Particle Detection with Drift Chambers (Particle Acceleration and Detection)

✍ Scribed by Walter Blum, Werner Riegler, Luigi Rolandi

• Publisher: Springer
• Year: 2008
• Tongue: English
• Leaves: 457
• Category: Library

✦ Synopsis

A drift chamber is an apparatus for measuring the space coordinates of the trajectory of a charged particle. This is achieved by detecting the ionization electrons produced by the charged particle in the gas of the chamber and by measuring their drift times and arrival positions on sensitive electrodes. When the multiwire proportional chamber, or ‘Charpak chamber’ as we used to call it, was introduced in 1968, its authors had already noted that the time of a signal could be useful for a coordinate determination, and rst studies with a drift ch- ber were made by Bressani, Charpak, Rahm and Zupanci c in 1969. When the rst operational drift-chamber system with electric circuitry and readout was built by Walenta, Heintze and Schurlein ¨ in 1971, a new instrument for particle experiments had appeared. A broad study of the behaviour of drifting electrons in gases began in laboratories where there was interest in the detection of particles.

✦ Table of Contents

Gas Ionization by Charged Particles and by Laser Rays
Gas Ionization by Fast Charged Particles
Ionizing Collisions
Different Ionization Mechanisms
Average Energy Required to Produce One Ion Pair
The Range of Primary Electrons
The Differential Cross-section d/dE
Calculation of Energy Loss
Force on a Charge Travelling Through a Polarizable Medium
The Photo-Absorption Ionization Model
Behaviour for Large E
Cluster-Size Distribution
Ionization Distribution on a Given Track Length
Velocity Dependence of the Energy Loss
The Bethe--Bloch Formula
Energy Deposited on a Track -- Restricted Energy Loss
Localization of Charge Along the Track
A Measurement of Neff
Gas Ionization by Laser Rays
The nth Order Cross-Section Equivalent
Rate Equations for Two-Photon Ionization
Dependence of Laser Ionization on Wavelength
Laser-Beam Optics
References
The Drift of Electrons and Ions in Gases
An Equation of Motion with Friction
Case of E Nearly Parallel to B
Case of E Orthogonal to B
The Microscopic Picture
Drift of Electrons
Drift of Ions
Inclusion of Magnetic Field
Diffusion
Electric Anisotropy
Magnetic Anisotropy
Electron Attachment
Results from the Complete Microscopic Theory
Distribution Function of Velocities
Drift
Inclusion of Magnetic Field
Diffusion
Applications
Determination of () and l() from Drift Measurement
Example: Argon--Methane Mixture
Experimental Check of the Universal Drift Velocity for Large
A Measurement of Track Displacement as a Function of Magnetic Field
A Measurement of the Magnetic Anisotropy of Diffusion
Calculated and Measured Electron Drift Velocities in Crossed Electric and Magnetic Fields
References
Electrostatics of Tubes, Wire Grids and Field Cages
Perfect and Imperfect Drift Tubes
Perfect Drift Tube
Displaced Wire
Wire Grids
The Electric Field of an Ideal Grid of Wires Parallel to a Conducting Plane
Superposition of the Electric Fields of Several Grids and of a High-Voltage Plane
Matching the Potential of the Zero Grid and of the Electrodes of the Field Cage
An Ion Gate in the Drift Space
Calculation of Transparency
Setting of the Gating Grid Potential with Respect to the Zero-Grid Potential
Field Cages
The Difficulty of Free Dielectric Surfaces
Irregularities in the Field Cage
References
Amplification of Ionization
The Proportional Wire
Beyond the Proportional Mode
Lateral Extent of the Avalanche
Amplification Factor (Gain) of the Proportional Wire
The Diethorn Formula
Dependence of the Gain on the Gas Density
Measurement of the Gain Variation with Sense-Wire Voltage and Gas Pressure
Local Variations of the Gain
Variation of the Gain Near the Edge of the Chamber
Local Variation of the Gain Owing to Mechanical Imperfections
Gain Drop due to Space Charge
Statistical Fluctuation of the Gain
Distributions of Avalanches in Weak Fields
Distributions of Avalanches in Electronegative Gases
Distributions of Avalanches in Strong Homogeneous Fields
Distributions of Avalanches in Strong Non-uniform Fields
The Effect of Avalanche Fluctuations on the Wire Pulse Heights
A Measurement of Avalanche Fluctuations Using Laser Tracks
References
Creation of the Signal
The Principle of Signal Induction by Moving Charges
Capacitance Matrix, Reciprocity Theorem
Signals Induced on Grounded Electrodes, Ramo's Theorem
Total Induced Charge and Sum of Induced Signals
Induced Signals in a Drift Tube
Signals Induced on Electrodes Connected with Impedance Elements
Application to a Drift Tube and its Circuitry
Alternative Methods for the Calculation of the Signal
Signals Induced in Multiwire Chambers
Signals Induced on Wires
Signals Induced on Cathode Strips and Pads
References
Electronics for Drift Chambers
Linear Signal Processing
Laplace and Fourier Transforms
Transfer Functions, Poles and Zeros, Delta Response
CR, RC, Pole-zero and Zero-pole Filters
Cascading of Circuit Elements
Amplifier Types, Bandwidth, Sensitivity, and Ballistic Deficit
Signal Shaping
Unipolar and Bipolar Signal Shaping
Signal Tail Cancellation
Signal Pileup, Baseline Shift, and Baseline Fluctuations
Input Circuit
Noise and Optimum Filters
Noise Characterization
Noise Sources
Noise in Wire Chambers
A Universal Limit on the Signal-to-Noise Ratio
Electronics for Charge Measurement
Electronics for Time Measurement
Influence of Electronics Noise on Time Resolution
Influence of Pulse-Height Fluctuations on Time Resolution
Influence of Electron Arrival Time Fluctuations on Time Resolution
Three Examples of Modern Drift Chamber Electronics
The ASDBLR Front-end Electronics
The ATLAS CSC Front-end Electronics
The PASA and ALTRO Electronics for the ALICE TPC
References
Coordinate Measurement and Fundamental Limits of Accuracy
Methods of Coordinate Measurement
Basic Formulae for a Single Wire
Frequency Distribution of the Coordinates of a Single Electron at the Entrance to the Wire Region
Frequency Distribution of the Arrival Time of a Single Electron at the Entrance to the Wire Region
Influence of the Cluster Fluctuations on the Resolution -- the Effective Number of Electrons
Accuracy in the Measurement of the Coordinate in or near the Wire Direction
Inclusion of a Magnetic Field Perpendicular to the Wire Direction: the Wire E -.4 B Effect
Case Study of the Explicit Dependence of the Resolution on L and q
The General Situation -- Contributions of Several Wires, and the Angular Pad Effect
Consequences of (7.33) for the Construction of TPCs
A Measurement of the Angular Variation of the Accuracy
Accuracy in the Measurement of the Coordinatein the Drift Direction
Inclusion of a Magnetic Field Parallel to the Wire Direction: the Drift EB Effect
Average Arrival Time of Many Electrons
Arrival Time of the Mth Electron
Variance of the Arrival Time of the Mth Electron: Contribution of the Drift-Path Variations
Variance of the Arrival Time of the Mth Electron: Contribution of the Diffusion
Accuracy Limitation Owing to Wire Vibrations
Linear Harmonic Oscillator Driven by Random Pulses
Wire Excited by Avalanche Ions
Accuracy Limitation Owing to Space Charge Fluctuations
References
Geometrical Track Parameters and Their Errors
Linear Fit
Case of Equal Spacing Between x0 and xN
Quadratic Fit
Error Calculation
Origin at the Centre of the Track -- UniformSpacing of Wires
Sagitta
Covariance Matrix at an Arbitrary Point Along the Track
Comparison Between the Linear and Quadratic Fits in Special Cases
Optimal Spacing of Wires
A Chamber and One Additional Measuring Point Outside
Comparison of the Accuracy in the Curvature Measurement
Extrapolation to a Vertex
Limitations Due to Multiple Scattering
Basic Formulae
Vertex Determination
Resolution of Curvature for Tracks Through a Scattering Medium
Spectrometer Resolution
Limit of Measurement Errors
Limit of Multiple Scattering
References
Ion Gates
Reasons for the Use of Ion Gates
Electric Charge in the Drift Region
Ageing
Survey of Field Configurations and Trigger Modes
Three Field Configurations
Three Trigger Modes
Transparency under Various Operating Conditions
Transparency of the Static Bipolar Gate
Average Transparency of the Regularly Pulsed Bipolar Gate
Transparency of the Static Bipolar Gate in a Transverse Magnetic Field
References
Particle Identification by Measurement of Ionization
Principles
Shape of the Ionization Curve
Statistical Treatment of the n Ionization Samplesof One Track
Accuracy of the Ionization Measurement
Variation with n and x
Variation with the Particle Velocity
Variation with the Gas
Particle Separation
Cluster Counting
Ionization Measurement in Practice
Track-Independent Corrections
Track-Dependent Corrections
Performance Achieved in Existing Detectors
Wire Chambers Specialized to Measure Track Ionization
Ionization Measurement in Universal Detectors
References
Existing Drift Chambers -- An Overview
Definition of Three Geometrical Types of Drift Chambers
Historical Drift Chambers
Drift Chambers for Fixed-Target and Collider Experiments
General Considerations Concerning the Directions of Wires and Magnetic Fields
The Dilemma of the Lorentz Angle
Left--Right Ambiguity
Planar Drift Chambers of Type 1
Coordinate Measurement in the Wire Direction
Five Representative Chambers
Type 1 Chambers without Field-Shaping Electrodes
Large Cylindrical Drift Chambers of Type 2
Coordinate Measurement along the Axis -- Stereo Chambers
Five Representative Chambers with (Approximately) Axial Wires
Drift Cells
The UA1 Central Drift Chamber
The ATLAS Muon Drift Chambers (MDT)
A Large TPC System for High Track Densities
Small Cylindrical Drift Chambers of Type 2 for Colliders (Vertex Chambers)
Six Representative Chambers
Drift Chambers of Type 3
Double-Track Resolution in TPCs
Five Representative TPCs
A Type 3 Chamber with a Radial Drift Field
A TPC for Heavy-Ion Experiments
A Type 3 Chamber as External Particle Identifier
A TPC for Muon-Decay Measurements
Chambers with Extreme Accuracy
References
Drift-Chamber Gases
General Considerations Concerning the Choice of Drift-Chamber Gases
Inflammable Gas Mixtures
Gas Purity, and Some Practical Measurementsof Electron Attachment
Three-Body Attachment to O2, Mediated by CH4, i-C4H10 and H2O
Poisoning' of the Gas by Construction Materials, Causing Electron Attachment The Effect of Minor H2O Contaminationon the Drift Velocity Chemical Compounds Used for Laser Ionization Choice of the Gas Pressure Point-Measuring Accuracy Lorentz Angle Drift-Field Distortions from Space Charge Deterioration of Chamber Performancewith Usage (Ageing')
General Observations in Particle Experiments
Dark Currents
Ageing Tests in the Lower-Flux Regime
Ageing Tests in the High-Flux Regime
References
Index