1 / 36

Detector Development for the ILC

Detector Development for the ILC. Roman Pöschl DESY Hamburg ILC Summer School Beijing China 15.-20. July 2005. Part I : Introduction to the Physics of Particle Detectors Part II : Detector Concepts and the Concept of Particle Flow

trent
Télécharger la présentation

Detector Development for the ILC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Detector Development for the ILC Roman Pöschl DESY Hamburg ILC Summer School Beijing China 15.-20. July 2005 Part I : Introduction to the Physics of Particle Detectors Part II : Detector Concepts and the Concept of Particle Flow Part III: Vertexing & Tracking Part IV: Calorimetry & Software Tools

  2. Part I Introduction to the Physics of Particle Detectors Roman Pöschl ILC School Beijing China 15-20 July 2005

  3. Outline • Interactions of Particles with Matter • Gaseous Detectors • Shower Counters • Electromagnetic Counters • Hadronic Counters • Detectors based on Semi-Conductors Roman Pöschl ILC School Beijing China 15-20 July 2005

  4. Particle Detectors Geiger’ Müller Counter Human Eye High Energy Physics Detector Roman Pöschl ILC School Beijing China 15-20 July 2005

  5. Interactions of Particles with Matter Outgoing Particle (p’) Incoming Particle (p) Scattering Center: Nucleus or Atomic Shell Detection Process is based on Scattering of particles while passing detector material Energy loss of incoming particle: E = p0 - p’0 Roman Pöschl ILC School Beijing China 15-20 July 2005

  6. Energy Loss of Charged Particles in Matter Regard: Particles with m0 >> me E = 0: Rutherford Scattering E 0: Leads to Bethe-Bloch Formula z - Charge of incoming particle Z, A - Nuclear charge and mass of absorber re, me - Classical electron radius and electron mass NA - Avogadro’s Number = 6.022x1023 Mol-1 I - Ionisation Constant, characterizes Material typical values 15 eV Fermi’s density correction Tmax - maximal transferrable energy (later) Roman Pöschl ILC School Beijing China 15-20 July 2005

  7. Discussion of Bethe-Bloch Formula IDescribes Energy Loss by Excitation and Ionisation !!We do not consider lowest energy losses ‘Kinematic’ drop ~ 1/ Scattering Amplitudes: Large angle scattering becomes less probable with increasing energy of incoming particle. Drop continues until  ~ 4 Roman Pöschl ILC School Beijing China 15-20 July 2005

  8. Discussion of Bethe-Bloch Formula IIMinimal Ionizing Particles (MIPS) dE/dx passes broad Minimum @  4 Contributions from Energy losses start to dominate kinematic dependency of cross sections typical values in Minimum [MeV/(g/cm2)] [MeV/cm] Lead 1.13 20.66 Steel 1.51 11.65 O2 1.82 2.6·10-3 Role of Minimal Ionizing Particles ? Roman Pöschl ILC School Beijing China 15-20 July 2005

  9. Intermezzo: Minimal Ionizing Particles Minimal Ionizing Particles deposit a well defined energy in an absorberTypical Value: 2 MeV/(g/cm2) Cosmic-Ray  have roughly  4  Ideal Source for Detector Calibration Cosmic Muons detected in ILC Calorimeter Prototype Signals show Landau-Distribution: Average (à la Bethe-Bloch) Real Typical for thin absorbers Thick Absorbers: Average = Real Landau Distribution Gauss-Distribution Cosmic  spectrum at Sea Level Rate ~ 1/(dm2sec.) Roman Pöschl ILC School Beijing China 15-20 July 2005

  10. Discussion of Bethe-Bloch Formula IIILogarithmic Rise ‘Visible’ Consequence of Excitation and Ionization Interactions. Dominate over kinematic drop Interesting question: Energy distribution of electrons created by Ionization. -Electrons In the relativistic case an incoming particle can transfer (nearly) its whole energy to an electron of the Absorber These -electrons themselves can ionize the absorber ! Non relativistic: E1 ≈M Relativistic: |p1| ≈M Roman Pöschl ILC School Beijing China 15-20 July 2005

  11. -Electrons -Electron Production in a Bubble Chamber Probability to produce a -Electron e- e-e-e+ Number of -electrons allow the determination of charge and velocity of ionizing particle Be careful: Neglection of -Electrons led to ‘discovery’ of free quarks (McCusker 1969) -Electrons Roman Pöschl ILC School Beijing China 15-20 July 2005

  12. Discussion of Bethe-Bloch Formula IVFermi’s Density Correction - ‘Tames’ logarithmic rise Interaction with absorber medium Energy losses not treated as statistically independent processes  Single  elm. wave Basic Effect: Amplitude felt by Atom at P is shielded by other Atoms  Damped wave !!! P does not contribute to energy loss ! Density Correction more important in Solids than in Gases Remark: Density Correction tightly coupled to Čerenkov-Effect P Roman Pöschl ILC School Beijing China 15-20 July 2005

  13. Discussion of Bethe-Bloch Formula VRadiative Losses - Not included in Bethe-Bloch Formula Particles interact with Coulomb Field of Nuclei of Absorber Atoms Energy loss due to Bremsstrahlung Important for e.g. Muons with E > 100 GeV Dominant energy loss process for electrons (and positrons) Detailed discussion later Roman Pöschl ILC School Beijing China 15-20 July 2005

  14. Interactions of Photons with Matter Photonabsorption Cross Section in Pb barns/atom Phot. incoh. Coh. Pair Nuc. Pair Elek. E[MeV] General: Beer’s Absorption Law: I= I0e-x,  = Absorptioncoefficientl Three main processes Photoeffect: Phot.+Atom  Atom+ + e- E mc2 I0 << E<< mc2 aB = Bohr radius, re = class. Electronradius Compton Effect: coh., incoh. +e-+e- Klein-Nishina: E << mc2. E>> mc2 From: http://www.nist.gov Roman Pöschl ILC School Beijing China 15-20 July 2005

  15. Pair Production Process e+ Energy Spectrum of e+e- Photon interacts in Coulomb Field of Nucleus (or Shell Electron) e- From Kinematics: Threshold Energy 1.2 MeV Absorption Coefficient Some Values: X0,Air=30 420 cm X0,Al = 8.9 cm X0,Pb = 0.56 cm Radiation length Characterizes the behavior of high energetic  and e in Matter Roman Pöschl ILC School Beijing China 15-20 July 2005

  16. Bremsstrahlungs Process Energy Loss for High Energetic electrons (and muons) Molière Radius RM: Transversal deflection of e- after passing X0 due to multiple scattering c = critical Energy Energy where energy losses due to ionization excitation start to dominate X0, RM and c are most important characteristics of electromagnetic shower counters Typical Values for Pb: c[MeV] RM [cm] Pb 7.2 1.6 NaJ 12.5 4.4 Roman Pöschl ILC School Beijing China 15-20 July 2005

  17. Gaseous Detectors Basic Principle: Charged particle ionizes gas embedded in an electrical field Chamber Gas V0 Particle Trajectory + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - Induced charge produces voltage pulse at R ~ Particle Energy R Questions: - Charge Transportation in Gases - Gas Amplification - An Example: MWPC - Operation Modes of Gaseous Detectors Roman Pöschl ILC School Beijing China 15-20 July 2005

  18. Drift Velocity Regard motion of Electrons ! Charged Particle drifts in Electrical Field and undergo Collisions with Gas Atoms In general there is also a magnetic Field (B-Field) present. Equation of Motion Q(t) - Friction Term Slowdown of Electrons due to Collisions ! Compensates for acceleration in E-Field. Averaging over time >> Time between collisions For B=0:  = Mobility Typical value: vD 5 cm/s vD,Ion = vD,Electron/1000 ! Roman Pöschl ILC School Beijing China 15-20 July 2005

  19. - - - - - - - Gas Amplification • So far: Signal from collecting charge from ionization • Yields relatively small signal • Increasing of E ? • Secondary charges gain kinetic energy in E-Field and ionize themselves A=1 C = Chamber Capacitance + + First Townsend Coefficient  Number of Electron-Ion Pairs produced per unit length by a secondary Electron + + + + Gas Amplification: A = ex Typical Value: 104 At A  108 spark production Townsend Avalanche close to an anode wire in a cylindrical gas counter Roman Pöschl ILC School Beijing China 15-20 July 2005

  20. - - - - - - - - - - - - - - - - - -  Diffusion in Gases Dilution of Ionization Pattern in Gas t0 t0 +t t0 + nt •  = Time between two collisions • w = e-t/T Probability for no collision • = Mean free path <v> =  = average thermal velocity of e- thermodynamic equilibrium E=0: Extension of Cloud before first collision No Influence on long. Diffusion In the thermal limit t is independent of E (e.g. CO2) Transversal Diffusion ? After n = t/ collisions with: Particles curl around Fieldlines D= Diffusion Coefficient Longitudinal Diffusion B-Field tames Diffusion Diffusion depends on Drift Velocity Transversal Diffusion Roman Pöschl ILC School Beijing China 15-20 July 2005

  21. Multiwire Proportional Chambers (G. Charpak, Noble Price 1992) Particle Trajectory Cathode 20m Anode 16mm 2mm Cathode Detector for energy measurement dE/dx and spatial resolutionl • Secondary Particles drift along Fieldlines • to Anode Wires => Spatial information • Constant Field at Cathode • Cylindrical Symmetry at Anode • Field strength increases with decreasing • distance to Anode • Avalanche Generation => Signal proportional to • primary Ionization Field Configuration MWPC in a Detector (SFM at CERN 70s): Spatial Resolution 1 mm Time Resolution 10 ns Spatial Resolution is better in other types of gaseous detectors, e.g. Drift Chambers Roman Pöschl ILC School Beijing China 15-20 July 2005

  22. Drift Chambers (similar to MWPC) Time t between particle passage and arrival of charge cloud at anode Cathode - + Anode + - x = v t, v = Drift Velocity - + - + Time Measurement allows for reduction of wires compared to MWPC x Cylindrical Drift Chamber “Many” MWPCs Field by wires put on different potentials Large Drift Volume allows the measurement of particle trajectory Track Measurement If B-Field: Measurement of particle momentum p = 0.3 B  Track x x x x x = Cathode Wire o = Anode Wire x o x o x x x x o x o x x x x x x o x o o x o x x x x x x x x x o x o x x o x o x x x x x x x x x o x o x o x o x x x x x x x x x o x o x o x o x x x x Outer Radius: O(1m) Roman Pöschl ILC School Beijing China 15-20 July 2005

  23. Operation Modes of Gaseous Detectors # of Ions Limited Proportionality Ionization Chamber Ionization Chamber Proportional Counters V[Volt] Roman Pöschl ILC School Beijing China 15-20 July 2005

  24. Calorimetry Basic Principle: High energetic particle is stopped in a dense absorber. Kinetic energy is transferred into detectable signal Absorber with Z >> 1 • Only way to measure to measure electrically neutral particles • - Only way to measure particles at high energies (although … see later) Need to distinguish: Electromagnetic Calorimeters Hadronic Calorimeters Creation and readout of detectable Signals ? Roman Pöschl ILC School Beijing China 15-20 July 2005

  25. Electromagnetic Calorimeters - Shower Development Energy loss of electron by Bremsstrahlung: Photons convert into e+e--Pairs Simple Shower Model (see Longo for detailed discussion) - Energy Loss after X0: E1 =Eo/2 • - Photons -> materialize after X0 • E±=E1/ 2 • Number of particles after t: N(t) = 2t • Each Particle has energy • Shower continues until particles • reach critical energy (see p. 16) where • tmax = ln(E0/c) • Shower Maximum increases • logarithmically with Energy of • primary particle • (Important for detector design !!!) t=x/X0 N.B.: Some relevant numbers: for e induced showers for  induced showers Roman Pöschl ILC School Beijing China 15-20 July 2005

  26. (Electromagnetic) Calorimeter - Technical Realization Example: Sampling Calorimeters Homogenous Calorimeters  Homework Only sample of shower passes active medium Production of shower particles is statistical process with N (t) ~ E (E) ~ E Indeed e.g. BEMC (H1 detector): Alternating structure of Absorber and Scintillation medium Light is generated by charged particles with E < c Photomultiplier Plastic Scintillators Two Component organic Material (Benzole Type) Spectral sensitvity of Photocathodes Dynodes  Signal Absorption by Basic Component Emission by “primary” Scintillator Intensity Photocathode (e.g. Bialkali) Anode Dynodes Photoeffect at Cathode:  0.2e-/ Amplification by Dynodes  (10 outgoing e-/incoming e-) Total Amplifcation: G ~ n, n = Number of Dynodes  Roman Pöschl ILC School Beijing China 15-20 July 2005

  27. Hadronic Showers Hadronic Showers are dominated by strong interaction ! Distribution of Energy Example 5 GeV primary energy - Ionization Energy of charged particles 1980 MeV - Electromagnetic Shower (by 0->) 760 MeV - Neutron Energy 520 MeV - g by Excitation of Nuclei 310 MeV - Not measurable E.g. Binding Energy 1430 MeV 5000 MeV 1st Step: Intranuclear Cascade 2nd Step: Highly excited nuclei Fission followed Evaporation by Evaporation Distribution and local deposition of energy varies strongly Difficult to model hadronic showers e.g. GEANT4 includes O(10) different Models Further Reading: R. Wigman et al. NIM A252 (1986) 4 R. Wigman NIM A259 (1987) 389 Roman Pöschl ILC School Beijing China 15-20 July 2005

  28. Comparison Electromagnetic Shower - Hadronic Shower hadronic Shower elm. Shower Characterized by Interaction Length: Characterized by Radiation Length: SizeHadronic Showers >> Sizeelm. Showers Roman Pöschl ILC School Beijing China 15-20 July 2005

  29. Response to energy depositions S(e), S(h) = Signal created by electron, hadron e/mip (hi/mip) = Visible energy deposition of electrons (hadrons) normalized to energy deposition by mip fem = Electromagnetic Component of hadronic shower Important Relation: e.g. Non linear response to hadrons since fem ~ ln(E/1 GeV) Goal for detector planning: e/mip = h/mip  S(e) = S(h) fion: hadronic component of hadronic shower which is deposited by by charged particles fn: fraction deposited by neutrons f: fraction of energy deposited by nuclei  fB: fraction of binding energy of hadronic component Evaporation-n Binding energy “lost” for signal can be compensated by detecting neutrons h/mip increases if e.g. n/mip and/or fn is increased Neutron Energy with En < 20 MeV Spallation-n Roman Pöschl ILC School Beijing China 15-20 July 2005 Losses by Binding energy

  30. Compensation Calorimetry Goal: Hardware Weighting Software Weighting e.g. increase number of neutrons by selecting absorber with high Z falling Z/A Higher neutron yield in nuclear reactions Need to detect n Choose active medium with high fraction of hydrogen Correct energy response ‘offline’ reduce e/mip Apply small weight to signal component induced by electromagnetic part of hadronic shower No Weighting 50 GeV Weighting 50 GeV Roman Pöschl ILC School Beijing China 15-20 July 2005

  31. Detectors Based on Semi Conduction Employed in: High Precision Gamma Spectroscopy Measurement of charged particles with E < 1 MeV Vertex finding, I.e. determining the interaction of a high energy reaction Takes relatively small energy deposition to create a signal Comparison: O(100 eV) to create a -quant in a scintillator 3.6 eV to create a electron-hole pair in Silicium Roman Pöschl ILC School Beijing China 15-20 July 2005

  32. Principle of Particle Detection Ionization of the detector material - Bethe Bloch Charge Collection in an electrical field (E-Field extends over depletion zone, capacitance) Electronic Amplification and measurement of the signal Number of charges is proportional to deposited energy Segmentation of electrodes allows for high spatial resolution Base Material e.g. Si doted with e.g. As  n-doted (Donator) B  p-doted (Acceptor) n+ doted region - + + - p doted region (depletion zone) + - + - + - + - p+ doted region Typical values: Dotation ND = 1012 cm-3, NA=1016 cm-3 Extension of depletion zone 300 m Specific resistance of depletion zone 10km à la Lutz Feld Universität Freiburg Roman Pöschl ILC School Beijing China 15-20 July 2005

  33. pn transition in Reverse-Biasing Mode - Semiconducting Detectors based in pn-transition which is connected in Reverse-Biasing - E-Field is given by Poissonian Equation NA = Acceptor Concentr. ND = Donator Concentr. xp = Thickness of depletion region p+-side xn = Thickness of depletion region n-side Linear in region of depletion zone - For a highly doted p type layer on a n-type substrat the total thickness of the depletion zone is given by - Dark current by thermal fluctuations V = Bias Voltage Roman Pöschl ILC School Beijing China 15-20 July 2005

  34. d q q1 q2 x 0 x2 Spatial Resolution -  Strip Detector • MIP creates roughly 80 e/hole pairs • Q = 24000 e- in 300m Si • Application of electrostatical model since Collection Time 20 ns Integration Time 120 ns Losses by Capture 1ms S Spatial Resolution: typ. 15m Simple Model: Signals only on neighbored strips Readout current those of a capacitance Induced Charges: if q=q(x)  if q(x) = const. Roman Pöschl ILC School Beijing China 15-20 July 2005

  35. tt Production at the TEVATRON Roman Pöschl ILC School Beijing China 15-20 July 2005

  36. Pixel Detectors - Principles Vi Vi+i Put neighbored strips on different potential Vi < Vi+1 Vi+1 builds a potential wall and charge drifts exclusively to strip (pixel) i Collected charge is transferred to readout unit Typical Values: Pixel Size 50x50 m2 Readout with several MHz Frequency Employed widely at the LHC (ATLAS, CMS) Technical Choice also for ILC (see later) Roman Pöschl ILC School Beijing China 15-20 July 2005

More Related