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Cherenkov Detectors27L27.pdf P627 YK3/26/2012

Cherenkov radiation e.g. from the core of the water cooled research reactor

References:

PDG chapters 27-29

Čerenkov Radiationand its applicationsby J.V. Jelly, Pergamon Press,1958

Cherenkov radiation is an effect similar to sonic booms when velocity of the object exceeds the velocity of the sound

2

Cherenkov emission band

PMT sensitivity

range

2 ; n

red UV

( )

( )

( )

1cos ; ? for gas and solid

1

c c

T

cCherenkov Radiation : v

n

n

Threshold velocity n

l

q qb l

bl

>

=⋅

=

Cherenkov light emission

ct

J.D. Jackson, Classical Electrodynamics3-rd edition, page 638

22222 1112

nβλπα

dxdNd

mostly UV

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Total Cherenkov-radiation energy losses are included in Bethe-Bloch formula [ ref. Fano ] !

( )

( )

2 22 2 1 1sin 370 sin

1 of moving particle

integrated over visible light spectrum

c cd N z

E eV cmdE dx c

z

gg

aq q - -= »

=

222

22 112n

zdxd

Nd

( )

( )( )

max

min

2

2 2 2

If is a sensitivity of photodetector:

2 11

S

dN zd S

dx n

l

l

l

pal l

l b l

æ ö÷ç ÷ç= ⋅ ⋅ - ÷ç ÷ç ÷÷çè øò

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From “Cherenkov Radiation and its applications”J.V. Jelley, Pergamon Press, 1958

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Simple threshold Cherenkov beam counter

Refractive indices of Cherenkov radiators:

Differential Cherenkov beam counter

Beam of

With careful design velocity resolution 104 105can be obtained

Thresholdgn

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Ring Imaging Cherenkov Counter

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Ring Imaging Cherenkov (RICH or CRID )

10 GeV/c

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Air Cerenkov Detectors

A picture of the Whipple Observatory Air Cerenkov detector (NASA)

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http://www-sk.icrr.u-tokyo.ac.jp/sk/index1.html

Event in Super-K

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SNO Cherenkov detector:http://www.sno.phy.queensu.ca/

Particle identification in Super-K

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Conversion of UV to detectable light in KamLAND LS

Energy transferred by emission and re-absorption, and by molecular

collisions—Forster mechanism.

Detectable PPO emissionUV Cherenkov

incident

Dodecane Pseudocumene PPO

Measured -source response in KamLAND LS is non-linear due to converted Cherenkov contribution

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DIRC in BaBar experiment

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Particle pair Mom. range for 3 separation

e / p 5 GeV/c

/ K 0.23 GeV/c p 20 GeV/c

K / p 0.82 GeV/c p 30 GeV/c

Momentum range for 3 separation in the SLD ring-imaging Cherenkov detector

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Transition Radiation Detectors

Since E = m, combination of particle momentum measurement or energy measurement together with TRD results in particle identification

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TRD in ALICE detector

Generic TRD detector

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Performance of several detectors used for electron pion separation in different experiments. The rejection is the efficiency for pions at the efficiency of electrons given in the row below.

8098.7878090909990efficiency e (%)

0.51028100.050.065efficiency (%)

CH 2CH 2CH 2CH 2LiCH 2CH 2Liradiator

4424238122number layers

6011013022557036055length (cm)

NA24NA31E769UA2UA6NA34E715R806Experiments

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Performance of the HELIOS TRD. The first figure shows how the rejection power improves by including information on the position of the track. The information was first obtainable at the offline analysis. The secondfigure indicates the effect of having a high occupancy environment withmany overlapping tracks in the proton-nucleus collisions.

Separation can be enhanced with the number of independent detectors