator Physics Center (APC)
Vladimir Shiltsev
Director of Accelerator Physics Center
at Fermi National Accelerator Lab
Nikolai Mokhov
Head of the Energy Deposition
Department in the Accelerator Physics
Center
Beam extraction from the Recycler Ring*
Beam extraction from the Recycler Ring*
Crystal and beam
Crystal and beam
parameters**:
parameters**:
E = 8
E = 8
GeV
GeV
Crystal length = 1mm
Crystal length = 1mm
Crystal thickness = 1mm
Crystal thickness = 1mm
Bending angle = 0.5mrad
Bending angle = 0.5mrad
*
*
V.
V.
Shiltsev
Shiltsev
, FNAL,
, FNAL,
No. DE
No. DE
-
-
AC02
AC02
-
-
07CH11359;
07CH11359;
**A.I. Drozhdin, FNAL,
No. DE-AC02-
07CH11359.
Possible application:
Possible application:
Extraction of
Extraction of
very intensive beam
very intensive beam
for:
for:
Neutrino experiments
Neutrino experiments
(
(
ArgoNeuT
ArgoNeuT
,
,
MINERvA
MINERvA
,
,
MiniBooNE
MiniBooNE
, MINOS,
, MINOS,
NOvA
NOvA
, LBNE)
, LBNE)
Experiments with
Experiments with
muons
muons
(Mu2e, MICE)
(Mu2e, MICE)
The capture probability increase bycrystal cut
V.V.Tikhomirov, JINST, 2(2007)P08006
beam
cut
crystal
z1
z2
z3
0
x
y
z
Channeling fraction increase by the cut
The cut increases channeling fraction from 85 to 99%
with Alexei Sytov
INP, BSU, FNAL, CERN
Cut modification for Recycler Ring
Cut modification for Recycler Ring
Phase space at the crystal entrance
(the first crystal hit)
with cut
with-
out cut
Channeling efficiency vs
R.M.S. incident angle
Phase space at the beam Dump
(without cut)
Phase space at the beam Dump
(with cut)
Outline
Crystallcollimation idea
UA9 collimation experiment and the role of crystal
miscut
Multiple Volume Reflection effectand its amplification
by channeling effect
Channeling capture increase by the crystal cut and its
application to beam transfer at FNAL
An idea of crystal accelerator
Conclusions
Change of HEP acceleration paradigm by D.V. Shiltsev
Some “resonance”at 127.5 GeVwas found at CERN in 1986
BelkacemA. etal.// Phys. Lett. 1986. Vol. B177. P. 211.
Eddectof radiativecoolingpredicted in
BaryshevskiiV. G., DubovskayaI. Ya.Phys. Lett. A62 (1977)45.
Explains the Belkacempeak in
TikhomirovV. V.PLA. 125(1987)411, NIM. B36(1989)282.
Conclusions
Simulation tools used for crystal collimation need to be
considerably improved
UA9 collimation experiment difficulties can be
explained by the influence of crystal miscut
However crystal miscutis not “dangerous”for the LHC
Multiple Volume Reflection effectis better suited for the
“large angle”halo fraction collimationand can be
additionally amplified be channeling effect
Channeling capture increase by the crystal cut can be
applied to beam manipulation at FNAL acc. complex
“Crystal accelerator”is possible due to radiativecooling