History of Particle Detectors

Cloud Chamber ICloud chamber (1911 by Charles T. R. Wilson, Noble Prize 1927)chamber with saturated water vapourcharged particles leave trails of ionswater is condensing aound ionsvisible track as line of small water dropletsUK Science MuseumAlso requiredhigh speed photographic methodsinvented by Arthur M. Worthington 1908to investigate the splash of a dropultra short flash light produced by sparksFirst photographs of ray particles 1912Charles T. R. Wilson430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 4

Nuclear Emulsion IPioneered by Marietta Blau between1923 – 1938 (no Nobel Prize)photographic emulsion layer, 10 – 200 µm thick,uniform grains of 0.1 – 0.3 µm sizevery high resolution for particle tracksanalysis of developed emulsion by microscopenuclear disintegrationfrom cosmic rays,observed1937 for thefirst timeMarietta BlauSince early 20 th centuryimportant role of photography tostudy radioactivitybut capability to make individualtracks visible not seen until nuclearemulsion technique was developed430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 7

Nuclear Emulsion IIDiscovery of the pion in cosmic rays byCecil Powell 1947 (Nobel Prize 1950)Discovery of the kaon 1949 (G. Rochester)pion stops and decayselectronCecil Powellpionmuonmuon stopsand decayspion100 µmother pion decays,muon has always same length (energy) 2-body decay pionpionkaon430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 8

Nuclear Emulsion IIICNGS beamStill used in actual experiments with highestprecision requirements over a large volume beam sent from CERN to Gran Sasso Underground lab in Italy (732 km)OPERA experiment is searching for appearance after neutrino oscill. need to reconstruct decays ( + N - + X) (few ~100 µm track length)bricks235'000 “bricks” (1.7 ktons) of lead + emulsion sheetsdecaysingle brickOPERA at Gran Sasso interactionautomatic emulsion scanning430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 9

Bubble Chamber IIntented 1952 by Donald Glaser (Noble Prize 1960)similar to could chamberDonald Glaserchamber with liquid (e.g. H 2 ) at boiling point (“superheated”)charged particles leave trails of ionsformation of small gas bubbles around ionswas used at discovery of the “neutral current”(1973 by Gargamelle Collaboration, no Noble Prize yet) e - Z 0 e -LBNL Image Library400 MeV electron Gargamelle bubble chamberCERNNOT this track...CERN430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 10

Bubble Chamber IIBEBC (Big European Bubble Chamber) at CERN, 1973 – 1984largest bubble chamber ever built (and the last big one...), 3.7 m6.3 million photographs taken, 3000 km of developed filmnow displayed in permanent exhibition at CERNBEBCBEBC pistonproduction of D* mesonwith long decay chain430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 11

Bubble Chamber IIIparticle ID by eye...photon conversion e + e –μ -K - -decayπ -individual ionizationclustersK -δ-electronse -thick tracks, no individualclusters, high dE/dx, low βγ430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 12

Bubble Chamber IVAdvantages of bubble chambersliquid isBOTH detector medium AND targethigh precisionDisadvantagesSLOW!!!event pictures taken with cameras on filmfilm needs to be developed, shipped to institutesand optically scanned for interesting eventsNeed FASTER detectors (electronic!)However:Some important social side effects of bubble chamber era...scanning was often done by young “scanning girls” (students)......who later got married with the physicists...TableMirrorFilms (multiple views)and projection systemScanning table (1972)CERN430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 13

Early “Electronic” Detectors - Spinthariscope1911: Ernest Rutherford + studied (elastic) scattering of particles on gold atoms (famous Rutherford experiment)discovery of atomic nucleus:small (heavy) positively charged nucleus orbited by electronsZinc sulfide screen with microscope(spinthariscope by William Crookes 1903)was used to detect scattered particleslight flash was observed by eyeto increase light sensitivity, “bella donna”(from the deadly night shade plant = Tollkirsche)was often used to open eye's pupilHans GeigerErnest RutherfordUK Science Museumdeadly night shade430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 14

Early Electronic Detectors - ElectroscopeGold-leaf electroscope already invented 1787by Abraham BennetEnd of 19 th century raising interest onelectricity in gasescathode ray tubes, glow dischargesobservation:charged electroscope is loosing its charge in dry air after some timesource of conductivity? ionisation by recently discovered radioactivity?Victor Hess discovered cosmic rays 1912 (Nobel Prize 1936)used calibrated string electrometerby Theodor Wulffound increasing ionisation athigher altitudes at a series ofballoon ascentsnot related to sun radiation!pair of wiresearly cathode ray tubeVictor Hessin balloon430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 15

Geiger-Müller TubeThe Geiger-Müller tube (1928 by Hans Geiger and Walther Müller)anode wireTube filled with inert gas (He, Ne, Ar) + organic vapourCentral thin wire (20 – 50 µm ) , high voltage (several 100 Volts)between wire and tubeStrong increase of E-field close tothe wire-+~100 µmprimary electronstarting to ionizeelectron gains more and more energyabove some threshold (>10 kV/cm)electron energy high enough to ionizeother gas moleculesnewly created electrons also start ionizingavalance effect: exponentialincrease of electrons (and ions)measurable signal on wireorganic substances responsible for“quenching” (stopping) the discharge430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 16

Coincidence Units“Zur Vereinfachung von Koinzidenzzählungen”,Walther Bothe 1929 (Nobel Prize 1954)single tube has no information on directionof incoming particletwo or more tubes giving signals withinthe same time window give directionalso information if two particles comefrom the same decaycoincidence unit with vacuum tubesfor 2 Geiger-Müller tubesWalther Bothecosmic ray telescope 1934the430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 17

Photo Multiplier Tubes (PMT)Invented 1934 by Harley Iams and Bernard Salzberg (RCACoorperation)plastic scintillatorphoto cathodebased on photo effect and secondary electron emissionsensitive to single photons, replaced human eye + belladonna at scintillator screenfirst device had gain ~8 only but already operated at >10 kHz(human eye: up to 150 counts/minute for a limited time)nowadays still in use everywhere, gain up to 10 8recent developments: multi-anode (segmented) PMTs, hybrid and pure silicon PMsSilicon PM =array of avalancephoto diodesdynodes:secondaryelectronemissionanodeclassic PMT430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 18

Multi Wire Proportional Chambers IGeiger-Müller tube just good for single tracks withlimited precision (no position information inside tube)in case of more tracks more tubes are needed or...Multi Wire Proportional Chamber (MWPC)(1968 by Georges Charpak, Nobel Prize 1992)put many wires with short distance between two parallel platescathode plane (-)Georges CharpakEEcharged particleanode plane (+),many wires,a few mm apartcathode plane (-)Georges Charpak, Fabio Sauli and Jean-Claude SantiardCERN430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 19

Multi Wire Proportional Chambers IIMulti Wire Proportional Chamber (MWPC)was first electronic device allowing high statistics experimentswith multiple channels and reasonable resolutionTypically several 100 – 1000 wires, ~ 1 mm spacingif charged particle is passing the MWPC → one wire gives signalresolution: x≈d e.g. for d = 1 mm → ~300 µm1 2we don't know where the particle went through withinthe 1 mm spacing = “flat” probability distribution,this is the width of an equivalent Gaussian distributionIf many MPWCs are put one after each otherProbabilityeach particle creates one point per MWPC (~300 µm resolution per point)d/2σ xcan reconstruct track with e.g. 4 pointscharged particleMWPCswire hitone coordinate only, use additional MWPCstilted by 90 o to get other coordinate430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 20

Drift ChamberResolution of MWPCs limited by wire spacingbetter resolution → shorter wire spacing → more (and more) wires...larger wire forces (heavy mechanical structures needed)(too) strong electrostatic forces when wires too close to each otherSolution by A. H. Walenta, J. Heintze, B. Schürlein 1971obtain position information from drift time of electrons (fewer wires needed)drift time = time between primary ionization and arrival on wire (signal formation)start signal (track is passing drift volume)has to come from external source:scintillator or beam crossing signalNeed to know drift velocity v Dto calculate distance s to wire(= track position within the detector)t s t o ps =∫t s t a r tv Dd t430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 21

Time Projection Chamber (TPC)A 3D-imaging chamber with rather long drift lengthcathode planeyxBEdriftanode planez2 mPEP-4 TPChomogeneous B- and E-fieldsanode plane equipped with MWPC wire chambersdrifting electronszyavalanchewirepadswiresProblem: pads have to belarge (otherwise notenough induced charge)Limits number of pointsand double track resolutionxyprojected track430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 22

Time Projection Chamber (TPC)Invented by David Nygren (Berkeley) in 1974Proposed as central tracking device for the PEP-4 detector atthe PEP e + e - collider at SLAC 1976More (and even larger) TPCs werebuilt or are planned at other collidersTRISTAN (KEK, 2 x 32 GeV e + e - , 1986 – 1995)TOPAZLEP (CERN, 2 x 104 GeV e + e - , 1989 – 2000)ALEPH, DELPHIRHIC (BNL, 2 x 100 GeV/nucleus, 2001 – )STARLHC pp and Pb-Pb collider (CERN)ALICEILC e + e - colliderILDDavid Nygren430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 23

Recent Developments:Micro Pattern Gas Detectors (MPGD)Replace wires at TPC with Micro Pattern Gas DetectorsMicroMegas (metallic micromesh)GEM (Gas Electron Multiplier)Concept2D structureswith holes + underlying padsGas amplification inside holes,collect electrons on small pads,few mm2MicroMegasØ 50-70 µm2 mmGEMHVKapton Copper430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 24

Wire Chambers – AgeingWire Chambers don't work/live forevergas avalance region close to wire is region of plasma formation...and plasma chemistry not well understood in generalAvalance regiondissociation of detector gas and pullutantsformation of highly active radicalspolymerization of organic quenchersinsulating deposits on anodes and cathodeshard deposits,typically SiO 2 (quartz)black magic...whiskers,typically carbon fibersAnode: increase of wire diameterreduced and variable E-fieldvariable gain and energy resolutionCathode: ions on top of insulating layer cannot recombinebuilt-up of strong E-field across insulating layerelectron field emission and microdischarges“Malter effect”, first seen by L. Malter in 1936:L. Malter; Phys. Rev. 50 (1936), 48Conclusions of an ageing workshop many years ago:CO 2 helps with water, and alcohol admixtures...430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 25

Gaseous Detectors in LHC ExperimentsMainly used in Muon Systems (ALICE, ATLAS, CMS, LHCb)precise muon tracking (drift tubes) and triggering (RPC plates)Also in Inner Tracking system (ALICE, ATLAS, LHCb, TOTEM)mainly straw tubes = small, light weighted tubesbut not the innermost detector layerdomain of semi conductor (silicon) detectorsSpecific LHC challenges (for gaseous detector systems)high track rate (25 ns) and density (~1000 tracks per bunch crossing)need short drift times (avoid integrating over too many bunch crossings)+ high granularity = fast gases, small sized detectorsneed “ageing-free” gases/detectorslots of effort spent over years in this fieldextensive irradiations with Gamma irradiation source, lab studies with X-ray sources etc.430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 26

Solid State DetectorsFirst transistor was invented 1947by William B. Shockley, John Bardeenand Walter Brattain (Nobel Prize 1956)transistors and diodes became common soon afterGermanium diodes were used for particle detectionp-type and n-type doped silicon material is put togetherand operated with reversed voltageBardeenShockleyBrattainmore holes more electrons around junction of p- and n-typematerial depletion zone is createdPdepletionzoneNchargedparticlezone free of charge carriersno holes, no electronsthickness of depletion zone depends onvoltage, doping concentrationcharged particle typically creates 20'000 – 30'000 electron/hole pairsin 300 µm thick material -> sufficient signal size430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 27

Silicon Strip DetectorsNow take a large Si crystal, e.g. 10 x 10 cm 2 , 300 µm thick+make bottom layer p-typeand subdivide the top n-type layer intomany strips with small spacing-many diodes next to each other(like MWPC at wire chambers)with position informationAdvantage compared towire/gas detectorsstrip density (pitch) can berather high (e.g. ~20 µm)high position accuracybut also many electronics channelsneeded430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 28

The first Silicon Strip DetectorFirst operational silicon strip detector used in an experiment(NA11 at CERN) by J. Kemmer, R. Klanner, B. Lutz et al. 1983B. Lutz was founder of MPI Halbleiterlabor in MunichNA11 aimed to search for new short lived particlesfirst observation of D smany branching ratio and lifetime measurements8 silicon strip planes(4 groups of 2 planes eachwith tilted strips to measurexy coordinate)D – decay24 x 36 mm 2 size per chip1200 strips, 20 µm pitch240 read-out strips4.5 µm single hit resolution430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 29

Si-Detector Electronics and Si-PixelsSilicon strip detectors have a laaaarge number of electronicschannels, ~10 7 each for ATLAS and CMS Si trackersrequires highly integrated chips for amplification, shaping,zero suppression (only information of strips with signals is read-out)and multiplexing (put all strip signals on a few cables only)electronics is directly connected to the sensor (the “multi-diode”) viawire bondsSi-strip detectors provide only 1 coordinate,Pixel detectors are 2D detectorswire bondsSensorPixel detector need“bump” bondingand have even morechannels, ~10 8 - 10 9430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 30

Recent Developments: Hybrid TechnologiesCombine MPGD gaseous detector with silicon pixel detectorUse MediPix2/TimePix chip as active TPC “padplane” for ILCdetectorMediPix2 = 256x256 pixels with 55x55 µm2 size for medical applications(X-ray film replacement)MicroMegas mesh (provides gas amplification) integrated on top of pixelchipcosmic ray trackionizationclustersIndividual ionization visible:the digital Bubble Chamber is in reach430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 31

Detector HistoryCloud Chambers, Nuclear Emulsions + Geiger-Müller tubesdominated until the early 1950sCloud Chambers now very popular in public exhibitions related to particle physicsBubble Chambers had their peak time between 1960 and 1985last big bubble chamber was BEBC at CERNWire Chambers (MWPCs and drift chambers) startedto dominate since 1970sSince late 1980s solidstate detectors are in common usestarted as small sized vertexdetectors (at LEP and SLC)now ~200 m 2 silicon surfacein CMS trackerMost recent trend: hybrid detectorscombining both gaseous and solid state technologies430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 32

A typical Today's Particle DetectorCut-away view of CMSTracker Calorimeter Coil Muon Detector and iron return yoke430. Heraeus Seminar – History of Particle Detectors Michael Hauschild - CERN, 27-Apr-2009, page 33

History of Particle Detectors

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