Transcript Sytov

CRYSTAL-BASED COLLIMATION SYSTEM
AS AN ALTERNATIVE WAY TO SOLVE
THE COLLIMATION PROBLEM FOR
FUTURE HIGH ENERGY ACCELERATORS
ALEXEI SYTOV
Research Institute for Nuclear Problems,
Belarusian State University
The LHC luminosity upgrade
The beam luminosity will increase
with a factor 10!
2 1
L  10 cm s 10
34
Collimation system for removing halo particles
Halo particles can damage the LHC equipment
because of their large amplitude of betatron oscillations. So we should remove them using collimation
system:
old collimation
system
(after the LHC luminosity
upgrade becomes insufficient)
Absorber
new collimation
system
Absorber
The remarkable feature of crystals in high energy
physics is very strong electric fields applied to
particle beam with accuracy of Angstrom.
How can we deflect high energy
particles using bent crystal?
Different effects in crystal
Volume
reflection
θL0
Channeling
Advantages and disadvantages of
different effects
Channeling in Bent crystals ─ large
deflection,
but small acceptance
VR ─ large acceptance,
but small deflection
Advantages and disadvantages of
different effects
Channeling in Bent crystals ─ large
deflection,
but small acceptance
VR ─ large acceptance,
but small deflection
MVR ─ large acceptance,
increased deflection
MVR indeed increases reflection angle
5 times in comparison with VR
Multiple Volume Reflection (MVR)*
Axes form
many inclined
reflecting planes
Θ
x Θy
Z
Y
X
*V. Tikhomirov,
PLB 655 (2007) 217;
V. Guidi, A. Mazzolari
and V. Tikhomirov,
JAP 107 (2010) 114908
A trajectory
δθX,Y, μrad
θY
θX
Angular acceptance increase by MVR*)
3
MVROC 1mm, Vx=-273urad, Vy=100urad
Si
N r /N, %
cut 2um, 8um
2
VR
Channeling
Crystal
with cut
1
MVR
0
-200
-100
0

100
cr
*) MVR orientation with Θ = -273μrad, Θ = 100μrad and R=2m
X0
Y0
A technique to improve crystal channeling
efficiency of charged particles till 99,9%*
A narrow plane cut near the crystal surface
considerably increases the probability of capture into
the stable channeling motion of positively charged
particles.
Crystal
Beam
z
cut
0 z1
z2
z3
*V. Tikhomirov . JINST, 2 P08006, 2007.
zc
Conclusion 1.
MVR is very good for collimation because
of high collimation efficiency.
We can increase the collimation efficiency
by application of channeling regime if we
solve some additional problems.
Problems of the channeling effect
for the collimation
UA9 experiment at SPS (CERN) *
Dependence of inelastic nuclear interaction number
of protons on the angular position of the crystal C1:
The UA9 experimental layout:
experiment
simulation
*W.Scandale et al.
Phys. Let.,
B692 78-82, 2010.
Miscut angle
First crystal hit
First crystal hit
UA9: more than
90% of particles
for both miscut
cases
Probability of nuclear reactions in the crystal collimator
vs miscut angle at perfect crystal alignment*
*V. Tikhomirov, A. Sytov.
arXiv:1109.5051 [physics.acc-ph]
Probability of nuclear reactions in the crystal collimator
vs miscut angle at perfect crystal alignment*
×4,5
*V. Tikhomirov, A. Sytov.
arXiv:1109.5051 [physics.acc-ph]
Probability of nuclear reactions in the crystal collimator
vs miscut angle at perfect crystal alignment*
UA9
×4,5
*V. Tikhomirov, A. Sytov.
arXiv:1109.5051 [physics.acc-ph]
What is the miscut
influence at the LHC?
Particle distribution in impact parameter for
the UA9 (SPS) and the LHC*
miscut
influence
zone
average
impact
parameter
miscut
influence
zone
average
impact
parameter
*V. Tikhomirov, A. Sytov. arXiv:1109.5051 [physics.acc-ph]
Conclusion 2
Both the positive and negative miscut
angles can be the reason of considerable
decreasing of the collimation efficiency.
The usual miscut angle can increase
the probability of nuclear reactions
with a factor 4,5 for the UA9 case.
The LHC functioning will not
be considerably disturbed
by the influence of crystal miscut.
In addition, the performance of
the crystal collimator can be drastically
improved by the narrow plane cut.
Conclusion 2
Both the positive and negative miscut
angles can be the reason of considerable
decreasing of the collimation efficiency.
The usual miscut angle can increase
the probability of nuclear reactions
with a factor 4,5 for the UA9 case.
The LHC functioning will not
be considerably disturbed
by the influence of crystal miscut.
In addition, the performance of
the crystal collimator can be drastically
improved by the narrow plane cut.
Conclusion 2
Both the positive and negative miscut
angles can be the reason of considerable
decreasing of the collimation efficiency.
The usual miscut angle can increase
the probability of nuclear reactions
with a factor 4,5 for the UA9 case.
The LHC functioning will not
be considerably disturbed
by the influence of crystal miscut.
In addition, the performance of
the crystal collimator can be drastically
improved by the narrow plane cut.
Conclusion 2
Both the positive and negative miscut
angles can be the reason of considerable
decreasing of the collimation efficiency.
The usual miscut angle can increase
the probability of nuclear reactions
with a factor 4,5 for the UA9 case.
The LHC functioning will not
be considerably disturbed
by the influence of crystal miscut.
In addition, the performance of
the crystal collimator can be drastically
improved by the narrow plane cut.
What is crystal application for the ILC?
What is crystal application for the ILC?
speeding up of
the electromagnetic
showers generation.
e± crystal collimation
decrease of size of
electromagnetic calorimeters
polarization generation/measurement
positron source for ILC
Summary
Both the MVR and channeling phenomena
can be successfully used for the crystal
collimation at the LHC.
The channeling can provide better efficiency
than the MVR but the MVR is easier to use with
high efficiency.
There are many additional crystal applications
for the ILC.
Thank you for attention!
Particle distribution in deflection angle for
the UA9 (SPS) and the LHC*
*V. Tikhomirov, A. Sytov. arXiv:1109.5051 [physics.acc-ph]
Average impact parameter vs average beam
diffusion step for the SPS UA9 and the LHC*
*V. Tikhomirov, A. Sytov. arXiv:1109.5051 [physics.acc-ph]
Measured in cm average length <Δz> of scattering of particles
entering the crystal through the lateral crystal surface vs both
miscut angle and diffusion step at perfect crystal alignment*
Miscut angle
Uncaptured particles
after the first crystal passage:
UA9: ~95%
~92%
First MVROC observation
W. Scandale et al, PLB 682(2009)274
MVROC indeed increases reflection angle 5 times
Phase space in accelerator at the crystal coordinate
3
-
{
4
-
{
{
3
{
-
-
-
-
Distribution of angle of deflection by crystal
after the first crystal passage
3
4
3
Channeling
Volume
reflection
x, mm
1.0 mm
0.3 mm
0.5 mm
0.05 mm
Count
0.05 mm
0.5 mm
0.3 mm
1.0 mm
1.0 mm
0.5 mm
0.3 mm
0.05 mm
x', μrad
Crystal
Crystal thickness choice
Crystal thickness
Crystal thickness
amorphous
θdef,μrad
fraction
Dependence of inelastic nuclear interaction
fraction of protons on the crystal thickness
Dcr=∞
Dcr, mm
Secondary beam problem
Secondary
beam
Absorber
Particles flowing from
the opposite side of the crystal
the experimental equipment hit
W.Scandale et al. Phys. Let,
B692 78-82, 2010.
count
UA9 experiment interpretation*
experiment
simulation
My simulation:
θmc=0μrad
Miscut angle:
θmc=+200μrad
θmc=-200μrad
θmc=+200μrad
(Crystal width=2mm)
*W.Scandale et al.
Phys. Let.,
B692 78-82, 2010.
θcr,μrad
z=zc
2'
3'
x,
x, Å
2
θ/θch
1
θ/θch
z>z1
z=z1
With cut
z=0
Without cut
θ/θch
θ/θch
θ/θch
Phase space transformations
*V.V.Tikhomirov .
Å JINST, 2 P08006, 2007.
z=z2
3
z>z2
4
z=zc
5
x, Å
Dependence of the 7 TeV proton dechanneling
probability in a 1cm bent Si crystal on the r.m.s.
incidence angle*
Without cut
With cut
*V.V.Tikhomirov. JINST, 2 P08006, 2007.
UA9 collaboration references:
•
•
•
•
•
•
W. Scandale et al. PRL 98, 154801 (2007)
W. Scandale et al. PRL 101, 234801 (2008)
W. Scandale et al. PRL 101, 164801 (2008)
W. Scandale et al. PRL 102, 084801 (2009)
W. Scandale et al. Phys. Let. B688, 284 (2010)
W. Scandale et al. Phys. Let., B692 78 (2010)
V.V.Tikhomirov’s references:
•
•
•
•
•
•
V.V. Tikhomirov. Phys. Lett. B 655 (2007), 217
V.V.Tikhomirov . JINST, 2(2007), P08006
V. Guidi, A. Mazzolari, V. V. Tikhomirov. J. of Phys. D: Applied Physics, 42
(2009), 165301
W. Scandale, V.V.Tikhomirov. Phys. Lett. B. 682 (2009), 274
V. Guidi, A. Mazzolari, V.V. Tikhomirov. J. Appl. Phys. 107 (2010), 114908
W. Scandale et al…V. V. Tikhomirov. EPL, 93 (2011), 56002