crystal-based collimation system as an alternative way to solve the collimation problem for future...

CRYSTAL-BASED COLLIMATION SYSTEM CRYSTAL-BASED COLLIMATION SYSTEM AS AN ALTERNATIVE WAY TO SOLVE AS AN ALTERNATIVE WAY TO SOLVE

THE COLLIMATION PROBLEM FOR THE COLLIMATION PROBLEM FOR FUTURE HIGH ENERGY ACCELERATORSFUTURE HIGH ENERGY ACCELERATORS

ALEXEI SYTOVALEXEI SYTOV

Research Institute for Nuclear Problems,Research Institute for Nuclear Problems,

Belarusian State UniversityBelarusian State University

The LHC The LHC luminosity upgradeupgrade The beam luminosity will increaseThe beam luminosity will increase

with a factor with a factor 1010!!

1010 1234 scmL

Halo particlesHalo particles can damage the LHC equipment because of their can damage the LHC equipment because of their large amplitude of betatron oscilla-tions. So we should remove them large amplitude of betatron oscilla-tions. So we should remove them using using collimation systemcollimation system::

Absorber

Absorber

new new collimation collimation systemsystem

Collimation system for removing halo particlesCollimation system for removing halo particles

oldold collimation collimationsystemsystem

(after the LHC luminosity (after the LHC luminosity upgrade becomes upgrade becomes insufficientinsufficient))

The remarkable feature of crystals in high energy The remarkable feature of crystals in high energy physics is very strongphysics is very strong electricelectric fields applied to fields applied to particle beam with accuracy of Angstrom.particle beam with accuracy of Angstrom.

How can we deflect high energy How can we deflect high energy particles using bent crystal?particles using bent crystal?

Different effects in crystalDifferent effects in crystal

θL0

Channeling

Volume Volume reflectionreflection

Channeling in Bent crystals ─ large deflection,

but small acceptance

VR ─ large acceptance, but small deflection

Advantages and disadvantages of Advantages and disadvantages of different effectsdifferent 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

Advantages and disadvantages of Advantages and disadvantages of different effectsdifferent effects

Multiple Volume Reflection Multiple Volume Reflection (MVR)*(MVR)*

X

Y

Z ΘyΘx

Axes form many inclined

reflecting planes

<11

1>

**V. Tikhomirov, PLB 655 (2007) 217;

V. Guidi, A. Mazzolariand V. Tikhomirov,

JAP 107 (2010) 114908

A trajectoryA trajectory

θX

θY

δθX

,Y,μ

rad

*) MVR orientation with ΘX0 = -273μrad, ΘY0 = 100μrad and R=2m

Angular acceptance increase by MVRAngular acceptance increase by MVR*)*)

-200 -100 0 100

0

1

2

3

Nr/N

, %

cr

MVROC 1mm, Vx=-273urad, Vy=100urad Si cut 2um, 8um

ChannelingVR

MVR

Crystalwith cut

Crystal

0 z1 z2 z3

Beam zcut

A technique to improve crystal channelingA technique to improve crystal channelingefficiency of charged particles till 99,9%efficiency of charged particles till 99,9%**

A narrow plane cut near the crystal surfaceA narrow plane cut near the crystal surfaceconsiderably increases the probability of capture intoconsiderably increases the probability of capture intothe stable channeling motion of positively chargedthe stable channeling motion of positively chargedparticles.particles.

zc*V. *V. TikhomirovTikhomirov . JINST, 2 P08006, 2007. . JINST, 2 P08006, 2007.

Conclusion 1.Conclusion 1.

MVR is very good for collimation because MVR is very good for collimation because of high collimation efficiency.of high collimation efficiency.

We can increase the collimation efficiency We can increase the collimation efficiency by application of channeling regime if we by application of channeling regime if we solve some additional problems.solve some additional problems.

Problems of the channeling effect Problems of the channeling effect for the collimationfor the collimation

The UA9 experimental layout:

experiment

simulation

UA9UA9 experiment at SPS (CERN) experiment at SPS (CERN) **Dependence of Dependence of inelasticinelastic nuclear interactionnuclear interaction number number of protonsof protons on the angular position of the crystal C1:on the angular position of the crystal C1:

*W.Scandale et al. *W.Scandale et al. Phys. Let., Phys. Let., B692 78-82, 2010B692 78-82, 2010..

Miscut angleMiscut angle

First crystal hitFirst crystal hit

First crystal hitFirst crystal hit

UA9: more than UA9: more than

9090%% of particles of particles for both miscutfor both miscut

casescases

Probability of nuclear reactions in the crystal collimator Probability of nuclear reactions in the crystal collimator vs miscut angle at perfect crystal alignment*vs miscut angle at perfect crystal alignment*

*V. *V. TikhomirovTikhomirov, A. Sytov. , A. Sytov. arXiv:1109.5051 [physics.acc-ph]arXiv:1109.5051 [physics.acc-ph]



×4,5



UA9

×4,5

What is the miscut What is the miscut influence at the LHC?influence at the LHC?

miscutinfluence

zone

miscutinfluence

zone

Particle distribution in impact parameter for Particle distribution in impact parameter for the UA9 (SPS) and the LHC*the UA9 (SPS) and the LHC*

*V. *V. TikhomirovTikhomirov, A. Sytov. arXiv:1109.5051 [physics.acc-ph], A. Sytov. arXiv:1109.5051 [physics.acc-ph]

averageimpact

parameter

averageimpact

parameter

Both the Both the positivepositive and and negativenegative miscutmiscut angles can be the reason of considerableangles can be the reason of considerabledecreasing of the collimation efficiency.decreasing of the collimation efficiency.

The usual The usual miscut anglemiscut angle can increase can increase the probability of nuclear reactions the probability of nuclear reactions with a factor with a factor 4,5 4,5 for the UA9 case.for the UA9 case.

The The LHCLHC functioning will not functioning will not be considerably disturbed be considerably disturbed by the influence of crystal miscut. by the influence of crystal miscut.

In addition, the performance of In addition, the performance of the crystal collimator can be the crystal collimator can be drasticallydrastically improved by the narrow plane cut.improved by the narrow plane cut.

Conclusion 2Conclusion 2


The usual The usual miscut anglemiscut angle can increase can increase the probability of nuclear reactionsthe probability of nuclear reactionswith a factor with a factor 4,5 4,5 for the UA9 case.for the UA9 case.





The usual The usual miscut anglemiscut angle can increase can increase the probability of nuclear reactions the probability of nuclear reactions with a factor with a factor 4,5 4,5 for the UA9 case.for the UA9 case.




What is crystal application for the ILC?What is crystal application for the ILC?

What is crystal application for the ILC?What is crystal application for the ILC?speeding up of speeding up of

the electromagnetic the electromagnetic showers generation.showers generation.

ee±± crystal collimation crystal collimationdecrease of size of decrease of size of

electromagnetic calorimeterselectromagnetic calorimeters

polarization generation/measurementpolarization generation/measurement

positron source for ILCpositron source for ILC

Both the Both the MVRMVR and and channeling channeling phenomena phenomena can be successfully used for the crystal can be successfully used for the crystal collimation at the collimation at the LHCLHC..

The The channeling channeling can provide better efficiencycan provide better efficiencythan the than the MVRMVR but the but the MVR MVR is easier to use with is easier to use with

high efficiency.high efficiency.

There are many additional crystal applicationsThere are many additional crystal applicationsfor the for the ILCILC..

SummarySummary

Thank you for attention!

Particle distribution in deflection angle for Particle distribution in deflection angle for the UA9 (SPS) and the LHC*the UA9 (SPS) and the LHC*


Average impact parameter vs average beam Average impact parameter vs average beam diffusion step for the SPS UA9 and the LHC*diffusion step for the SPS UA9 and the LHC*


Measured in cm average length <Δz> of scattering of particles Measured in cm average length <Δz> of scattering of particles entering the crystal through the lateral crystal surface vs both entering the crystal through the lateral crystal surface vs both miscut angle and diffusion step at perfect crystal alignment*miscut angle and diffusion step at perfect crystal alignment*

Miscut angleMiscut angle

~95%UA9: ~92%

Uncaptured particles after the first crystal passage:

First MVROC observationW. Scandale et al, PLB 682(2009)274

MVROC indeed increases reflection angle 5 times

Phase space in accelerator at the crystal coordinatePhase space in accelerator at the crystal coordinate

Distribution of angle of deflection by crystalDistribution of angle of deflection by crystalafter the first crystal passageafter the first crystal passage

-- - -

- ---

{44 443333 33 33

{ {{

x', μ

rad

x, mm θdef,μradC

oun

t0.

05 m

m

0.3

mm

0.5

mm

1.0

mm

0.05

mm

0.3

mm

0.5

mm

1.0

mm0.05

mm

0.3

mm

0.5

mm

1.0

mm

Ch

ann

elin

g

Cry

stal

Crystal thicknessCrystal thickness

Crystal thickness choiceCrystal thickness choice

amorphous

Volumereflection

Dcr, mm

Dependence of inelasticDependence of inelastic nuclear interactionnuclear interaction fraction of protonsfraction of protons on the crystal thicknesson the crystal thickness

frac

tion

frac

tion

Dcr=∞

Absorber

Particles flowing from the opposite side of the crystal

Secondary beam problemSecondary beam problem

Secondarybeam

the experimental equipment hit W.Scandale et al. Phys. Let, W.Scandale et al. Phys. Let, B692 78-82, 2010.B692 78-82, 2010.

experiment

simulation

My simulation:

Miscut angle:

θmc=+200μrad

θmc=0μrad

θmc=-200μrad

θcr,μrad

*W.Scandale et al. *W.Scandale et al. Phys. Let., Phys. Let., B692 78-82, 2010.B692 78-82, 2010.

θmc=+200μrad(Crystal width=2mm)

coun

tUA9 experiment interpretationUA9 experiment interpretation**

Phase space transformations1 2 3z=0 z=z1 z=z2

z=zc

Wit

hout

cut

x, Å x, Å

42' x, Å

θ/θc

hθ/

θch

θ/θc

h

θ/θc

h

θ/θc

h

53'

z>z1 z>z2

z=zc

*V.V.*V.V.TikhomirovTikhomirov . . JINST, 2 P08006, 2007.JINST, 2 P08006, 2007.

Wit

h cu

t

Dependence of the 7 TeV proton dechanneling Dependence of the 7 TeV proton dechanneling probability in a 1cm bent Si crystal on the r.m.s. probability in a 1cm bent Si crystal on the r.m.s.

incidence angleincidence angle**

Without cut

With cut

*V.V.*V.V.TikhomirovTikhomirov. JINST, 2 P08006, 2007.. JINST, 2 P08006, 2007.

UA9 collaboration references:UA9 collaboration 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

V.V.Tikhomirov’s references:V.V.Tikhomirov’s 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)

crystal-based collimation system as an alternative way to solve the collimation problem for future...

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crystal c1

perfect crystal alignment

high collimation efficiency

collimation problem

nuclear problems

high energy particles

bent crystals large

mangular acceptance