Slide 1

Cherenkov Radiation (and other shocking waves). Perhaps also the ones of the fish? http://www.newscientist.com/lastword/answers/lwa674bubbles.html http://www.pbs.org/wgbh/nova/barrier/ Shock Waves May Confuse Birds Internal Compass

Slide 2

The density effect in the energy loss is intimately connected to the coherent response of a medium to the passage of a relativistic particle that causes the emission of Cherenkov radiation. Calculate the electromagnetic energy flow in a cylinder of radius a around the track of the particle. Define If a is in the order of atomic dimension and | a|1, we get ( after some steps ): If has a positive real part the integrand will vanish rapidly at large distances all energy is deposited near the track If is purely imaginary the integrand is independent of a some energy escapes at infinite as radiation Cherenkov radiation and or and a subscript 1 : along particle velocity 2, 3 : perpendicular to we assume real as from now on

Slide 3

Let us consider a particle that interacts with the medium The behavior of a photon in a medium is described by the dispersion relation Conservation of energy and momentum W.W.M. Allison and P.R.S. Wright RD/606-2000-January 1984 Argon at normal density

Slide 4

2 eV345 A particle with velocity v/c in a medium with refractive index nn=n( ) may emit light along a conical wave front. The angle of emission is given by and the number of photons by

Slide 5

cos( ) = 1/ n m = p/ m/m = [( p/p) 2 + ( 2 tg ) 2 ] set : n1.28 (C 6 F 14 ) p/p 2 5 10 -4 15 mrad L 1 cm 1/ 1 -1/ 2 = 1/2200 - 1/1800 ( in A) with Q=20% p K max = 38.6 o min =.78

Slide 6

Threshold Cherenkov Counter Flat mirror Photon detector Particle with charge q velocity Spherical mirror Cherenkov gas To get a better particle identification, use more than one radiator. A radiator : n=1.0024 B radiator : n=1.0003 Positive particle identification :

Slide 7

Directional Isochronous Selfcollimating Cherenkov (DISC) Cherenkov radiator n=f(photon energy) r=f( n) (r)=f(resolution) More general for an Imaging Detector Transformation Function 200nm 150 N photons N=f( ) (n-1)*10 6

Slide 8

The Cherenkov radiator Q The particle The light cone

Slide 9

http://banzai.msi.umn.edu/leonardo/

Slide 10

Cherenkov media Focusing Mirror Detector e-e+ E Proportional Chamber Quartz Plate Photon to Electron conversion gap e e e Hey! Did I mention TMAE to you?! Did I?!?

Slide 11

Particle Identification in DELPHI at LEP I and LEP II 2 radiators + 1 photodetector n = 1.28 C 6 F 14 liquid n = 1.0018 C 5 F 12 gas /K /K/p K/p /h /K/p K/p 0.7 p 45 GeV/c 15 165

Slide 12

Particle Identification with the DELPHI RICHes Liquid RICH Gas RICH p (GeV) Cherenkov angle (mrad) From data p from K from D * from K o http://delphiwww.cern.ch/delfigs/export/pubdet4.html DELPHI, NIM A: 378(1996)57

Slide 13

Yoko Ono 1994 FRANKLIN SUMMER SERIES, ID#27 I forbindelse med utstillingen i BERGEN KUNSTMUSEUM, 1999 ABB.com More beautiful pictures (which has next to nothing to do with) Cherenkov radiation

Slide 14

An exact calculation of Transition Radiation is complicated J. D. Jackson ( bless him ) and he continues: A charged particle in uniform motion in a straight line in free space does not radiate A charged particle moving with constant velocity can radiate if it is in a material medium and is moving with a velocity greater than the phase velocity of light in that medium (Cherenkov radiation) There is another type of radiation, transition radiation, that is emitted when a charged particle passes suddenly from one medium to another. If

If p2 > p1 then max -1 Total radiated power S 10 -2 (eV) which is a small number All this for a small number?

Slide 16

Coherent addition in point P (-1) k : The field amplitude for successive interfaces alternate in sign A( k ) : Amplitude k = (R/c-t) : phase factor = 2 10 4 l 1 = 25 m l 2 = 0.2 mm polypropylene - air Egorytchev, V ; Saveliev, V V ;Monte Carlo simulation of transition radiation and electron identification for HERA-B ITEP-99-11. - Moscow : ITEP, 17 May 1999. Periodic radiator for Transition Radiation.

Slide 17

Production with multi foils Absorption in foils Conversion t=0t=T Pulse Height -electron MIP X radiation Threshold 10 keV M.L. Cerry et al., Phys. Rev. 10(1974)3594 + saturation effect due to multi layer