Developments Toward a Germanium ACT

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Developments Toward a Germanium ACT
UC Berkeley Steve Boggs, R. Lin, D. Smith, G.
Holland, R. Millan Centre dEtude Spatiale des
Rayonnements P. Jean, P. von Ballmoos Lawrence
Berkeley National Laboratory M. Amman, P. Luke,
N. Madden, E. Hull, M. Burks Lawrence Livermore
National Laboratory W. Craig, K. Ziock
ACT Workshop, 3 April 2001, Baltimore MD
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ACT Nuclear Science

• Ge ACT Technology Goals
• optimized for lines 0.5-2 MeV
• compact, high efficiency
• low background
• lt0.3 spectral resolution
• high polarization modulation

• Advantages of Germanium
• high spectral resolution (780 km/s at 0.847 MeV)
• large, uniform volumes (85 cm3)
• Z 32 -- converter absorber
• excellent BG rejection capabilities

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GeD Development Status

• fabricated 1919 strip, 2-mm pitch, 12-mm thick
  GeD
• demonstrated 0.1mm amorphous Ge contacts
• compact, low-power FETs using surface mount
  components
• demonstrated 3-D positioning
• prototyped full 3-D readout electronics (lt2-mm
  for E gt 50 keV)
• begun design of full 38 38 strip, 2-mm pitch,
  15-mm thickness GeDs

Luke, IEEE NSS, 39, 1992
Fabris, Madden Yaver, NIM A424, 1999
(courtesy Madden Ziock)
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3-D Positioning
Amman Luke, NIM A452, 2000.
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Compact GeCT Designs

• Advantages
• High Efficiency
• Active Shielding
• Excellent Polarimetry
• Analysis Flexibility

COMPTEL
(Schönfelder et al, ApJS 86, 657,1993)
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Background Rejection

• Techniques
• Compton Imaging
• Actively Shielded
• Event Analysis -- Very Powerful Tool

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Polarimetry
Crab Nebula (0.2-0.5 MeV) 15 ksec ConUS Flight
Observation

• Most Sensitive
• lt1 MeV
• Right-angle Scatters

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Narrow-Line Sensitivity
Compact GeCT Performance
Polarization Sensitivity
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Effective Spectral Resolution
Compact GeCT Performance
1 MeV ARM Distribution
ARM Resolution
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• Summary of Compact 3-D GeCT
• high efficiency, optimized 0.5-2 MeV
• high spectral resolution
• excellent polarimetry
• active shielding
• unexplored phase space for BG rejection
• event analysis flexibility