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F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 1 TITLE RADIATION DETECTION AND MEASUREMENT Prof. Glenn Knoll, organizer Short Courses November 10-11 2002.

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Presentation on theme: "F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 1 TITLE RADIATION DETECTION AND MEASUREMENT Prof. Glenn Knoll, organizer Short Courses November 10-11 2002."— Presentation transcript:

1 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 1 TITLE RADIATION DETECTION AND MEASUREMENT Prof. Glenn Knoll, organizer Short Courses November IEEE NSS/MIC Norfolk, November 10-16, 2002

2 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 2 INTRODUCTION PARALLEL PLATE COUTER MULTIWIRE PROPORTIONAL CHAMBER TIME PROJECTION CHAMBER DRIFT CHAMBERS CHERENKOV RING IMAGING STREAMER TUBES STRAWS PESTOV COUNTER RESISTIVE PLATE CHAMBERS AVALANCHE CHAMBERS MICROSTRIP CHAMBERS MICROWELL MICROGAP COMPTEUR A TROUS GAS ELECTRON MULTIPLIER MICROMEGAS TRANSITION RADIATION TRACKER GASEOUS DETECTORS’ FAMILY TREE PROPORTIONAL COUNTER

3 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 3 PART 1 IONIZATION DRIFT AND DIFFUSION CAPTURE LOSSES AVALANCHE MULTIPLICATION

4 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 4 IONIZATION PRIMARY IONIZATION: ELECTRON-ION PAIRS COULOMB INTERACTIONS OF CHARGED PARTICLES WITH MOLECULES Minimum ionizing particles: Argon DME n (ion pairs/cm) dE/dx (keV/cm) GAS (STP) Xenon CH P k n  n k k! e  n Statistics of primary ionization: Poisson: n: average k: actual number (Maximum) detection efficiency:  1  e  n thickness  Argon GAS (STP) 1mm91.8 2mm 99.3 Helium Helium 1mm45 2mm 70

5 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 5 IONIZATION SECONDARY AND TOTAL IONIZATION CLUSTERS AND DELTA ELECTRONS: N: total ion-electron pairs n N ~ 3 _ CLUSTER SIZE DISTRIBUTION: P(m)~ W m 2 H. Fischle et al, Nucl. Instr. and Meth. A301(1991)202 Argon DME n (ion pairs/cm)cm) GAS (STP) Xenon 44 CH 4 16 N (ion pairs/cm) Helium 6 8

6 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 6 IONIZATION CONSEQUENCES OF ENERGY LOSS STATISTICS LANDAU DISTRIBUTION OF ENERGY LOSS: For a Gaussian distribution:  N ~ 21 i.p. FWHM ~ 50 i.p N (i.p.) Counts 4 cm Ar-CH4 (95-5) 5 bars N = 460 i.p. PARTICLE IDENTIFICATION Requires statistical analysis of hundreds of samples N (i.p) Counts 0 protonselectrons 15 GeV/c I. Lehraus et al, Phys. Scripta 23(1981)727 FWHM~250 i.p.

7 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 7 IONIZATION LOCALIZATION ACCURACY IN DRIFT CHAMBERS WORSENED BY LONG-RANGE ELECTRONS: Drift Time 5% of events! F. Sauli, Nucl. Instr. and Meth. 156(1978)147

8 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 8 IONIZATION STRONG ANGULAR DEPENDENCE OF POSITION ACCURACY G. Charpak et al, Nucl. Instr. and Meth. 167 (1979) 455 Position accuracy as a function of the track angle to the normal to the chamber: CENTER OF GRAVITY OF INDUCED CHARGE READOUT

9 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 9 IONIZATION F. Van den Berg et al, Nucl. Instr. and Meth. A349 (1994) 438 ANGULAR DEPENDENCE OF POSITION ACCURACY IN MICRO-STRIP CHAMBERS:

10 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 10 IONIZATION DECLUSTERING EFFECT IN TIME PROJECTION CHAMBERS: Data: D. Decamp et al, Nucl. Instr. and Meth. A269(1990)121 Simulation: A. Sharma, CERN Drift B offset B=1.5 T

11 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 11 IONIZATION LIMITED TIME RESOLUTION OF WIRE AND MICROPATTERN CHAMBERS: Space distribution of the cluster closer to an electrode: Time distribution of the cluster closer to an electrode: w: drift velocity w = 5 cm/µs

12 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 12 IONIZATION PARALLEL PLATE CHAMBERS: SUB-NANOSECOND RESOLUTION FAST SIGNAL INDUCTION DURING AVALANCHE DEVELOPMENT: Useful gap R. Arnaldi et al, Nucl. Phys. B 78(1999)84

13 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 13 DRIFT ELECTRIC FIELD E = 0: THERMAL DIFFUSION ELECTRIC FIELD E > 0: CHARGE TRANSPORT AND DIFFUSION E IONS ELECTRONS DRIFT AND DIFFUSION OF CHARGES IN GASES

14 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 14 DRIFT DRIFT AND DIFFUSION OF IONS (CLASSIC KINETIC THEORY OF GASES) Ions remain thermal up to very high fields Maxwell energy distribution: Average (thermal) energy: Diffusion equation Fraction of ions at distance x after time t: D: diffusion coefficient RMS of linear diffusion: Molecules diffuse rapidly in the available volume (leaks!)

15 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 15 DRIFT IONS DRIFT VELOCITY (Almost) linear function of field Mobility: ~ constant for a given gas (at fixed P and T) IONS DIFFUSION (Einstein’s law): Same for all ions! E. McDaniel and E. Mason The mobility and diffusion of ions in gases (Wiley 1973) GAS ION µ + (cm 2 V -1 s -1 Ar Ar CH 4 CH Ar-CH CH MWPC: 1 cm gap, Ar-CH 4, 5 kV/cm Total ions drift time T + ~ 120 µs TPC: 1 m drift, Ar-CH4, 200 V/cm Total ions drift time T + ~ 300 ms

16 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 16 DRIFT DRIFT AND DIFFUSION OF ELECTRONS IN GASES Electron Swarm Drift Electric Field  s,  t Drift velocity: s Space diffusion rms: Drift velocity and diffusion are gas and field dependent: P : pressure Townsend expression:  : mean collision time

17 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 17 DRIFT LARGE RANGE OF DRIFT VELOCITIES AND DIFFUSIONS DRIFT VELOCITY: DIFFUSION:

18 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 18 DRIFT ELECTRON TRANSPORT THEORY BALANCE BETWEEN ENERGY ACQUIRED FROM THE FIELD AND COLLISION LOSSES Energy distribution probability: Fractional energy loss in collisions Mean free path between collisions  : electron-molecule cross section) Drift velocity: Diffusion coefficient: Frost and Phelps, Phys. Rev. 127(1962)1621 V. Palladino and B. Sadoulet, Nucl. Instr. and Meth. 128(1975)323 G. Shultz and J. Gresser, Nucl. Instr. and Meth. 151(1978)413 S. Biagi, Nucl. Instr. and Meth. A283(1989)716

19 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 19 DRIFT CHARGE TRANSPORT DETERMINED BY ELECTRON-MOLECULE CROSS SECTION: S. Biagi, Nucl. Instr. and Meth. A421 (1999) 234 MAGBOLTZ

20 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 20 DRIFT COMPUTED DRIFT VELOCITY IN MIXTURES

21 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 21 DRIFT Longitudinal diffusion ( µm for 1 cm drift) Transverse diffusion ( µm for 1 cm drift) LONGITUDINAL DIFFUSION (// E) Drift E Field TT LL SMALLER THAN TRANSVERSE DIFFUSION: LONGITUDINAL DIFFUSION:TRANSVERSE DIFFUSION:

22 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 22 DRIFT DRIFT TIME ACCURACY: DEPENDS ON IONIZATION DENSITY Drift Anode Wire LL Single electron Several electrons Many electrons Detection threshold Error on first electron electron: N=100  1 ~ 0.4  L RESOLUTION LIMITS OF DRIFT TUBES: G. Scherberger et al, Nucl. Instr. and Meth. A424(1999)495 W. Riegler et al, Nucl. Instr. and Meth. A443(2000)156

23 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 23 DRIFT EFFECTS OF MAGNETIC FIELD THE SWARM IS ROTATED BY AN ANGLE  B IN THE PLANE PERPENDICULAR TO E AND B THE MAGNETIC DRIFT VELOCITY IS w B  w 0 THE TRANSVERSE DIFFUSION IS REDUCED  //  : mean collision time Larmor frequency  B  L T  w B

24 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 24 DRIFT DRIFT IN MAGNETIC FIELD: SIMPLE MODEL:

25 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 25 DRIFT TRANSVERSE DIFFUSION IN SEVERAL GASES REDUCTION IN MAGNETIC FIELD // E

26 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 26 DRIFT COMPUTED FROM TRANSPORT THEORY (MAGBOLTZ)

27 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 27 DRIFT MAGNETIC FIELD EFFECTS: DISTORSIONS IN DRIFT CHAMBERS W. de Boer et al, Nucl. Instr. and Meth. 156(1978)249

28 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 28 DRIFT MAGNETIC FIELD EFFECT: COORDINATE DISTORSIONS IN MICRO-STRIP CHAMBERS F. Angelini et al, Nucl. Instr. and Meth. A347(1994)441

29 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 29 DRIFT TRANSVERSE DIFFUSION: SUBSTANTIALLY REDUCED IN SOME GASES TIME PROJECTION CHAMBER: Center-of-gravity of cathode signal B=0B>0 // D. Nygren, TPC proposal (PEP4, 1976)

30 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 30 DRIFT STABILITY OF OPERATION VOLTAGE AND PRESSURE THE DRIFT VELOCITY IS A FUNCTION OF REDUCED FIELD E/P DRIFT VELOCITY SATURATION: INSENSITIVE TO VARIATIONS OF E AND P

31 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 31 DRIFT STABILITY OF OPERATION TEMPERATURE AT LOW FIELDS (THERMAL ELECTRONS): G. Shultz and J. Gresser, Nucl. Instr. and Meth. 151(1978)413 At high fields, the thermal coefficient in some gases decreases and even becomes negative: E (V/cm) A CO 2 Methylal C 4 H 10 CH 4 A-C4H10-Methylal  w/w/ºC

32 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 32 CAPTURE ELECTRON CAPTURE LOSSES ON ELECTRONEGATIVE GASES The attachment cross section is energy-dependent, therefore strongly depends on the gas composition and electric field Attachmant coefficient of oxygen: Electrons surviving after 20 cm drift (E = 200 V/cm):

33 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 33 CAPTURE ELECTRON CAPTURE - VERY SENSITIVITE TO GAS MIXTURE ARGON-ETHANE DIMETHYLETHER R. Openshaw, TRIUMF (private, 2000) 5.9 keV X-rays“Hot” gas “Cold” gas Energy resolution of a proportional counter with two gas fillings (and some leaks!):

34 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 34 DRIFT USE OF CF 4 AS QUENCHER REPLACING CH 4 IN TPCs - FAST DRIFT VELOCITY - SMALL DIFFUSION - NO HYDROGEN (REDUCED NEUTRON SENSITIVITY) - NON-FLAMMABLE L. G. Christophorou et al, Nucl. Instr. and Meth.163(1979)141

35 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 35 CAPTURE ELECTRON CROSS SECTIONS IN CF 4

36 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 36 MULTIPLICATION INCREASING THE FIELD TOWARDS CHARGE MULTIPLICATION IONIZATION 15.7 eV EXCITATION 11.6 eV Electrons energy distribution at increasing fields:

37 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 37 MULTIPLICATION IONIZATION CROSS SECTION AND TOWNSEND COEFFICIENT Mean free path for ionization N: molecules/cm 3 Townsend coefficient Ionizing collisions/cm S.C. Brown, basic data of plasma physics (MIT press, 1959)

38 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 38 MULTIPLICATION AVALANCHE MULTIPLICATION IN UNIFORM FIELD Multiplication factor or Gain E x Ions Electrons Combined cloud chamber-avalanche chamber: H. Raether Electron avalanches and breakdown in gases (Butterworth 1964)

39 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 39 MULTIPLICATION MEASUREMENT OF THE TOWNSEND COEFFICIENT Radiation V I Current vs voltage for constant charge injection in a parallel plate counter: 1 M s

40 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 40 MULTIPLICATION A. Sharma and F. Sauli, Nucl. Instr. and Meth. A334(1993)420 TOWNSEND COEFFICIENT IN GAS MIXTURES ARGON-CH 4 : in Argon

41 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 41 MULTIPLICATION PARALLEL PLATE COUNTERS: A charge +Q between two conductors induces two negative charge profiles (image charge) Moving the charge modifies the induced charge profile on the conductors and generates detectable signals +Q towards an electrode: positive induced signal Induced signals are equal and opposite on anode and cathode SIGNAL DEVELOPMENT

42 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 42 MULTIPLICATION ANODE CATHODE s 0 s +Q V=0 V= -V 0 Charge induced on each electrode by +Q moving through the difference of potential dV: PARALLEL PLATE COUNTERS: SIGNAL DEVELOPMENT (CHARGE COLLECTION ONLY) Integrating over s (or time t): w: drift velocity Single charge +Q: Electrons- ion pair (-Q and +Q) released at the same distance s from the cathode : w - (w + ) : electron (ion) drift velocity T - (T + ) : total electron (ion) drift time Total signal: (+Q on cathode, -Q on anode)

43 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 43 MULTIPLICATION PARALLEL PLATE COUNTERS: SIGNAL DEVELOPMENT (CHARGE MULTIPLICATION) During the avalanche development, the increase in the number of charges after a path ds is: and the total after a path s: The incremental charge induction due to electrons after a path s: Integrating over s: and the corresponding current : The current signal iduced by the ions is instead given by: s 0 s -V 0 0

44 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 44 MULTIPLICATION PARALLEL PLATE COUNTERS: SIGNAL DEVELOPMENT (CHARGE MULTIPLICATION) Fas electron signal Slow ion tail

45 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 45 MULTIPLICATION WIRE PROPORTIONAL COUNTERS: Thin anode wire coaxial with cathode Electric field: Cathode radius b Anode radius a Avalanche development around a thin wire: SIGNAL DEVELOPMENT

46 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 46 MULTIPLICATION ln M Voltage Attachment Collection Multiplication Streamer PROPORTIONAL COUNTERS: GAIN CHARACTERISTICS Breakdown IONIZATION CHAMBER PROPORTIONAL COUNTER Saturation n1n1 n2n2

47 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 47 MULTIPLICATION PROPORTIONAL COUNTERS: SIGNAL DEVELOPMENT Incremental charge induced by Q moving through dV: Assuming that the total charge of the avalanche Q is produced at a (small) distance from the anode, the electron and ion contributions to the induced charge are: and The total induced signal ison the anode ( on the cathode) The ratio of electron and ion contributions: For a counter with a=10µm, b=10 m: q - /q + ~1% The electron-induced signal is negligible Neglecting electrons, and assuming all ions leave from the wire surface: Total ions drift time:

48 F. Sauli-Short Courses-IEEE-NSS 2002-PART 1 48 MULTIPLICATION t (ns) i(t) CHARGE SIGNAL: CURRENT SIGNAL: t (µs) q(t) t (µs) Q T+T+ t (ns) AMPLIFIER TIME CONSTANT; q(t) 300 ns 100 ns 50 ns


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