Gaseous detectors and applications I · 2018. 11. 16. · Gaseous detectors I th4 School of High-energy Physics, 26/04/2014 P. Fonte •Applications ofgaseous particle detectors •High

P.Fonte

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Gaseous detectors and applications I

Gaseous detectors I 4th School of High-energy Physics, 26/04/2014 P. Fonte

• Applications of gaseous particle detectors • High Energy and Nuclear Physics • Medical Instrumentation, space, etc.

• The physical detection principles • Interaction of high-energy radiation with gases • Transport and amplification of charges

• Technology • Common requirements/problems • Wire-based devices • Planar devices • Micropattern devices • Miscellaneous

• Some current detector physics research topics • Conclusion

Summary


Applications High Energy Physics

@ CERN/LHC

MWPC

TPC

RPC


Applications High Energy Physics

The OPERA neutrino oscillation experiment at the underground “Laboratorio Nacional de Gran Sasso” (LNGS), Italy, which takes a neutrino beam from CERN.

RPC (180m2)

RPC (1380m2)

RPC (1380m2)


Applications Nuclear Physics

Collaboration (GSI, Darmstadt, Germany) High Acceptance Di-Electron Spectrometer

MDC MDC

MDC MDC MWPC

photodetector

MWPC (SQS mode) RPC

Not gaseous!


Applications Nuclear Physics

Super heavy-nuclei synthesis experiment, JINR, Dubna

PPC time-of-flight detectors


Applications Ion microscopy

Indestructible detection medium (no rad. damage) Better resolution than Si for the heavier ions

[M.D

oeb

eli,

Pilt

vice

20

10

]

@1MeV 2D STIM

PIN diode Gas ionization chamber

[A.C

.Mar

qu

es e

t al

, IC

NM

TA 2

01

2]

56×56 m2 grid

224×224 m2 scales on a

butterfly wing


Applications Low-level medium-energy (100’s keV) gamma detection

High-pressure Xe ionization chambers Large SEALED sensitive volume Excellent (few %) energy resolution Commercially available

[H.S

. Kim

, 19

98

]


Applications Astronomy

X-ray telescope (Beppo-Sax satelite)

Gaseous Scintillation Proportional Counter (GSPC)

X-ray image and spectrum of the Cygnus-X1 galaxy


Applications Neutrinoless double beta decay (search for)

The NEXT experiment

TPC readout by a Gaseous Scintillation Proportional Counter (GSPC) To be installed at Canfranc, Spain


Applications Astronomy

X-ray polarimeter on-board HXMT satelite

Gas pixel polarimeter

GEM

The photoelectron’s direction correlates with the X-ray polarization

[E. C

ost

a et

al.,

20

01

]

pixelized readout chip


Applications Medicine diagnostics

XCT Gas Avalanche Detector for digital radiography (Xcounter AB)

PPC or RPC



Ultra low dose whole-body digital radiography

(Biospace EOS)

MICROMEGAS

[P. D

esp

rés

et a

l., 2

00

4]



[J.E

.Bat

eman

et

al.,

19

84

]

MWPC inside

0

5000

10000

15000

20000

25000

30000

0 30 60 90 120 150 180 210 240

Axial Field of View (cm)

3D

Tru

es S

en

sit

ivit

y (

kcp

s/m

Ci/cc)

GE Advance - 11 Rings (Lewellen et al)

GE Advance - 11 Rings (this simulation)

GE Advance - 17 Rings (Lewellen et al)

GE Advance - 17 Rings (this simulation)

60 Plates - 5.7 degrees

60 Plates - 15 degrees



60 Plates - Full Acceptance

120 Plates - 5.7 degrees




120 Plates - Full Acceptance

G E Ad v an ce (A F O V =15 cm )

Lew e llen e t a l T h is s im u la tion

11 1020 1013

17 1248 1160

T ru es sen s itiv ity

(kcp s /u C i/cc ))R ing

D iffe rence

20-fold higher sensitivity compared with the GE ADVANCE tomograph

RPC inside

[Co

uce

iro

20

07

]

Low cost human Positron Emission Tomography (PET)

(in development)


Applications Biology

High resolution Positron Emission Tomography (PET) for small animals

MWPC inside

RPC inside

0.47 mm FWHM

(FBP algorithm) 50

100

150

200

-10 -5 -1 1 5 100

10

20

30

40

Distance (mm)

Counts

/100

m

50

100

150

200

-10 -5 -1 1 5 10 0

10

20

30

40

Distance (mm)

1 1 9mm

Almost physics-limited resolution

[Bla

nco

20

06

]

Resolution: 0.9 mm FWHM


Why gaseous detectors? (despite strong competition from solid state)

Very large areas/volumes are possible Low cost per unit area or readout channel (no light sensor) Very low average specific mass Quite good, sometimes outstanding, position and time accuracy

- Often limited in rate capability - Most types are vulnerable to dangerous sparks - Mostly “homemade”


Interaction of high-energy radiation with gases Heavy charged particles

Gas

High-energy charged particle

Electromagnetic collisions Electrons ejected with energies following a “Landau distribution” Randomly distributed “ionization clusters” (most <0.1mm diameter) ~few ionization clusters/mm (gas and particle energy dependent) Nr. of electron-ion pairs/cluster follows ~1/N2 distribution

Ionization minimum (=p/mc3)


Interaction of high-energy radiation with gases Heavy charged particles

Particle identification (PID) by energy loss ( number of clusters/mm) in a gas

[Par

ticl

e D

ata

Bo

ok]

Highly accurate measurement of the

cluster density

requires large volumes of gas


10-3

10-2

10-1

100

101

102

10-2

10-1

100

101

102

103

104

Photon energy (MeV)

Abso

rbtio

n le

ngth

(m

)

Xe, 1 atm

photoelectric

Compton

pair production

Total

Interaction of high-energy radiation with gases Photons

• Single photoelectric, Compton or pair-production interaction site • Electrons (ionizing or not) are injected into the gas

Gas

Deep UV or low-energy X-ray)

ejected electrons

X- or gamma-ray

Surrounding material (converter plate)

Photocathode

e.g.: CsI

Near UV (down to ~300 nm)


Interaction of high-energy radiation with gases neutrons

• Nuclear interaction on fissile nucleus with large n cross-section (energy dependent) • Ionizing fission fragments are injected into the gas

Fe converter plate

Gas rich in 3He or 10BF3

ejected ionizing fission

products

10B converter layer

higher n energies

lower n

energies

Neutron interactions in 3He visualized with scintillating GEM + optical readout


Transport and amplification of charge

basic features

Typical drift electric field ~1kV/cm

Primary electrons drift towards the amplification region with velocity v(E), strongly gas-dependent.

A Townsend avalanche (streamer, spark…) develops in the amplification region. Electrical or optical signals are generated.

Drifting electrons are subject to attachment (to be avoided) and diffusion (detrimental to localization accuracy)

Typical amplification electric field: 10 to 100 kV/cm

Drift (charge collection)

region

Amplification region

v

E

Gas volume

Electrical signal Optical signal


Common requirements/problems drift region

Drift (charge collection) region ‐No electron attachment ‐Most often high ionization density is desired but for photodetectors it is good to be “particle-blind” ‐For some applications with long, precise, drifts

• Low diffusion • Drift velocity not much dependent on E field

e-

Ionizing

particle


Common requirements/problems amplification region (gas + electrodes)

Amplification region

Electrical signals Optical signal

Related to charge amplification • Large average gas gain (typical range: 103-108)

• Reduced UV photon emission (to avoid photon feedback) • Resistance to the avalanche streamer transition (larger spark-free gain)

• Favourable avalanche statistics (narrow distribution of gain) Resistance to polymerization “aging“ If optical signal is sought, efficient visible/near UV light emission

For some applications requiring precise drifts: minimization of ion backflow to avoid E-field distortion

photon and ion production

e-

i+

e-

Secondary avalanches

Coupling structure (transfer optimization, spark protection)

Pickup electrode structure (avalanche localization, spark protection)

UV


Some special configurations Multistep (cascaded)

amplification Ionization chamber

Allows slightly larger total gain

(still space-charge limited)

e-

Drift region

Signal

Very high particle rate (e.g.: beam dosimetry) Highly ionizing particles

(e.g.: alphas, fragments, ions)

Driftless

Reduced efficiency Simplicity

Excellent timing

Amp. region 1

e-

Transfer drift

Collection drift

Amp. region 2

Transfer drift

Amp. region 3

Signal

signal drift

Amp. region

Signal

Each primary charge

sees a different gain

unfavourable gain

statistics: ~1/Q


Almost all detectors work at atm. pressure for technical convenience

DRIFT: electronegative gases forbidden Noble gases as main mixture components • He: light “filler” gas for particle-blind detectors (e.g.: photodetectors) • Ar, Xe: heavy gases for high primary charge density + a few % of more complex molecules to “quench” the UV light emission hydrocarbons • CH4: light quencher, some UV emission some photon feedback • C4H10: excellent quencher but strongly polymerizes aging • vapours also possible (e.g.: alcool, acetone, trimethylolethane (TME), etc) other • CO2: very light quencher. Doesn’t work in many detector types. However it provides very fast drift and doesn’t polymerize. • CF4: also very light quencher, but very luminous in visible/near UV. DRIFTLESS: electronegative gases allowed • Fluorinated mixtures work very well. Huge, saturated, gain before

discharges appear (e.g. “RPC mixture”: 85% C2H2F4 + 10% SF6 + 5% C4H10)

Choice of gas mixtures (alta cozinha)


Wire-based devices cylindrical counter

Proportional Geiger Self-quenched streamer (SQS)

Geiger mode: photon-mediated discharge propagation

Self-quenched streamer (SQS) mode streamer “dies” in the strong non-uniform E-field around the wire Drift

Drift

Amplification

[G.D

.Ale

ksee

v et

al.,

19

79

]


IEEE October 2003, Portland, US Mar Capeans 6

Barrel straw

Wire joint

Twister

Wire

30 mEnd plug

Straws embedded in radiators

and supported by dividers and

endplates; connected across the module by a C-fibre shell

C-fiber shell

Radiator

Straws

Tension plate

Tension plate

Wire-based devices cylindrical counter (proportional mode)

Modern example: the ATLAS (CERN) Transition Radiation Tracker (TRT) made with ~400.000 “straw tubes”

Electrons with

radiator

Electrons without radiator

Electrons with

radiator

Electrons without radiator


Wire-based devices multi-wire proportional chamber (MWPC)

“sense” HV wires typ. 20m

drift region

drift region

High E field (up to 100kV/cm) amplification region

Cathode wires or strips

Position resolution 0.1mm (by the centroid of the charges induced in the cathodes)

Time resolution ~50ns (variable drift distances)

Difficult mechanics. Any wire rupture compromises the whole chamber.

Potential and field lines Monte-Carlo simulation of electron trajectories

at low pressure

High-accuracy position readout (“cathode strip chamber” - CSC)

The workhorse of modern particle

detectors G.Charpak Nobel laureate 1992

[H. P

ruch

ova

et

al.,

19

79

]


Wire-based devices Drift Chamber, Time projection chamber (TPC)

A neat recent development: the negative-ion drift chamber • primary electron capture in CS2, drift of CS2

- , e- released in the amp. space and amplified; • dramatically decreases diffusion in the drift volume.

MWPCs for 2D (x,y)

and drift time (z)

measurement

z

y

TPC electron drift

Huge gas volume

Drift chamber

Beam Beam

x E The TPC of the DELPHI

experiment

In many senses the most perfect gaseous detector

(huge, high accuracy, PID)

• Measures trajectories in 3D • Low count rate owing to the huge drift time


Wire-based devices Multidrift chamber (MDC)

Actual event

Cellular structure of anode and cathode wires •Multiple measurements of the same particle

provide excellent position and angle information in 2D.

• Much higher rate capability than TPC •Extremely demanding construction

Equipotential and field lines

radius=

drift time


Planar geometry with drift (multistep possible) Top drift electrode (solid or wire mesh)

Upper gap electrode (wire mesh or micromesh)

Lower gap electrode (solid or wire mesh)

Signal pickup electrode (patterned, mesh or solid)

may be used as the lower gap electrode also

Amplification gap

Drift gap

d

Signal gap

[Gio

mat

aris

, 19

96

]

if d> ~1 mm: Parallel-Plate Avalanche Chamber (PPAC) if d< ~1 mm: MicroMEsh GAseous Structure (MICROMEGAS) (to be considered as a “micropattern” detector)


Planar geometry with drift Gaseous Scintilation Proportional Chamber (GSPC)

Much used for soft X-ray

detection

[CA

N C

on

de,

A. P

olic

arp

o 1

96

7]

• Detector based on the emission of light from optimized mixtures of noble gases

• The statistical characteristics of light emission are more favourable than those of charge multiplication, so, for soft X-rays below about 2 keV, GPSCs energy resolution outperforms any other type of large area detector, either cooled or room temperature.

Schematic of a GPSC:

1. first grid;

2. second grid;

3. gas outlet to purifier

4. entrance window;

5. stainless steel

enclosure.


Planar geometry - driftless

Amplification gap d~4 mm Upper gap electrode (solid, foil)

Lower gap electrode (solid, foil)

Parallel-Plate Chamber (PPC)

All planar detectors with metallic electrodes are prone to sparking, so…

Only successful application: timing of fission fragments at low pressure

Spark Chamber

Electronics

HV pulse

External detector

None of these configurations is

much used in practice today


Planar geometry - driftless Resistive Plate Chamber (RPC)

A very successful detector

[San

ton

ico

, 19

81

]

The current is limited by the resistive electrodes: no sparks by construction • Deployed in huge areas (~10000 m2) • Outstanding time resolution (50 ps) – the standard technique today for

large-area time-of-flight measurements on relativistic particles • Main drawbacks: quite limited rate capability

quite insensitive to primary energy deposition

Resistive electrode

Resistive electrode

Gas gap (from 0.2mm to a few mm)

Medium resistivity layer

(e.g. Graphite)

transparent to the induced

signals

High resistivity layer

(e.g. PET)

X pickup strips (at ground potential)

Y pickup strips (at ground potential)

+HV

-HV Resistive electrodes

(glass, bakelite)


Gas

Substrate

Streamer

Very high E-field point

An

od

e

Micropattern detectors Microstrip Gas Chamber (MSGC)

A very original idea

• Thin anode strips and wider cathode strips deposited by industrial lithographic methods on a glass substrate. A kind of solid MWPC.

• Abandoned because it is extremely prone to sparking, melting the thin strips.

• The surface strongly facilitates the streamer progression for electrostatic reasons.

In the 90’s hundreds of people worked on this detector and its infinite

variations and derivatives

[A.Oed, 1988]


Micropattern detectors MICROMEGAS (already mentioned)

Gas electron Multiplier (GEM)

•Flexible detector made by chemically drilling small holes in a thin kapton printed circuit board.

•Cascadable

Very fashionable detectors today

Optical detection of alpha tracks (in CF4)

[F.S

auli,

19

97

]


Micropattern detectors Micro-Hole & Strip Plate (MHSP)

GEM

+

MSGC

• Somewhat higher gain • Reduced ion backflow

[J.F

.C.V

elo

so, 2

00

0]


Micropattern detectors Compteur a trou (CAT) MicroDot

Laid in silicon

[S.F

. Bia

gi e

t al

. 19

95

]

[M. L

emo

nn

ier,

19

95

]


Other micropattern detectors (likely not an exhaustive list)

[F. Angelini et al.,1993]

[R. Bellazzini et al, 1998]

[R. Bellazzini et al, 1999]

[A.H. Walenta et al., 1998]

[C. Labbé, 1998]

[B. Adeva et al, 1999]

Micro Gap (MGC) Micro WELL Micro Groove Micro CAT Micro Slit (MSGD) Micro Wire (µWD)

[H. Sakurai et al, 1996] Capillary Plate Gaseous Detector (CPGD)


Main characteristics of the different amplification structures WIRE (cylindrical)

Somewhat resilient to sparking owing to the very non-homogeneous E field (SQS mode) Hugely applied - Reduced count rate capability (ion pile-up at the wire reduces E field) - Inherently anisotropic: the position resolution is better along the wire - Timing not so good owing to variable drift distances for each primary charge (~50ns)

PLANAR - metallic Simple mechanics Reasonable rate capability - Prone to sparking, as the streamer develops well in the uniform E-field

PLANAR – resistive (RPC) Very high gain (by construction, only small discharges allowed, not sparks) Simple mechanics Outstanding timing (~50 ps) - Limited rate capability

MICROPATTERN High rate capability Very good position resolution even in digital readout mode (hit-counting) Good timing (~5ns) Industrial production methods, derived from electronics industry - Small gain (mostly limited by imperfections on tiny structures, leading to sparking)


Some open physics issues in gaseous detectors The limits of charge amplification

[Iva

nio

uch

enko

v 1

99

9]

Rate-induced

breakdown

Ma

xim

um

ach

ieva

ble

ga

in

Rate density (counts/s/mm2)

Forbidden

region

(by sparks)

Gain-induced

breakdown

Superimposed limits of many detector types


Some open physics issues in gaseous detectors gain-induced breakdown

Meek and Raether’s “streamer”/”Kanalaufbau” mechanism

Gain

Typical “precursor” structure can be easily

reproduced by numerical calculations

[Fo

nte

19

94

]

Higher space-

charge generated

E-field allows the

cathode streamer

but a secondary

process is

needed to feed

the high-gain

region Gas self-photoionization

This process exists in all tested gas mixtures (and we tried a lot…) Is there an universal process for gas self-photoionization close to the Townsend avalanche conditions?


Hydrodynamic approach to streamer calculation

Charge transport

2( , )( ) ( )

e e e e

drift pile up

transportcreation

ee e e e e e

otherdiffusionW n n Wsources multiplication

attachment

n r tS W n W n D n

t

electrons

good reference: [DAV73]

( , ) charge density inspaceand time

( ) velocity of charges

( , ) electricfield:applied+spacecharge

=first Townsend coefficient

=diffusion coefficient

n r t

W E

E r t

D

( , )

( , )

ie e

ie e

n r tS W n

t

n r tW n

t

Ions, assuming

stationary ions

Space-charge + applied field

2

0

( )i e i

eV n n n

Boundary conditions

,initialdensities: ( ,0)

behaviour of chargesat theelectrodes

Electrostatic B.C.

e in r

Slight drawback: no avalanche statistics


Numerical approach: finite elements

Used the commercial program COMSOL Multiphysics

Solves a coupled set of a basic

differential equation,

with arbitrary coefficients (any function of

any variable) in a mesh (finite elements).

Covers most cases needed for applied

physics.

[COMSOL]


GEM lateral (ring) avalanche

hole: 60 µm

gap: 100 µm

N0=100 e-

V=1250V


GEM lateral (ring) avalanche

hole: 60 µm

gap: 100 µm

N0=100 e-

V=1250V

Notice the precursor!


Cathodeless CAT

Will the streamer be able to

grow out of the hole?


Cathodeless CAT

Not completely successful, but

it sparks at a rather large

charge.

Maybe such geometries can

be optimized for SQS mode.


Some open physics issues in gaseous detectors rate-induced breakdown

Reason unknown… Observations

5 A

1 s

PPAC - high rate, low gain – single sparks

200 nA

500 ms

20 A

1 s

[IVA98]

500 nA

500 ms

500 nA

500 ms

(Cu cathode)

(Si cathode)

afterpulses after irradiation PPAC - medium rate - higher gain

continuous sparking regime

+ memory effect (cannot reach same gain for hours)

[Iva

nio

uch

enko

v 1

99

8]

[Iac

ob

aeu

s 2

00

2]


Conclusion

• Despite a venerable history, gaseous particle detectors are very versatile, offer unique capabilities and have still today many applications

• The innovations have been constant over the last decades. Recent examples include micropattern detectors, the negative-ion drift chamber and time-of-flight measurement capability on minimum-ionizing particles.

• Some aspects of the avalanche to streamer transition remain to be clarified, as well as the origin of high-rate breakdown.

Documents

Gaseous detectors and applications I · 2018. 11. 16. · Gaseous detectors I th4 School of High-energy Physics, 26/04/2014 P. Fonte •Applications ofgaseous particle detectors •High