Transcript Using crystals to facilitate the LHC upgrade

Victor Tikhomirov
Institute for Nuclear Problems
Minsk
Using crystals facilitates
the LHC upgrade
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Outline
The LHC luminosity upgrade
Beam halo scraping by crystals
Volume reflection of particles in bent crystals
Volume reflection amplification by crystal axes
Channeling capture increase by the crystal cut
Conclusions
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The LHC upgrade need
Fifteen years of planning and R&D, followed by
over 10 years of construction, should be followed
by a comparable period of exploitation.
Luminosity upgrade: L  1034 cm2 s 1 10
Energy upgrade:
  7TeV  2
What is better?
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Luminosity upgrade in more effective at M < 3.5 TeV
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Statistics is too low for a clear separation among
possible models at integrated luminosity of 100fb-1
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Thus, the luminosity upgrade
have to be very effective
2 1
L  10 cm s 10
34
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However luminosity increase will
intensify the beam halo formation
8
y/y
4
0
-4
-8
-8
-4
0
x/x
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4
8
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Halo sources:
– beam physics and operational instabilities
– intra beam scattering
– scattering with residual gas
– synchrotron radiation
– collective instabilities
…
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Collimation is used to scrape the halo
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Crystals improve collimation efficiency
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Crystals are used in both channeling
and volume reflection regimes
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Crystals bending
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How it must look at the LHC
crystal
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Proton
absorption
Background reduction by channeling at FNAL
Deflection of channeling protons reduce
ssss than 4 times
the background more
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Volume Reflection prediction
A.M.Taratin and
S.A.Vorobiev, Phys.Lett.
A119 (1987) 425
and
A.M.Taratin and
S.A.Vorobiev, NIM in PR
B26 (1987) 512
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Volume reflection CERN H8-RD22
experiment Sept 2006
channeling
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Volume
capture
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Volume
reflection
Volume reflection by crystal axes
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Axes form reflecting planes
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Protons are reflected from many
crystal plane sets of one crystal
(413)
30
(011)
(154)
(615)
(110)
(132) (121) (231)
(321) (211) (312)
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(413)
(514)
(615)
(101)
VY0
VY(rad)
20
10
(123)
0
(121)
inc

(213)
(121)
111
-60
-40
0
-20
VX(rad) - 
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20
40
VX0
60
Reflection from many crystal planes
increase VR angle 4 times - 1
high- index
16
planes
-X(rad)
(101)  (011)
12
(312)  (132)
(211)  (121)
8
(321)  (231)
4
(110)
0
0
5
10
15
20
R/Rmin
ssss
25
30
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Reflection from many crystal planes
increase VR angle 4 times - 2
-1
dN/dX(rad )
0,4
R=200m, (110) plane
0,3
0,2
100m
0,1
50m
R=200m
0,0
-20
-10
X(rad)
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0
10
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Typical distribution of multiple reflected protons
30
Y(rad)
20
10
0
-10
-20
-30
-20
-10
0
10
20
X(rad)
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30
40
50
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Reflection from
different crystal planes
allows to increase
the volume reflection angle
about 4 times
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The capture probability can be
increased by a plane cut
y
z
x
cut
z3
z2
0
z1
crystal
beam
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Transverse energy reduction by the cut - 1
V, e , eV
v0
Vmax
v1
e
V(x 1)
v2
e
V(x 2)
x0 x1
.
.
x2
.
d .
x, A
The cut diminishes the potential energy
conserving the transverse
kinetic one
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Transverse energy reduction by the cut - 2


0 = 0.25 ch
= 0.10 ch

0
= 0.32ch

0
20
ε, ε ,

eV
25
15
10
5
0
xp d
xp d
0
1
2
0
1
x0, Å
2
xp d
0
1
2
Only 1-2% of protons avoid the transverse
energy reduction
by the cut
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Proton phase space transformation by the cut

/ ch
1.0
a
b
c
1.5 1.0
e
0.5
0.0
-0.5

/ ch
0.5
d
1.0
1.0
x, Å
0.5
0.5
0.0
0.0
-0.5
-0.5
-1.0
-1.0
0.0
0.5
1.0
x, Å
1.5
d
0.0
0.5
1.0
x, Å
1.5
Protons are moved away from the
high nuclearssss
density regions
d
Dechanneling suppression by the cut
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30
Pdech, %
25
20
15
10
5
0
0.0
0.2
0.4
0.6
0.8
1.0

, rad
rms
The cut decreases the dechanneling
probability from 18 to 1-2%
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A pair of crystals with cuts bent in orthogonal
planes allows to deflect 99.9% of protons
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The cut allows to increase
the proton (nuclei) deflection
efficiency and to decrease the
accompanying proton absorption
by 1-2 orders of magnitude
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Conclusion:
The LHC luminosity upgrade
acquired new technical means
which need
further investigation
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