physics 663 - psd computing templatetheory.uchicago.edu/~smaria/sony_pcg/support/det3.pdf · 2002....

Physics 663, lecture 6 1

Physics 663

Par t icle Physics Phenomenology

Apr il 30, 2002


Det ect or s

• I nt er act ion of Char ged Par t icles and Radiat ion wit h Mat t er

– I onizat ion loss of char ged par t icles

– Coulomb scat t er ing– Radiat ion loss by elect r ons

– Absor pt ion of J�-r ays in Mat t er

• Det ect or s of Single Char ged Par t icles– Pr opor t ional count er s, Spar k and st r eamer chamber s, Dr if t chamber s,

Scint illat ion count er s, Cer enkov count er s, Solid-st at e count er s,

– Bubble chamber s

• Shower Det ect or s and Calor imet er s

– Elect r omagnet ic-shower det ect or s– Hadr on-shower det ect or s

• Ref er ences: Donald H. Per kins, I nt r oduct ion t o High Ener gy Physics, Four t h Edit ion


Elect r onic Det ect or s

• Scint illat or s

• Pr opor t ional count er s• Mult i-wir e pr opor t ional count er s• Wir e dr if t chamber s

• Time pr oj ect ion chamber


Scint illat or s

• Cer t ain mat er ials scint illat e when excit ed byionizing par t icles

• Rut her f or d had his gr ad st udent s count ing t hescint illat ions f r om zinc-sulf ide

• Plast ic or polyst yr ene ar e in common use t oday,but ot her mat er ial scint illat e as well

• Or ganic– cr yst alline– liquid– plast ic

• I nor ganic


Scint illat or s


Or ganic Scint illat or s

• Most applicat ions in HEP ar e plast ic or liquid• wide r ange of applicat ions, ext r emely ver sat ile


Plast ic Scint illat or s

• Plast ic scint illat or s ar e r eliable, r obust , and convenient , butt her e ar e issue t hat must be dealt wit h– aging and handling

• exposur e can r educe light yield, and sur f ace cr azing dest r oys lightt r ansmission

– at t enuat ion lengt h• car e must be t aken t o ensur e good t r ansmission

– af t er glow• long-lived luminescence

– at mospher ic quenching• decr ease light yield

– magnet ic f ield• small ef f ect s on light yield

– r adiat ion damage• r educed light yield, and at t enuat ion lengt h


I nor ganic Scint illat or s


Phot omult iplier Tubes• Light f r om scint illat or is

r ecor ded by phot omult ipliert ubes

• phot cat hode coat ed by alkalimet als

• amplif icat ion t hr ough dynodechain– 108 f or 14 dynodes

• t r ansit t ime ~ 50 nsec• j it t er ~ nsec• quant um ef f iciency ~25%


Typical Phot ot ube - 931A


Super K Phot ot ubes

• Super Kamiokande– 11,146 t ubes (20-inch diamet er )


Phot odiodes• Higher quant um ef f iciency• Lower power consumpt ion• Mor e compact• I mpr oved r uggedness• I mmune t o magnet ic f ields• Good t ime r esponse


Light Pat h in Scint illat or

• Light may be ext r act ed f r om scint illat or t o phot ot ube byint er nal r ef lect ion (mult iple r ef lect ion down light guide)

• Alt er nat ive appr oach - wavelengt h shif t er bar s along edgeof scint illat or– blue light f r om scint illat or r e-emit t ed as gr een


Pr opor t ional Count er• Developed over a cent ur y ago• Gas-f illed cylindr ical t ube of r adius r 2 at negat ive pot ent ial,

wit h cent r al anode wir e of r adius r 1 at posit ive pot ent ial


Pr opor t ional Count er• For pot ent ial dif f er ence V0, t he elect r ic f ield is

• Liber at ed elect r ons dr if t t owar d anode, gaining ener gy.• An avalanche is init iat ed if ener gy gain exceeds ionizat ion

ener gy• Gas amplif icat ion of ~105 is t ypical, but independent of t he

number of pr imar y ions “pr opor t ional count er ”


Mult iwir e Pr opor t ional Count er (MWPC)

• Ar ound 1968, Char pak developed t he MWPC• Many par allel anode wir es in a plane bet ween t wo cat hode

planes• Each wir e is an independent det ect or• Typical: 20 µm diamet er wir es, 5/ cm, 12mm bet ween

cat hodes, 5kV, ar gon-isobut ane gas



• Elect r ic Field Lines



• Fast r ise t ime (0.1 nsec) ar ising f r om f ir st ar r iving elect r ons• Posit ive ions ar e slower , r esult ing in pulses of ~30 nsec

dur at ion• Spat ial r esolut ion ~ 0.7 mm f r om anode pulses• Cat hode st r ips can be used t o measur e spat ial coor dinat e of

t he avalanche (wit h about 0.05 mm pr ecision)


Wir e Dr if t Chamber s

• MWPCs r equir e lar ge number of wir es and ar e limit ed t or esolut ions of about 1 mm and t ime r esolut ions of about 30 ns

• By dr if t ing t he char ge, t he number of wir es can besignif icant ly r educed, and t he r esolut ions impr oved.

• Dr if t in f ield of ~ 1 kV/ cm over 10 cm, amplif y at anode– ar r ival t ime give measur e of posit ion



• SLD Dr if t Chamber




~100 Pm r esolut ion


Time Pr oj ect ion Chamber

• Unif or m elect r ic f ielddr if t s ionizat ion elect r onst o a 2D ar r ay of det ect or sat t he end.– dr if t along t he

magnet ic f ielddir ect ion t o eliminat ev x B f or ce

ALEPH TPC


Cer enkov Count er s

• Thr eshold det ect or s• Dif f er ent ial det ect or s• Ring I maging det ect or s



• Par t of t he light emit t ed as a par t icle passest hr ough a dielect r ic medium at a velocit yexceeding t he speed of light in t he mediumappear s as a coher ent wavef r ont



• Cer enkov r adiat ion

• blue light pr edominat es– well known blue glow f r om

r eact or• Tot al r at e of ener gy loss:

– a small f r act ion of t he ener gyloss



• The angle of emission of r adiat ion is a measur e oft he velocit y of t he par t icle


Thr eshold Cer enkov Count er s

• I f t wo par t icles of dif f er ent mass car r y t he samemoment um, t he light er par t icle may emit Cer enkov r adiat ion,while t he heavier does not

•For example, in helium atNTP, t he t hr eshold f orr adiat ion is J = 123

• A 100 GeV/ c pion has a J�|

700, above t he t hr esholdwhile a 100 GeV/ c pr ot on hasa J�| 106, below t hr eshold


Dif f er ent ial Cer enkov Count er s

• Since t he angle of emission of r adiat ion is a measur e of t hevelocit y of t he par t icle, by measur ing t he angle, one candet er mine velocit y


Ring I maging Cer enkov Count er s

• eg. SLD and DELPHI

light at angle θc is f ocussedby mir r or of r adius Ron r ing CD



Muon in liquid (C6F14) Muon in gas (87% C5F12 13% N2)


Solid St at e Det ect or s

• Silicon det ect or s in nuclear physics• Micr ost r ip det ect or s• Hybr id pixels det ect or s• CCDs• CMOS det ect or s


Det ect or s

• I nt er act ion of Char ged Par t icles and Radiat ion wit h Mat t er

– I onizat ion loss of char ged par t icles

– Coulomb scat t er ing– Radiat ion loss by elect r ons

– Absor pt ion of J�-r ays in Mat t er

• Det ect or s of Single Char ged Par t icles– Pr opor t ional count er s, Spar k and st r eamer chamber s, Dr if t chamber s,

Scint illat ion count er s, Cer enkov count er s, Solid-st at e count er s,

– Bubble chamber s

• Shower Det ect or s and Calor imet er s

– Elect r omagnet ic-shower det ect or s– Hadr on-shower det ect or s

• Ref er ences: Donald H. Per kins, I nt r oduct ion t o High Ener gy Physics, Four t h Edit ion

physics 663 - psd computing templatetheory.uchicago.edu/~smaria/sony_pcg/support/det3.pdf · 2002....

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