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New experimental techniques:
recent developments in particle detectors
Rita De Masi
IPHC-Strasbourg
Ecole Doctorale de Physique et Chimie Physique - Mai 2010
1
Outline of the course
• Interaction of particles with matter.
• Micro-pattern gas detectors.
• New generation semiconductor detectors.
• Transition radiation detectors.
• Cherenkov detectors and RICH.
• Nuclear emulsions.
• Calorimeters and bolometers.
• Two examples of detector systems:
• CMS @ LHC
• COMPASS @ SPS
2
Outline
• Interaction of particles with matter.
• Charged particles
• The special case of electrons and positrons
• Photons
• Neutrons
• Neutrinos
• What are detectors good for?
3
Interaction of particles with matter
Why:
• particle detection
• radiation shielding
• effects on living organism
Interactions:
• electromagnetic
• strong
• weak
4
Interaction of particles with matter
Why:
• particle detection
• radiation shielding
• effects on living organism
Interactions:
• electromagnetic
• strong
• weak
⇒ all charged particles, photons (neutrons)
⇒ hadrons (protons, neutrons, …)
⇒ in particular neutrinos!
5
Charged particles (but electrons)
• collisions with e• ionisation of atoms
• loss of energy
approximate mean rate energy loss by Bethe-Bloch formula
~1% accuracy for mips, otherwise corrections needed
• straggling
β = v/c
γ2 = 1/ (1-β2)
MeV g-1 cm2
- dE = Kz2 Z 1 1 ln 2me c2 β2 γ2 Tmax - β2 - δ
dx
A β2 2
I2
2
6
Mean energy loss
From Particle Data Book
7
Fluctuations in energy loss
8
Material dependence
9
Energy loss at low energies
Bragg peak
0
the heavier the projectile, the sharper the peak
application in nuclear radiation therapy
10
Multiple scattering
θplane = 13.6 MeV z √(x/X0) [1 + 0.038 ln(x/X0)]
βcp
11
Electrons and positrons
12
Photons
I = I0 e-σnx
13
Neutrons
• Indirect detection
• Nuclear reaction -> detection of secondary particles
• Scattering ->Scattered nucleus further ionises
• I = I0 e-σnx
14
What’s about neutrinos?
• Neutrinos interact only by weak interaction!
• Detection of the particles produced in its interaction.
νμ
μ
W
e
νe
15
Bibliography
• Particle Data Book,
http://pdg.lbl.gov/2009/reviews/rpp2009-rev-passage-particles-matter.pdf
• W. Leo, Techniques for Nuclear and Particle Physics Experiments, Springer-Verlag
• Typically any first chapter of text books on detectors
16
What are detectors good for?
17
What are detectors good for?
18
Micro-pattern gas detectors
Rita De Masi
IPHC-Strasbourg
1
Outline
• Problematic
• Working principle
• Gas Electron Multiplier (GEM)
• Micro-Mesh Gaseous Structure (Micromegas)
• Applications
2
Gas detectors working principle
charged particle
-
Charges migrate to the electrodes
⇓
signal
ΔV
- +
+ + - +
- + Gas volume
+ - +
+ -
+
Depending on ΔV (and the type of the gas) the detector will
work in ionisation mode, proportional mode, Geiger-Müller
mode, breakdown.
Wire chambers, drift tubes, resistive plate chambers, time
proportional chambers, …
3
Problematic
First gas detector in 1908!
Largely used in particle, nuclear and astro-particle physics, as well as for
imaging, material science, security inspection.
Advantages:
• Large surface (and limited price)
• Very low material budget
• Lot of know-how
Disadvantages:
• Limited granularity (O(100μm))
• Electrical discharges
• Aging
• Rate limitations
• Custom made (and very laborious)
4
Micro-pattern detectors
• Photolithography technology
• Multiplication stage in small region of space
• Independent of read-out pattern
5
Gas Electron Multiplier
F. Sauli et al., NIM A386(1997) 531
50 μm thick kapton foil, copper clad on each side and perforated by high
surface density (50-100/mm2) of bi-conical channels.
31 x 31 cm2
6
Gas Electron Multiplier
tiny proportional chamber
Field lines
Ε ~ 100 kV/cm ΔV ~ 500V
7
GEM detectors
charged particle
+ -
- +
+ + - +
- +
+ - +
8
Triple GEM
Triple GEM
reduced gain/foil
⇓
negligible discharge probability
9
10
Characteristics of GEM detectors
•
•
•
•
•
•
•
•
spatial resolution 50 μm
gain 105 → single electron detection
ion feedback suppression
efficiency ~ 100%
rate capability 1MHz/mm2
minor dependence from drift field
highly radiation tolerant
flexible detector shapes and read-out patterns
11
GEM applications
•
•
•
•
•
•
•
•
•
Detectors for HEP (also in TPC and RICH detectors)
Dark matter search
Neutron detectors
Plasma monitoring
Photomultiplier
Muon tomography
Medical imaging
Irradiation monitoring during cancer treatment
…
12
GEM applications
•
•
•
•
•
•
•
•
•
Dark matter search
Neutron detectors
Plasma monitoring
Photomultiplier
Muon tomography
Medical imaging
…
13
GEM applications
•
•
•
•
•
•
•
•
•
Dark matter search
Neutron detectors
Plasma monitoring
Photomultiplier
Muon tomography
Medical imaging
…
14
MICROMEsh GAseous Structure
Y. Giomataris et al., NIM A376(1996) 29
15
MicroMeGaS characteristics
•
•
•
•
•
•
spatial resolution 12 μm
ion feedback suppression
efficiency ~ 100%
rate capability 109 particles/mm2/s
highly radiation tolerant
flexible detector shapes and read-out patterns
16
A MicroMeGaS application: Gossip/GridPix
• low drift field (100-700 V/mm)
• High amplification field (~10kV/mm) to induce gas avalanche
• Micromegas holes centred on pads pixel chip
• Avalanche broadened by diffusion to 15-20 μm
17
Others MicroMeGaS applications
• High energy physics
• Neutron beam profile monitoring
• …
• Potentially similar to GEM
18
The future?
Electron emission foil with vacuum Micro-Channel Plate
Minimum Ionising Particle (MIP)
electron emission foil
H. van der Graaf, VCI 2010
19
Bibliography
• http://gdd.web.cern.ch/GDD/ GEM
• http://vci.hephy.at/2010 slides and proceedings
• http://mpgd.web.cern.ch micropattern gas detectors
20
Semiconductor detectors
Rita De Masi
IPHC-Strasbourg
1
Outline
• Working principle and radiation damage
• Hybrid detectors
• Monolithic detectors
•
•
•
CCD
DEPFET
MAPS
• Integration techniques
• Bonding
• 3D
• 3D detectors
• APD
• Diamond
2
Semiconductor detectors working principle
only 3.7 eV to create an e--h pair
(~30 eV for gas )
~ 80 e- created in 1μm
O(100 μm)
charged particle
- +
+ + - +
- + semiconductor
+ - +
+ -
they may recombine with thermally generated free charge carriers
3
Semiconductor detectors working principle
charged particle
-
ΔV
O(100 μm)
n+
p+
- +
+ + - +
- + semiconductor
+ - +
+ +
• p-n junction inversely biased for detection
• free charge carriers are removed from sensitive volume
• signal is collected and processed
4
Semiconductors
• Silicon (Si) → most commonly used
• Germanium (Ge) → x-ray, infrared, but require cooling
• Compound (GaAs, CdTl, SiC, …)
5
Advantages of semiconductor detectors
Semiconductor detectors crucial for charm discovery!
• High granularity (O(1μm))
• High density ⇒ thin (O(100μm))
• High rate capability
• Rigidity
• Electronic can be integrated on the substrate
Some disadvantage:
• Cost
• Material budget
• Radiation damage
6
Radiation damage
charged particle
• ionising and non-ionising radiation
• surface and bulk damage
• Frenkel pair
• NIEL
vacancy + interstitial
7
Impact on the detector performances
• New energetic levels in the forbidden gap
• Leakage current
• Charge recombination
• Collection time
Conduction band
⇓
decrease of signal-to-noise ratio
Valence band
can be improved with time, temperature, material engineering, sensor design, …
8
Working principle
charged particle
-
ΔV
O(100 μm)
n+
p+
- +
+ + - +
- + semiconductor
+ - +
+ +
9
Strip and pixel detectors
p/n side segmented ⇒ position sensitive device
2n
Strip
• less channels (2n)
• multiple hit ambiguity
• double sided segmentation possible, but complex
• material budget
• better suited for large areas
n2
Pixel
• more channels (n2)
• no multiple hit ambiguity
• 1 sensor gives 2 spatial coordinates
• vertex detectors
10
Hybrid pixel detectors
Used in almost all LHC experiments, X-rays imaging, space radiation detector,…
11
An example: a Medipix2 detector
MEDIPIX2 readout chip
(series developed for mammography first, for LHC later…)
• 1.4 x 1.4 mm2 active area
• 55 μm pitch
• counting rate 1MHz
• noise free
• coupled to photon sensitive devices (GaAs, …) for low dose imaging
• sensitivity to single photons
MEDIPIX
FILM
http://medipix.web.cern.ch/MEDIPIX
12
Monolithic detectors
• Sensing volume and electronics on the same substrate
• Thickness, simpler, only one technology
13
Charge-Coupled Device (CCD)
• Invented in the sixties
• Nobel price in 2009
• Shift register
• High quantum efficiency (70%)
• Light detector (found in cameras)
• Application in astrophysics, medical imaging, …
• Moderate speed
• Need trigger to determine position
• Sensitive to radiation damage
Signal treatment
• Needs cooling
14
CCD in high energy physics: the SLD vertex detector
• completed in 1996
• ~ 3 x 108 pixels
• 96 CCD
• 80 x 1.6 cm2 sensitive area each
• liquid nitrogen cooling
• 20 μm pitch
• σIP =14 μm for high energy particles
• enhancement of heavy quarks measurement performances
• J. Brau, Design and performances of the new CCD vertex detector at SLD and implications for the next
linear collider, Nucl.Inst.Meth.A 418-1 (1998) 52
• C.Damerell, Charge-coupled devices as particle tracking detectors, Rev.Sci.Intrum. 69 (1998) 1549
15
DEPleted Field Effect Transistor (DEPFET)
• developed in ’90s
• in-pixel detection and amplification
• depleted volume
• low capacitance -> low noise
• low power consumption
• collect-read-clear
• tracker and X-rays imager
J. Kemmer and G. Lutz, Experimental confirmation of a new semiconductor detector principle,
Nucl.Inst.Meth.A 288 (1990) 92
16
Monolithic Active Pixel Sensor (MAPS)
• CMOS technology
• alternative to CCD in commercial application (cameras, video recorder, …)
• in-pixel signal treatment
17
18
MAPS sensing principle
Signal collection
•
•
•
Charges generated in epitaxial layer → ~1000 e- for MIP.
Charge carriers propagate thermally.
In-pixel charge to signal conversion.
Advantages
•
•
•
•
High granularity (< 10 μm pitch).
Thickness ( <50μm).
Integrated signal processing.
Standard process (cost, prototyping, …)
Issues
•
Undepleted volume limitations .
•
•
•
•
radiation tolerance.
intrinsic speed.
Small signal O(100e-)/pixel.
In-pixel μ-circuits with NMOS transistors only.
19
Basic performances
• Room temperature operation.
• Noise ~10-15e-.
• Signal to noise ratio ~ 15-30.
• Detection efficiency ~100% @ fake hit rate O(10-4 -10-5).
• Radiation tol. > 1MRad and 1013neq/cm2 with 10μm pitch (2x1012neq/cm2 with 20μm pitch).
• Spatial resolution 1-5 μm (pitch and charge-encoding dependent).
• Macroscopic sensors (Ex. MIMOSA-5: 1.7 x 1.7 mm2, 106 pixels).
• Used in beam telescopes and VTX demonstrators.
http://www.iphc.in2p3.fr/-CMOS-ILC-.html
20
An example of sensor: Mimosa-26
Fast full scale sensors: ~10kFrame/s
column parallel architecture + integrated zero-suppression
13.7 mm
• Active area ~2 cm2.
Pixel array: 576 x 1152, pitch: 18.4 µm
Active area: ~10.6 x 21.2 mm2
• 0.35 μm technology.
• Binary output (3.5 - 4 μm spatial resolution).
• In-pixel CDS + preamp.
• Column level discrimination.
• Power dissipated ~280 mW/cm2 (rolling shutter).
1152 column-level discriminators
Zero suppression logic
• Integration time ~100μs.
Memory IP blocks
21.5 mm
21
MIMOSA-26 beam test
• TAPI = IPHC-Strasbourg BT for MIMOSA development.
• Test @ CERN-SPS (120 GeV π- beam).
• 6 MIMOSA-26 sensors running simultaneously at 80 MHz.
• 3 x 106 triggers.
y
z
x
ε = 99.5 ± 0.1 (stat.) ± 0.3 (prel.) %
@ fake hit rate O(10-4)
22
A vertex detector for the International Linear Collider
Accelerator
a (μm)
b (μm GeV)
LEP
25
70
SLD
8
33
LHC
12
70
RHIC-II
13
19
ILC
<5
< 10
σ IP = a ⊕ b/psin3/2θ
a depends on the intrinsic resolution and
inner radius
Sensor requirements
• Single point resolution ~ 3μm.
• Material budget 0.16/0.11% X0/layer.
• Integration time 25 – 100 μs.
• 16/15 mm inner radius.
• Radiation tolerance ~0.3MRad, few 1011neq/cm2.
• O(103) hit pixels/cm2/10 μs on the inner layer.
• Averaged power dissipated << 100 W.
b depends on material budget
23
Other HEP applications
STAR @ RHIC pixel detector
CBM @ FAIR Micro vertex detector
Beam telescopes, interest from ALICE @ sLHC, …
24
Other (non HEP) applications
ebCMOS:
• IPHC-IPNL-PHOTONIS.
• Single (visible) photon detection.
• Fluorescence microscopes.
X-rays :
• Direct illumination below 10 keV
• Converter above 10keV (Columnar CsI crystals from Hammamatsu)
• Dosimetry, surgery camera, telescope for hadron therapy, …
25
Integration techniques: bonding
Connect the sensor to its readout electronics
• wire bonding
• bump bonding
26
Further developments: 3D IT
Benefits:
• Increase integrated processing.
• 100% sensitive area.
• Select best process per layer task.
To be assessed:
• Material budget?
• Power dissipation?
Example
• Tier1: charge collection.
• Tier2: analog signal processing.
• Tier3: digital signal processing.
• Tier4: data transfer.
R. Yarema, ILC Vertex 2008, Menaggio (IT)
27
3D sensors
•
Increase tolerance to non-ionising radiation
•
lower depletion voltage
•
thicker detectors
•
fast signal
•
smaller trapping probability
•
higher capacitance
•
more complicated fabrication
Parker, Nucl.Instr.Meth. A, 395(1997) 328
28
Avalanche Photo Diodes (APD)
charged particle
-
ΔV
O(100 μm)
n+
p+
ΔV
~ 100 V → ~ 1000 V
charge multiplication
- +
+ + - +
- + semiconductor
+ - +
+ +
• only e- create secondary charge
• single photon detection
• proportional mode
•
•
•
sensitive to voltage and temperature changes
amplification needed
low single photon efficiency
• Geiger mode
•
•
high efficiency
low fluxes
29
Silicon Photomultiplier (SiPM)
• matrix of APDs on a common substrate
• output proportional to the number of photons
• compact and robust
• high quantum efficiency
• large gain
• fast
• can be operated in a magnetic field
• calorimeters, medical applications, air-shower Cherenkov telescopes
30
Diamond detectors
• no doping
• low signal
• low leakage current
• low capacitance
• high thermal conductivity
• very fast
• radiation hard
• expensive
• RD42 collaboration
• ATLAS Beam Conditions Monitor
31
More bibliography
General
• G. Lutz, Semiconductor radiation detector , Springer (1999)
• H.G. Moser, Silicon detector systems in high energy physics, Progress in
Particle and Nuclear Physics 63 (2009) 186-237
Radiation Damage
M. Moll, Radiation damage in silicon particle detectors, PhD Thesis (1999)
and several talk at the VCI 2010 conference…
32
Cherenkov and transition radiation
detectors
Rita De Masi
IPHC-Strasbourg
1
Outline
• Cherenkov and transition radiation
• Working principle
• Applications
2
Cherenkov light
• discovered in 1934 (Nobel prize in 1958)
• charged particle in medium radiates if v > c/n
• cos ( θ ) = 1/(βn) β = v/c
• threshold effect
• no energy loss
θ
3
Where do you see Cherenkov light
• nuclear reactors
• cosmic rays → air-shower Cherenkov telescopes
• labelled bio-molecules
4
Cherenkov detectors
• exploit the Cherenkov effect to identify particles
• v > c/n
• two particles with same momentum but different mass will have different
velocity
5
Ring Imaging CHerenkov (RICH) detectors
separate particles as function of θ
6
Where are the RICHes?
• nuclear and particles experiments
• astroparticles
• neutrino physics
SuperKamiokande
50000 tons of water
7
Transition radiation
• predicted by Ginsburg and Frank in 1945 (J.Phys. 9 (1945) 353)
• particle traversing a boundary of two media with different dielectric properties
• no energy loss
• ultra-relativistic particles emit TR in the X-band
• radiated energy is proportional to the particle’s energy
• particle identification at high energy
• average number of photons emitted at boundary ~ 1/137
8
ATLAS Transition Radiation Tracker (TRT)
• LHC experiment aimed at Higgs boson discovery and physics beyond the
Standard Model
• straw tubes in radiator
• 420000 channels
9
Standard Model
• 420000 channels
10
Standard Model
• 420000 channels
11
ALICE TRD
• LHC experiment
• quark-gluon plasma
12
TRACER
• direct measurements of heavy cosmic ray nuclei (O to Fe) @ 1013 -1014 eV
• 4 plastic fibre radiators + double layer of proportional tubes
• balloon experiment
http://tracer.uchicago.edu
13
Alpha Magnetic Spectrometer (AMS)
• search for dark matter and anti-matter
• to be launched end of 2010 towards ISS
http://www.ams02.org
14
Bolometers
Rita De Masi
IPHC-Strasbourg
1
Definition
• Measurement of electromagnetic radiation via temperature
changes
• Absorber + heat sink
• Optimal for sub-millimetre astronomy (200μm – 1 mm)
• Need to be cooled down (tens – hundreds of mK)
• Slow
• No particle discrimination
• Excellent energy resolution
(~ 10 eV @ few KeV)
ΔT
2
Bolometers in nuclear and particle physics
• low energy rare events (a few KeV)
• WIMP search
• low energy neutrino interactions (double β-decay)
• very rare nuclear decays
3
Scintillating bolometers in WIMP searches: CRESST
• scintillating material @ low temperature
• light vs. heat discrimination technique
• CaWO4
• feeble scintillating nuclear recoil (WIMP)
• electron recoil (large β and γ background)
• Gran Sasso laboratories (under ~ 1400 Km rock)
• 10 Kg detector (33 modules)
• Tungsten superconducting thermometers
http://www.cresst.de
4
A semiconductor bolometer: EDELWEISS
• Germanium crystals @ low temperature
• ionisation vs. heat discrimination technique
• Laboratories @ Modane (under Frejus mountain)
• 30 Kg detector
http://www.edelweiss2.in2p3.fr
5
Nuclear emulsions
Rita De Masi
IPHC-Strasbourg
1
Working principle
ionising particle
emulsion of silver salts (AgBr)
++-+
+-+
• exposing
• developing
• observing
2
Applications
• discovery of cosmic rays (1910)
• discovery of pions (1947)
• astrophysics
• medical radiography
• photography
3
Characteristics
• 3-D spatial information
• high granularity ~ 300 hits/mm
• high spatial resolution <1μm
• continuously sensitive
• offline analysis
⇒ short lived particles
⇒ low cross section experiments
neutrino physics
micro-autoradiography
4
OPERA experiment
• νμ → ντ oscillations
• neutrino beam from CERN to Gran Sasso (O(1000 Km))
• emulsion cloud chamber (ECC)
http://operaweb.lngs.it
5
Scanning
2 cm2/h → 20 cm2/h
http://iopscience.iop.org/1742-6596/41/1/023/pdf/jpconf6_41_023.pdf
6
The COMPASS experiment
Rita De Masi
IPHC-Strasbourg
1
Physics goals
• nucleon spin structure
•
•
•
gluon polarisation
helicity and transverse parton distribution functions
generalised parton distributions
• hadron spectroscopy
•
•
•
•
pion/kaon polarisability
glueballs
hybrids
double charmed baryons
2
a ins
r
Ju nta
ou
m
COMPASS
LHC
La
cL
ém
an
SPS
N
3
3
The experiment
• fixed (polarised) target experiment
• polarised muon/hadron beams (~ 160 GeV)
• ~ 108 particles/s
• taking data since 2001
μ filter
ECal & HCal
μ filter
50
SM2
m
RICH
SM1
MWPC
Straws
6LiD
or
NH3 Target
GEMs
μ
V
e
G
0
16
SciFi Silicon
Drift chambers
Micromegas
4
The beam reconstruction
μ filter
ECal & HCal
μ filter
m
0
5
SM2
RICH
SM1
6LiD
or
NH3 Target
MWPC
Straws
GEMs
Drift chambers
μ
V
Ge
Micromegas
0
6
1
SciFi Silicon
14 μm spatial resolution
350 ps time resolution
5
The target
3He
– 4He dilution
refrigerator (T~50mK)
6LiD
or NH3
50/90% polarization
40/16% dilution factor
μ
solenoid
2.5T
dipole magnet 0.5T
acceptance
± 180 mrad
6
The tracking system
m
50
SM2
SM1
MWPC
Straws
GEMs
Drift chambers
Micromegas
Stage 1 (Large Angle Spectrometer)
•1Tm
•Δp/p ~ 1%
•5-50GeV
Stage 2 (Small Angle Spectrometer)
•5.2 Tm
•Δp/p ~1%
•30-100GeV
7
The particle identification
μ→ μ filter
π, K, p separation → RICH
e, γ → ECAl
hadrons → HCal
μ filter
ECal & HCal
μ filter
RICH
8
The data acquisition system (DAQ)
∼200000 detector channels
up to 100kHz trigger rate
40kByte/event → up to 4000MByte/s
SPS duty cycle
4.8s
12 s
9
Event reconstruction
tracking
vertexing
PID
complete event
10
Data analysis
11
The CMS experiment
Rita De Masi
IPHC-Strasbourg
1
Main physics goals
• Higgs boson
• Extradimensions
• Dark matter
• SUSY
•…
2
La
cL
ém
an
a ins
r
Ju nta
ou
m
CMS
LHC
SPS
N
3
3
The detector
proton-proton collider (7+7 TeV)
4
The detector
5
One typical event
6
The GRID
5
• 5 petaBytes/year of data (1015!!!!)
• similar to the WEB, but also sharing computing
power and storage capacity
• presently 200 sites (20000 computers)
• simulation of drugs against avian flu and malaria
•…
7

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