Using crystals facilitatesUsing crystals facilitates
the LHC upgradethe LHC upgrade
Victor TikhomirovVictor Tikhomirov
Institute for Nuclear ProblemsInstitute for Nuclear Problems
MinskMinsk
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INPOutline
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
Luminosity upgrade:
Fifteen years of planning and R&D, followed by over 10 years of construction, should be followed
by a comparable period of exploitation.
Energy upgrade: 7 2TeV
What is better?
The LHC upgrade need
34 2 1 010 1L cm s
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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
34 2 1 010 1L cm s
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-8 -4 0 4 8
-8
-4
0
4
8
y/ y
x/x
However luminosity increase will intensify the beam halo formation
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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
crystalProton absorption
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Background reduction by channeling at FNALINP
Deflection of channeling protons reduce the background more than 4 times
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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 Volume reflection
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Volume capture
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Volume reflection by crystal axesINP
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Axes form reflecting planesINP
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-60 -40 -20 0 20 40 60
0
10
20
30
VY0
VX0
(121)(615)(615)(413)(413)(110)(321)(211)(312)(514)(101)(213)(123)(011)(154)(132)(121)(231)111(121)
INPProtons are reflected from many crystal plane sets of one crystal
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Reflection from many crystal planes increase VR angle 4 times - 1
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0 5 10 15 20 25 300
4
8
12
16 high-index planes
(110)(101) (011)(312) (132)(211) (121)(321) (231)
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-20 -10 0 100,0
0,1
0,2
0,3
0,4
(110)
INPReflection from many crystal planes increase VR angle 4 times - 2
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-20 -10 0 10 20 30 40 50-30
-20
-10
0
10
20
30 Y
(ra
d)
X(rad)
Typical distribution of multiple reflected protons
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Reflection from
different crystal planes
allows to increase
the volume reflection angle
about 4 times
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INPThe capture probability can be increased by a plane cut
beam
cut
crystalz1
z2
z3
0
x
y z
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V, , eVe
x, A
e
x1x2
V(x )2
V(x )1
. . ..
Vmax
d
v1
v2
v0
e
x0
The cut diminishes the potential energy conserving the transverse kinetic one
Transverse energy reduction by the cut - 1
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0 1 20
5
10
15
20
25
x0, Å
ε ,
eVε
,
xp
d
0
0 1 2
ch
= 0.25 ch
= 0.320 0
0 1 2
xp
d dxp
ch
= 0.10
INPTransverse energy reduction by the cut - 2
Only 1-2% of protons avoid the transverse energy reduction by the cut
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-0.5
0.0
0.5
1.0a
0.5 1.0 1.5
b
c
0.0 0.5 1.0 1.5
-1.0
-0.5
0.0
0.5
1.0
dd
dx, Å
0.0 0.5 1.0 1.5
-1.0
-0.5
0.0
0.5
1.0
x, Åx, Å
ch
e
/ ch
/
Protons are moved away from the high nuclear density regions
Proton phase space transformation by the cut
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0.0 0.2 0.4 0.6 0.8 1.00
5
10
15
20
25
30
Pde
ch,
%
rms, rad
INPDechanneling suppression by the cut
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
