Irradiation%20Goals

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Irradiation Goals

• Confirm that the breakdown performance improves
  with dose-Done
• Check that breakdown does not appear after
  inversion on n-type sensors-Done
• Confirm Ibias, Vdep changes as expected for
  proton/neutron irradiation
• Test CCE, resolution, etc. performance after
  proton irradiation with pixel telescope

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Proton Irradiation
Phi Sensors
R Sensors

• Irradiated 2 sets (n-type,p-type) of phi sensors
  and R sensors
• Phi sensor 1.47x1015 p/cm2 ? 9x1014 niel/cm2 (7
  years _at_ 8mm)
• R sensor 1.4x1015 p/cm2 ? 8.5x1014 niel/cm2 (6.6
  years _at_ 8mm)
• Built 1 set into double-R and double-Phi modules
  for FNAL test beam and laser test
• Other set used for CV measurements

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N-type R Sensor CV
After 30 min_at_60 C equiv. 11 day_at_20 C Dep V560 V
With no annealing, it is difficult to say if part
depletes. The three clear kinks in the CV
correspond to unirradiated left , partly
irradiated middle, and fully irradiated right of
sensor. So annealed to lower depletion point.
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P-type R Sensor CV
After 30 min_at_60 C equiv. 11 day_at_20 C Dep V530 V
With no annealing, it is difficult to say if part
depletes. The three clear kinks in the CV
correspond to unirradiated left , partly
irradiated middle, and fully irradiated right of
sensor. So annealed to lower depletion point.
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Laser Test-Proton Irradiation
N-type Irr

• Laser tested double-R and double-phi modules
  while cooled (-7 C at sensor)
• Stability of laser focus, intensity difficult to
  control
• See similar fraction (Irr/Non-Irr) of charge in
  both p-type and n-type
• Somewhere between 50-70
• 8.5x1014 niel/cm2
• From previous proton irradiaton on minis expect
  40 (1.8x1015 niel/cm2)
• 68 (6.6x1014 niel/cm2)
• With annealing to minima, expect 10-15 more
  charge collected
• Will try to anneal during FNAL test-beam

N-type non-Irr
P-type non-Irr
P-type Irr
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Proton Irradiation Conclusions

• From RD48 damage constants, expect 480 V
  depletion voltages after annealing for measured
  dose of proton for n-type and p-type silicon
• We measured somewhere between 530-560 V for the
  n-type and p-type
• From previous proton irradiations of n-in-p
  minis, we expect to collect 60 of the max
  charge
• From laser, get 50-70 pre-annealing
• Will confirm with test beam
• Thus, I would expect modules to be fully
  efficient after this dose (6.6 years _at_ 8 mm)

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Irradiation Results-IV
P-type
5x1013 /cm2
1.5x1014 /cm2
N-type
1.5x1014 /cm2
1.5x1014 /cm2
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Low dose (4-5x10-13 neq/cm2, expected 5x10-13
neq/cm2)
High dose (1.3-1.6x10-14 neq/cm2, expected
1.5x10-14 neq/cm2)
Error dominated by uncertainty in annealing time
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Neutron Irradiation Results-CV
P-type
VdepPre81V VdepPost167 V DVdep86 V
VdepPre81V VdepPost393 V DVdep312 V
5x1013/cm2
1.5x1014/cm2
N-type
VdepPre21V VdepPost299 V DVdep320 V
VdepPre25V VdepPost277 V DVdep302 V
1.5x1014 /cm2
1.5x1014/cm2
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Irradiation Results

• Irradiation with neutrons at Ljubljaba
• Breakdown behaviour gone
• P-type and n-type IV similar after doses
• For neutron irradiation, p-type sensors have
  higher Vdep
• 390 vs. 280-300 after 1.5x1014 neq/cm2
• Expect Vdep to be similar for n and p-type
  sensors with 1014 neq/cm2 proton irradiations
• Changes in depletion voltages close to expected
• From TDR, 1.3x1014neq/cm2 in 5 month LHC dose
  DVdep250 V
• Scaling for 5x1013neq/cm2, measured DVdep86 V,
  expected DVdep96 V
• Scaling for 1.5x1014neq/cm2, measured
  DVdep302-320 V, expected DVdep288 V
• Differences between measured and expected may be
  due to annealing

• Irradiation of 136 kRads with 6 MeV photons
• Hard breakdown behaviour improved greatly due to
  radiation
• Charge in oxide
• Soft breakdown behaviour (semi-ohmic) improved
  only in 1 of 3 sensors (2 unchanged)
• Should improve with neutron/proton irradiation
  which causes more bulk damage

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