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  • 1
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    A position-sensitive germanium detector for gamma-ray astronomy (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The critical problem in high-resolution cosmic gamma-ray spectroscopy in the energy range from 0.02 to 10 MeV is the limited spectral sensitivity of the detectors used. This results from the small effective area of the detectors and the high background noise due to induced radioactivity and scattering in the detectors' high-energy particle environment. The effective area can be increased by increasing the number of detectors, but this becomes prohibitive because of the size and expense of the resulting instrument. We have taken a new approach: a segmented large-volume germanium gamma-ray detector which can effectively discriminate against internal background yet maintain the high spectral resolution and efficiency of conventional coaxial Ge detectors. To verify this concept, a planar detector divided into two segments has been fabricated and laboratory measurements agree well with Monte Carlo calculations. A large coaxial detector which will be divided into five segments is being built using the techniques developed for the planar detector. Monte Carlo calculations show that the sensitivity (minimum detectable flux) of the segmented coaxial detector is a factor of 2-3 better than conventional detectors because of the reduction in the internal background.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-31; 300-306
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Feasibility of KTa(1-x)Nb(x)O3 as a dielectric or pyroelectric microcalorimeter (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: We are developing a dielectric microcalorimeter for X-ray spectroscopy. We will present the results of our measurement of the dielectric permittivity, the spontaneous polarization, and the pyroelectric coefficient of the mixed-crystal quantum ferroelectric KTa(1-x)Nb(x)O3 with a doping of x = 0.012, as a function of temperature and bias voltage across the device. The effects of surface layers on the permittivity and the pyroelectric coefficient are discussed. We also show the signal results from infrared LED and alpha-particle radiation.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: EUV, X-ray, and gamma-ray instrumentation for astronomy III; Proceedings of the Meeting, San Diego, CA, July 22-24, 1992 (A93-29476 10-35); p. 380-390.
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Electronic considerations for externally segmented germanium detectors (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The dominant background source for germanium gamma ray detector spectrometers used for some astrophysics observations is internal beta decay. Externally segmented germanium gamma ray coaxial detectors can identify beta decay by localizing the event. Energetic gamma rays interact in the germanium detector by multiple Compton interactions while beta decay is a local process. In order to recognize the difference between gamma rays and beta decay events, the external electrode (outside of detector) is electrically partitioned. The instrumentation of these external segments and the consequence with respect to the spectrometer energy signal is examined.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: International Symposium on Gamma-Ray Line Astrophysics; Dec 10, 1990 - Dec 13, 1990; Paris; France
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    NASA TECHNICAL REPORTS
  • 4
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    A new thermal sensor for X-ray microcalorimetry (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A concept for a detector is introduced which exploits the significant temperature dependence of the dielectric constant in ferroelectric materials. The concept permits the use of a microcalorimeter without the resistive sensors which are associated with heat dissipation and increased Johnson noise in the electronic conversion circuit. General calorimeter features are listed, and the concepts related to dielectric calorimeters are discussed in terms of operational and detection advantages. The use of the device is delineated both theoretically and experimentally with the results of an operational dielectric material. The mixed-crystal quantum ferroelectric is employed and detects 6 MeV alpha particles while operating at 1.2 K in the first detection conducted. The temperature dependence of the dielectric constant in the materials allows for the elimination of resistive sensors in microcalorimeters, thereby improving the ultimate sensitivity of the instrument.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: High-energy astrophysics in the 21st century; Dec 11, 1989 - Dec 14, 1989; Taos, NM; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Test results of a prototype dielectric microcalorimeter (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa(1-x)Nb(x)O3 (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. A nonthermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: EUV, X-ray and Gamma-Ray Instrumentation for Astronomy; Jul 11, 1990 - Jul 13, 1990; San Diego, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
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