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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Fluctuations in energy loss and their implications for dosimetry and radiobiology

Serious consideration of the physics of energy deposition indicates that a fundamental change in the interpretation of absorbed dose is required at least for considerations of effects in biological systems. In addition, theoretical approaches to radiobiology and microdosimetry seem to require statistical considerations incorporating frequency distributions of the magnitude of the event sizes within the volume of interest.

Baily, N. A.↗
NASA NTRS1972

Methods and approaches to dosimetry

The development of a dosimetric system capable of determining energy depositions in tissue regions that are smaller than a few 100 nanometers is projected. These objectives are met by evaluation of the data produced by a macro-subsystem and a micro-subsystem. Both systems are in essence multiple ionization chambers that are normally operated in a gated pulse mode. The macro-system yields absorbed radiation dose as a function of location in a phantom of the human trunk when it operates in the dose mode; it registers only those sections as a signal in which the primary particle or any of its secondaries have passed, in the pulse mode. The function of the micro-system is to provide detailed information of the track structure by determining lateral energy spread due to delta ray formation or other secondary particle production.

Rossi, H. H.↗
NASA NTRS1972

Dosimetry for radiobiological studies of the human hematopoietic system

A system for estimating individual bone marrow doses in therapeutic radiation exposures of leukemia patients was studied. These measurements are used to make dose response correlations and to study the effect of dose protraction on peripheral blood cell levels. Three irradiators designed to produce a uniform field of high energy gamma radiation for total body exposures of large animals and man are also used for radiobiological studies.

Beck, W. L.↗
NASA NTRS1972

Radiation dosimetry for the Gemini program

The principal source of radiation for low-earth-orbit, low inclination space flights is in the area of the South Atlantic magnetic anomaly. None of the Gemini dose measurements reported in the paper are of high enough intensity to be considered hazardous. There is a trend toward larger doses as missions are flown higher and longer. Extended orbital operations between 1400 and 4400 kilometers would encounter high interior radiation levels. Pronounced spacecraft geometry effects have been measured in manned spacecraft. Instrumentation for radiation measurements on Gemini spacecraft is described.

Richmond, R. G.↗
NASA NTRS1972

Iridium and tantalum foils for spaceflight neutron dosimetry.

Description of a two-foil system of iridium and tantalum which can measure thermal and intermediate energy neutrons at flux densities of 1 neutron/sq cm-sec over a ten-day lunar mission (1,000,000 neutrons/sq cm). The foils are chemically inert and nontoxic, weigh less than 1 g each, and require only routine gamma pulse height analysis for activation measurement. Detection of fluences below 1,000,000 neutrons/sq cm are achieved for counts of foil activity made as late as two months following neutron exposure. Tantalum foils flown in Apollo 11 indicated a mean dose equivalent to the astronauts of less than 16 mrem from thermal plus intermediate energy neutrons, while nuclear emulsion track analysis indicated approximately 17 mrem from neutrons of energy greater than 0.6 MeV. Iridium foils flown on Apollo 12 indicated dose equivalents of 1.8 to 2.8 mrem from thermal neutrons, excluding tissue thermalized SNAP-27 neutrons.

English, R. A.↗
NASA NTRS1973

Thermoluminescent dosimetry for the Apollo 16 microbial response to space environment experiment (M191)

Lithium fluoride thermoluminescent chips were used to provide an integrated dose from the broad spectrum of ionizing radiation to the Microbial Response to Space Environment Experiment (M191). The chips were positioned in the flight hardware to provide data on ionizing radiation within specific volume segments. A uniform radiation dose of 4.8 x 0.001 plus or minus 2 x 0.0001 joule/kg resulted.

Brown, R. D.↗
NASA NTRS1973

Apollo 14 and Apollo 16 heavy-particle dosimetry experiments.

Doses of heavy particles at positions inside the command modules of Apollo missions 8, 12, 14, and 16 correlate well with the calculated effects of solar modulation of the primary cosmic radiation. Differences in doses at different stowage positions indicate that the redistribution of mass within the spacecraft could enhance safety from the biological damage that would otherwise be expected on manned, deep-space missions.

Fleischer, R. L.↗