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Compact Tissue-equivalent Proportional Counter for Deep Space Human Missions.

Straume T, Braby LA, Borak TB, Lusby T, Warner DW, Perez-Nunez D - Health Phys (2015)

Bottom Line: This was accomplished by assigning sequential sampling intervals as detectors “1” and “2” and requiring the intervals to be brief compared to the change in dose rate.Tests with g rays show that the prototype instrument maintains linear response over the wide dose-rate range expected in space with an accuracy of better than 5% for dose rates above 3 mGy h(-1).Limited tests with fission spectrum neutrons show absorbed dose-rate accuracy better than 15%.

View Article: PubMed Central - PubMed

Affiliation: *NASA Ames Research Center, Moffett Field, CA 94035; †Texas A&M University, College Station, TX 77843; ‡Colorado State University, Ft. Collins, CO 80523.

ABSTRACT
Effects on human health from the complex radiation environment in deep space have not been measured and can only be simulated here on Earth using experimental systems and beams of radiations produced by accelerators, usually one beam at a time. This makes it particularly important to develop instruments that can be used on deep-space missions to measure quantities that are known to be relatable to the biological effectiveness of space radiation. Tissue-equivalent proportional counters (TEPCs) are such instruments. Unfortunately, present TEPCs are too large and power intensive to be used beyond low Earth orbit (LEO). Here, the authors describe a prototype of a compact TEPC designed for deep space applications with the capability to detect both ambient galactic cosmic rays and intense solar particle event radiation. The device employs an approach that permits real-time determination of yD (and thus quality factor) using a single detector. This was accomplished by assigning sequential sampling intervals as detectors “1” and “2” and requiring the intervals to be brief compared to the change in dose rate. Tests with g rays show that the prototype instrument maintains linear response over the wide dose-rate range expected in space with an accuracy of better than 5% for dose rates above 3 mGy h(-1). Measurements of yD for 200 MeV n(-1) carbon ions were better than 10%. Limited tests with fission spectrum neutrons show absorbed dose-rate accuracy better than 15%.

Show MeSH
(left) TEPC detector assembly, (center) attached to pre-amplifier circuit boards before the wire cage and vacuum chamber were added, and (right) enclosed in gold-plated vacuum chamber.
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Figure 1: (left) TEPC detector assembly, (center) attached to pre-amplifier circuit boards before the wire cage and vacuum chamber were added, and (right) enclosed in gold-plated vacuum chamber.

Mentions: The radiation detector is based on the concepts of a spherical TEPC. Specifically, the design incorporates features described by Benjamin et al. (1968). The objective was to improve the uniformity of the electric field along a single anode surrounded by a spherical conducting shell (Fig. 1). The spherical shell has an inside diameter of 18 mm and an outside diameter of 24 mm. The wall thickness is 3 mm. Wall material is A‐150 tissue-equivalent plastic. The thickness of the wall was selected to provide sufficient buildup of delta rays into the spherical gas cavity without causing excessive fragmentation of HZE particles penetrating the plastic wall or attenuation of MeV-energy neutrons (Rademacher et al. 1998; Gersey et al. 2002; Guetersloh et al. 2004).


Compact Tissue-equivalent Proportional Counter for Deep Space Human Missions.

Straume T, Braby LA, Borak TB, Lusby T, Warner DW, Perez-Nunez D - Health Phys (2015)

(left) TEPC detector assembly, (center) attached to pre-amplifier circuit boards before the wire cage and vacuum chamber were added, and (right) enclosed in gold-plated vacuum chamber.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4554228&req=5

Figure 1: (left) TEPC detector assembly, (center) attached to pre-amplifier circuit boards before the wire cage and vacuum chamber were added, and (right) enclosed in gold-plated vacuum chamber.
Mentions: The radiation detector is based on the concepts of a spherical TEPC. Specifically, the design incorporates features described by Benjamin et al. (1968). The objective was to improve the uniformity of the electric field along a single anode surrounded by a spherical conducting shell (Fig. 1). The spherical shell has an inside diameter of 18 mm and an outside diameter of 24 mm. The wall thickness is 3 mm. Wall material is A‐150 tissue-equivalent plastic. The thickness of the wall was selected to provide sufficient buildup of delta rays into the spherical gas cavity without causing excessive fragmentation of HZE particles penetrating the plastic wall or attenuation of MeV-energy neutrons (Rademacher et al. 1998; Gersey et al. 2002; Guetersloh et al. 2004).

Bottom Line: This was accomplished by assigning sequential sampling intervals as detectors “1” and “2” and requiring the intervals to be brief compared to the change in dose rate.Tests with g rays show that the prototype instrument maintains linear response over the wide dose-rate range expected in space with an accuracy of better than 5% for dose rates above 3 mGy h(-1).Limited tests with fission spectrum neutrons show absorbed dose-rate accuracy better than 15%.

View Article: PubMed Central - PubMed

Affiliation: *NASA Ames Research Center, Moffett Field, CA 94035; †Texas A&M University, College Station, TX 77843; ‡Colorado State University, Ft. Collins, CO 80523.

ABSTRACT
Effects on human health from the complex radiation environment in deep space have not been measured and can only be simulated here on Earth using experimental systems and beams of radiations produced by accelerators, usually one beam at a time. This makes it particularly important to develop instruments that can be used on deep-space missions to measure quantities that are known to be relatable to the biological effectiveness of space radiation. Tissue-equivalent proportional counters (TEPCs) are such instruments. Unfortunately, present TEPCs are too large and power intensive to be used beyond low Earth orbit (LEO). Here, the authors describe a prototype of a compact TEPC designed for deep space applications with the capability to detect both ambient galactic cosmic rays and intense solar particle event radiation. The device employs an approach that permits real-time determination of yD (and thus quality factor) using a single detector. This was accomplished by assigning sequential sampling intervals as detectors “1” and “2” and requiring the intervals to be brief compared to the change in dose rate. Tests with g rays show that the prototype instrument maintains linear response over the wide dose-rate range expected in space with an accuracy of better than 5% for dose rates above 3 mGy h(-1). Measurements of yD for 200 MeV n(-1) carbon ions were better than 10%. Limited tests with fission spectrum neutrons show absorbed dose-rate accuracy better than 15%.

Show MeSH