SiLi Detector Development

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Si(Li) Detector Development Richard Kroeger Jim
Kurfess, Eric Grove, Neil Johnson, Bernard
Phlips, Mark Strickman Naval Research
Laboratory Ethan Hull, Paul Luke, Richard Pehl,
Craig Tindall Lawrence Berkeley National
Laboratory
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Si(Li) Technical Challenge
Si(Li) cannot tolerate high-temperature
processing steps (annealing) used to fabricated
instrinsic silicon detectors
Develop segmentation technique (ultrasonic
machining) - or - Develop a-Si contacts (vapor
deposition contacts)
a-Ge contacts
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LBNL Detectors at NRL
Two Si(Li) devices tested at NRL 3 mm thick,
5.5 cm active diameter

• Detector I
• First Si(Li) device
• 2 D-segments Si(Li)

• Detector II
• Second Si(Li) device
• 2-mm wide strip
• 2-D segments

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Detector I Results
Capacitance vs. Vbias 20 C
Leakage vs. Temperature
Leakage vs. Voltage
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Detector I Results
-180 C D section of Detector I Vacuum cryostat
122 keV 2.6 keV 1000 V
60 keV 2.7 keV 2000 V
662 keV 3.3 keV 1000 V
Similar spectra 250 V th. 2000 V
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Array Technology
Germanium
One more
Si(Li) alternative 6 float zone silicon largest
available resistivity 0.5-2 kW-cm considerably
less than required for intrinsic silicon 7 mm
thick 300 V bias, 10-12 mm possible 10x10 cm
devices
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3D readout
Depth of interaction affects time of charge
collection
3D readout board under test
Lab test 122 keV in Ge det.
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CMOS Electronics

• 10-30 pF detector 3 pF, interconnect lt5 pF,
  strip capacitance 10-20 pF
• lt236 e rms noise (2 keV FWHM)
• Peak detect dynamic range from 4 K through 400 K
  electrons (1100)
• 3-D readout via 10 ns timing TDC on each

• A variety of implementations are under evaluation
  for fast timing
• Latch an analog time signal
• Latch a digital counter
• Digitize full waveform on each channel

NOVAs RENA-1 CMOS RENA-2 specs (now under
development) could meet the ACT requirements for
timing and dynamic range.
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Plans

• Several new Si(Li) devices shall be produced this
  year by LBNL
• Contact fabrication techniques shall be explored
• Segmentation techniques shall be explored
• Devices shall taken to the IUCF for radiation
  damage testing
• NRL will test devices and develop system
  architecture
• NRL will test segmented devices
• Large stacked array mechanical and cooling design
  shall be evaluated
• Readout electronics shall be developed
• Simulations and trade studies