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 1.Why/How we need detector? 2.What do we want to measure? 3.Interaction with material 4.Gas Chamber basics 5.Other detectors 6.PHENIX experiment and Silicon Detector 7.Summary

4 Importance of Detector PhysicsdetectorHuman 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 1.Particle penetrates or stops at detector 2.Particle interacts with material of detector 3.Generating some signal 4.Amplification mechanism 5.Analog to Digital conversion 6.Getting into computer 7.Analyze at digital data ->physics Sensor Particle electric signal (analog) Analog to digital conversion Amp. PC Digital signal Scintillator Semiconductor Detectors Coaxial cable Data taking

6 Particle mass Particle has its own mass. – electron 0.511MeV –  105MeV –  +,  - 140MeV,  0 135MeV – Proton 928MeV –J/  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 P 2 = E 2 - | p| 2 = m 2 Where P : 4-momentum E : Energy p : 3-momentum ( px, py, pz ) m : invariant mass

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

9 Particle decay Energy conservation Momentum conservation Invariant mass If particle 0 is rest, and m 0 >>m 1, m 2 then  12 =180deg,  1,  2 ~1 (E, p) (E 1,p 1 ) (E 2,p 2 )   1 0 2

10 Example for  0 decay Mass of  0 is 135MeV Decay into 2   (photon) is mass less.  0 is at rest. 00 11 22 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  = p/E : particle velocity measure timing deference between 2 known location particle Calorimeter Energy (value) particle L t1t1 t2t2  = V/c = L/(t 2 -t 1 )/c

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 Path length [cm] Energy loss [MeV/cm] 5.49MeV  particle in air electric nuclear Particle energy [MeV]

15 Bethe-Bloch formula Energy loss [MeV cm 2 /g] β= v / c vvelocity of the particle Eenergy of the particle xdistance travelled by the particle cEnergyLoss.bmpEnergyLoss.bmpspeed of light particle charge echarge of the electronelectron meme rest mass of the electron nelectron density of the target Imean excitation potential of the target permittivitypermittivity of free space Particle charge Particle energy [MeV]

16 Typical Energy Loss dE/dX ~ 1MeV cm 2 /g for Minimum ionizing particle Energy loss / Unit length ~ 2MeV cm 2 /g * Material density [g/cm 3 ] For example at Al dE/dX = 1.615MeV cm 2 /g Aluminum  =2.70g/cm 3 Energy loss =0.60MeV/cm Particle energy [MeV] Minimum Ionizing Particle

17 Multiple Scattering for M.I.P. Z: particle charge x: material thickness X 0 : 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 X 0 =24.01 [g/cm 2 ] / 2.699[g/cm 3 ]=8.9[cm] x/X 0 =0.11

20 Typical Wire Chamber

21 Gas Chamber 1.Energetic particle passing through gas. 2.Gas molecules are ionized -> electrons and ions. 3.Electrons and ions are drifted to electro load with minus and plus voltage 4.Avalanche near by wire 5.Getting electrical signal

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

23 Ionization Ar: dE/dX = 1.519MeV cm 2 /g electron-ion = 97 /cm density = g/L pair creation energy = 26 eV #electron-ion = 1.519MeV cm 2 /g * 106 eV/MeV * 1.662g/l*1000cm 3 /l /26eV = 97 /cm

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

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

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

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

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

29 Voltage to Digital 1.Array of comparators with different voltage 2.Get lowest High bit. 3.Decode into binary code. Measure charge

30 Drift chamber Wire Electron drift Incident particle r 1.Determine when particle passing through by other sensor device such as scintillator :T1 2.Measure time when wire has hit:T2 3.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 * 100  m/nsec = 2200  m

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) Position sensitivity Timing sensitivity Detector dead time after a hit

35 Precise Time measurement detector Plastic scintillator Light guide Photo Multiplier Tube Timing pulse Charged particle 1.Charged particle is penetrating 2.Lower energy electron is exited to upper state 3.Upper state electron drops into lower state and emits a photon 4.Propagate to P.M.T. 5.P.M.T. generates electric pulse.

36

37 Photo Multiplier Tube

38 Cherenkov Radiation  c: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  c > c/n, then Cherenkov radiation cos  =1/n 

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

40 Typical Detector System Magnetic field Wire Chambers Scitillator Timing = t1 Scitillator Timing =t2 P [MeV/c] = 3 * r[cm] * B[T] r: curvature radius, B: magnetic field L: length  = V/c = L/(t 2 -t 1 )/c E=P/  m 2 =E 2 +P 2 Determine 4-momentum Calorimeter Energy =E

41 Principle of Si sensor electrode P type N type Diode Sensor Depletion Layer Charged particle electron eeeee hhhhh

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

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

45 Requirements for Vertex Tracker High precision tracking for displaced vertex measurement. 50  m displaced vertex resolution, c  ~ 100  m(D), ~400  m(B) Large coverage tracking capability with momentum resolution (|  |<1.2, and full azimuthally with  /P ~ 5%P) High charged particle density ‘ dN/d  ’ ~  =0 High Radiation Dose High Luminosity 2*10 32 cm -2 s -> High rate readout Low Material Budget <- avoid multiple scattering and photon conversion for electron measurement by outer detectors. Physics side Environment side

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

47 VTXLayerR1R2R3R4 Geometrical dimensions R (cm)  z (cm) Area (cm 2 ) Channel countSensor size R  z (cm 2 ) 1.28  1.36 (256 × 32 pixels) 3.43 × 6.36 (384 × 2 strips) Channel size 50  425  m 2 80  m  3 cm (effective 80  1000  m 2 ) Sensors/ladder 4  4 56 Ladders Sensors Readout chips Readout channels1,310,7202,621,440138,240239,616 Radiation length (X/X0) Sensor0.22%0.67 % Readout0.16%0.64 % Bus0.28% Ladder & cooling0.78% Total1.44%2.1 % Pixel detectorStrip detector VTX parameters (in proposal) BEAM Strip Pixel LayerradiusDetectorOccupancy in Central Au+Au collision Layer 12.5 cmPixel0.53 % Layer 25.0 cmPixel0.16% Layer cmStrip4.5 % (x-strip)4.7 % (u-strip) Layer cmStrip2.5 % (x-strip)2.7 % (u-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 , USA Z. Li Brookhaven National Laboratory, Instrumentation Division, Upton, NY , USA J.S. Haggerty, J.T. Mitchell, C.L. Woody Brookhaven National Laboratory, Physics Department, Upton, NY , 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 , 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 , 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 , 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 M. Finger :Charles University,, Czech Republic L. Tomasek, V. Vrba :Institute of Physics, Academy of Sciences, Czech Republic As of May 2006 Proposal to DOE, 92 authors from 20 institutions Budget DOE (4.7M$) RIKEN(3M$), IN2P3 Ecole Polytechnique, LLR (0.1M$)

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

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

51 Pixel detector module Sensor module consists of 4 ALICE Pixel readout chips Bump-bonded to silicon sensor Sensor Half stave is mounted on the support structure Thermo plate + cooling Pixel BUS to bring data out and send control signal in to the readout chip is mounted on the half stave Each detector module is built of two half staves, read out on the barrel ends Half stave Pixel BUS Data One readout unit, half stave, made from two sensor modules Full stave 22cm 1.4cm ALICE LHCB1 chip SensorSensor Module

52 Pixel Readout Overview Half stave 11cm 60cm Bus (25cm ) + Extender (<35cm)

53 Q/A test of ALICE chip and sensor module Mean Minimum Threshold for this chip = 1508 e - ~ 22 mV Average noise level = 116 e - ~ 1.8 mV Results of threshold scan for all individual pixel on column (256 curves are superimposed) MIP signal in 200 m sensor ~ 14,000 e -

54 Bus structure Power 50  m Al GND 50  m Al 6 layers structure GND, Power and 4 signal lines Signal 2; (Vertical line) line connected with pixel chip with wire bonding Signal 4; (for manufacture reason) Signal-4 3  m Cu Signal-3 3  m Cu Signal-2 3  m Cu Signal 1; (for Surface Mount Device) Signal-1 to Signal-4 are connected with through hole Signal lines; 60  m pitch Material Budget; Total ~ 0.26 % Final configuration Signal-1 3  m Cu Signal 3; (Horizontal line) send signal to Pilot Module connected with vertical line with through hole Thermo-plate Sensor module Wire bonding Al Power Al GND Through hole Signal layer Total 188 lines 25cm long 1.4cm wide

55 250mm Readout Bus Extender Ver mm

56 ＜セットアップ＞ ピクセルラダー ３ layer Layer １ － Layer １：左側バス + １センサー + ガラス板 Layer ２ － Layer ２：左側バス + ２センサー + ステイブ － Layer ３：左側バス + ２センサー PHENIX 用 DAQ ： DCM+FEM トリガー：各ラダーの FastOR + シンチレーター Layer 1 Layer 3 Layer 2 陽子ビーム Optical cables lab Layer 1 PC FEM SPIRO 3 Extender Pixel senor Layer 2 SPIRO 3 Extender Pixel senor Layer 3 SPIRO 1.1J Extender Pixel senor USB cable 3cm ladder 1.5cm ladder B 1.5cm ladder C ( 冷却パイプ付 ) PDAQ 120GeV 陽子ビーム Optical cables

57 Layer 1 Layer 2 Layer 3 col row 13mm 57mm センサー チップ ×4 32 × 4 pixels 256 pixels 256 rows 32 columns preliminary 425  m 50  m 32×256 = 8192 pixels 425  m×50  m / pixel ビーム試験の結果、 PHENIX 用 DAQ 環境下で ３ピクセルラダーの動作を確認できた。

58 General Charactersirty Sensitivity Detector Response Energy resolution Response function Response time Detector Efficiency Dead time

59 Summary We need to have detector to investigate nature. You have to build and/or be familiar with detector for your own experiments I explain wire chamber and some other detector as typical example.

60 Measurement of the momentum Magnetic filed Precise momentum measurement Need more space points Smaller wire spacing or thicker detector Better position resolution at each points