Tracking with Semiconductor Particle...
Transcript of Tracking with Semiconductor Particle...
Tracking with Semiconductor Particle Detectors
Carl HaberPhysics Division
Lawrence Berkeley National Laboratory
Nov 16, 2005 UC Davis Physics Carl Haber LBNL1
Suggestions for further reading
R.N.Cahn and G.Goldhaber, The Experimental Foundations of Particle Physics, Cambridge, 1989
W. Blum and L. Rolandi, Particle Detection with Drift Chambers, Springer-Verlag, 1993
T. Ferbel, Experimental Techniques in High Energy Nuclear and Particle Physics,World Scientific, 1992
R.P. Shutt, Bubble and Spark Chambers Volumes 1 and 2, Academic Press, 1967
J.Orear, Notes on Statistics for Physicists, Cornell Laboratory for Nuclear Science note CNLS 82/511
Particle Data Group, The Review of Particle Properties, European Physical Journal C 15, (2000) p.157-204
D.H. Perkins, Introduction to Particle Physics, 4 Ed edition (2000) Cambridge Univiversity Press
A.S. Grove, Physics and Technology of Semiconductor Devices, (1967) John Wiley & Sons; ISBN: 0471329983
R.Ruchti, Scintillating Fibers for Charged Particle Tracking, Annual Review of Nuclear and Particle Science, 46, (1996) 281-319
J.Va’vra, in Instrumentation for Experimental Particle Physics, AIP Conference Proceedings 422, edited by Herrara Corral and Sosa Aquino, Woodbury, NY, 1998
H. Spieler, Semiconductor Detector Systems, Oxford Science Publications, 2005
Nov 16, 2005 UC Davis Physics Carl Haber LBNL2
Outline
• Physics motivation• Colliding beam experiments• Tracking fundamentals• Semiconductor detectors• Radiation issues• Future directions
Nov 16, 2005 UC Davis Physics Carl Haber LBNL3
Introduction• Particle physics progresses by increased beam energy
and luminosity.• Experiments in particle physics are based upon three
basic measurements.– Energy flow and direction: calorimetry– Particle identification (e,µ,π,K,ν…) – Particle momentum: tracking in a magnetic field
• Ability to exploit increased energy and luminosity are driven by detector and information handling technology.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL4
Searching for Particles
• Event rates are governed by– Cross section σ(Ε) [cm2] - physics– Luminosity [cm-2s-1] = N1N2 f / A
• N1N2 = particles/bunch• f = crossing frequency• A = area of beam at collision
– Nevents = σ Ldt– Acceptance and efficiency of detectors
• Higher energy: threshold, statistics• Higher luminosity: statistics
∫
Nov 16, 2005 UC Davis Physics Carl Haber LBNL5
Experimental Program• Series of accelerators with
increasing energy and luminosity
• 25 years: domination of colliders• Proton colliders
– “broadband” beams of quarks and gluons, - “search and discovery” and precision measurements
• Electron colliders– “narrowband” beams, clean,
targeted experiments and precision measurements
Nov 16, 2005 UC Davis Physics Carl Haber LBNL6
Nov 16, 2005 UC Davis Physics Carl Haber LBNL7
CERN SppS Collider 1980-88CERN ISR ~1975
CERN LHC 2008-?Fermilab Tevatron 1985-2009
Nov 16, 2005 UC Davis Physics Carl Haber LBNL8
Hadron Collider HistoryMachine C.M.S.
EnergyLuminosity Year Role Detector
Innovations
ISR 31 GeV 2 x 1032 1970’s Exploratory, IVB search
W, Z, jets
Top quark
Higgs,…?
SppS 640 GeV 6 x 1030 ’80 -’88
High rate electronics
Hermetic and projective calorimeters, magnetic trackingPrecision tracking, advanced triggers
Tevatron 1.9 TeV 1030-1032 ’85 -’08
LHC 14 TeV 1033-1035 ’08 - ? Fast detectors, radiation resistances
Nov 16, 2005 UC Davis Physics Carl Haber LBNL9
Proton collider event structure• Most interesting physics is
due to hard collision of quark(s) or gluon(s)
• That production is central (and rare) and “jet” like
• Remaining “spectators” scatter softly, products are distributed broadly about the beam line and dominate the average track density
Nov 16, 2005 UC Davis Physics Carl Haber LBNL10
Outer muonchamber (blue)
Solenoidalmagnet coil(purple)
Inner muonchamber (yellow)
Hadroncalorimeter (dark blue)
Electromagnetic calorimeter(red)
beampipe
Central drift chamber
Silicon microvertexdetector
ab
de
fg
c
muon
pion
photon
electron
a: beampipe b:vertex tracker c: central tracker d: solenoid coil e: electromagnetic calorimeter f: hadronic calorimeter/muon filter g: muon tracking chambers
Nov 16, 2005 UC Davis Physics Carl Haber LBNL11
Nov 16, 2005 UC Davis Physics Carl Haber LBNL12
Tracking
• The process of sampling a particle's trajectory and determining its parameters. – Momentum– Direction– Decay points
• High energy– Small fraction of energy deposited in instrument
• The trajectory should be disturbed minimally by this process.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL13
Method• Charged particles ionize matter along their path.• Tracking is based upon detecting ionization trails.• An “image” of the charged particles in the event.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL14
Specifications• Performance on reconstruction of track parameters• Defined in terms of:
– parameters of the system (layout, magnetic field, etc)– performance of position sensing elements.
• Initially evaluate with simple parametric analyses.• Full simulation• Performance of position sensing elements
– hit resolution, timing resolution, effects of data transmission
– defined by physics of detecting medium/process and general considerations such as segmentation and geometry.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL15
Technology
• Old: Emulsions, cloud, and bubble chambers– Continuous media– Typically gave very detailed information but were
slow to respond and awkward to read out• New: Electronic detectors, wire chambers,
scintillators, solid state detectors– Segmented– Fast, can be read out digitally, information content
is now approaching the “old” technology
Nov 16, 2005 UC Davis Physics Carl Haber LBNL16
770 microns15 microns
15 microns
n=1.59n=1.49
n=1.42
fiber
cladding
track
mirror
scintillating section clear section photon detector
Nov 16, 2005 UC Davis Physics Carl Haber LBNL17
Technical Background
• Define tracking parameters• Basic constraints on performance
– Geometry– Material– Point resolution
• Point resolution and multi-hit response– The problem of 2D
Nov 16, 2005 UC Davis Physics Carl Haber LBNL18
Trajectory
θ
z
x
y
x*
y*
z*
φ D
Rx0,y0
z0
• Charged particle in a magnetic field B=Bz
• 3D Helix : 5 parametersC = half curvature
(1(sgn)/R)z0 = offsetD = signed impact
parameter (distance of closest approach)
Azimuth φ = angle of track at closest approach
θ = dip anglex = x0 + Rcosλy = y0 + Rsin λz = z0 + Rλ tanθ
Nov 16, 2005 UC Davis Physics Carl Haber LBNL19
Nov 16, 2005 UC Davis Physics Carl Haber LBNL20
Simple case: Measure sagitta s of track with radius R, over projected arc length L (cm, KGauss, MeV/c), assuming R>>L
θθθ cos3.08
8 using
cos83.0
cos3.0
2
22
BLsp
pp
sLR
sBLBRp
sagitta
∆=⎟⎟
⎠
⎞⎜⎜⎝
⎛ ∆⇒===
where ∆s is the error on the sagitta measurement.
Effect of material: multiple scattering
21
22
02
222
cos8.52
cos316)(
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛ ∆+⎟⎟
⎠
⎞⎜⎜⎝
⎛ ∆=
∆
=⎟⎟⎠
⎞⎜⎜⎝
⎛ ∆⇒=∆
MCSsaggitaTOTAL
MCS
MCS
pp
pp
pp
LXBppLs
θθσ s
Momentum resolution
0.01
0.1
1
10
100
Del
ta P
/P
1000
0.1 1 10 100 1000
B=15 KG, Delta s=0.1 mmL=100 cm
momentum GeV/c
P error %Delta P/PCO2LArIronθcos3.0
8 2BLsp
pp
sagitta
∆=⎟⎟
⎠
⎞⎜⎜⎝
⎛ ∆
21
22
0 cos8.52
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛ ∆+⎟⎟
⎠
⎞⎜⎜⎝
⎛ ∆=
∆
=⎟⎟⎠
⎞⎜⎜⎝
⎛ ∆
MCSsaggitaTOTAL
MCS
pp
pp
pp
LXBpp
θ
•Minimize sagitta error•Maximize B,L•Minimize material
Nov 16, 2005 UC Davis Physics Carl Haber LBNL21
( ) ( )
( ) ( ) ( )
xxya
xyby
yby
ybb
xbyxxxyyyya
xyy
xxyyb
bxay
yyyxx
∆+=
∆=⇒⎟
⎠
⎞⎜⎝
⎛∂∂
+⎟⎠
⎞⎜⎝
⎛∂∂
=
−=⎟⎠⎞
⎜⎝⎛
∆+
−−+==
∆−
=−−
==
+=
==
812
221
21212121
21intercept
212121slope
errors with points, measured 2,1planest measuremen 2,1
22
22
2
δδ
δδδδδ
δ
for good resolution on angles (φ and θ) and intercepts (d, z0 )•Precision track point measurements•Maximize separation between planes for good resolution on intercepts•Minimize extrapolation - first point close to interaction
Vertex Resolution
x1 x2
y1
y2
a
Nov 16, 2005 UC Davis Physics Carl Haber LBNL22
xxya
yyyxx
∆+=
==
812
errors with points, measured 2,1planest measuremen 2,1
δδ
δ
for good resolution on angles (φ and θ) and intercepts (d, z0 )•Precision track point measurements•Maximize separation between planes for good resolution on intercepts•Minimize extrapolation - first point close to interaction•Material inside 1st layer should be at minimum radius (multiple scattering)
Vertex Resolution: Material
x1 x2
y1y2
a
Nov 16, 2005 UC Davis Physics Carl Haber LBNL23
Correct treatment of errors utilizes fitting and parameter estimation techniques such as the least squares method.
χ 2 = ( yi − F( xi ;αi , j = 0
N
∑ )) Eij− 1 ( y j − F( x j ;α ))
with ∂χ 2
∂α k
= 0
Eij ≡ error matrix, if points are uncorrelated then
E ij =
σ 02 0 .... 0
0 • .... 00 .... • 00 .... .... σ n
2
⎛
⎝
⎜ ⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟ ⎟
note: elements are additive, errors can be combined.
if F ( x i;α ) can be written in the form F ( x i; α ) = α nn
∑ fn (x i )
where the fn ( x i ) are a linearly independant set, the parameters α can be found by a matrix inversion,
α = V g
where gm = y jjk
∑ fm (x k )E jk− 1
and Vmn−1 = fm ( x j )
jk∑ fn ( xk ) E jk
−1
and the errors 2 (or covariances) of the α m ,
α mα n[ ]= α mα n − α m α n are given by the elements of Vmn
Nov 16, 2005 UC Davis Physics Carl Haber LBNL24
Point Resolution: Segmentation
• Discrete sensing elements (binary response, hit or no hit), on a pitch p, measuring a coordinate x
• Discrete sensing elements (analog response with signal to noise ratio S/N) on a pitch p, where f is a factor depending on pitch, threshold, cluster width
12p
x =σ
)(~SNfpxσ
p
x
Nov 16, 2005 UC Davis Physics Carl Haber LBNL25
Multi-hit performance• Binary response (hit or no hit), on pitch p, two hit separation
requires an empty element. – Wide pitch most hits are single element, separation = 2p– Narrow pitch double element hits, separation = 3p
• Analog response: can use local minima in a merged cluster
Nov 16, 2005 UC Davis Physics Carl Haber LBNL26
2D• The problem of 2 dimensions:
– crossed array of n elements each on pitch p gives equal resolution on both coordinates.
• m hits m2 combinations with m2 – m false combinations– Small angle stereo geometry, angle α
• False combinations are limited to the overlap region but resolution on second coordinate is worse by 1/sin(α)
Nov 16, 2005 UC Davis Physics Carl Haber LBNL27
2D
• Pixel structure: n x m channels– Ultimate in readout structure– Expensive in material, system issues, technology
• Pixels and strips can also be thought of as 2 extremes of a continuum (super-pixels, short-strips,…..)– Some potential for optimizations of performance vs.
complexity but needs to be analyzed on a case by case basis• Novel 2D structures with 1D readout which rely on
assumptions about hit characteristics
Nov 16, 2005 UC Davis Physics Carl Haber LBNL28
Semiconductor Detectors
• Since mid-80’s use of position sensitive “silicon detectors” became widespread
• Can resolve track positions to ~10 microns• Used to measure momentum and identify
secondary vertices due to decays of primary particles
• Handle high particle rates and radiation dose
Nov 16, 2005 UC Davis Physics Carl Haber LBNL29
Nov 16, 2005 UC Davis Physics Carl Haber LBNL30
• Semiconductor band structure energy gap• Asymmetric diode junction: example p(+) into contact with n
(NA >> ND)• Space charge region formed by diffusion of free charges,
can be increased with "reverse bias“
Silicon Detectors
p+ nV=0 VRB>0
W
( ) ( )
bias reverse applied V) 0.8(~ potentialin built
101e
1 material n type ofy resistivit
11.9 mobility,electron 5.02 :idthjunction w
0
==
Ω−≈==
==
+=+=
RBBI
D
RBBIRBBI
VV
cmkN
VVmVVW
µρ
εεµρµµρε
Response to Ionization
• Electron-hole pairs formed in the depletion zone drift under the influence of the electric field
• Drift time determined by mobility and field– ~7 ns to cross 300 microns
• Drifting charge is a current which can be measured
p+ nV=0 e-
Nov 16, 2005 UC Davis Physics Carl Haber LBNL31
VRB>0h+h+
h+ e-
e-
Planar Processing• Using micro-lithographic techniques arrays of diode
structures can be patterned on silicon wafers.• The “Silicon Microstrip” detector was introduced in
the late 1970’s and is the basis of all precision types in use today
Al readout strip
oxide layer
p+implant
high resistivity n material
n+layer
Al contact
25-200 microns
200-300 micronsall other layers of 1 micron scale
Nov 16, 2005 UC Davis Physics Carl Haber LBNL32
6 mm
Nov 16, 2005 UC Davis Physics Carl Haber LBNL33
2D Pixel StructureCharge sensitive Preamp + shaping,signal processing, pipelines, digitization
Single sided configurationPixel readout
Diagram courtesy of Z.Li and V.Radeka
Nov 16, 2005 UC Davis Physics Carl Haber LBNL34
Signal Processing Issues
• Signal: expressed as input charge, typically 25,000 electron-hole pairs (4 fC)
• Gain: determined by feedback and capacitance
• Noise: various sources, must be small compared to signal (S/N > ~10)
V bias
R bias
integrator shaper
t rise TM
V out
n+
np+
oxideCb
G
Nov 16, 2005 UC Davis Physics Carl Haber LBNL35
Leakage Current
• Leakage current– DC component blocked
by oxide capacitor– Before (after) radiation
damage ~ 1 nA (1 ma) – AC component is seen
by pre-amp: noise source
V bias
R bias
integrator shaper
t rise TM
V out
n+
np+
oxideCb
G
areajunction density trap
velocityermalcarrier thsection crossion recombinat
ionconcentratcarrier intrinsic2
)(
==
===
=
ANv
n
WANvenI
T
thermal
i
TthermaliL
σ
σ
( ) kTEL
aeTTI 2/2 −∝Nov 16, 2005 UC Davis Physics Carl Haber LBNL
36
Noise
• Fluctuations ~ Gaussian σN– Leakage Current– Preamp “input noise charge”,
white noise, decreases with pre-amp current, increases with faster risetime where a,bare constants and CD is the detector capacitance
– Bias resistor: source of thermal noise
V bias
R bias
integrator shaper
t rise TM
V out
n+
np+
oxideCb
G
MLEAKN TI∝σ
DN bCa +∝σ
BIASN R
1∝σ
Nov 16, 2005 UC Davis Physics Carl Haber LBNL37
pre-ampleakage
(ignore scale, just an example)
Signal readout is a (delicate) balance “between” S/N, speed, power,…
Nov 16, 2005 UC Davis Physics Carl Haber LBNL38
Readout Electronics
• Large channel count and complexity require custom readout chips (ASICs)• On-chip complexity increases with process evolution• Speed and noise performance have kept up with requirements but S/N
always remains an issue.• Mixed analog-digital signals on the same chip
Nov 16, 2005 UC Davis Physics Carl Haber LBNL39
Historical Note• First silicon tracker for a hadron collider was proposed ~1985 by the INFN Pisa
group for CDF at Fermilab the “SVX”– 4 layers of silicon microstrips, 2-7 cm radii– 50K channels– Expected luminosity was 1029 (100 nb-1), (dose ~few KRad)– Primary purpose was to discover top by (real) W tb– Not expected to do any significant B physics
• Many were skeptical about this application– “it will flood the rest of the detector with secondaries” – “it will be impossible to maintain required mechanical precision”– “it will be inefficient”– “it will burn up due to radiation”– “it will be unreliable or never work at all”– “anyway there is no physics to do with it…”
• This device was crucial to the discovery of the top quark by CDF and opened up the field of precision B physics at hadron colliders.
• All collider detectors now include silicon tracking
Nov 16, 2005 UC Davis Physics Carl Haber LBNL40
Nov 16, 2005 UC Davis Physics Carl Haber LBNL41
1995-2005Top Quark 10th Anniversary
Nov 16, 2005 UC Davis Physics Carl Haber LBNL42
Nov 16, 2005 UC Davis Physics Carl Haber LBNL43
Developmentgeneration year luminosity ∆T channels dose readout
1CDF SVX
1990 1029 3.5 µs
3.5 µs
128 ns
25 ns
12 ns (?)
50K 25 Krad 3 µm CMOS
2CDF SVX*
1995 1030 100K 100 Krad 1.2 µm RHCMOS
3Run 2
2000 1032 500K 1 Mrad, 1013 .8 µmRHCMOS
4CERNLHC
2008 1034 106 strips108 pixels
10 Mrad1015
.25 µm CMOSCommercialBiCMOS
5SuperLHC
2015 1035 107 strips109 pixels
100M 1016 0.13 µm CMOSCommercial
Nov 16, 2005 UC Davis Physics Carl Haber LBNL44
CERN ATLAS tracker (4th generation, beam in 2008)
2 m.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL45
Radiation Environment
• Primary source are collision products– High energy charged particles– Neutrals from interactions
• Additional component due to “accidents”• Collisions occur over extended line – many cm• Primary field falls with radius as ~r -(1-2)
• Each interaction yields ~7 particles/angular unit– Sum crossings– Sum interactions/crossing
Nov 16, 2005 UC Davis Physics Carl Haber LBNL46
Radiation Levels
• Fluence and dose have increased >104 since mid-80’s– Near future expect unprecedented dose
• 100 Mrad absorbed energy (units)• 1015-1016 particles/cm2
• Compare to: space (~1 MRad), nuclear weapons (~1013)
Nov 16, 2005 UC Davis Physics Carl Haber LBNL47
Radiation Effects: Ionizing• Incident particle interacts with atomic electrons• Measure in energy absorbed (rads (Si))• e/h pairs created, recombine or trap• Transient effect
– Actual signal formation– Single event upset condition in circuits
• Electronics: charge trapping at Si/SiO2 interface (largely controlled by rad-hard circuit designs or thinner oxides)
• Detectors: surface effects
Nov 16, 2005 UC Davis Physics Carl Haber LBNL48
Electronics
• For presently operating systems commercial radhardCMOS has provided sufficient resistance.
• For next generation plan to use commercial deep submicron CMOS– Thin oxides provide automatic hardness– Augment design rules with enclosed gate geometries to
block radiation induced leakage paths (at some circuit density penalty)
– Tests have demonstrated sufficient resistance
• Certain bipolar technologies are also radhard (analog)Nov 16, 2005 UC Davis Physics Carl Haber LBNL
49
Radiation Effects: Non-ionizing
• Incident particle interacts with atom– Displacement damage – permanent or slow to
reverse– 2nd order effects as defects interact over time
• Depends upon particle type and energy • Measure in particles/cm2
Nov 16, 2005 UC Davis Physics Carl Haber LBNL50
Radiation Effects: Detectors
• Damage to the periodic lattice creates mid-gap states
• Increased leakage– Shot noise– Power– Heat
areajunction density trap
velocityermalcarrier thsection crossion recombinat
ionconcentratcarrier intrinsic2
)(
==
===
=
ANv
n
WANvenI
T
thermal
i
TthermaliL
σ
σ
( ) kTEL
aeTTI 2/2 −∝
Nov 16, 2005 UC Davis Physics Carl Haber LBNL51
Reverse current with fluence and time
degrees) 7every doubles(current 0@2 LHC @/1010 Flux Incident
102 Volume
1032constant Damage
21514
33
17
CAIcmparticles
cmVcm
AmpVI
oµ
α
α
≈∆⇒
−≈Φ
×≈
×−≈
Φ=∆
−
−
Nov 16, 2005 UC Davis Physics Carl Haber LBNL52
Thermal Run-away
Power density µw/mm2
Nov 16, 2005 UC Davis Physics Carl Haber LBNL53
Change in effective acceptor concentration
Effective space charge (Neff ⇒ Vfd) with fluence and time
∆Νeff(Φeq,t,T) = Na(Φeq,t,T) + NC(Φeq) + NY(Φeq,t,T)= beneficial annealing + stable damage + reverse annealing
Nov 16, 2005 UC Davis Physics Carl Haber LBNL54
• Creation of new acceptor states or removal of donor states
– Effective change of resistivity– Semiconductor type inversion: n becomes p– Depletion voltage changes in proportion to absolute value
of number of effective acceptors higher voltage operation required
– Dramatic time and temperature dependence
Nov 16, 2005 UC Davis Physics Carl Haber LBNL55
Charge Collection• Reduction in charge collection efficiency (CCE)
– Ne,h(t) = N0 exp (-t/τtrap)– Ratio of collection and charge trapping time constants
evolves with fluence
Nov 16, 2005 UC Davis Physics Carl Haber LBNL56
GregorKramberger, Ljubljana
Methods to Control Radiation Effects
• Most represent some tradeoff• Size matters
– Smaller volumes generate less leakage current (but require more channels, power, heat…)
– Thinner detectors deplete at lower voltage (but usually means less signal)
• Temperature– Low temperature (-10 C) operation can “stabilize” reverse
annealing for < 1014
– Reduce leakage current effects
Nov 16, 2005 UC Davis Physics Carl Haber LBNL57
• Integration time– Current noise is reduced for short shaping times at the expense of
increased pre-amp noise, power.• Biasing schemes
– Reduce value of parallel biasing resistor to reduce voltage drop due to ILeakRbias at the expense of increased thermal noise
• HV operation– Configure detectors to withstand higher voltage operation– Tolerate increased depletion voltage– Operate in partial depletion (collection issues)
• Low noise electronics– Tolerate reduced signal due to CCE and partial depletion
• Configuration– p in n substrate – simple, type inverts– n in n substrate – 2 sided process, can be operated in partial depletion
after inversion– n in p – a bit exotic, does not invert
Nov 16, 2005 UC Davis Physics Carl Haber LBNL58
Nov 16, 2005 UC Davis Physics Carl Haber LBNL59
Udepl vs time (total fluence 1.4e14)
0
50
100
150
200
250
300
0 365 730 1095 1460 1825 2190 2555 2920 3285 3650
Time [days]
Dep
letio
n vo
ltage
[Vol
t]
2 days at 20°C, 28 days at 17°C
2days at 20°C, 14 days at 17°C
2 days at 20°C, 7 days at 17°C
2 days at 20°C
no maintenance (always -7°C)
251 V at t=3385d
218 V at t=3385d
197 V at t=3385d
174 V at t=3385d
160 V at t=3385d
Simulation of 10 year operating scenarios for silicon tracking at the LHCL= 1033-1034
Design of silicon strip detectors with multiple guard ringstructures to tolerate HV=500 V operation
Nov 16, 2005 UC Davis Physics Carl Haber LBNL60
New developments• RD efforts organized at CERN
– RD42: development of diamond as detector– RD48: radiation damage to silicon– RD50: development of radiation resistant detectors– RD39: cryogenic detectors and systems– http://rdXY.web.cern.ch/rdXY
• Engineered materials• New configurations• Cryogenics• Other materials
Nov 16, 2005 UC Davis Physics Carl Haber LBNL61
Engineered Silicon
• Microscopic understanding of damage mechanisms, defects, and kinetics– Modeling– Measurements– Time and temperature dependence
• Engineer the silicon for greater radiation resistance
Nov 16, 2005 UC Davis Physics Carl Haber LBNL62
Neff: 24 GeV/c protons. No benefit with neutrons.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL63
Nov 16, 2005 UC Davis Physics Carl Haber LBNL64
3D silicon detectors were proposed in 1995 by S. Parker, and active edges in 1997 by C. Kenney.
Combine traditional VLSI processing andMEMS (Micro Electro Mechanical Systems)technology.
Electrodes are processed inside the detectorbulk instead of being implanted on the Wafer's surface.
The edge is an electrode! Dead volume at the Edge < 2 microns! Essential for -Large area coverage-Forward physics
3D Detectors 3D Detectors
1. NIMA 395 (1997) 328 2. IEEE Trans Nucl Sci 464 (1999) 12243. IEEE Trans Nucl Sci 482 (2001) 1894. IEEE Trans Nucl Sci 485 (2001) 1629 5. IEEE Trans Nucl Sci 48 6 (2001) 2405 6. CERN Courier, Vol 43, Jan 2003, pp
23-267. NIMA 509 (2003)86-91
Nov 16, 2005 UC Davis Physics Carl Haber LBNL65
12 µm
Dd
An early test structure by Julie Segal, etched and coated (middle, right), showing conformal nature of poly coat.
An electrode hole, filled,broken (accidentally) in a plane through the axis, showing grain structure (below). The surface poly is later etched off.
290 µm
coated, top
coated, bottom
uncoated
Examples of etching and coating with polysilicon.
1. 3D lateral cell size can be smaller than wafer thickness, so
2. in 3D, field lines end on cylinders rather than on circles, so
3. most of the signal is induced when the charge is close to theelectrode, where the electrode solid angle is large, so planarsignals are spread out in time as the charge arrives, and
4. Landau fluctuations along track arrive sequentially and may cause secondary peaks (see next slide)
5. if readout has inputs from both n+ and p+ electrodes,
6. for long, narrow pixels and fast electronics,
Speed: planar 3D
1. shorter collection distance
2. higher average fields for any given maximum field (price: larger electrode capacitance)
3. 3D signals are concentrated in time as the track arrives
4. Landau fluctuations arrive nearly simultaneously
5. drift time corrections can be made
6. track locations within the pixel can be found
4.
4.
4.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL66
Cryogenic operation
• Palmieri et al (1998) recovery of lost CCE at cryogenic temperatures
• “Lazarus Effect” due to freeze-out of traps
• R&D activity centered at CERN (RD39)
• Practical difficulty for “low mass” tracker if substantial cryogenic engineering and infrastructure is required.
Nov 16, 2005 UC Davis Physics Carl Haber LBNL67
Alternate Materials
• The development of precision tracking for particle physics has benefited greatly from the existence of a worldwide semiconductor industry and technology base built around the element Si
• None-the-less the question can be asked whether other materials could offer advantages
• Would require considerable fabrication capacity somewhere
Nov 16, 2005 UC Davis Physics Carl Haber LBNL68
Nov 16, 2005 UC Davis Physics Carl Haber LBNL69
Diamond
• Very active R&D effort for >10 years– http://rd48.web.cern.ch/RD48/
• Most work has been on pCVD material– Significant improvement in charge collection
• New results on single crystal materials – but small samples
Nov 16, 2005 UC Davis Physics Carl Haber LBNL70
Harris Kagan http://rd42.web.cern.ch/RD42/
Nov 16, 2005 UC Davis Physics Carl Haber LBNL71
Thanks to: Alexander Oh
Nov 16, 2005 UC Davis Physics Carl Haber LBNL72
Nov 16, 2005 UC Davis Physics Carl Haber LBNL73
New Technical Directions
• In support of tracking systems which operate at very high luminosity a number of new technical directions are being explored.– Rad hard devices and electronics– Lower mass materials, supports, services– Segmentation– Large area coverage– Data readout, transmission, and processing
(triggers)
Nov 16, 2005 UC Davis Physics Carl Haber LBNL74
Segmentation• Silicon strip sensor designs and geometries• Pixel geometries• Pixel-Strip transition• Z readout methods• Front end readout electronics in evolving processes
– 0.25, 0.13… mm– SiGe
• Interconnections– bump bonding methods at finer pitch (r < 20 cm– Pixel readout of superpixel geometry
Nov 16, 2005 UC Davis Physics Carl Haber LBNL75
Interleaved Stripixel Detector (ISD) -illustration of the concept (BNL Group Z.Li)
X-cell(1st Al)
Contact to2nd Al onX-pixel
Line connecting Y-pixels
(1st Al)
FWHM for chargediffusion
X-stripreadouts(2nd Al)
Y-stripreadouts
Y-cell(1st Al)The gaps between pixels
are enlarged for clearer illustration
Nov 16, 2005 UC Davis Physics Carl Haber LBNL76
Lower Mass• Large area and precision low mass mechanics• Alignment technology (lasers, sensors)
– Drop stiffness requirements in favor of active monitoring and feedback (lesson from the telescope builders).
• Low mass electrical and mechanical components including discretes & substrates– Power distribution schemes, current mode power with local regulation,
less redundancy, grounding issues– Technologies for hybrid circuits – thick, thin films, laminates
• Cooling technology – materials, coolants, delivery systems– Simplified coolant distribution– Heat pipe schemes– Cooling integrated with FE electronics– Reduced power consumption
Nov 16, 2005 UC Davis Physics Carl Haber LBNL77
Example of reduced mass structure for silicon detectors
Silicon Sensors4mm separation
Carbon Fiber Skin
Peek Cooling channels
Embedded electricalBus cable
Hybrid electronics
Foam Core
Material/stave: • 1.8% RL • 124 grams
Includes cooling, services and most of support
Nov 16, 2005 UC Davis Physics Carl Haber LBNL78
Fraction of Total RL:• Hybrids 13%• Sensors 39%• Bus Cable 17%• CF/Coolant 29%
Large Area Coverage
• Robotic assembly and test methods• Large area and precision low mass mechanics• Project organization• Reliability and redundancy methods
Nov 16, 2005 UC Davis Physics Carl Haber LBNL79
Example of robotics & large scale organization: CMS assembly with identical systems at 7 sites to produce ~20K modules
Nov 16, 2005 UC Davis Physics Carl Haber LBNL80
Data readout, transmission, and processing
• Optical data transmission• Wireless data transmission• Pattern recognition and data reduction methods• Large area and fine line lithographic methods
– Cables to link sensors to remote front end chips– Power cables– Signal distribution networks
• Fast track trigger processors – Vertex triggers (CDF SVT)– Momentum measurement
Nov 16, 2005 UC Davis Physics Carl Haber LBNL81
Technology Development Shopping List
• Radiation resistance of silicon and other solids• Radiation hard electronics – smaller feature size IC’s• Signal processing and circuit design• Pixel architectures, monolithic and active pixel sensors• Fast CCD and CMOS imagers, rad hard• Real time fast trigger processors• Large area and precision low mass mechanics• Alignment technology (lasers, sensors)• Low mass electrical and mechanical components including discretes & substrates• Cooling technology – materials, coolants, delivery systems• Pattern recognition and data reduction methods• Reliability and redundancy methods• Large area, fine line, lithographic methods• Robotic methods for assembly and test• Wireless data transfer• Optical readout methods
Nov 16, 2005 UC Davis Physics Carl Haber LBNL82
Conclusions
• Significant progress ~20 years to build trackers using semiconductor technology
• Much significant science done with these devices
• Progress in understanding and compensating for effects of radiation over a range of 104
• R&D underway for next generation
Nov 16, 2005 UC Davis Physics Carl Haber LBNL83