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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Radiation dosimetry measurements with real time radiation monitoring device (RRMD)-II in Space Shuttle STS-79

The real-time measurement of radiation environment was made with an improved real-time radiation monitoring device (RRMD)-II onboard Space Shuttle STS-79 (S/MM#4: 4th Shuttle MIR Mission, at an inclination angle of 51.6 degrees and an altitude of 250-400km) for 199 h during 17-25 September, 1996. The observation of the detector covered the linear energy transfer (LET) range of 3.5-6000 keV/micrometer. The Shuttle orbital profile in this mission was equivalent to that of the currently planned Space Station, and provided an opportunity to investigate variations in count rate and dose equivalent rate depending on altitude, longitude, and latitude in detail. Particle count rate and dose equivalent rate were mapped geographically during the mission. Based on the map of count rate, an analysis was made by dividing whole region into three regions: South Atlantic Anomaly (SAA) region, high latitude region and other regions. The averaged absorbed dose rate during the mission was 39.3 microGy/day for a LET range of 3.5-6000 keV/micrometer. The corresponding average dose equivalent rates during the mission are estimated to be 293 microSv/day with quality factors from International Commission on Radiological Protection (ICRP)-Pub. 60 and 270 microSv/day with quality factors from ICRP-Pub. 26. The effective quality factors for ICRP-Pub. 60 and 26 are 7.45 and 6.88, respectively. From the present data for particles of LET > 3.5keV/micrometer, we conclude that the average dose equivalent rate is dominated by the contribution of galactic cosmic ray (GCR) particles. The dose-detector depth dependence was also investigated.

manned↗
NASA NTRS2015

Initial Results from the Radiation Dosimetry Experiment (RaD-X) Balloon Flight Mission

The NASA Radiation Dosimetry Experiment (RaD-X) high-altitude balloon mission was successfully launched from Fort Sumner, New Mexico USA on 25 September, 2015. Over 15 hours of science data were obtained from four dosimeters at altitudes above about 25 km. The four dosimeters flown on the RaD-X science payload are a Hawk version 3.0 Tissue Equivalent Proportional Counter (TEPC) manufactured by Far West Technologies, a Liulin dosimeter-spectrometer produced by the Solar Research and Technology Institute, Bulgarian Academy of Sciences, a total ionizing dose detector manufactured by Teledyne Microelectronic Technologies, and the RaySure detector provided by the University of Surrey.

Mertens, Christopher J.↗
NASA NTRS1967

Neutron detector simultaneously measures fluence and dose equivalent

Neutron detector acts as both an area monitoring instrument and a criticality dosimeter by simultaneously measuring dose equivalent and fluence. The fluence is determined by activation of six foils one inch below the surface of the moderator. Dose equivalent is determined from activation of three interlocked foils at the center of the moderator.

Dvorak, R. F.↗
NASA NTRS1996

Neutron fluences and dose equivalents measured with passive detectors on LDEF

Neutron fluences were measured on LDEF in the low energy (< 1 MeV) and high energy (> 1 MeV) ranges. The low energy detectors used the 6Li(n,alpha)T reaction with Gd foil absorbers to separate thermal (< 0.2 eV) and resonance (0.2 eV-1 MeV) neutron response. High energy detectors contained sets of fission foils (181Ta, 209Bi, 232Th, 238U) with different neutron energy thresholds. The measured neutron fluences together with predicted spectral shapes were used to estimate neutron dose equivalents. The detectors were located in the A0015 and P0006 experiments at the west and Earth sides of LDEF under shielding varying from 1 to 19 g/cm2. Dose equivalent rates varied from 0.8 to 3.3 microSv/d for the low energy neutrons and from 160 to 390 microSv/d for the high energy neutrons. This compares with TLD measured absorbed dose rates in the range of 1000-3000 microGy/d near these locations and demonstrates that high energy neutrons contribute a significant fraction of the total dose equivalent in LEO. Comparisons between measurements and calculations were made for high energy neutrons based on fission fragment tracks generated by fission foils at different shielding depths. A simple 1-D slab geometry was used in the calculations. Agreement between measurements and calculations depended on both shielding depth and threshold energy of the fission foils. Differences increased as both shielding and threshold energy increased. The modeled proton/neutron spectra appeared deficient at high energies. A 3-D model of the experiments is needed to help resolve the differences.

LDEF Project↗
NASA NTRS1999

Relative Efficiency of TLD-100 to High Linear Energy Transfer Radiation: Correction to Astronaut Absorbed Dose

Response of thermoluminescent detectors (TLD-100) to high linear energy transfer (LET) particles has been studied using helium, carbon, silicon, and iron ions from the Heavy Ion Medical Accelerator at Chiba (Japan), iron ions from the Brookhaven National Laboratory (NY) Alternate Gradient Synchrotron, and 53, 134, 185, and 232 MeV protons from the Loma Linda accelerator. Using the measured relative (to 137Cs) dose efficiency, and measured LET spectra from a tissue equivalent proportional counter (TEPC) on 20 Space Shuttle flights, and 7 Mir flights, the underestimation of absorbed dose by these detectors has been evaluated. The dose underestimation is between 15-20% depending upon the flight inclination and shielding location. This has been confirmed by direct correlation of measured dose by TEPC and TLD-100 at a low shielded location in the Shuttle mid-deck. A comparison of efficiency- LET data with a compilation of similar data from TLD-700, shows that shapes of the two curves are nearly identical, but that the TLD-100 curve is systematically lower by about 13%, and is the major cause of dose underestimation. These results strongly suggest that TLDs used for crew dose estimation be regularly calibrated using heavy ions.

Badhwar, G. D.↗
NASA NTRS1999

Relative Efficiency of TLD-100 to Linear Energy Transfer Radiation: Correction to Astronaut Absorbed Dose

Response of thermoluminescent detectors (TLD-100) to high linear energy transfer (LET) particles has been studied using helium, carbon, silicon, and iron ions from the Heavy Ion Medical Accelerator at Chiba (Japan), iron ions from the Brookhaven National Laboratory (NY) Alternate Gradient Synchrotron, and 53, 134, 185, and 232 MeV protons from the Loma Linda accelerator. Using the measured relative (to (137)Cs dose efficiency, and measured LET spectra from a tissue equivalent proportional counter (TEPC) on 20 Space Shuttle flights, and 7 Mir flights, the underestimation of absorbed dose by these detectors has been evaluated. The dose underestimation is between 15-20% depending upon the flight inclination and shielding location. This has been confirmed by direct correlation of measured dose by TEPC and TLD-100 at a low shielded location in the Shuttle mid-deck. A comparison of efficiency- LET data with a compilation of similar data from TLD-700, shows that shapes of the two curves are nearly identical, but that the TLD-100 curve is systematically lower by about 13%, and is the major cause of dose underestimation. These results strongly suggest that TLDs used for crew dose estimation be regularly calibrated using heavy ions.

Badhwar, Gautam D.↗
NASA NTRS2006

Time Serial Analysis of the Induced LEO Environment within the ISS 6A

Anisotropies in the low Earth orbit (LEO) radiation environment were found to influence the thermoluminescence detectors (TLD) dose within the (International Space Station) ISS 7A Service Module. Subsequently, anisotropic environmental models with improved dynamic time extrapolation have been developed including westward and northern drifts using AP8 Min & Max as estimates of the historic spatial distribution of trapped protons in the 1965 and 1970 era, respectively. In addition, a directional dependent geomagnetic cutoff model was derived for geomagnetic field configurations from the 1945 to 2020 time frame. A dynamic neutron albedo model based on our atmospheric radiation studies has likewise been required to explain LEO neutron measurements. The simultaneous measurements of dose and dose rate using four Liulin instruments at various locations in the US LAB and Node 1 has experimentally demonstrated anisotropic effects in ISS 6A and are used herein to evaluate the adequacy of these revised environmental models.

Wilson, John W.↗
NASA NTRS1995

Ionizing radiation measurements on LDEF: A0015 Free flyer biostack experiment

This report covers the analysis of passive radiation detectors flown as part of the A0015 Free Flyer Biostack on LDEF (Long Duration Exposure Facility). LET (linear energy transfer) spectra and track density measurements were made with CR-39 and Polycarbonate plastic nuclear track detectors. Measurements of total absorbed dose were carried out using Thermoluminescent Detectors. Thermal and resonance neutron dose equivalents were measured with LiF/CR-39 detectors. High energy neutron and proton dose equivalents were measured with fission foil/CR-39 detectors.

Benton, E. V.↗
NASA NTRS1992

Radiation exposure of LDEF: Initial results

Initial results from LDEF include radiation detector measurements from four experiments, P0006, P0004, M0004, and A0015. The detectors were located on both the leading and trailing edges of the orbiter and also on the Earthside end. This allowed the directional dependence of the incoming radiation to be measured. Total absorbed doses from thermoluminescent detectors (TLDs) verified the predicted spatial east-west dose ratio dependence of a factor approx. 2.5, due to trapped proton anisotropy in the South Atlantic Anomaly. On the trailing edge of the orbiter a range of doses from 6.64 to 2.91 Gy were measured under Al equivalent shielding of 0.42 to 1.11 g/sq cm. A second set of detectors near this location yielded doses of 6.48 to 2.66 Gy under Al equivalent shielding of 0.48 to 15.4 g/sq cm. On the leading edge, doses of 2.58 to 2.10 Gy were found under Al equivalent shielding of 1.37 to 2.90 g/sq cm. Initial charged particle LET (linear energy transfer) spectra, fluxes, doses and dose equivalents, for LET in H2O greater than or = 8 keV/micron, were measured with plastic nuclear track detectors (PNTDs) located in two experiments. Also preliminary data on low energy neutrons were obtained from detectors containing (6)LiF foils.

Benton, E. V.↗
NASA NTRS1991

Radiation exposure of LDEF: Initial results

Initial results from Long Duration Exposure Facility (LDEF) include radiation detector measurements from four experiments; P0006, P0004, M0004, and A0015. The detectors were located on both the leading and trailing edges of the orbiter and also at the Earthside end. This allowed the directional dependence of the incoming radiation to be measured. Total absorbed doses from thermoluminescent detectors (TLDs) verified the predicted spatial east-west dose dependence of a factor of approx. 2.5, due to trapped proton anisotropy in the South Atlantic Anomaly (SAA). On the trailing edge of the orbiter, a range of doses from 664 to 291 rad were measured under nominal shielding of 0.42 to 8.45 g/sq cm. A second set of detectors near this locations results are also given. On the leading edge, doses of 258 to 210 rad were found under shielding of 1.25 to 2.48 g/sq cm. Initial charged particle LET (linear energy transfer) spectra, fluxes, doses, and dose equivalents, for LET in H2O greater than or = 5 keV/micron, were measured with plastic nuclear track detectors located in the four experiments. Also, preliminary data on low energy neutrons were obtained from detectors containing (6)LiF foils.

Benton, E. V.↗
NASA NTRSDate not supplied

LEIA: An Investigation of Radiation Risks to Biology at the Lunar South Pole

Radiation and reduced gravity pose biological risks to crewed deep space exploration. At the cellular level, radiation damage can be amplified by reduced gravity. Empirical evidence on cellular responses to beyond low Earth orbit (BLEO) environments is imperative to develop effective countermeasures for crew health and in-space biomanufacturing. The Lunar Explorer Instrument for Space Biology Applications (LEIA) project is developing an instrument suite to be delivered to the south polar region of the Moon by the Commercial Lunar Payload Services (CLPS) program. This presentation will provide an overview of the LEIA hardware, experiments, and mission timeline. The LEIA instruments include the BioSensor, the ARES charged particle detector, and the Mini-FND. The BioSensor is an autonomous light emitting diode (LED)-based spectrophotometer and microfluidic incubator. The BioSensor activates yeast cultures and can measure cell growth, metabolic activity, and carotenoid production. The ARES is a Timepix-based charged particle radiation detector that measures dose, dose rate, and linear energy transfer spectra. The Mini-FND is a fast neutron detector that measures albedo neutron flux and energy spectra. Combined, these instruments will be used for yeast genetics experiments to quantify growth, metabolism, and synthetic biology-enabled production of human nutrients, while taking real time measurements of biologically relevant radiation exposure on the lunar surface. These data will be used to test the importance of selected DNA damage repair and reactive oxygen species defense pathways in mitigating cellular damage from lunar surface radiation.

Yeast↗
NASA NTRSDate not supplied

LEIA: An Investigation of Radiation Risks to Biology at the Lunar South Pole

Radiation and reduced gravity pose biological risks to crewed deep space exploration. At the cellular level, radiation damage can be amplified by reduced gravity. Empirical evidence on cellular responses to beyond low Earth orbit (BLEO) environments is imperative to develop effective countermeasures for crew health and in-space biomanufacturing. The Lunar Explorer Instrument for Space Biology Applications (LEIA) project is developing an instrument suite to be delivered to the south polar region of the Moon by the Commercial Lunar Payload Services (CLPS) program. This presentation will provide an overview of the LEIA hardware, experiments, and mission timeline. The LEIA instruments include the BioSensor, the ARES charged particle detector, and the Mini-FND. The BioSensor is an autonomous light emitting diode (LED)-based spectrophotometer and microfluidic incubator. The BioSensor activates yeast cultures and can measure cell growth, metabolic activity, and carotenoid production. The ARES is a Timepix-based charged particle radiation detector that measures dose, dose rate, and linear energy transfer spectra. The Mini-FND is a fast neutron detector that measures albedo neutron flux and energy spectra. Combined, these instruments will be used for yeast genetics experiments to quantify growth, metabolism, and synthetic biology-enabled production of human nutrients, while taking real time measurements of biologically relevant radiation exposure on the lunar surface. These data will be used to test the importance of selected DNA damage repair and reactive oxygen species defense pathways in mitigating cellular damage from lunar surface radiation.

Yeast↗
NASA NTRS2002

Passive dosimetry aboard the Mir Orbital Station: internal measurements

Passive radiation dosimeters were exposed aboard the Mir Orbital Station over a substantial portion of the solar cycle in order to measure the change in dose and dose equivalent rates as a function of time. During solar minimum, simultaneous measurements of the radiation environment throughout the habitable volume of the Mir were made using passive dosimeters in order to investigate the effect of localized shielding on dose and dose equivalent. The passive dosimeters consisted of a combination of thermoluminescent detectors to measure absorbed dose and CR-39 PNTDs to measure the linear energy transfer (LET) spectrum from charged particles of LET infinity H2O > or = 5 keV/micrometers. Results from the two detector types were then combined to yield mean total dose rate, mean dose equivalent rate, and average quality factor. Contrary to expectations, both dose and dose equivalent rates measured during May-October 1991 near solar maximum were higher than similar measurements carried out in 1996-1997 during solar minimum. The elevated dose and dose equivalent rates measured in 1991 were probably due to a combination of intense solar activity, including a large solar particle event on 9 June 1991, and the temporary trapped radiation belt created in the slot region by the solar particle event and ensuing magnetic storm of 24 March 1991. During solar minimum, mean dose and dose equivalent rates were found to vary by factors of 1.55 and 1.37, respectively, between different locations through the interior of Mir. More heavily shielded locations tended to yield lower total dose and dose equivalent rates, but higher average quality factor than did more lightly shielding locations. However, other factors such as changes in the immediate shielding environment surrounding a given detector location, changes in the orientation of the Mir relative to its velocity vector, and changes in the altitude of the station also contributed to the variation. Proton and neutron-induced target fragment secondaries, not primary galactic cosmic rays, were found to dominate the LET spectrum above 100 keV/micrometers. This indicates that in low earth orbit, trapped protons in the South Atlantic Anomaly are responsible for the major fraction of the total dose equivalent. c2002 Elsevier Science Ltd. All rights reserved.

NASA Experiment Number 9401620↗
NASA NTRS1996

The calculation of radial dose from heavy ions: predictions of biological action cross sections

The track structure model of heavy ion cross sections was developed by Katz and co-workers in the 1960s. In this model the action cross section is evaluated by mapping the dose-response of a detector to gamma rays (modeled from biological target theory) onto the radial dose distribution from delta rays about the path of the ion. This is taken to yield the radial distribution of probability for a "hit" (an interaction leading to an observable end-point). Radial integration of the probability yields the cross section. When different response from ions of different Z having the same stopping power is observed this model may be indicated. Since the 1960s there have been several developments in the computation of the radial dose distribution, in the measurement of these distributions, and in new radiobiological data against which to test the model. The earliest model, by Butts and Katz made use of simplified delta ray distribution functions, of simplified electron range-energy relations, and neglected angular distributions. Nevertheless it made possible the calculation of cross sections for the inactivation of enzymes and viruses, and allowed extension to tracks in nuclear emulsions and other detectors and to biological cells. It set the pattern for models of observable effects in the matter through which the ion passed. Here we outline subsequent calculations of radial dose which make use of improved knowledge of the electron emission spectrum, the electron range-energy relation, the angular distribution, and some considerations of molecular excitation, of particular interest both close to the path of the ion and the outer limits of electron penetration. These are applied to the modeling of action cross sections for the inactivation of several strains of E-coli and B. subtilis spores where extensive measurements in the "thin-down" region have been made with heavy ion beams. Such calculations serve to test the radial dose calculations at the outer limit of electron penetration. We lack data from which to test these calculations in regions close to the path of the ion aside from our earliest work on latent tracks in plastics, though it appears that the criterion then suggested for the threshold of track formation, of a minimal dose at a minimal distance (of about 20 angstroms, in plastics), remains valid.

NASA Discipline Radiation Health↗
NASA NTRS2002

Dosimetric results from the Mir orbital station

The Mir Orbital Station provided a unique platform on which to carry out a variety of space radiation dosimetry measurements. A number of experiments were conducted using a combination of passive detectors on the interior of the Mir during 1996-97. Thermoluminescent detectors were used to measure absorbed dose. CR-39 plastic nuclear track detectors were used to measure the LET spectra > or =5 keV.microm(-1). Results from TLDs and CR-39 PNTDs were combined to determine total dose and dose equivalent. Mean dose rate was found to decrease while mean dose equivalent rate and average quality factor increased with increasing shielding. Secondary particles from proton-induced target fragmentation interactions, not primary HZE particles, were found to be the largest contributor to the LET spectrum above 100 keV.microm(-1). During the 1997 measurements, mean quality factor was found to vary from 1.7 to 2.1 as a function of location within the Mir.

long duration↗
NASA NTRS2007

A Radiation Dosimeter Concept for the Lunar Surface Environment

A novel silicon detector configuration for radiation dose measurements in an environment where solar energetic particles are of most concern is described. The dosimeter would also measure the dose from galactic cosmic rays. In the lunar environment a large range in particle flux and ionization density must be measured and converted to dose equivalent. This could be accomplished with a thick (e.g. 2mm) silicon detector segmented into cubic volume elements "voxels" followed by a second, thin monolithic silicon detector. The electronics needed to implement this detector concept include analog signal processors (ASIC) and a field programmable gate array (FPGA) for data accumulation and conversion to linear energy transfer (LET) spectra and to dose-equivalent (Sievert). Currently available commercial ASIC's and FPGA's are suitable for implementing the analog and digital systems.

Adams, James H.↗