RaDI-N (RaDI-N) - 10.08.14
ISS Science for Everyone
Science Objectives for Everyone
(RaDI-N) will measure neutron radiation levels while onboard the International Space Station (ISS). RaDI-N uses bubble detectors as neutron monitors which have been designed to only detect neutrons and ignore all other radiation.
Science Results for Everyone
Bubble detectors which provide instant and accurate measurements of neutron doses, were used to determine the neutron energy at various locations inside the space station. Results indicate that the dose at different depths is not significantly different, suggesting that someone could wear a bubble detector for an accurate reading of a dose received inside the body. Calculations indicate that charged particles (protons and heavy ions) contribute very little to bubble count on the station, answering a long-standing question about the detector’s response and confirming that it is not necessary to correct for charged-particle contributions when calculating neutron dose measured by a bubble detector in space.
Bubble Technology Industries, Incorporated, Chalk River, Ontario, Canada
Sponsoring Space Agency
Canadian Space Agency (CSA)
ISS Expedition Duration
March 2009 - March 2010
Previous ISS Missions
- RaDI-N is a follow-up to the Matroshka-R experiment. RaDI-N will add more data to the results of Matroshka-R by monitoring the incidence and energy range of neutron radiation throughout the ISS.
- Crewmembers will measure neutron radiation levels onboard the ISS by placing bubble detectors around various modules.
Space radiation consists of highly charged particles that are extremely energetic and move at nearly the speed of light. Some space radiation comes from the deepest regions of the universe as galactic cosmic rays; some as solar particles emitted in sun flares; and others as particles trapped in the Earth's magnetic field. Crewmembers travel along a low-Earth orbit, which provides them with modest protection via the Earth's atmosphere and magnetosphere. Unfortunately, crewmembers are still exposed to much higher doses of radiation than people on Earth. Neutron radiation has been shown to make up 10-30% of this exposure. In space, neutrons are produced when primary radiation particles collide with physical matter; such as the ISS; and scatter. Since neutrons do not carry an electric charge, they can penetrate deeply into living tissue. These unstable particles have the potential to damage or mutate DNA which may cause cataracts and cancer. RaDI-N uses finger-sized instruments called bubble detectors as neutron monitors. These detectors have been designed to only detect neutrons and ignore all other radiation. Bubble detectors first started being used for space studies in 1989, and have since become popular due to their accuracy and convenience. Crewmembers will place eight of these finger-sized instruments around various modules on the ISS. Each detector will be filled with a clear polymer gel containing liquid droplets. When a neutron strikes the test tube portion, a droplet is vaporized, followed by a visible gas bubble in the polymer. Each bubble representing neutron radiation is then counted by an automatic reader. RaDI-N is a follow-up to the Matroshka-R experiment. Matroshka-R used a spherical dummy, known as a “phantom”, to simulate a person's body. Bubble detectors were placed in and around the phantom to record the neutron exposure that tissues and organs receive in low-Earth orbit. The results indicated that the internal organs absorbed more neutron radiation than scientists expected. They hypothesized that cosmic rays were interacting with the phantom itself, creating a secondary source of neutrons. RaDI-N will add more data to the results of Matroshka-R by monitoring the incidence and energy range of neutron radiation throughout the ISS. The RaDI-N team is confident that their findings will provide an invaluable resource for accurate risk assessment of neutron radiation in space. This could help reduce astronauts' exposure to radiation during future missions.
The RaDI-N team is confident that their findings will provide an invaluable resource for accurate risk assessment of neutron radiation in space. This could help reduce astronauts' exposure to radiation during future missions.
Data provided from RaDI-N can lead to further understanding of how neutron radiation may damage or mutate DNA which may cause cataracts and cancer on Earth as well as in space. While the levels of neutron radiation are much higher in space than on Earth, any understanding into the way radiation may alter DNA function is extremely useful.
At the beginning of each session, 8 SBDs will be activated and initialized using the SBR located in the SM (Service Module). Six spectrometric SBDs will be placed on a wall of the ISS (SM-first session, US Lab-second session and JEM-3rd session) next to the area radiation detector, TEPC (Tissue Equivalent Proportional Counter) - a microdosimetric instrument that measures radiation dose and dose equivalent in complex radiation fields (fields containing a mixture of particle types). Detectors will be photographed at the places of deployment and remain their unattended for 5 to 7 days. At the end of the data collection period, detectors will be collected and "read-out" using the SBR. SBDs will then be deactivated and stored away until the next session. Data will be recorded and transmitted to Earth via downlink.
Three sessions of data collection are planned for Expeditions 20 and 21. For each session, 6 spectrometric SBDs are placed on a wall of the ISS near the TEPC; one SBD is placed near the sleeping quarters of the crewmember, and one SBD is worn as a personal detector by the crewmember. Each session is planned to last approximately 5 to 7days. After each session, the SBDs will be read using the SBR located in the Russian Service Module. Data will then be recorded and transmitted to Earth via downlink.
The Radi-N experiment, conducted during ISS-20/21 in 2009, used bubble detectors to characterize the neutron radiation field in three locations in the US Orbital Segment (USOS) of the ISS. The goal of the experiment was to compare the neutron dose and energy distribution in Columbus, the US Laboratory, and the Japanese Experiment Module (JEM). The data collected provided some important conclusions regarding neutron radiation in the ISS (Smith 2013). The measured neutron energy distributions agreed well with previous measurements and did not show a strong dependence on the location in the ISS. These energy distributions showed that approximately 40% of the neutron dose measured was due to high-energy neutrons (> 15 MeV). Measurements with bubble dosimeters showed that the neutron dose received in the sleeping quarters (in the JEM) was less than that received during daily activities around the ISS. Furthermore, experiments with a water shield in the JEM showed that the neutron dose on the inner side of the shield was reduced to 72% of the value on the outer side of the shield. A follow-up experiment, Radi-N2, commenced in 2012 and is ongoing.
Lewis BJ, Smith M, Ing H, Andrews HR, Machrafi R, Tomi L, Matthews TJ, Veloce L, Shurshakov VA, Chernykh IV, Khoshooniy N. Review of Bubble Detector Response Characteristics and Results from Space. Radiation Protection Dosimetry. 2011; 150(1): 1-21.
Machrafi R, Garrow K, Ing H, Smith M, Andrews HR, Akatov YA, Arkhangelsky VV, Chernykh IV, Mitrikas VG, Petrov VP, Shurshakov VA, Tomi L, Kartsev IS, Lyagushin VI. Neutron Dose Study with Bubble Detectors Aboard the International Space Station as Part of the Matroshka-R Experiment. Radiation Protection Dosimetry. 2009; 133(4): 200-207. DOI: 10.1093/rpd/ncp039.
Smith M, Akatov YA, Andrews HR, Arkhangelsky VV, Chernykh IV, Ing H, Khoshooniy N, Lewis BJ, Machrafi R, Nikolaev IV, Romanenko RY, Shurshakov VA, Thirsk RB, Tomi L. Measurments of the Neutron Dose and Energy Spectrum on the International Space Station During Expeditions ISS-16 to ISS-21. Radiation Protection Dosimetry. 2013; 153(4): 509-533. DOI: 10.1093/rpd/ncs129. PMID: 22826353.
Hallil A, Brown M, Akatov YA, Arkhangelsky VV, Chernykh IV, Mitrikas VG, Petrov VP, Shurshakov VA, Tomi L, Kartsev IS, Lyagushin VI. MOSFET dosimetry mission inside the ISS as part of the Matroshka-R experiment. Radiation Protection Dosimetry. 2010 Nov; 138(4): 295-309. DOI: 10.1093/rpd/ncp265.
Chernykh IV, Liagushin VI, Akatov IA, Arkhangelsky VV, Petrov VM, Shurshakov VA, Mashrafi R, Garrow H, Ing M, Smith M, Tomi L. Results of measuring neutron dose inside the Russian segment of the International Space Station using bubble detectors in experiment Matreshka-R. Aviakosmicheskaia i Ekologicheskaia Meditsina (Aerospace and Environmental Medicine). 2010 May - June; 44(3): 12-17. PMID: 21033392. [Russian]
Smith M, Khulapko S, Andrews HR, Arkhangelsky VV, Ing H, Lewis BJ, Machrafi R, Nikolaev IV, Shurshakov VA. Bubble-detector measurements in the Russian segment of the International Space Station during 2009-12. Radiation Protection Dosimetry. 2014 April 8; epub. DOI: 10.1093/rpd/ncu053.
Ground Based Results Publications
El-Jaby S, Tomi L, Sihver L, Sato T, Richardson RB, Lewis BJ. Method for the prediction of the effective dose equivalent to the crew of the International Space Station. Advances in Space Research. 2014 March; 53(5): 810-817. DOI: 10.1016/j.asr.2013.12.022.
El-Jaby S, Lewis BJ, Tomi L. A model for predicting the radiation exposure for mission planning aboard the international space station. Advances in Space Research. 2014 April; 53(7): 1125-1134. DOI: 10.1016/j.asr.2013.10.006.
RaDI-N Neutron Field Study
Image of liquid droplets dispersed throughout a clear polymer gel within a bubble detector. Image courtesy of Bubble Technology Industries.
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Image of bubbles being counted by the BDR-III automatic reader. Image courtesy of Bubble Technology Industries.
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