As Flown on Cosmos Missions
Measurement of the high-LET (linear energy transfer) particle radiation is passively accomplished with plastic radiation detectors. Plastics used are cellulose nitrate and Lexan polycarbonate. The minimum LET value that can be detected with these plastics is °100 keV/micrometer tissue. Plastic films used in detectors have a thickness of 100 micrometers (cellulose nitrate) and 250 micrometers (Lexan). The films are layered together in various combinations and placed about the interior of the spacecraft to measure the flux, integral LET spectrum, and spatial distribution of HZE (high-energy ionized) particles.
Latent particle tracks in the plastics are developed by chemically etching the exposed films. In this process, the damaged region along the path of the particle is preferentially attacked by the etchant. The resulting track appears as a hole in the plastic film, whose size is determined by the duration of the development process.
Cosmos 782: On Cosmos 782, two different PNTD configurations were used to make measurements. Thin detectors consisting of seven layered thin plastic films, held together with tape, measured the flux and integral LET spectrum. Thin stacks measured 5 cm2 and 0.15 cm thick. Aluminized mylar was wrapped around the stack to protect the plastics from any ultraviolet light exposure. A total of 12 detectors were placed on centrifuged and stationary containers housing US carrot culture and Killifish development experiments. Thick detector stacks consisting of 75 layered plastic films measured the charge spectrum. The thick stacks were 9 cm2 and 2 cm thick. Two thick detectors were placed on the stationary platform inside the biosatellite. Only PNTD stacks were used for radiation measurements onboard Cosmos 782.
Cosmos 936: On Cosmos 936, PTND stack configurations were flown in conjunction with a variety of other radiation detectors. (See Cosmos 936 Radiation Detector Packets.) Two films of each type of plastic were layered together and sealed, along with three nuclear emulsion tilms sealed in plastic, inside a black polyethylene envelope, to measure HZE flux, integral LET spectrum, and spatial distribution. The area of the plastic films was 4.5 x 6 cm. Eighteen detectors were located inside the US-USSR flight container: 12 detectors were attached in pairs to each of the six faces of a pyrel foam cude (7.7 cm3) centrally located in the joint portion of the flight package; and six detectors were attached to the face of the US package at one end of the container. To measure the Z spectrum, a stack composed of 97 micrometers thick layers of cellulose nitrate and 188 micrometers thick layers of Lexan was located in the joint portion of the flight container; the layer sequence was 10 layers of cellulose nitrate, 200 layers of Lexan, 65 layers of cellulose nitrate, 200 layers of Lexan, and 10 layers of cellulose nitrate.
Other Cosmos Missions: On subsequent Cosmos missions (Cosmos 1129, 1887, and 2044), PNTD stacks were flown on both the interior and exterior of the biosatellite. The plastics used in these stacks differ with the experiment objectives and evolving dosimetry materials/techniques. See Cosmos 1129 Radiation Detector Packets and Cosmos 2044 and 1887 Radiation Dosimeters for more details.