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Status of the RDs on Diamond Particle Detectors
Mara Bruzzi University of Florence - INFN Firenze
For the RD42 Collaboration November 6, 2002 -
VERTEX2002

• Outline of the Talk
• Introduction
• 2001/2002 Milestones
• Status of PolyCrystalline Diamond Particle
  Detectors
• Single Crystal Diamond Particle Detectors
• Summary and RD42 Plans

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The RD42 Collaboration
http//rd42.web.cern.ch/RD42/
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Introduction
LHC L 1034 cm-2s-1 in 10 years f 1015
n/cm2 for pixels SLHC L 1035 cm-2s-1 fast
hadron f up to 1016 cm-2 ? Inner tracking
layers must survive ? provide high precision
tracking to tag b, t, Higgs

• Diamond Properties
• Radiation hardness
• Low Dielectric Constant ? Low Capacitance
• Low Leakage Current ? Low readout noise
• Room Temperature Operation , Fast signal
  collection time

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2001/2002 Milestones
Priorities of Research in 2001/2002

• Increase charge collection distance in a
  dedicated program with industry to gt 250mm
• Test the Tracking and radiation tolerance
  properties of the newest diamonds
• Establish the performance of pixel detectors with
  radiation hard front-end chips from ATLAS and CMS
• Establish the performance of large detectors
• Test diamond trackers with LHC specific
  electronics (SCTA128 chip )
• Irradiate modules sensors and front-end chips
  together
• Finalize the geometry and metalization of diamond
  LHC pixel detectors

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Status of PolyCrystalline Diamond Detectors

• Chemical Vapour Deposition - DeBeers
• Wafer diameter 5-6 inch
• Metalization Cr/Au, Ti/Au, Ti/W ? new
• 1V/mm Operation, Drift velocity saturated
• Test procedure dot ? strip ? pixel

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RD with DeBeers Ind. Diamond
Latest Polycrystalline Diamonds Measured with a
90Sr Source

• System Gain 124 e/mV
• QMP 60mV 7400e
• Mean Charge 76mV 9400e

• Source data well separated from 0
• Collection distance now 270mm
• Most Probable Charge now 8000e
• 99 of PH distribution now above 3000e
• FWHM/MP 0.95 ? Si has 0.5
• This is diamond is available in large size

The research program worked!
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History of ccd progress
Now
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Material Properties of PolyCrystalline Diamond

• Grain-boundaries, dislocations, native defects in
  Polycrystalline Diamond
• limits carrier lifetime, mobility and charge
  collection distance
• give rise to polarization and pumping effects
• affect the radiation hardness ( spatial
  resolution improves, leakage current decrease,
  mean signal decreases )

Grain size 10-100mm
Growth side of PolyDiamond produced by the
Florence group
State-of-art DeBeers PolyDiamond growth side
after lapping
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Basic Research on Defects in PolyCrystalline
Diamond
Thermally Stimulated Currents Analysis TSC
Vrev
Native defects at grain boundaries Main
peak_at_520K RT tail Et 1eV, s 10-12-10-19cm2,
Nt 1015-1019cm-3
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Optimising CCE through Material Removal
Columnar growth in PolyDiamond films
Single-Crystal Line
Picture from sample made in Florence
Removal from growth (?) and substrate (?)
Higher grain-boundary density on substrate
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Recent Tracking Studies - CERN Test beam setup

• 100 GeV/c pion/muon beam
• 7 planes of CVD diamond strip sensors each
  2cmx2cm
• 50mm pitch, no intermediate strips ?new
  metalization procedure
• 2 additional diamond strip sensors for test
• several silicon sensors for cross checks
• strip electronics ( 2ms ) ENC 100e 14 e/pF

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Recent Tracking Studies
Results

• Uniform signals on all strips
• Pedestal separated from 0 on all strips
• 99 of entries above 2000e
• Mean signal charge 8640e
• MP signal charge 6500e

.. Work in progress

• Module with fully radiation hard SCTA128
  electronics
• Tested with Sr90 ? ready for beam test and
  irradiation
• Charge distribution clearly separated from the
  noise? S/N 8/1
• efficiency will be measured in test beams at
  40MHz clock rate
• Improve position resolution by measuring charge
  sharing between strips

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Radiation Hardness
Signal to Noise
Resolution

• Dark Current decreases with fluence
• S/N decreases at 2x1015cm-2
• Resolution improves at 2x1015 cm-2

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Other Radiation Effects
Pumping and Trapping
f 5x1014 n/cm2

• Pumping effect less evident
• Defects at Et 1eV partially removed or
  compensated

f 2.0x1015 n/cm2
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Single Crystal CVD Diamond Particle Detectors

• Single Crystal films produced by DeBeers
  Microwave plasma-assisted CVD Homoepitaxial
  diamond films grown from HPHT synthetic diamond
  substrates.
• Samples size 390-690mm thick, 6mm diameter
• Carrier mobility _at_ RT mn 4500 cm2/Vs
• mh 3800 cm2/Vs
• factor 2 higher than for natural single-crystal
  diamond
• Carrier lifetime exceeds 2ms
• Dramatic improvement as compared with natural
  and polycrystalline CVD diamond ( few ns)
• Dislocation less than 106 cm-2
• Nitrogen content of the order of 1015cm-3

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Performance of Single Crystal Diamond Detector
New metalization ( Al, no carbide involved )
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Single Crystal CVD Diamond Detector CCE
Charge Collection Distance Device Thickness (
over 90-95) ? 100 Charge Collection
Efficiency
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Single Crystal CVD Diamond Detector Pumping
Stable Signal, with no evidence of
priming/polarization effects! ? Single Crystal
Diamonds do not pump like polycrystalline
material.
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Summary
Polycrystalline Diamond I Charge
collection 270mm collection distance MP signal
?8000 e 99 of charge distribution above
3000e FWHM/MP ? 0.95 Tracking Results Operated
a 7 plane telescope with 50mm pitch
detectors high efficiency and tracking precision
of 10-20mm Rad-hard SCTA128 electronics (DMILL )
built Source tests indicate high efficiency at
40MHz Beam test and irradiation this
year Radiation Hardness dark current decreases
with fluence some loss of S/N with
fluence Resolution improves with fluence
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Summary
Polycrystalline Diamond II Diamond Pixel
Detectors Successfully tested ATLAS and CMS
pixels patterns Bump-bonding yield ?
100 Excellent correlation between telescope and
pixel data Reasonable spatial resolution
attained Radiation hard chips just
arrived Single Crystal Diamond Future ?
Material Characteristics mn 4500 cm2/Vs ,
mh 3800 cm2/Vs Carrier lifetime exceeds 2ms
low native defect content Detector
performance no pumping effect 100 charge
collection efficiency over 550mm
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Future Plans of RD42

• Charge Collection
• collection distance ? 300mm
• improved uniformity
• correlation between defects and detector
  performance
• Radiation hardness of diamond trackers and pixel
  detectors
• Irradiation with p, p, n up to 5x1015cm-2
• Beam tests with Diamond Trackers and Pixel
  detectors
• Trackers with SCTA Electronics
• Pixel detectors with ATLAS and CMS and rad hard
  elect.
• Construct the full ATLAS diamond pixel module