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Workshops on Radiation Monitoring for the International Space Station

Eleventh WRMISS Workshop

The 11th Workshop took place on 6-8 September 2006 at St. Peters College in Oxford, UK The local organizers were Luke Hager (luke.hager@hpa-rp.org.uk) and David Bartlett (david.bartlett@hpa-rp.org.uk).

Besides a session on the ICCHIBAN calibrations, a session covering the MATROSHKA-1 experiment results was held. As the results from MATROSHKA-1 are still preliminary, no links to the presentations of this session are provided, but interested scientists can contact the presenters by e-mail and see if the results obtained so far can be useful.

Participant list

Name Affiliation
David Bartlett HPA, Chilton, England
Rudolf Beaujean Univ. Kiel, Germany
Peter Beck ARC Seibersdorf Research, Seibersdorf, Austria
Eric Benton Oklahoma State Univ., Stillwater, USA
Thomas Berger DLR, Köln, Germany
Pawel Bilski IFJ, Krakov, Poland
Soenke Burmeister Univ. Kiel, Germany
Marco Casolino Univ. Roma Tor Vergata, Rome, Italy
Sandor Deme KFKI-AERI HAS Budapest, Hungary
Jan Dettmann ESA, ESTEC, Noordwijk, The Netherlands
Günther Dietze ICRPTG67, Braunschweig, Germany
Beata Dudás KFKI-AERI HAS Budapest, Hungary
Larry Dungan NASA JSC, EHS, Houston, USA
Jean-Louis Genicot SCK-CEN, Mol, Belgium
Luke Hager NRBP, Chilton, England
Michael Hajek Atominstitute, Vienna, Austria
Attila Hirn KFKI-AERI HAS Budapest, Hungary
Myung-Hee Kim Wyle Laboratories, Houston, USA
Hisashi Kitamura NIRS, Chiba, Japan
Kerry Lee Lockheed Martin Aerospace, Houston, USA
Marlies Luszik-Bhadra PTB, Braunschweig, Germany
Stephen McKeever Oklahoma State Univ., Stillwater, USA
Aiko Nagamatsu JAXA, Japan
Bart Quaghebeur BIRA, Brussels, Belgium
Denis O'Sullivan DIAS, Dublin, Ireland
Joe Pálfálvi KFKI-AERI HAS Budapest, Hungary
Lawrence Pinsky Univ. Houston, USA
Guenther Reitz DLR, Köln, Germany
Gabriel O. Sawakuchi Oklahoma State Univ., Stillwater, USA
Edward Semones NASA JSC, SRAG, Houston, USA
Jordanka Semkova STIL-BAS, Sofia, Bulgaria
Mark Shavers Lockheed Martin Aerospace, Houston, USA
František Spurný NPI, Prague, Czech Republic
J. Szabó KFKI-AERI HAS Budapest, Hungary
Norbert Vana Atominstitute, Vienna, Austria
Filip Vanhavere SCK-CEN, Mol, Belgium
Mark Weyland NASA JSC, SRAG , Houston, USA
Nakahiro Yasuda NIRS, Chiba, Japan

Abstracts and presentations

Welcome/Organizational Issues

D.T. Bartlett

Introduction/Actions of last meeting

G. Reitz

Quantities for Radiation Protection in Space

D.T. Bartlett
Health Protection Agency, Chilton, Oxon, OX11 0RQ, UK.
Fundamental radiometric quantities are used to characterize the radiation field in space. Also required are interaction coefficients and related quantities in order to understand and interpret the interactions of the radiation fields with matter, including biological tissue. Further, dosimetric and radiation protection quantities are needed to assess prospectively and retrospectively, radiation effects on physical and biological systems so as to minimize or limit effects and to comply with regulations and guidance. Various of these quantities are also used to determine the performance of instrumentation, intercompare systems and to validate calculations.

Passive Space Radiation Dosimetry using Optically and Thermally Stimulated Luminescence

S.W.S. McKeever
Department of Physics, Oklahoma State University, Stillwater, OK 74078, USA
This presentation reviews the use of optically stimulated luminescence (OSL) and thermoluminescence (TL) in space dosimetry applications. Each method relies upon the absorption of energy from the radiation field and the storage of that energy in the form of trapped electronic charge species in non-equilibrium states within the crystalline structure of the dosimetry material. Readout of this stored energy, which is proportional to the absorbed radiation dose, is achieved by either optical stimulation (in OSL) or thermal stimulation (in TL) of the dosimetric material. In each case the intensity of the luminescence emitted during the stimulation process is monitored as a function of time and is taken to be the parameter that is proportional to the absorbed dose. Although ostensibly similar phenomena, the different modes of stimulation of the luminescence signal during OSL or TL lead to different interpretations of the evaluated absorbed dose when the dosimeter has been exposed to a mixed radiation field consisting of a wide variety of energetic ions, as in space radiation. The paper will discuss the time evolution of the OSL and TL signals during readout, the efficiencies of the different energetic ions at producing OSL and TL, and the different materials that can be used in these applications. The advantages and limitations of the different readout techniques will be discussed and summarized.

Measurement of LET Spectrum using CR-39 Plastic Nuclear Track Detector for Space Radiation Dosimetry

E. Benton
Oklahoma State University, Dept. of Physics and Eril Research, Inc.
CR-39 plastic nuclear track detector (PNTD) is a passive radiation detector that is routinely used to measure the LET spectrum, dose, and dose equivalent from particles of LET H2O 5 keV/m accrued in space. CR-39 PNTD can be used in combination with thermoluminescence or optically stimulated luminescence detectors to measure total dose and dose equivalent exposure during space flight and this method is currently used by NASA to obtain the astronaut dose of record. Dosimetric data has been collected from CR-39 PNTD exposed aboard the NASA Space Shuttles, the Russian Mir Space Station, the International Space Station, numerous unmanned, recoverable satellites, and high altitude balloons spanning a 25 year period. This presentation describes the methods involved in measuring LET spectrum in CR-39 PNTD exposed in space. Examples from recent space flight experiments, including Matroshka I, are used to illustrate the method. Recent research, particularly in the use of Atomic Force Microscopy (AFM) to analyze CR-39 PNTD, are also briefly mentioned.
Contact: Eric Benton

ICCHIBAN 8: Czech results obtained with thermoluminescent and track etched detectors

F. Spurný
Department of Radiation Dosimetry, Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic;
The thermoluminescent detectors (TLDs); and polyallyldiglycolcarbonate track etch detectors (PADC TEDs) were exposed during ICCHIBAN 8 run by He, O, Ar, and Fe-ions, with linear energy transfer (LET) in water up to ~ 400 keV/m.
The contribution will present an overview of results obtained during theirs evaluation: Further data on the relative response (RR) of TLD's as a function of LET have been received, newly also for CaSO4:Dy; new regression dependences RR = f(LET) for AlP glass and Al2O3:C have been established.
Exposures at known conditions have also permitted to verify calibration curves for PADC TEDs used for LET spectrometry. It was found that the track densities observed are lower than expected ones.
Registration probabilities have been determined for secondary particles formed in PADC after the irradiation with He-ions as well as for 197Au and 209Bi spallation fragments in Melinex TED.
The results of the treatment of detectors during "blind" exposures will be also presented and discussed.
Finally, some remarks on the usefulness of ICCHIBAN program and its further prolongation will be presented.

Keywords: space dosimetry, ICCHIBAN program, heavy charged particles, calibration

Corresponding author: Frantisek Spurný, Department of Radiation Dosimetry, Czech Academy of Sciences, Na Truhl�ce 39/64, 180 86 Praha 8, Czech Republic, Fax: +420 283842788, E-mail: spurny@ujf.cas.cz

ICCHIBAN-8 results: the updated calibration curve

J. Szabó, J. K. Pálfalvi, B. Dudás
Hungarian Academy of Sciences, KFKI Atomic Energy Research Institute P.O.B. 49, H-1525 Budapest, Hungary
The Radiation and Environmental Physics Department of the Atomic Energy Research Institute (Hungarian Academy of Sciences) participated in the ICCHIBAN-8 experiment with 16 standard and 1 "three dimensional" PADC detector stacks. The detectors were treated in a standard way: etched in 6 n NaOH at 70 C for 6 hours and then investigated by the VIRGINIA image analyzer.
In this contribution the composition of the detector stacks, the evaluation method and the updated calibration curve will be presented. Using the new calibration curve the LET spectra and dose values, deduced from measurements of the detectors exposed on the ISS will be given and they will be compared with our previous results. The effect of the modification of the calibration curve on the LET spectra will be discussed.

Heavy Ion Beam Characteristics of ICCHIBAN 7 and 8 Experiments and Brief Summary of the ICCHIBAN Experiments

H. Kitamura1, Y. Uchihori1, N. Yasuda1, E. Benton2, T. Berger3, M. Hajek4, J. Miller5, and ICCHIBAN Working Group
1. National Institute of Radiological Sciences, Chiba, 263-8555, Japan
2. Oklahoma State University, Stillwater, Oklahoma, 74074, USA
3. DLR Institute of Aerospace Medicine, Köln, 51147, Germany
4. Atomic Institute of the Austrian University, Vienna, 1020, Austria
5. Lawrence Berkley National Laboratory, Berkeley, California, 94720, USA
ICCHIBAN-7(IC-7) and IC-8 experiments were performed at NIRS-HIMAC in September 2005. IC-7 was carried out for the active dosimeters with 400 MeV/u Oxygen and 300 MeV/u Iron in HIMAC PH exposure room. At the same time, IC-8 was also carried out for passive dosimeters with 150 MeV/u Helium, 400 MeV/u Oxygen, 500 MeV/u Argon and 200 MeV/u Iron in HIMAC BIO exposure room. About 40 researchers from 19 institutes participated to IC-7 and/or IC-8.
Since 2002, ICCHIBAN working group performed the beam experiments 10 times at HIMAC, Loma Linda University, and NSRL in BNL. In this presentation, we will report the characteristics of the beams of last two experiments and discuss about the former experiments.

MATROSHKA - Overview 2004 - 2006

T. Berger, G. Reitz
DLR Insitute of Aerospace Medicine, 51147 Köln, Germany
The MATROSHKA facility aimed for the determination of skin and organ dose of astro - and cosmonauts during an extravehicular activity was launched in January 2004. The facility was mounted on the outside of the Russian Service Module in February 2004 (Start of MATROSHKA 1). The facility was positioned outside the International Space Station till autumn 2005. The overall outside exposure time was 600 days. After the return of the facility inside the ISS in autumn 2005 new passive detectors were installed in January 2006 (MATROSHKA 2 Phase A). The Phase A is an inside exposure phase of the facility to gain data for intercomparsion with the data gathered during MATROSHKA 1 outside the station. At the current time the preparation for MATROSHKA 2 Phase B - which will be a second inside exposure - including the active measurement devices - has almost been completed. A new passive detector set will be launched to the ISS in late autumn 2006. In Phase B MATROSHKA will be positioned in the Service Module of the Station. This talk is intended to give an overview of the experiment MATROSHKA in the years 2004 to 2006.

First TLD results of the MATROSHKA-1 experiment

P. Bilski, M. Ptaszkiewicz, M. Puchalska
Institute of Nuclear Physics (IFJ), Kraków, Poland
During the MATROSHKA-1 experiment an anthropomorphic phantom was exposed outside of the ISS for a period of 1.5 year. The main part of this experiment consisted of dose distribution measurements performed with thermoluminescent detectors within a 2.5 cm grid inside of the phantom torso. Institute of Nuclear Physics (IFJ) provided TL detectors for nearly half of measuring locations inside the phantom (785 of 1631 locations in total). In each location we used four types of TLDs: MTS-7 (7LiF:Mg,Ti), MTS-6 (6LiF:Mg,Ti), MCP-7 (7LiF:Mg,Cu,P) and MTT-7 (7LiF:Mg,Ti with changed activators concentration). The same types of TLDs were also used in the organ passive boxes, in the poncho and in the MLI packages. In total we located about 3600 TLDs in the M ATROSHKA facility.
The TLDs returned to IFJ in January 2006 and readouts were performed in the first months of this year. During presentation the first results for all TL detectors will be presented.
Contact: Pawel Bilski

Austrian results from Matroshka poncho and organ dose determination

M. Hajek, R. Bergmann, M. Fugger, N. Vana
Vienna University of Technology, Atomic Institute of the Austrian Universities, Austria
Cosmic rays from solar and galactic sources are attenuated in interaction processes within shielding structures and within the human body. Reliable assessment of health risks to astronaut crews is pivotal in the design of future interplanetary space exploration and requires knowledge of absorbed radiation doses in critical radiosensitive organs and tissues. Phase 1 of the international Matroshka phantom experiment - conducted under the aegis of the German Aerospace Center (DLR) - is aimed at simulating an astronaut's body during an extravehicular activity (EVA). The Atomic Institute of the Austrian Universities (ATI) provided more than 1100 thermoluminescence (TL) detectors of the types TLD-300 (CaF2:Tm), TLD-600 (6LiF:Mg,Ti), TLD-700 (7LiF:Mg,Ti) and TLD-700H (7LiF:Mg,Cu,P) for spatially resolved dosimetry. The TL chips were distributed within the phantom slices, specific organ dose boxes (at the location of the eye, lung, stomach, kidney and intestine), the poncho and a dosimeter stack accommodated in the multilayer insulation (MLI) protective cover. An overview of absorbed doses accumulated during the 18-month exposure from February 26, 2004 to August 18, 2005 is presented along with a description of the experimental methods applied. With few exceptions, a dose gradient was found towards the centre of the phantom body and from the head to the abdomen. TLD-700 absorbed doses within the slices, before subtraction of the residual background, ranged between 99mGy (slice 27) and 270mGy (slice 3). Repeated calibrations allowed estimating the precision of the single-chip measurements to be about 7%.
Contact: Michael Hajek

Preliminary results from Matroshka-1: Optically Stimulated Luminescence and Thermoluminescence results obtained at Oklahoma State University

G. Sawakuchi1, E. Yukihara1, E. Benton1,2, R. Gaza3, S. McKeever1
1. Department of Physics, Oklahoma State University, Stillwater, OK 74078
2. Eril Research, Inc., Stillwater, OK 74074-1541, USA
3. Space Radiation Analysis Group, NASA Johnson Space Center, Houston TX 77058-3696
The Radiation Dosimetry Laboratory at Oklahoma State University was among the 15 institutions that participated in the Matroshka-1 experiment led by the Institute of Aerospace Medicine at the German Aerospace Center. In this experiment an anthropomorphic phantom containing passive and active radiation detectors was exposed to the radiation environment outside the International Space Station (ISS) for 18 months. The OSU group participated with Al2O3:C Optically Stimulated Luminescence Detectors (OSLDs), LiF:Mg,Ti (TLD-100), and CaF2:Tm (TLD-300) Thermoluminescence Detectors (TLDs) placed in different positions to measure organ, skin and depth absorbed doses. This presentation will give an overview of the methodology and science objectives of the OSU group, present the absorbed doses obtained for the various detectors, and discuss the problems encountered.
Organ absorbed doses were measured with dosimeters placed in boxes (NTDP 1 to 5) in five different sites: eyes, lungs, stomach, kidney and descending colon. In addition, detectors were also placed on the top of the phantom's head (NTDP-6). The uncorrected values obtained by Al2O3:C OSLD were in the range from 122 mGy to 164 mGy for the organ sites, and 346 mGy on the top of the head. Skin doses were measured on the anterior, posterior and lateral sides of the phantom with detectors placed on the surface of the phantom ("Poncho Skin" 1 to 5: upper dorsal, mid dorsal, lower dorsal, lumbar, and upper thorax) and detectors place on the surface of the phantom inside polyethylene boxes ("Poncho" 1-6: mid thorax, upper abdomen, lateral right and left sides, mid dorsal and lumbar). The "poncho skin" detectors that were behind detector boxes (mid dorsal and lumbar) resulted in relatively low doses (230 mGy and 250 mGy) as compared to the upper dorsal, upper thorax, and lower dorsal (405 mGy, and 543 mGy, and 542 mGy, respectively). The doses for the anterior "Poncho" boxes were 498 mGy and 413 mGy, while the other boxes were in the range 319 mGy - 352 mGy. Depth doses were measured from anterior side to posterior side in four different positions: about the level of: left eye (Tube 4G: 6 depths), third right rib (Tube 16C: 7 depths), liver (Tube 21C: 7 depths), right kidney (Tube 23C: 7 depths), and ascending colon (Tube 28C: 7 depths). It was observed that the doses in positions close to the surface were higher than at the middle of the phantom.

A discussion will be made on the usefulness of additional information contained in the shape of the OSL decay curve from OSLDs. The shape of the OSL decay curves exposed in the Matroshka-1 experiment were compared to the shape of the OSL curves for various particle/energy combination (various LET values). Assuming that the corresponding LET is the dominant component of the radiation field, the absorbed doses were corrected for the efficiency at that LET value. The correction decreased the difference between the OSL absorbed doses measured in different experimental conditions.
Contact: Gabriel Sawakuchi

Space radiation dosimetry by PADLES on an exposed area of the MATROSHKA project (phase 1)

A. Nagamatsu1,2, K. Murakami1, H. Kumagai3, K. Kitajo3, H. Tawara1,4
1. Japan Aerospace Exploration Agency (JAXA)
2. KEK Grad. Univ. Advanced Studies
3. Advanced Engineering Services Co., Ltd.
4. High Energy Accelerator Research Organization (KEK) (e-mail:nagamatsu.aiko@jaxa.jp)
We have developed a PADLES (Passive Dosimeter for Life-Science Experiments in Space) system in JAXA's Space Environment Utilization Center, which newly includes a series of programs (AUTO PADLES, TLD PADLES) for a fast and systematic analysis of the PADLES dosimeters. The PADLES package consists of two types of passive and integrating dosimeters, a CR-39 plastic nuclear track detector (PNTD) and a thermoluminescence (TLD) dosimeter. PADLES is to be utilized for radiation dosimetry in biological experiments and for Japanese astronauts aboard the Japanese Experiment Module 'Kibo' of the ISS. The PADLES packages were applied to the MATROSHKA project (phase 1) conducted by DLR. The project is for estimating an astronaut's exposed dose during an EVA with various passive and active dosimetors. A human phantom in pressurized container which meets the mean shielding thickness of a space suit was set up on an exposed area of the Russian segment for 538 days. The total in ISS loading period was 621 days from 01/19/2004 to 10/11/2005. We carried out ground-based experiments using 252cf neutron and 60 Co gamma ray source to obtain the TLD and CR-39 fading and aging effect at down link temperatures (-24.6 to 21.5) measured by sensors inside the MATROSHKA phantom, running parallel to the MATOROSHKA space experiments. We confirmed the TLD and CR-39 PNTD dose not have a thermal fading and aging effect under the temperature condition of the MATROSHKA generally. We will report the results in ground based experiments and space radiation measurements of the MATROSHKA project using the PADLES system.
Contact: Aiko Nagamatsu

Evaluation of the track etch detector stacks exposed inside and on the MATROSHKA phantom. Phase I, 2004-2005.

J.K. Pálfalvi, J. Szabó, and B. Dudás
KFKI-Atomic Energy Research Institute of the Hungarian Academy of Sciences P. O. Box 49, H-1525 Budapest 114, Hungary
Two types of track etch detector stacks were constructed, one for the organ dose measurements in the lung and kidney of the phantom, the other one for the skin dose measurements attached to the poncho of the phantom. The detector assembly allows to determine the combined LET spectra of primary GCR particles and of the secondary ones generated by trapped protons and GCR particles by nuclear reactions, including target and projectile fragmentation. The track detectors were evaluated by an image analyzer and from the track parameter measurements the absorbed dose, the equivalent dose and the mean quality factor were calculated.
The configuration of the stacks, the methods of the calibration and evaluation and the preliminary results will be presented.
Contact: J.K. Pálfalvi

Radiation Measured for Matroshka-1 with Passive Dosimeters

D. Zhou1, 2, D. O'Sullivan3, E. Semones1, E.R. Benton4, M. Weyland1
1. Johnson Space Center - NASA, Houston 77058, USA 2. Universities Space Research Association, Houston 77058, USA 3. Dublin Institute for Advanced Studies, Dublin 2, Ireland 4. Eril Research Inc., Stillwater, OK 74074
Radiation in low Earth orbit (LEO) is mainly from Galactic Cosmic Rays (GCR) and solar energetic particles. The impact of cosmic ray particles on astronauts depends strongly on the particles' linear energy transfer (LET) and is dominated by high LET radiation. The best active dosimeters used for all LET are the tissue equivalent proportional counter (TEPC) and silicon detectors. The preferred passive dosimeters for radiation measurement are thermoluminescence dosimeters (TLDs) or optically stimulated luminescence dosimeters (OSLDs) for low LET and CR-39 plastic nuclear track detectors (PNTDs) for high LET. CR-39 PNTDs, TLDs and OSLDs were used to investigate the radiation for Matroshka-1 exposure by researchers from different groups. LET spectra and radiation quantities (fluence, absorbed dose, dose equivalent and quality factor) were measured for the exposure by JSC-DIAS researchers with CR-39 PNTDs and TLDs. This paper introduces the operation principles for these dosimeters, describes the method to combine the results measured by CR-39 PNTDs and TLDs, presents the measured results of LET spectra and the combined radiation quantities and compares the dose equivalent measured by passive dosimeters and by silicon dosimeter DOSTEL.
Contact: D. Zhou

Results from MATROSHKA 1 using the HPA neutron dosemeter

L. Hager
Health Protection Agency, Chilton, Oxon, OX11 0RQ, UK.
The results from using the HPA PADC dosemeter on the MATROSHKA 1 experiment will be presented. The HPA dosemeter is routinely used for neutron personal dosimetry where a standard electrochemical etch is used to determine the dose from short-range recoils. In the ISS radiation field, using the standard etch and read method counts both short and long-range particles of LET > ~40 keV m-1 from both neutron interactions and incident heavy charged particles, without discrimination. Methods of determining the neutron component will be discussed.
Contact: Luke Hager

MATROSHKA 1 - Results from DLR - passive data intercomparison, and some remarks

T. Berger, G. Reitz
DLR Insitute of Aerospace Medicine, 51147 Köln, Germany
In the framework of the MATROSHKA 1 experiment - where the facility was positioned outside the ISS for 600 days - DLR provided around 25% of the 6000 thermoluminescence detectors distributed in the phantom torso, at the skin and at the MLI of the MATROSHKA. Most of the detectors were placed in the tubes, which where distributed in the 33 slices of the phantom. DLR had at each measurement point in the tubes TLDs of the the types TLD 600 (6LiF: Mg, Ti) and TLD 700 (7LiF:Mg, Ti). Further on in the NTDP packages additionall TLDs of the types TLD 600H (6LiF:Mg, Cu, P) and TLD 700H (7LiF: Mg, Cu, P) were placed. The TL-efficiency to heavy ions of these detectors was determined in the framework. of the ICCHIBAN project as well as in a research project of DLR and the ATI, Vienna at the Heavy Ion Medical Accelerator HIMAC in Chiba Japan.
First results of the depth dose distribution, the organ doses, the reference doses for the detectors inside the station as well as for the MLI depth dose measurements will be presented.
In addition a first data intercomparison of passive TL/OSL - data from the participating groups of the MATROSHKA experiment for the organ dose boxes as well as for the poncho boxes will be presented and should be the baseline for further discussions about the MATROSHKA data interpretation.
Contact: Thomas Berger

The Silicon Scintillator Devices (SSDs) inside the MATROSHKA Phantom

R. Beaujean1, S. Burmeister1, G. Reitz2
1. Universität Kiel/IEAP, 24098 Kiel, Germany
2. DLR Köln/Flugmedizin, 51147 Köln, Germany
The Silicon Scintillator Devices (SSDs) consist of a 10 x 10 x 20 mm BC430 plastic scintillator surrounded by four 20 x 10 mm and two 10 x 10 mm PIN-photodiodes. The four 20 x 10 mm photodiodes are optically coupled to the scintillator and are designed for both light detection and the detection of penetrating charged particles. The measured pulse heights from these four detectors are digitized and stored. The two 10 x 10 mm photodiodes are not optically connected to the scintillator and provide only an anticoincidence signal for penetrating charged particles. By comparison of the measured pulse heights from the four optically coupled diodes for each individual particle, one can separate signals of charged particles from those induced by neutral particles which produce only light signals in the scintillator.
A detailed description of the SSD design and its positions inside the phantom will be given and preliminary results from the SSD measurements will be presented.
Contact: Rudolf Beaujean

Dose Rates measured with DOSTEL on Top of the MATROSHKA Phantom

S. Burmeister1, R. Beaujean1, G. Reitz2
1. Universität Kiel/IEAP, 24098 Kiel, Germany
2. DLR Köln/Flugmedizin, 51147 Köln, Germany
The DOSimetry TELescope (DOSTEL) measures the dose and LET spectra at the head of the MATROSHKA phantom. The MATROSHKA DOSTEL consists of a telescope of two 300m Canberra PIPS (Passivated Implanted Planar Silicon) detectors and two additional Hamamatsu 300 m PIN diodes. The circular PIPS detectors have an active area of 6.93 cm and the rectangular PIN detectors active area is 2.31 cm (2.1 x 1.1 cm). The PIN diodes are arranged perpendicular to each other and the telescope axis. The MATROSHKA facility has been mounted outside the Russian Module (Zvezda) of the International Space Station ISS for 539 days from Feb 26th 2004 till Aug 18th 2005 during the declining phase of solar cycle 23. In 2004 DOSTEL was active for about 100 days. The overall mean dose equivalent rate determined by the DOSTEL instrument was 1265 Sv/d. The mean daily dose includes 828 Sv/d by the galactic cosmic rays and 437 Sv/d by the trapped particles during the crossings of the South Atlantic Anomaly (SAA). A description of the MATROSHKA DOSTEL design, mean dose rates, LET spectra and deduced dose equivalent rates will be presented.
Contact: Soenke Burmeister

Measurements Of The Absorbed Dose Distribution In The Spherical Tissue Equivalent Phantom In MATROSHKA-R Space Experiment

V.A. Shurshakov1, Yu.A. Akatov1, I.S. Kartsev2, V.I. Petrov2, V.M. Petrov1, B.V. Polenov2, A.Yu. Kalery3, S.K. Krikalev3, V.I. Lyagushin3
1. State Research Center of the Russian Federation Institute of Biomedical Problems Russian Academy of Sciences, Moscow, Russia, shurshakov@imbp.ru
2. Science and Engineering Center NIC SNIIP, Moscow, Russia
3. S.P. Korolyov Rocket Corporation Energia, Korolyov, Moscow Region, Russia
The spherical tissue equivalent phantom at 35 cm diameter and 10 cm central spherical hole is known to simulate the shielding properties of a human body. The phantom has been installed in the star board crew cabin of the ISS Service Module since Feb. 2004. The phantom is a multi-user experimental facility of the Matroshka-R project that allows installing of numerous passive and active detectors specially designed to study the absorbed dose distribution in a human body in space flight. Based on the comparison of the shielding functions the detector locations in the phantom can be attributed to the critical organs of a human body. The were 2 experimental sessions with the spherical phantom, (1) from Jan. 29, 2004 to Apr. 30, 2004 and (2) from Aug. 11, 2004 to Oct. 10, 2005. Preliminary results obtained from the passive detectors returned to the ground after each session showed the dose difference on the phantom surface as much as a factor of 1.9, the highest dose being observed close to the outer wall of the crew cabin, and the lowest dose being in the opposite location along the phantom diameter. The dose distribution obtained in the phantom can be used for estimating the dose in cosmonaut's critical organs in an orbital space flight.

Radiation Measured for ISS-Expedition 12 with Different Dosimeters

D. Zhou1, 2, E. Semones1, R. Gaza1, 2, S. Johnson1, M. Weyland1 1. Johnson Space Center - NASA, Houston 77058, USA 2. Universities Space Research Association, Houston 77058, USA
The radiation in low Earth orbit (LEO) is mainly from Galactic Cosmic Rays (GCR) and solar energetic particles. The impact of cosmic ray particles to astronauts depends strongly on the particles' linear energy transfer (LET) and is dominated by high LET radiation. It is important to investigate the LET spectrum for the radiation field and the influence of radiation on astronauts. The best active dosimeters used for all LET are the tissue equivalent proportional counter (TEPC) and silicon detectors. The best passive dosimeters for radiation measurement are thermo- luminescence dosimeters (TLDs) or optically stimulated luminescence dosimeters (OSLDs) for low LET and CR-39 plastic nuclear track detectors (PNTDs) for high LET. TEPC, CR-39 PNTDs, TLDs and OSLDs were used to investigate the radiation for space mission Expedition 12 (ISS-11S) in LEO. LET spectra and radiation quantities (fluence, absorbed dose, dose equivalent and quality factor) were measured for the mission with these different dosimeters. This paper introduces the operation principles for these dosimeters, describes the method to combine the results measured by TLDs/OSLDs and CR-39 PNTDs, presents the experimental LET spectra and the radiation quantities.
Contact: D. Zhou

Current Status of CPDS Data Analysis

K. Lee
Lockheed Martin Aerospace, Houston, Texas, USA
The low-Earth orbit (LEO) radiation environment has been directly observed by the IV and EV charged particle directional spectrometers (CPDS) aboard the International Space Station (ISS). The EV instrument is mounted on the S0 truss of the ISS and consists of three separate silicon detector telescopes which are oriented in different directions. The IV instrument is a single silicon detector telescope located inside the USA Laboratory module of the ISS. We report on the current state of the data analysis for these instruments, which includes the proton and He stopping particle spectra, relative CNO abundances, and measured dose rate as a function of time. We also report on the status of the simulation of the CPDS instruments.

Status and results of the Alcriss project on board the International Space Station.

V. Bengin1, M. Casolino2, M. Durante3, C. Lobascio4, A. Nagamatsu5, G. Reitz6
3. University of Napoli Federico II
4. Alcatel Alenia Spazio
5. Jaxa
6. DLR
The Altcriss project aims to perform long term measurement of the radiation environment in different points of the International Space Station. To achieve this goal, it employs an active silicon detector, Sileye-3/Alteino, to monitor nuclei up to Iron in the energy range above 40 MeV/n. Both long term modulation of galactic cosmic rays going toward solar minimum and solar particles events will be observed. A number of different dosimeters are being employed to measure the dose and compare it with the silicon detector data. Another aim of the project is to monitor the effectiveness of shielding materials in orbit: a set of polyethylene tiles is placed in the detector acceptance window and particle flux and composition is compared with measurements in the same locations without shielding. Dosimeters are thus placed behind the shielding material and in an unshielded location to cross-correlate this information. Another set of multimaterial shielding is also being tested with various dosimeters. The observation campaign begun in December 2005 and is expected to run for three years, with joint observations in the framework of the MATROSHKA experiment in the duration of expedition 14. In this work we will describe the program of operations and preliminary results based on data obtained during expedition 12.

TL dose measurements on board the Russian segment of the ISS by the "Pille" system during Expedition-11 and -12

S. Deme1, I. Apáthy1, Yu.A. Akatov2, V.V. Arkhangelsky2, L. Bodnár3, S.K. Krikalev4, T. Pázmándi1, P. Szántó1, V.I. Tokarev4
1. KFKI Atomic Energy Research Institute, H-1525 Budapest, P.O.B. 49, Hungary
2. Institute for Biomedical Problems, State Scientific Center, 123007A Moscow, Russia
3. BL-Electronics, H-2083, Solym�, Sport 5., Hungary
4. Russian Federal Space Agency
The most advanced version of a thermoluminescent (TL) dosimeter system ("Pille-MKS") consisting of ten CaSO4:Dy bulb dosimeters and a compact reader, developed by the KFKI Atomic Energy Research Institute (KFKI AEKI) and BL-Electronics for application in space is continuously in use on board the ISS since October, 2003. The Pille-MKS dosimeter system is applied for the routine and EVA individual dosimetry of astronauts as part of the service system as well as for onboard experiments and operated by the Institute for Biomedical Problems (IBMP). It is unique providing accurate and high resolution TL dose data already on board the space station which became increasingly important during the suspension of the Space Shuttle flights.
Seven dosimeters are located at several places of the Russian segment of the ISS and read out once a month, two dosimeters are dedicated for EVAs and one dosimeter is kept in the reader and read out automatically every 90 minutes providing high resolution in time dose measurements.
During particular events like coronal mass ejections, hitting Earth incidental measuring campaigns are intercalated with frequent readouts.
In this paper we report results of dosimetric measurements made aboard the International Space Station during Expedition-11 and -12 using the "Pille" portable TLD system and compare them with our previous measurements on the ISS and previous space stations.

Spatial distribution and high LET component of absorbed dose measured by passive radiation monitors in ISS Russian segment

N. Yasuda1, Y. Uchihori1, H. Kitamura1, Yu. Akatov2, V. Shurshakov2, I. Kobayashi3,H. Ohguchi4, Y. Koguchi4
1. National Institute for Radiological Sciences, Chiba, Japan
2. Institute for Biomedical Problems, Moscow, Russia
3. Nagase Landauer, ltd., Nihombashi, Tokyo, 103-8487, Japan.
4. Chiyoda Technol Corporation, Oarai-machi, Ibaraki, 311-1313, Japan
We conducted an intercomparison experiment for passive radiation dosimeters as a part of the BRADOS experiment on the International Space Station in 2004. Simultaneously, five dosimeter boxes with passive detectors from IMBP and NIRS were also exposed at different five locations on the Russian segment of the ISS for a period of 268.5 days as phase-2 experiment. The detector package consists of LiF TLDs, Glass detectors and CR-39 detectors with some Al targets. We employed two different kinds of CR-39s named HARZLAS TD-1 and BARYOTRAK. According to the calibration using HIMAC, the detection threshold of BARYOTRAK have been measured to be about 60 keV/ m, thus it can record only the high LET particles above 60 keV/ m. Preliminary data from five locations are presented with the effectiveness to use the BARYOTRAK to measure the higher LET component.

To the neutron contribution to the exposure level onboard International Space Station

F. Spurný1, O. Ploc1, 2, Ts. Datchev3
1. Dept. of Radiation Dosimetry, Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic;
2. Dept. of Dosimetry and Application of Ionizing Radiation, Czech Technical University, Prague, Czech Republic
3. Solar-Terrestrial Influence Laboratory (STIL), Bulgarian Academy of Sciences (BAS), Sofia
Neutron contribution to the spacecraft crew exposure could represent up to several tens percents of the total value of the dose equivalent. The determination of this contribution represents rather complex and difficult task, both through experimental as theoretical estimation.
The contribution will present an attempt to determine the neutron contribution onboard International Space Station (ISS) using the data measured by means of a Si-diode based energy deposition spectrometer, MDU-Liulin equipment, developed at the STIL BAS.
We have analysed the data measured with this equipments onboard of ISS during 2001 year and onboard FOTON M2 capsule at 2005.
We have treated separately the data accumulated during the passage through and/or out of South Atlantic Anomaly (SAA). Out of SAA, i.e. at prevailing contribution of galactic cosmic rays, the data were treated supposing that the neutron spectra are similar to those onboard aircraft and/or at CERF high energy radiation field. The excess of deposited energy in the region above 1 MeV, when comparing to the aircraft field, was expected to represent primary heavy charged particles.
Data registered during the SAA passage were treated separately, supposing that the energy deposition spectra in MDU issued mostly from SAA protons.
Total dosimetric characteristics obtained in this way are in reasonable agreement with other data, neutron contribution representing about 30 % of the total dose equivalent.
Keywords: space dosimetry, neutron contribution, Si-diode based energy deposition spectrometer, neutron energy spectra

Corresponding author: Frantisek Spurný, Department of Radiation Dosimetry, Czech Academy of Sciences, Na Truhl�ce 39/64, 180 86 Praha 8, Czech Republic, Fax: +420 283842788, E-mail: spurny@ujf.cas.cz


B. Dudás, J K. Pálfalvi, J. Szabö
MTA KFKI-Atomic Energy Research Institute, P. O. B. 49, H-1525 Budapest, Hungary
In the frame of the "Biology and Physics in Space" ESA project, a returning satellite - Foton-M2 - was orbiting an external container, the BIOPAN-5, loaded among others with facilities for radiation dosimetry (RADO). The galactic cosmic rays and secondary particles as neutrons were detected by a track etch detector stack composed of 10 PADC plastic sheets and different charged particle converters. This set-up was appropriate to differentiate between the primary trapped protons and the protons induced by secondary neutrons. The system was calibrated at high energy particle accelerators, at neutron generators, with 1 MeV proton (Van de Graaf) and with collimated 210Po alpha source. After the etching method the detectors were investigated by an image analyser. From the track parameters the linear energy transfer (LET) spectra were determined. Based on the LET spectra above 15 keV/ m the total particle absorbed dose was deduced which is 26 Gy/d for Z 1. Utilising the CERF CT neutron spectrum, also the secondary neutron flux was estimated below 5 MeV and found to be 2.4 cm-2 s-1. From this result the absorbed dose could be calculated (2.5 Gy/d). The construction of the stack allowed to investigate the neutrons also from the direction of the carrying satellite where the flux was found somewhat higher.

Charged Particle Measurements in Mars Orbit from 2002 to 2006

C. Zeitlin1, K.T. Lee2
1. Lawrence Berkely National Laboratory
2. Lockheed Martin Aerospace Co.
The instrument payload aboard the Mars Odyssey orbiter included three instruments capable of measuring energetic charged particles from the GCR and solar particle events. One, MARIE, the dedicated particle detector, ceased functioning during the huge solar storm of October/November 2003. The other two, the Gamma Ray Spectrometer (GRS) and the scintillator component of the High Energy Neutron Detector (HEND), continue to work well and to return useful charged-particle data. Data from all three detectors are, for various reasons, quite difficult to normalize to absolute flux, dose, and dose equivalent. In the case of MARIE data, a large background from particles entering the detector from the "backward" direction requires a detailed model of the complex spacecraft mass distribution, coupled with a transport model to simulate the passage of energetic particles through the spacecraft mass. Work is in progress to finalize this model, but as of this writing the work is not complete. In the case of GRS and HEND, only count rates are recorded, and since the HEND rate is a neutron count, a very complicated unfolding (again requiring the spacecraft mass model and a transport code) would be required to convert those counts to charged particle flux.
Despite these difficulties, an intercomparison between the instruments has been performed. As a first step, count-rate data from each instrument were normalized to the 2002 quiet-time rates (i.e., count rate with only GCR present). Using these constants for the entire period of data collection allows us to observe the modulation of the GCR as well as interesting variations during SPE. For the time period from March 2002 to October 2003, all three instruments can be compared, and it is invariably the case that the response of the MARIE A1 counter (sensitive to protons above 20 MeV) is the most sensitive, with MARIE A2 (protons above 30 MeV) being second-most sensitive. In most cases in this time period, the HEND count rates track well with the MARIE A2 rates. And in almost all cases, the GRS response is the least sensitive. Since the GRS response to incident protons is binary (count or no count, depending on the energy deposited), the most likely explanation is that it has a higher effective energy threshold for detecting protons, probably 35-40 MeV, though this is not completely understood. In a few instances, the normalized GRS count rates during SPEs exceed those of HEND. This is likely related to the complexity of the HEND response to the charged particle environment, since it dominantly detects secondary neutrons produced in the spacecraft (as well as those produced in the Martian atmosphere and on the Martian surface).
The results, some of which are shown in figure 1 below, indicate that the GCR flux as measured by the GRS has increased slightly compared to 2002, whereas the flux measured by HEND is more difficult to charcterize - it rose throughout 2004 and the first half of 2005, then fell, then rose again in late 2005. This behavior is not understood at present but may be related to spectral changes in the GCR flux. Though absolute normalization remains elusive, the count rate data may nonetheless be re-plotted in terms of dose and dose equivalent by making a few assumptions.

Figure 1. Relative count rates in the GRS Upper-Level Discriminator (ULD), shown in red, and in the HEND Scintillation Block (SB), shown in green.

First, in the absence of spectral changes, it is reasonable to assume that the GCR dose rate is simple proportional to the count rate. Second, one can estimate dose equivalent inclusive of SPEs by assuming that an average quality factor of 5.3 (determined using the Badhwar-O'Neill model) applies to GCR counts and a quality factor of 1.0 applies to SPE counts. Results for 2005 are shown in Figure 2 below.

Figure 2. Relative dose equivalent seen by the two detectors. A value of 5.3 corresponds to GCR only at the quiet-time levels of 2002, near solar maximum. Values above 5.3 are due to increased GCR flux and solar events.

Estimation of organ doses from solar particle events for future space exploration missions

Myung-Hee Y. Kim1, F.A. Cucinotta2
1. Wyle Laboratories, Houston, TX 77058, USA
2. NASA Johnson Space Center, Houston, TX 77058, USA
Radiation protection practices define the effective dose as a weighted sum of equivalent dose over major organ sites for radiation cancer risks. Since a crew personnel dosimeter does not make direct measurement of the effective dose, it has been estimated with skin-dose measurements and radiation transport codes for ISS and STS missions. If sufficient protection is not provided near solar maximum, the radiation risk can be significant due to exposure to sporadic solar particle events (SPEs) as well as to the continuous galactic cosmic radiation (GCR) on future exploratory-class and long-duration missions. For accurate estimates of overall fatal cancer risks from SPEs, the specific doses at various blood forming organs (BFOs) were considered, because proton fluences and doses vary considerably across marrow regions. Previous estimates of BFO doses from SPEs have used an average body-shielding distribution for the bone marrow based on the computerized anatomical man model (CAM). With the development of an 82-point body-shielding distribution at BFOs, the mean and variance of SPE doses in the major active marrow regions (head and neck, chest, abdomen, pelvis and thighs) will be presented. Consideration of the detailed distribution of bone marrow sites is one of many requirements to improve the estimation of effective doses for radiation cancer risks.

Calibration results of Liulin-5 charged particle telescope obtained in ICCHIBAN-7 experiment. New instrumentation for radiation monitoring on interplanetary missions

J. Semkova1, R. Koleva1, St. Maltchev1, G. Todorova1, Ts. Dachev1, V. Benghin2, V. Shurshakov2, V. Petrov2
1. Solar-Terrestrial Influences Laboratory, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 3, 1113, Sofia, Bulgaria
2. State Scientific Center of Russian Federation Institute of Biomedical Problems, Russian Academy of Sciences, 76a, Khoroshevskoye sh., 123007, Moscow, Russia, jepero@stil.acad.bg, Fax +35928700178
Described is the current status of particle telescope Liulin-5 developed for investigation of the radiation environment dynamics within the Russian sphere tissue-equivalent phantom on ISS. Liulin-5 experiment will be a part of the international project MATROSHKA-R on ISS. Presented are the preliminary calibration results of Liulin-5 exposure to heavy ions, obtained in ICHIBAN project. Liulin-5 is planned to be flown on the ISS in 2006 year.
Adaptations of the Liulin-5 techniques will be used for investigation of the radiation hazards during future Phobos-Grunt space mission. The proposed instrumentation will qualitatively and quantitatively characterize, in terms of dose rate and linear energy transfer (LET) spectrum, the radiation environment in interplanetary and near-Mars space. Data obtained will be used for the evaluation of radiation environment and radiation shielding requirements on future manned Mars mission. Furthermore these measurements will allow to verify and to improve methods for radiation detection and dosimetry during long-duration space flight as well as calculation models for particles transport and dose assessment. Described are experimental requirements and preliminary technical specifications of the new instrumentation.

Electronic personal neutron dosemeters for high energies: calculation of pulse height spectra using the PHITS code

M. Luszik-Bhadra1, M. Nakhostin2
1. Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany
2. Cyclotron and Radioisotope Center, Tohoku University, Sendai, Japan
Deposited energies in the silicon diodes used within the electronic neutron personal dosemeter prototypes DOS-2002 (40 m effective layer) and the DOS-2005 (6 m effective layer) have been determined using the PHITS code. This code is an Monte Carlo code which allows transport of all charged particles, neutrons, photons and electrons. First results are shown for normal incident neutrons and protons with energies up to 100 MeV. The calculated pulse height spectra are compared to measured ones in the neutron energy region from 144 keV up to 14.8 MeV. Implications of the results for the set-up of an electronic personal dosemeter suitable to use for astronauts is discussed.

A New Space Radiation Dosimeter Based on the Medipix Technology

L. Pinsky
University of Houston, Houston, Texas, USA
The CERN-based Medipix-2 Consortium, which was formed by 15 member groups from labs around Europe, has developed a pixel format electronics read-out integrated circuit where the circuitry needed by each individual pixel is embedded within the 55 micron square pixel footprint. This potentially allows for the gapless tiling of the detectors. Originally intended for medical imaging applications, this technology has reached a mature and robust status with the parallel development of a USB-2 interface, and when coupled with overlying charge capturing detector materials it has the clear potential for development into a portable active space radiation dosimeter. Data have been taken with a range of charged particle sources including exposure to heavy ion beams across the full range of LETs. Substantial work has also already been done within the Medipix Collaboration on detecting neutrons, and some recent developments offer the promise of significant improvements in the ability to do neutron spectroscopy over the range of incident neutron energies that are most likely to be of interest in the space radiation environment. Plans are being evolved to join the Medipix Collaboration in order to develop specific versions of the device that are suited for a space radiation dosimeter. The immediate goal is to deploy a prototype version within the next several years on a Shuttle flight or on the ISS. The current status of the evaluations of the device's performance as well as a synopsis of the plans for future developments will be presented.

Space Dosimetry with Tritel 3D Silicon Detector Telescope

A. Hirn1, T.� Pázmándi1, S. Deme1, I. Apáthy1, A. Csöke1, L. Bodnár2
1. Hungarian Academy of Sciences KFKI Atomic Energy Research Institute, H-1525 Budapest, P.O. Box 49, Hungary, hirn@sunserv.kfki.hu
2. BL-Electronics, H-2083 Solym�, Sport 5, Hungary
The objectives of this project are to develop and manufacture a three-axis silicon detector telescope, called Tritel, and to develop software for data evaluation of the measured energy deposition spectra. The 3D silicon telescope should be the first device of its kind used for measuring the dose astronauts are subjected to and to characterize the radiation field in terms of dose equivalent.
Research and development began in the KFKI Atomic Energy Research Institute several years ago. The geometric parameters of the three axis silicon LET telescope were defined, results of previous measurements were used as a benchmark. Features of various types and sizes of telescopes were analyzed. The electronic block diagram of the system, the planning of the electrical subsystems and the construction of the first model of the analog signal processing chain has been finished. The elements of the Tritel device together with the mechanical and electrical requirements and with the possibilities of data handling and data evaluation were analyzed. The construction of the telescope prototype and of the first model of the analog signal processing chain has been finished. Further optimization of the parameters and the calibration of the system are under way. Design, manufacturing and testing of the analog and digital circuits, the manufacturing of the housing of the detector unit and development and testing of the onboard and the on-ground software are still in progress.
Several flight opportunities have already come in sight:
The Russian space research (the Institute of Biomedical Problems (IBMP) in Moscow, the Russian Space Agency (RSA) and the Energia Corporation) has undertaken to launch and install Tritel on the Russian platform of the International Space Station (ISS) in the near future. In cooperation with IBMP Tritel is planned to be placed later onboard a Mars probe, too.
Within ESA's SURE (International Space Station: a Unique REsearch Infrastructure) project, funded by the European Commission under the 6th Framework Programme, we intend to carry out measurements with a complex system of a Tritel and passive detector stacks onboard the European module of the ISS. SURE is still in proposal evaluation and selection phase.
Within the framework of the Student Space Exploration and Technology Initiative (SSETI) created by the ESA Education Department in order to actively involve European students in real space missions, a more compact version of Tritel (Tritel-S) will be operated onboard the European Student Earth Orbiter (ESEO) in Geostationary Transfer Orbit. The device may be a precursor of a subsequent version of Tritel planned for a future Mars probe, too.

Microdosimetric GEANT4 and FLUKA Monte-Carlo Simulations and Measurements of Heavy Ion Irradiation of Silicon and Tissue

P. Beck1, M. Wind1, 2, S. Rollet1, M. Latocha1, 3, F.Bock1, 2, H. Böck2, Y. Uchihori4
1. ARC Seibersdorf research, Health Physics Division, 2444 Seibersdorf, Austria
2. Vienna University of Technology, Atomic Institute, 1020 Vienna, Austria
3. Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Kraków, Poland
4. National Institute of Radiological Sciences, (NIRS), Inage, Chiba, JAPAN

Last update: 8 January 2007