Detector Technologies for an

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Detector Technologies for an All-Semiconductor
Tracker at the sLHC Hartmut F.W.
Sadrozinski SCIPP, UC Santa Cruz
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Divide the sLHC Tracker into 3 radial regions
with 10x fluence increase Fluence is a factor 10
higher than at the same radius in LHC move
systems outward SCT - Straw tubes, Pixels -
SCT, need new Pixels System performance can then
be estimated. Guess at a specification of the
charge needed in the 3 regions
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Required Studies Tracking detector technologies
are limited by radiation The limiting process is
different in the different radial regions This
motivates different studies
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Simple SSD layout at Radius 20 cm 3 cm strip
length vs. 12 for SCT R 50 cm Single layers,
sz ? 1cm 20 single-sided sz ? 1mm Problem Confusion of
stereo assignment Mitigated by length reduction
But strips are much easier to build Explore
availability of p-type substrates No type
inversion Collect electrons Partial depletion
operation Potential for semi-3D?
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SSD technology for radius 20 cm Recent
results from ATLAS SCT beam test illustrates
problem with charge collection after type
inversion in common p-on-n detectors. N-on-p
would provide much more head room in bias
voltage (cheaper than n-in-n ?) But electrons
have larger Lorenz angle (tilt of SSD)
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• Technologies for Inner-most Pixels System
• Limitation Trapping
• 1. Charge Trapping in Si SSD
• Collected Charge Q Qoe(depletion) e(trapping)
• e(depletion) depends on Vbias , Vdep - effective
  detector thickness w
• e(trapping) exp(-tc/ tt),
• tc Collection time
• tt Trapping time
• Trapping time is reduced with radiation damage
• 1/ tt 5(F/1016) ns-1
• (same for electrons and holes, measured up to
  1015 cm-2)
• tt 1/ F
• tt 0.2ns for F 1016 cm-2

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2. Charge Collection in Si SSD of thickness
w Assume linear field (Diode case), field at
depth x E(x) Eo Em(x/w) Eo
2Vdep(x/w2) Collection time without
Saturation tc ?dx/v ?dx/(mE(x))
w2/(2mVdep)ln(1R)/(R(x/w)) R determines
the over-depletion R ½(Vbias
Vdep)/Vdep Vdep is approximately proportional to
fluence F Vdep (300um) ? 300V(F/1015), Vdep
(100um) ? 30V(F/1015), tc 1/ F, tt 1/
F ? Without saturation tc/ tt independent of
fluence !
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3. Charge Collection in Si including
Saturation Drift velocity saturates at v ? 107
cm/sec for E 5104 V/cm for electrons, v
about 30 -50 lower for holes Thus the
collection time tc depends on the thickness of
the depleted region tc w/v (w/100um) ns,
for heavily damaged detectors (large Vdep and
E) tc ? 1 ns for w 100um Saturation of the
drift velocity -- tc/ tt F tc/ tt 1 for
20 um after F 1016 cm-2 !
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4. Charge Collection in Si including Saturation
(Simple spread sheet study, agrees with data,
full simulations and V. Eremin)
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3-d Detectors
Differ from conventional planar technology, p
and n electrodes are diffused in small holes
along the detector thickness (3-d processing)
Depletion develops laterally (can be 20 to 100
?m) not sensitive to thickness
Depletion
n
n
n
p
p
50-100 ?m
Sherwood Parker et al., Edge-less detectors
n
n
n
Depletion / Collection de-coupled from
Generation Depletion and Drift over short
distance much higher radiation tolerance
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5. Detector Materials for Pixels for R 12
RD Topics P-type substrates work with Japanese
groups/HPK Find radiation source to irradiate
to F 1016 cm-2 Measure trapping on cryogenic
detectors Fabricate 3-D detectors with Japanese
groups/HPK