Content. Complex Detector Systems. Calorimeters Velocity Determination. Semiconductor detectors. Scintillation detectors. Cerenkov detectors

Transcription

1 Semiconductor detectors Semiconductor basics Sensor concepts Readout electronics Scintillation detectors General characteristics Organic materials Inorganic materials Light output response Calorimeters Velocity Determination Cerenkov detectors Cerenkov radiation Cerenkov detectors Transition Radiation detectors Content Phenomenology of Transition Radiation Detection of Transition Radiation Time-Of-Flight Complex Detector Systems

2 Transition Radiation Detectors

3 Transition radiation detectors Transition radiation detectors (there is an excellent review article by B. Dolgoshein (NIM A 326 (1993) 434)) TR predicted by Ginzburg and Franck in 1946 Electromagnetic radiation is emitted when a charged particle traverses a medium with a discontinuous refractive index, e.g. the boundaries between vacuum and a dielectric layer. A (too) simple picture medium vacuum electron A correct relativistic treatment shows that (G. Garibian, Sov. Phys. JETP63 (1958) 1079) or Jackson

4 Transition radiation detectors m Radiated energy per medium/vacuum boundary W = 1 α! ω pγ W γ Only high energy e ± will 3 emit TR. Identification of e ± ω p = Nee ε m 0 2 e plasma frequency! ω p 20eV (plastic radiators) m Number of emitted photons / boundary is small N ph W α!ω Need many transitions build a stack of many thin foils with gas gaps m X-rays are emitted with a sharp maximum at small angle θ 1 γ TR stay close to track

5 Transition radiation detectors m Emission spectrum of TR Typical energy:! ω! ω photons in the kev range 1 4 p γ Simulated emission spectrum of a CH 2 foil stack

6 Transition radiation detectors Electron with 0.5 GeV Pion with 100 GeV Number of photons vs. E/m

7 Intensity distribution

8 Formation length

9 Transition radiation detectors TR Radiators: stacks of CH 2 foils are used hydrocarbon foam and fiber materials Low Z material preferred to keep re-absorption small ( Z 5 ) R D R D R D R D sandwich of radiator stacks and detectors minimize re-absorption TR X-ray detectors: Detector should be sensitive for 3 E γ 30 kev. Mainly used: Gaseous detectors: MWPC, drift chamber, straw tubes Detector gas: σ photo effect Z 5 gas with high Z required, e.g. Xenon (Z=54)

10 Different Radiator Types

11 Several Radiator Foils incoh. addition absorption detection eff. (photabsorption) one foil several foils

12 TR Signature in Detector number of events pulse height

13 ATLAS TR-Tracker

14 ATLAS TRT

15 Straw Spectra for Pions and Electrons

16 ATLAS Pion Electron Separation

17 Time-Of-Flight (TOF)

18 Time-Of-Flight [ ] l t c l p m = t v l m p = = β γ Time to Digital Converter TDC Δ + Δ + Δ = Δ l l t t p p m m γ

19 For l 12 m Δt 150 ps Δp/p 1 % Time-Of-Flight

20 Time Difference 2 particles (m 1, m 2 ), momentum p length L p distance D relativistic particles E >> mc 2 : E pc and development of square root non relativistic particles:

21 Time Difference time difference after 1 m time resolution 300 ps è Kaon-pion separation up to 1 GeV/c for L = 3 m TOF limited for particles with p < GeV/c

22 TOF particle identification NA 49 particle multiplicity Belle mass from TOF measurement

23 ALICE (TOF) TOF with large multiplicity radius 3.6 m è 150 m 2! scintillators too expensive è gas detectors Multigap Resistive Plate Chamber (MGRPC) Signal electrode Cathode -10 kv (-8 kv) (-6 kv) (-4 kv) (-2 kv) Anode 0 V Signal electrode small gap è good time resolution many gaps è high efficiency resolution 50 ps

24 ALICE (TOF) 130 mm active area 70 mm Flat cable connector Differential signal sent from strip to interface card M5 nylon screw to hold fishing-line spacer connection to bring cathode signal to central read-out PCB honeycomb panel (10 mm thick) PCB with cathode pickup pads external glass plates 0.55 mm thick Honeycomb panel (10 mm thick) internal glass plates (0.4 mm thick) PCB with anode pickup pads 5 gas gaps of 250 micron PCB with cathode pickup pads Silicon sealing compound Mylar film (250 micron thick)

25 Combined Methods NA49 Particle identification by simultaneous de/dx and TOF measurement in the momentum range 5 to 6 GeV/c for central Pb+Pb collision m 2 = p l [ c t l ]

26 Lifetime measurement - Tagging p Primary vertex secondary vertex 0.1 mm p Beam pipe Identification of particles by their lifetime: e.g.: D ± τ = s c τ = 312 µm D 0 τ = s c τ = 123 µm B ± τ = s c τ = 501 µm B 0 τ = s c τ = 460 µm è excellent vertex resolution needed!

27 Summary of PID techniques A number of powerful methods are available to identify particles over a large momentum range. Depending on the available space and the environment, the identification power can vary significantly. A very coarse plot. TR TOF de/dx RICH e ± identification Pion-Kaon separation for different PID methods. π/k separation The length of the detectors needed for 3σ separation p [GeV/c]

28 Detector Systems Detector Systems Remember: we want to have info on... number of particles event topology momentum / energy particle identity Can t be achieved with a single detector! integrate detectors to detector systems

29 Detector Systems Geometrical concepts Fix target geometry Collider Geometry Magnet spectrometer 4π Multi purpose detector traget tracking muon filter N S beam magnet (dipole) calorimeter barrel endcap endcap Limited solid angle dω coverage rel. easy access (cables, maintenance) full dω coverage very restricted access

30 Detector Concepts Magnetic field configurations: solenoid B B toroid I magnet coil I magnet + Large homogenous field inside coil - weak opposite field in return yoke - Size limited (cost) - rel. high material budget Examples: DELPHI (SC, 1.2T) L3 (NC, 0.5T) CMS (SC, 4T) + Rel. large fields over large volume + Rel. low material budget - non-uniform field - complex structure Example: ATLAS (Barrel air toroid, SC, 0.6T)

31 Detector Concepts Typical arrangement of subdetectors µ + e - γ vertex location (Si detectors) ì p main tracking (gas or Si detectors) ì particle identification ì e.m. calorimetry ì magnet coil ì hadron calorimetry / return yoke ì muon identification / tracking ì

32 PANDA Spectrometer Detector requirements: 4π coverage (partial-wave-analysis) high rates (10 7 annihilations/s) good PID (γ, e, µ, π, K, p) momentum res. (~1%) vertexing für D, K 0 S, Λ (cτ = 123 µm for D0, p/m 2) efficient trigger (e, µ, K, D, Λ) no hardware trigger (raw data rate ~TB/s) Tobias Stockmanns, IKP FZ- Jülich 32

33 AntiProton Annihilation at Darmstadt 13 m

34 Target-System Clusterjet- oder Pellet-Target Antiprotonenstrahl Wechselwirkungspunkt

35 Magnet-System Solenoid-Magnet zur Messung des transversalen Impulses Dipol-Magnet zur Messung des longitudinalen Impulses für Spuren in Vorwärtsrichtung

36 Spurdetektoren

37 Spurdetektoren Straw-Tube-Tracker Luminositäts-Monitor Mikro-Vertex-Detektor GEM-Detektoren Vorwärts-Detektoren

38 Spurdetektoren

39 Teilchenidentifikation

40 Teilchenidentifikation Forward RICH Barrel DIRC Endcap DIRC

41 Teilchenidentifikation Vorwärts RICH Barrel DIRC Barrel TOF Endcap DIRC Vorwärts TOF

42 Teilchenidentifikation Myonen- Detektoren Vorwärts RICH Barrel DIRC Barrel TOF Endcap DIRC Vorwärts TOF

43 Teilchenidentifikation

44 Kalorimetrie

45 Kalorimetrie PWO Kalorimeter Vorwärts Shashlyk EMC Hadronisches Kalorimeter

46 PANDA

47 PANDA Ereignissimulation

48 PANDA Ereignissimulation