Basic of Detector

1. Basic of Detector Atsushi Taketani 竹谷篤 RIKEN Radiation-lab RIKEN Brookhaven Research Center

2. What I worked for detectors • Electron-Positron collider Experiment at 60GeV • Trigger electronics, TRD, EMCAL, Si Sensor • Proton-Antiproton collider experiment at 1.8TeV • Muon detector, Readout electrinics • Large scale Accelerator control at 8GeV • Distributed computing system hardware/software • Polarize proton-proton/ Heavy Ion collider experiment at 200GeV • Muon detector, Si detector Working higher energy

3. Index of this lecture • Why/How we need detector? • What do we want to measure? • Interaction with material • Gas Chamber basics • Other detectors • PHENIX experiment and Silicon Detector • Summary

4. Importance of Detector Physics detector Human • We need detector to understand physics • Detector innovation can arise new physics • Telescope : Newton mechanics • Velocity of light measurement : Relativity • High resolution hydrogen spectroscopy : Quantum mechanics

5. Major Detector Principle • Particle penetrates or stops at detector • Particle interacts with material of detector • Generating some signal • Amplification mechanism • Analog to Digital conversion • Getting into computer • Analyze at digital data ->physics PC Digital signal Amp. Analog to digital conversion Sensor Particle electric signal (analog) Data taking Scintillator Semiconductor Detectors Coaxial cable

6. Particle mass • Particle has its own mass. • electron 0.511MeV • m 105MeV • p+, p- 140MeV, p0 135MeV • Proton 928MeV • J/y 3069MeV (discovered by S.C.C. Ting and B. Richter) • If we know the mass of particle, we can identify the particle species.

7. 4-momentum • Treating the mass at relativity P2 = E2 - | p|2 = m2 Where P : 4-momentum E : Energy p : 3-momentum ( px, py, pz ) m : invariant mass

8. 4-momentum • (E, px, py, pz ) • Invariant mass : m2 = E2 - | p|2 • 3-momentum (velocity) v/c = b = p/E Where c is light velocity • If we can measure 3-momentum p, and Energy E or 3-momentum b, m can be obtained -> identifying particle.

9. (E1,p1) 1 0 (E, p) q12 2 (E2,p2) Particle decay Energy conservation If particle 0 is rest, and m0>>m1, m2 then q12=180deg, b1,b2 ~1 Momentum conservation Invariant mass

10. Example for p0 decay g1 • Mass of p0 is 135MeV • Decay into 2g • g (photon) is mass less. • p0 is at rest. p0 g2 Light velocity Momentum conservation

11. 3-momentum measurement • Momentum can be measured by using Lorentz force F: force, q: electric charge, E: electric field v: particle velocity = p/m, B: magnetic field Constant force -> Constant curvature -> particle track trajectory P [MeV/c] = 3 * r[cm] * B[T] r: curvature radius, B: magnetic field

12. Energy measurement • Particle stops at the material and measure all deposited energy by energy loss • b = p/E : particle velocity measure timing deference between 2 known location Calorimeter Energy(value) particle L b = V/c = L/(t2-t1)/c particle t2 t1

13. Particle and material interaction • Particle will hit, penetrate, or stop at material, including gas, liquid, solid. • Particle has some interaction with material, then we can detect it. -> Detector • Energy Loss, Multiple Scattering and So.

14. Energy Loss and stopping power 5.49MeV a particle in air electric Energy loss [MeV/cm] Energy loss [MeV/cm] nuclear Particle energy [MeV] Path length [cm]

15. Particle charge Bethe-Bloch formula Energy loss [MeV cm2/g] Particle energy [MeV]

16. Particle energy [MeV] Typical Energy Loss • dE/dX ~ 1MeV cm2/g for Minimum ionizing particle • Energy loss / Unit length ~ 2MeV cm2/g * Material density [g/cm3] For example at Al dE/dX = 1.615MeV cm2/g Aluminum r=2.70g/cm3 Energy loss =0.60MeV/cm Minimum Ionizing Particle

17. Multiple Scattering for M.I.P. Z: particle charge x: material thickness X0: radiation length

18. Atomic and Nuclear properties of materials

19. Example • Aluminum 1cm thickness with electron 50MeV • Estimate the angle deviation at exit, ignore energy loss. • Radiation length X0=24.01 [g/cm2] / 2.699[g/cm3]=8.9[cm] x/X0=0.11

20. Typical Wire Chamber

21. Gas Chamber • Energetic particle passing through gas. • Gas molecules are ionized -> electrons and ions. • Electrons and ions are drifted to electro load with minus and plus voltage • Avalanche near by wire • Getting electrical signal

22. - + Ionization • Ionization happens along charged particle track • #Electorn-Ion pair/unit length = dE/dX / Pair creation energy • Pair creation Energy • H2 37eV • Ar 26eV - + - + - + - + - + - + Gas Chamber

23. Ionization Ar: dE/dX = 1.519MeV cm2/g electron-ion = 97 /cm density = 1.662 g/L pair creation energy = 26 eV #electron-ion = 1.519MeV cm2/g * 106 eV/MeV * 1.662g/l*1000cm3/l /26eV = 97 /cm

24. Drift drift velocity =50~100mm/nsec = 5mm~10mm / 100 nsec Drift velocity[mm/nsec] Electric field and potential Electric field [KV/cm]

25. Avalanche E: electric field r: distance from wire V0: bias voltage a: radius of cylinder b: wire radius electron Electric filed gas molecule Gas multiplication

26. Gas Gain a/Pressure Multiplication Electric field/Pressure [V/cm /mmHg] Voltage [V]

27. Amplifier Cf Charge Q Cd -A Output V When A>> (Cd+Cf)/Cf, V = -Q/Cf

28. output Analog signal Vthreshold Discriminator (Comparator) Analog Vthreshold time Output time

29. Voltage to Digital • Array of comparators with different voltage • Get lowest High bit. • Decode into binary code. Measure charge

30. Drift chamber Incident particle Electron drift r Wire • Determine when particle passing through by other sensor device such as scintillator :T1 • Measure time when wire has hit:T2 • r = (T2-T1) * drift velocity

31. Time to Digital Particle wire clock Count #clock Time = #clock * Clock Interval = 11 * 2 nsec = 22 nsec Drift distance = 22nsec * 100mm/nsec = 2200mm

32. What we can measure by gas chamber • Hit location -> position sensitive momentum measurement • Total charge -> dE/dx in the gas depend on mass and velocity (momentum) • Timing drift chamber-> more precise position

33. Other 2-dimesional readout X plane Y plane

34. Other Major Detectors (include past) Detector dead time after a hit Position sensitivity Timing sensitivity

35. Precise Time measurement detector Plastic scintillator • Charged particle is penetrating • Lower energy electron is exited to upper state • Upper state electron drops into lower state and emits a photon • Propagate to P.M.T. • P.M.T. generates electric pulse. Charged particle Light guide Photo Multiplier Tube Timing pulse

37. Photo Multiplier Tube

38. Cherenkov Radiation bc:Particle velocity < c: light velocity in vacuum In material light velocity =c/n, when n is refractive index. But particle velocity is same. Cherenkov is as supersonic waves of light if bc > c/n, then Cherenkov radiation cosq =1/nb

39. Electric pulse ~ particle energy electron electron/positron P.M.T. NaI Crystal g Calorimeter Mass of electron is 511KeV g->e++e- for Eg>1.02MeV

40. Typical Detector System Magnetic field L: length Calorimeter Energy =E Wire Chambers Scitillator Timing =t2 Scitillator Timing = t1 P [MeV/c] = 3 * r[cm] * B[T] r: curvature radius, B: magnetic field b = V/c = L/(t2-t1)/c E=P/b m2=E2+P2 Determine 4-momentum

41. electrode h h h h h - P type + + - - + - + + - N type e e e e e electrode Sensor Diode Principle of Si sensor Charged particle electron Depletion Layer

42. Feature of Silicon Detector • High dE/dx ( ~ 2MeV /(g/cm^2) ) • Solid state detector comparing to gas chamber -> thin detector • Low e-h pair creation energy • 3.6 eV instead of 13.6 eV for gas chamber • Available Technology by industry • Small and precise • Huge number of read out channel • But no intrinsic amplification • Required low noise electronics

43. VTX will be installed into inner most detector from beam pipe PHENIX Where is VTX VTX p, Au • Good particle ID • High resolution • High trigger rate p, Au

44. Charm meson ~ 100μｍ Bottomed meson~ 300μｍ Charmed or bottomed meson Polarized proton Polarized proton Identify long lived particles Si sensor

45. Requirements for Vertex Tracker Physics side • High precision tracking for displaced vertex measurement. 50mm displaced vertex resolution, ct ~ 100mm(D), ~400mm(B) • Large coverage tracking capability with momentum resolution (|h|<1.2 , and full azimuthally with s/P ~ 5%P) • High charged particle density ‘dN/dh’ ~ 700 @h=0 • High Radiation Dose ~100KRad@10Years • High Luminosity 2*1032 cm-2 s-1@PP -> High rate readout • Low Material Budget <- avoid multiple scattering and photon conversion for electron measurement by outer detectors. Environment side

46. Full detector shape Inner 2 barrel with silicon Pixel Outer 2 barrel with silicon Stripixel

47. VTX parameters (in proposal) Pixel detector Strip detector BEAM Pixel Strip

48. Proposal for a Silicon Vertex Tracker (VTX) for the PHENIX Experiment M. Baker, R. Nouicer, R. Pak, A. Sukhanov, P. Steinberg Brookhaven National Laboratory, Chemistry Department, Upton, NY 11973-5000, USA Z. Li Brookhaven National Laboratory, Instrumentation Division, Upton, NY 11973-5000, USA J.S. Haggerty, J.T. Mitchell, C.L. Woody Brookhaven National Laboratory, Physics Department, Upton, NY 11973-5000, USA A.D. Frawley Florida State University, Tallahassee, FL 32306, USA J. Crandall, J.C. Hill, J.G. Lajoie, C.A. Ogilvie, A. Lebedev, H. Pei, J. Rak, G.Skank, S. Skutnik, G. Sleege, G. Tuttle Iowa State University, Ames, IA 56011, USA M. Tanaka High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan. N. Saito, M. Togawa, M. Wagner Kyoto University, Kyoto 606, Japan H.W. van Hecke, G.J. Kunde, D.M. Lee, M. J. Leitch, P.L. McGaughey, W.E. Sondheim Los Alamos National Laboratory, Los Alamos, NM 87545, USA T. Kawasaki, K. Fujiwara Niigata University, Niigata 950-2181, Japan T.C. Awes, M. Bobrek, C.L. Britton, W.L. Bryan, K.N. Castleberry, V. Cianciolo, Y.V. Efremenko, K.F. Read, D.O. Silvermyr, P.W. Stankus, A.L. Wintenberg, G.R. Young Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA Y. Akiba, J. Asai, H. En’yo, Y. Goto, J.M. Heuser, H. Kano, H. Ohnishi, V. Rykov, T. Tabaru, A. Taketani, K.Tanida, J. Tojo RIKEN (The Institute of Physical and Chemical Research,) Wako, Saitama 351-0198, Japan S. Abeytunge, R. Averbeck, K. Boyle, A. Deshpande , A. Dion, A. Drees, T.K. Hemmick, B.V. Jacak, C. Pancake, V.S. Pantuev, D. Walker Stony Brook University, Department of Physics and Astronomy, Stony Brook, NY 11794, USA B. Bassalleck, D.E. Fields, M. Malik University of New Mexico, Albuquerque, NM, USA As of May 2006 Proposal to DOE, 92 authors from 20 institutions Budget DOE (4.7M$) RIKEN(3M$), IN2P3 Ecole Polytechnique, LLR (0.1M$) M. Finger :Charles University,, Czech Republic L. Tomasek, V. Vrba :Institute of Physics, Academy of Sciences, Czech Republic

49. PIXEL (Sensor and Readout) • Readout by ALICE_LHCB1 chip • Amp + Discriminator / channel • Bump bonded to each pixel • Running 10MHz clock ( RHIC 106nsec ) • Digital buffer for each channel > 4msec depth • Trigger capability > FAST OR logic for each crossing • 4 event buffer after L1 trigger Pixel size( x z）50 µm x 425 µm Sensor Thickness 200mm r = 1.28cm, z = 1.36 cm (Active area) 256 x 32 = 8192 channel / sensor 4 chip / sensor 4 sensor / stave

50. Bump bonding 20μm Solder Bump bond to silicon pixel sensor