Applications of Silicon Detectors

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Applications of Silicon Detectors
Motivation Principle of Operations The Rise of
Silicon Detectors Applications Charged
Particle Tracking Photon Detection
2
Precision Particle Tracking Detectors

• In Particle Physics, many new phenomena tend to
  be associated with heavy quarks.
• The Higgs search will depend on tagging heavy
  flavor jets,
• CP violation is being measured in the b system.
  
• Heavy quarks have a finite life time t, and can
  be identified by the decay length in the lab Dz
  ? gbct ( 250um in BaBar).
• This requires detectors in close proximity (few
  cm) of the beams
• with an intrinsic position resolution of 10 -
  25um.
• High particle densities in jets require fast,
  fine-grained detectors.
• This is possible only with semiconductor
  detectors.

• Vertexing precision depends on
• distance of the detectors from the interaction
  point,
• the lever arm, and the
• intrinsic position resolution
• of the detector

3
Particle Tracking Detectors for Theorists
Choose a fine-grained detector to localize
charged particles Passing of particle leaves a
trail of temporal ionization (gt10,000e) (see
next) Take advice from your local guru and
collect it electronically -gt apply electric
field, record tiny current Is (ltuA in 10 ns)
signal Problem Resistivity of detector material
In V/R gives large current Way out block
current with capacitor Problem large current
still gives background noise ? In Ways
out Ultra-high resistivity materials
(Diamonds, SiC, few Mohm-cm) Reverse biased
diode on Si (few kOhm-cm, industry grade)
4
Electrostatics of Silicon Strip Detectors
Resistivity given by concentration of dopants N
(donors or acceptors) . Charge cant be
collected from the conductive bulk have to
deplete it of mobile carriers (e), leaving the
bulk charged Depletion depth depends on bias
voltage Capacitance measured the depletion
depth
1/C2
VBias
5
Dynamics of Silicon Strip Detectors
Charge Collection Drifting Charges Induce
Charges on Electrodes Drift Velocity E
operating field, m mobility Induced
Charges Vql Weighting Potential (Ramos,
1937) Signal Current due to drifting
charges Fk(x) Weighting Field
(Cap) Collection Time Scale Signal ends when
charge arrives at the strip
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Further Reading for the Curious
http//britneyspears.ac/lasers.htm
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Signal in Tracking Detectors
Charged Particle Energy Loss (aka Stopping Power,
Linear Energy Loss LET)
Bethe-Bloch
Signal-to-Noise Ratio Signal Thickness Noise
Area, 1/?ts
Directional Information compromised by Multiple
Scattering
Multiple Scattering angle
-gt Thin, low z materials -gt Improves at High
Energy Radiation Length Xo
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Properties of Silicon Strip Detectors
Reverse Bias of junction only thermal current
generation Scale Band gap 1.12eV vs. kT
1/40eV huge Boltzmann factor Cooling needed
only in ultra-low noise applications. Wafer
thickness 300um 0.3RL 23k e-h pairs
Depletion Voltage thickness2 lt100V
Collection Time of e-h pairs 20ns Area is
given by wafer size 4 6 gt Ladders
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Evolution of Silicon Detectors
Double-sided
Large Area
Si Drift
3-D
Hybrid Pixels Monolythic CCD, MAP
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The Rise of Silicon Detectors
Development of Area of SSD and of Electronics
Channels follow Moores Law Larger - CMS 10M
Channels, 230m2 Faster - ATLAS
22ns Cheaper - CMS 5/cm2
o
o
O SCIPP
o
o
o
o
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The Rise of Silicon Detectors
Limited Resources (Power) in Space
Long Ladders possible with Bonding and
Encapsulation
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The Rise of Silicon Detectors
Trends in the Cost of Silicon Detectors Cost of
processing wafers reduced 4x Increased Area 4
-gt 6 Better utilisation of area Improved
Quality e.g. GLAST detectors lt2nA/ cm2
lt210-4 bad channels
(Guestimates by HFWS)
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DC (Drift Chamber) vs. SSD (Silicon Strip
Detector)
DC Tasks SSD
Excellent Team Excellent
Control E, Gain Electrostatic Design Silicon Valley
Many tricky parts Manufacturing Silicon Valley, Modular
Job Shoppers Assembly Silicon Valley
Discreets Hybrids Read out ASICs
E, T, HV, Gas, Whiskers Operations Never Calibrate Low Power
d-rays, sparks Performance Fast, Big S/N
What to do next?
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Typical Low Tech University Jobs
What to do next?
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Typical Low Tech University Jobs
What to do next?
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Tracking Milestones Fixed Target
Thats how it all began Fixed Target experiments
with high rates Na11 (ACCMOR), Na14, E706.
E691 Detect heavy decaying particles through
their finite decay distance
Silicon Detectors 5cm x5cm
What to do next?
Fanout-Cables
Amplifiers
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Tracking Milestones Vertex Detectors
The big step forward in Mark2 ASICs (A. Litke
et al)
Vertex Detector Paradigm ASICs, Few thin
layers, Close in.
Every LEP Experiment has a Vertex Detectors
Double-Sided AC-coupled
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Tracking Detectors CCD
300M pixel CCD device for SLD (A. Seidem, T.
Schalk, B. Schumm) Few um resolution in two
coordinates
Follow the (Industrial) Leader..
X
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Tracking Milestones Speed and Rad.Hardness
LPS at HERA (D. Dorfan, N. Spencer, J. DeWitt,
N. Cartiglia, E. Barberis, A. Seiden, D.
Williams, HFWS ) Fixed Target at
Collider Importance of Electronics rad
hard fast low noise low power
56 planes, 50k channels Elliptical shapes! 2mm
from 800GeV beam
2 chip set BipolarCMOS

Hadron-Machines Radiation Damage
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Tracking Milestones Highest Luminosity LHC
ATLAS Silicon Tracker (A. Seiden, D. Dorfan, A.
Grillo, N. Spencer, S.Kachiguin, F. Rosenbaumm,
M. Wilder, HFWS) Simple Detectors,Optimized
Electronics Thermal management
Vertex Detector ? Inner Detector Change in
Paradigm coverage of large area electronics
inside tracker volume

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Tracking Milestones Highest Luminosity LHC

• Silicon has arrived
• all Silicon Inner Detector
• Si Area 223m2,
• 6 Wafers
• (Ariane Frey et al)

Continued Paradigm Change gt20 layers of Si,
outside radius 1.1m 1R.L. in tracking
volume almost exact size of old wire chambers!

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Technology Transfer of Silicon Detectors
Protons Biology
Small-scale
Large-scale
X-rays Medicine
g-Rays Space Science C.Rays
Charged Particle Tracking in HEP


Industrial Base
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Si Tracking in Space Sileye
Cosmonaut Adveev on Mir
Sileye Investigate light flashes seen by
Cosmo-/Astro-nauts during Orbital flights.

Occurrence of flashes well correlated with areas
of high flux of Cosmic ray particles.
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Photon Detection in Astronomy Direction,
Direction,..
Photon Attenuation Coefficient
Attenuation of Phtotons N(x) Noe- l x
l varies by 105!

• Attenuation coefficient
• (7/9)/Xo

lt 0.3 Conversions in one SSD!
Optical- X-rays Need Focus Lenses Mirrors Collima
tors Coded Masks Proximity
Pair- Production Direction
?
anticoincidence shield
Compton Partial Direction

• calorimeter
• (energy measurement)

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GLAST Pair Conversion Telescope
Gamma-rays convert into ee- pairs, are tracked
and their energy measured Gamma is reconstructed
from ee- tracks
Reconstruct Vertex
New ParadigmAdd material into tracking volume
Maximize Number of Converters
Converter Thickness t Conversion Probability
t Pointing RMS ?t
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GLAST Gamma-Ray Large Area Space Telescope
An Astro-Particle Physics Partnership Exploring
the High-Energy Universe
Design Optimized for Key Science Objectives

• Understand particle acceleration in AGN,
  Pulsars, SNRs
• Resolve the g-ray sky unidentified sources
  diffuse emission
• Determine the high-energy behavior of GRBs
  Transients

Proven technologies and 7 years of design,
development and demonstration efforts

• Precision Si-strip Tracker (TKR)
• Hodoscopic CsI Calorimeter (CAL)
• Segmented Anticoincidence Detector (ACD)
• Advantages of modular design
• NASA, DoE, DoD, INFN/ASI, Japan, CEA, IN2P3,
  Sweden

Challenges of Science in Space

• Launch
• Limited Resources
• Space Environment

Resolving the g-ray sky
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GLAST Large Area Telescope (LAT)

• Array of 16 identical Tower Modules, each with
  a tracker (Si strips SSD)
• 10,000 SSD
• 83m2 area
• 1M channels,
• 5M wire bonds
• A calorimeter (CsI with PIN diode readout) and
  DAQ module.
• Surrounded by finely segmented ACD (plastic
  scintillator with PMT readout).

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GLAST Silicon Tracker
SCIPP (R. Johnson, W. Atwood, W. Rowe, A.
Webster, N. Spencer, S. Kachiguine, W. Kroeger,
M. Hirayama, M. Sugizaki, B. Baughman, HFWS)
Tower Structure (walls, fasteners) Engineering
SLAC, Hytec Procurement SLAC I
SSD Procurement, Testing Japan, Italy, SLAC
I
SSD Ladder Assembly Italy I
10,368
Tower Assembly and Test SLAC (2) Italy (16)
2592
Tray Assembly and Test Italy I
342
Electronics Design, Fabrication Test UCSC, SLAC
I
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342
Cable Plant UCSC I
Composite Panel Converters Engineering SLAC,
Hytec, and Italy Procurement Italy
I
Most Production and Assembly Steps done in
Industry I
Testing Academic Research Institutions
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Typical High Tech University Jobs
2 trays and 2 observers
All done and all smiles.
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Application of Silicon Detectors No Limits
We build instruments to explore the structure of
our world from Quarks (lt10-20m) to the entire
Universe (gt1028m).
Silicon Detectors are used for experimentation
at every scale.
The largest SSD systems are in Astro- and
Particle Physics. We trying to play catch-up in
Life Sciences.
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1,000,000 TKR Channels 6,000,000
encapsulated Wire Bonds
TKR Interconnects Industry Job
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GLAST Front-End Electronics ASIC

• Binary Readout
• Low-power (200uW/channel)
• Peaking time 1.3 ms
• Low noise (Noise occupancy lt10-5)
• Threshold set in every ASIC
• Separate Masks for Trigger and Readout in every
  Channel
• Trigger OR of one Si plane (1536 channels)

Electron Events
Pulse Height Time over-Threshold on the OR of
every Si plane Distinguish single tracks
from two tracks in one strip
Photon Events
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Prototyping of the GLAST SSD
The SSD design has been finalized and procurement
is underway 11,500 SSD inlude 10 Spares Qualify
Prototypes from HPK (experience with 5 of
GLAST needs)
0.1specs
340
Additional Prototypes Micron (UK), STM (Italy),
CSEM (Switzerland)
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Radiobiology
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Some Basic Questions in Radiobiology

• Its the DNA, stupid!
• Are there different classes of damage depending
  on the Linear Energy Transfer (LET) and number of
  ionizations/DNA molecule?
• By-stander effect Damage is being transmitted to
  distant cells
• Effect of OH- radicals in the damage process
• Improve dosimetry of proton beam for cancer
  therapy

LET of Ionizations Damage
Low 1-5 Repairable ?
High 6-12 Irreparable ?
Very High gt12 Recombination Saturation ?
Collaboration (NASA-CalSpace) Loma Linda U.
UCSC (SCIPP CfO) (A. Seiden, R. Johnson, W.
Kroeger, P. Spradlin, B. Keeney, HFWS)
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Radiation Damage DNA
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Project Goals

• Establishment of a nanodosimetric gas model to
  simulate ionizations in DNA and associated water
• Plasmid-based DNA model to measure DNA damage
• Develop models to correlate nanodosimetry with
  DNA damage

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Principle of Nanodosimetry (Statistical Approach)
1nm solid
1 mm _at_ .001 atm (1 torr)
1 um _at_ 1 atm
X 1000
X 1000
DNA
Propane gas
Low pressure propane gas
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Schematic of Nanodosimeter
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Setup and Silicon Modules
VME CRATE
Localization of Protons 2 Silicon Strip Detector
(SSD) Modules
ND Vessel
SSD DAQ
PC W/ DAQ PCI Card
Ion counter
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ND Ion Cluster Spectra
Event with 6 ions
A primary particle event is followed by an ion
trail registered by the ion counter (electron
multiplier) For low-LET irradiation, most events
are empty
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ND Ion Cluster Spectra
Ion Cluster Spectra
Ion cluster spectra depend on particle type and
energy as well as position of the primary
particle track The average cluster size increases
with increasing LET
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Proton Energy Measurement
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Connection Nanodosimetry - Radiobiology
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Radiobiological Model

• Plasmid (pHAZE)
• Irradiation of thin film
• of plasmid DNA
• in aqueous solution
• Three structural forms
• superhelical (no damage)
• open circle (single strand break)
• linear (double strand break)
• Separation by agarose gel electrophoresis
• Fluorescent staining and dedicated imaging system

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What is needed?
Global (Nanodosimetry) Well in Hand ?
Correlation needed! Tag individual
Interaction, Investigate Damage in detail on
struck molecules
Local Needs Improvement No Radiometry
Measurement Correlated with Damage on individual
DNA Molecule
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Particle Tracking Silicon Microscope (PTSM)
Protons produce damage AND identify damaged
organism
Transfer to Automated Microscope when Occupancy
10
Worms in Liquid Phase (directly on SSD)
Double-sided SSD x-y coordinate, Energy,
Cluster characteristics.
Assay with Automated Microscope using stored x-y
coordinates
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Gametogenesis in the adult hermaphrodite of C.
elegans
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Chromosome structures in the gonad of the adult
hermaphrodite
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0-8h II (early embryogenesis) III (diakinesis
oocyte) 8-24h III IV V VI (diplotene to
pachytene nuclei)
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Medicine
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Application Compton Camera in Medicine
Compton Camera Silicon detector measures the
first scatter Calorimeter measures the energy and
direction
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Strip Detectors in Medicine Mammography
Large objects, proximity focussing Need large
detectors! Scan collimated X-ray Source across
Si strips
Gammex RMI phantom at 0.7 mGy MGD
Excized breast tissue 5 cm x 7 cm x 4 cm at 0.3
mGy MGD
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Strip Detectors in Medicine Mammography
Stationary Telescope of Flat Synchrotron beam
and Collimator and edge-on Si Detector Scan
Sample/Patient.
Edge-on Si strips Have high efficiency No Ghost
problem Pixels
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Acknowledgements

• LLUMC
• Vladimir Bashkirov
• George Coutrakon
• Pete Koss
• WIS
• Amos Breskin
• Rachel Chechik
• Sergei Shchemelinin
• Guy Garty
• Itzik Orion
• Bernd Grosswendt - PTB

• UCSD - Radiobiology
• John Ward
• Jamie Milligan
• Joe Aguilera
• UCSC - SCIPP
• Abe Seiden
• Hartmut Sadrozinsky
• Brian Keeney
• Wilko Kroeger
• Patrick Spradlin

The nanodosimetry project has been funded by the
National Medical Technology Testbed (NMTB) and
the US Army under the U.S. Department of the Army
Medical Research Acquisition Activity,
Cooperative Agreement DAMD17-97-2-7016. The
views and conclusions contained in this
presentation are those of the presenter and do
not necessarily reflect the position or the
policy of the U.S. Army or NMTB.
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A Silicon Telescope For Nanodosimetry
A collaboration between Loma Linda University
Medical Center, the Weizmann Institute of
Science, UC San Diego, and the
Santa Cruz Institute for Particle Physics, UC
Santa Cruz
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Collaborators

• Loma Linda University Medical Center
• Reinhard Shulte George Coutrakon
• Vladimir Bashkirov Peter Koss
• Weizmann Institute of Science
• Amos Breskin Guy Garty
• Rachel Chechik Itzhak Orion
• Sergei Shchemelinin
• University of California, San Diego
• John F. Ward Jamie Milligan
• Joe Aguilera
• Santa Cruz Institute for Particle Physics
• (University Of California, Santa Cruz)
• Abe Seiden Wilko Kroeger
• Hartmut Sadrozinski Patrick Spradlin
• Robert P Johnson Brian Keeney

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Radiation Damage To DNA
Ionization event (formation of water radicals)
Light damage- reparable
Primary particle track
delta rays
e-
OH
Water radicals attack the DNA
Clustered damage- irreparable
The mean diffusion distance of OH radicals before
they react is only 2-3 nm
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Bethe-Bloch in ND
Linear Energy Transfer LET Radiation
damage in DNA occurs within 2-3nm
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1nm solid
1 mm _at_ .001 atm.
1 m _at_ 1 atm.
X 1000
X 1000
Propane gas
DNA
Low pressure propane gas
61
4 Silicon Detectors give position and LET, allow
trigger on any combination of planes
Eweak
electron
Incoming Proton
Low Pressure Gas
X-Y
Y-X
Vacuum
Ion
Estrong
Ion Counter
Aperture
NOT TO SCALE
62
Setup and Silicon Modules
VME CRATE
Localization of Protons 2 Silicon Strip Detector
(SSD) Modules
SMD Readout
PC W/ DAQ PCI Card
Ion Counter
63
Time-Over-Threshold (TOT) Digitization of
Position and Energy with large Dynamic Range
TOT ? charge ? LET!
64
Charge Sharing in SMDs
65
TOT Spectra For Low-Energy Protons-An absolute
calibration of SMD
66
Results
Proton energy MeV Mean TOT us RMS TOT us Charge Deposition 400um Si fC TOT expected by Bethe-Bloch us
13,500 7 1.4 5.3 6.5
250 12.3 2.6 13.5 13.7
39 53.4 6.4 54 55
27 70.4 7.5 67.5 69
24 78.3 8.5 76.5 78
22 84.4 9.8 81 82
17.6 105 11.5 99 101
9.5 108 15 189 105
7.4 109 21 243 105
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TOT and Resolution Measured TOT expected
through Bethe-Bloch

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Proton Energy Measurement
sE ?E/?TOT sTOT 1/(?TOT/ ?E) sTOT
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Conclusion

• Silicon Detectors allow flexible triggering on
  primary particles.
• Silicon Detectors yield fantastic spatial
  resolution60
• We can Measure LET to 10-20 in each of 4 planes
• Given LET, we know Energy to 20-25 in each
  plane through Bethe-Bloch up to 250 MeV

Silicon detectors give Nanodosimetry position and
energy, making it possible to simulate ionization
of DNA in a gas.