New results of radiation

environment investigation by

Liulin-5 experiment in the human

phantom aboard the International

Space Station

Semkova J.1, Koleva R. 1, Maltchev S. 1, Benghin V.

2, Chernykh I. 2, Shurshakov V. 2, Petrov V. 2,

Bankov N. 3, Goranova M. 4

1) Solar-Terrestrial Influences Institute, Bulgarian Academy of Sciences , jsemkova@stil.bas.bg

2) Institute of Biomedical Problems, Russian Academy of Sciences

3) Space Research Institute, Bulgarian Academy of Sciences

4) Technical University, Bulgaria

OUTLINEOUTLINE

Introduction

Liulin - 5 instrument of

MATROSHKA-R experiment

Some resultsSome results

ConclusionsConclusions

Future worksFuture works

INTRODUCTION Experiment Liulin-5 for investigation of the radiation environment dynamics within the spherical tissue-equivalent phantom on ISS started in June 2007 on RS of ISS. Since then it runs on ISS.

Liulin-5 experiment is a part of the international project MATROSHKA-R.

We present some results of analysis of the data obtained during July 2007- March 2009 at the minimum of solar activity cycle and quiet solar and geomagnetic conditions.

Spherical Tissue – Equivalent Spherical Tissue – Equivalent PhantomPhantom

Size: 370x370x390 mm; mass: 32kg;

Radiation detectors –number of passive detectors and Liulin-5 charged paricle telescope.

Liulin-5 detector module is placed in a radial channel.

Liulin-5 Liulin-5 experiment experiment objectivesobjectives

Main objective - to study the depth-doseMain objective - to study the depth-dose distribution of the different components distribution of the different components of the orbitalof the orbital radiation fieldradiation field in a human in a human phantom. phantom.

AdditionalAdditional objectives are mapping of the objectives are mapping of the radiation environment in radiation environment in the phantom the phantom and its variationand its variationss with time with time and orbital and orbital parameters (such as solar cycle, solar parameters (such as solar cycle, solar flare eventflare eventss, inclination and altitude), inclination and altitude)..

Block - diagram of Liulin - 5 connections in the phantom

D2D3

28V

Passive detectors

Detector module of Liulin-5

Stand

D1Electronics of

Liulin - 5

LIULIN – 5 EXPERIMENT

Goals

Liulin-5 measures simultaneously at 3 different

depths of the radial channel of the spherical

phantom:

Energy Deposition Spectra, Dose Rate & Particle

flux - then Absorbed Dose D;

Measurement of the Linear Energy Transfer (LET)

spectra in silicon – then assessment of

LET(H2O), Q=f(LET), given in ICRP-60 and Dose

Equivalent H; H=DxQ.

Phantom

Detector ModuleElectronic Block

Liulin-5 in the spherical phantom

External view of Liulin-5

Two units: a detector

module and an electronic

block.

Parameters provided

Absorbed dose rate in the range 0.04 x10-6 Gy/h - 0.04 Gy/h;

Particle flux in the range 0 - 4x102 particle/(cm2.sec);

Energy deposition spectra in 512 spectral channels:

In 1-st and 2-nd detectors in the range 0.45 – 63 MeV;

in 3-rd detector in the range 0.2 –10 MeV;

LET (Si) spectra LET(H2O) spectra in the range 0.65 –

90 keV/µm.

All events exceeding the upper spectral limits are recorded in the 512 channel.

LIULIN-5 in the Phantom in Piers-1 module of ISS –activated 28 June 2007.

LIulin -5 in the Spherical PhantomSpherical Phantom on ISS

Detector module

Position of Piers module at the ISSPosition of Piers module at the ISS

Piers

Phantom in PIERS module

RESULTSRESULTS

Absorbed energy spectra, LET spectra.Absorbed energy spectra, LET spectra.

Dose distribution in the radial channel of the phantom.

Dosemetric quantities from the different components of the radiation environment in ISS.

Energy deposition spectra, dose rates, LET spectrum,

and quality factor estimationData for 03.07.2007-09.07.2009

3 upper panels – energy deposition spectra and absorbed dose rates in 3 detectors; Dose rates in the equal for all detectors range 0.65 LET 14 keV/um : D1av=8.2 uGy/h, D2av=7.9 uGy/h, D3av=4.5 uGy/h;

4-th panel - LET spectrum 0.65 keV/um and Q; DLET =13 uGy/h. The value Qav=3.2 is obtained when all events, exceeding the upper LET measurement limit (0.11%) are considered as events with LET 90 keV/µm (corresponding to maximum Q).

Absorbed dose depth distributionAbsorbed dose depth distribution

Averaged daily doses for 03.07-10.07.2007 measured at 40, 60 and 165 mm depth .

Fast mode- mainly SAA protons. Dose at 165 mm decreased by 2.7.

Standard mode – mainly GCR . Decreasing by 1.4

Total. The total absorbed dose at 165 mm depth in the phantom is 1.8 times less than that at 40 mm mainly due to self-shielding of the phantom against trapped radiation.

40 80 120 160 200Depth in the phantom [mm]

0

40

80

120

160

200

Do

se [

uG

y/d

ay]

Total dose

Fast Mode Dose

Standard Mode Dose

Comparison with measurements of Comparison with measurements of passive detectorspassive detectors

Typical depth-dose curve from TLDs along the diameter perpendicular to the space station wall -decreasing by 1.5-

1.6 between the doses measured at 40 mm and 165 mm from the phantom’s surface.

Distribution of dose rate in geographicDistribution of dose rate in geographic coordinates (coordinates (0606.02 -08.04.2008).02 -08.04.2008)

DDose rates distribution at 40 and 165 mm depth: D1 565 µGy/h, D3 188 µGy/h. Data from D1 is for 0.65LET90keV/µm, from D3

– for 0.3LET14keV/µm.

LET spectra (06LET spectra (06.02 -08.04.2008).02 -08.04.2008)

LET measurements in the range 0.65-90 keV/µm.

0.16% of all events of the total LET spectrum are in 512 channel - exceed the upper LET limit.

Absorbed dose rate [µGy/h]: SAA = 71.4 , GCR= 6.0 , Total =8.4

Radiation quantities obtained at 40 cm Radiation quantities obtained at 40 cm

distance from the phantom’s surface distance from the phantom’s surface

calculated from LET spectra, events in the last calculated from LET spectra, events in the last

LET channel ignoredLET channel ignored

0.650.65LET<LET< 90 keV/ 90 keV/µµmm

(06.02-08.04.2008) (06.02-08.04.2008)

Quantity Qav Daily absorbed dose [µGy/day]

Daily Dose equivalent [µSv/day]

Value 2.6 195 507

Radiation quantities from the different Radiation quantities from the different components of the radiation field at 40 cm components of the radiation field at 40 cm

distance from the phantom’s surface (06.02-distance from the phantom’s surface (06.02-08.04.2008, calculated from LET spectra,08.04.2008, calculated from LET spectra,

0.650.65LETLET 90 keV/ 90 keV/µµmmQuantity SAA protons GCR Trapped plus GCR plus

secondary radiation

Daily absorbed dose [µGy/day]

67

142 209

Qav* 1.5 5.4 4.15 Daily Dose equivalent [µSv/day]

100.5 767 867.5

Considering the events in the last spectral channel as events of 90 keV/µm, Qav increases significantly and the dose equivalent of the LET spectrum at 40 cm depth at the phantom increases with about

40%, compared to that with LET<90 keV/m. Dose equivalent in SAA only ~12% of total dose equivalent, dose equivalent from GCR- ~88%.

Strong dependence of dose rates and Strong dependence of dose rates and particle fluxes in SAA of the shielding particle fluxes in SAA of the shielding

andand ISS attitude ISS attitude

0 10000 20000 30000 40000Measurement N

0

10

20

30

40

Par

ticl

e F

lux

[par

t/cm

*2*s

]

D1 D2 D3

Flux and dose rates in D1 and D2 measured for 0.65LET90keV/µm, in D3 - 0.3LET14keV/µm. Data for:

1. 07.03-08.04.2008. -08.04.2008. Fluxes in D1&D2 bigger Fluxes in D1&D2 bigger than in D3. (07-12.03. and after 26.03). than in D3. (07-12.03. and after 26.03). During During 12-26.03 fluxes in SAA decreased 12-26.03 fluxes in SAA decreased more than 2 times due to ISS attitude more than 2 times due to ISS attitude changing and docking of the SHUTLLE changing and docking of the SHUTLLE ((STS-123).STS-123). Fluxes in D3 bigger than in D2 luxes in D3 bigger than in D2 and D3. and D3.

2. 24.01-09.03.2009. Docking of the 2. 24.01-09.03.2009. Docking of the Progress-M66 cargo vehicle on 11.02. Dose Progress-M66 cargo vehicle on 11.02. Dose rates in D2 decreased twice during 17-28.02.rates in D2 decreased twice during 17-28.02.

1

4000 8000 12000 16000 20000Measurement N

0

200

400

600

800

1000

Do

se r

ate

[uG

y/h

] D2

data for 24.01.2009-09.03.2009, D>20uGy/h,

docking

Progress M-66 docking 11.02.09

Progress M -66 2

The daily doses of 2 external detectors The daily doses of 2 external detectors decreased by factor of 1.3 during the docking decreased by factor of 1.3 during the docking of STS-122 and 119. The heavy shielded 3th of STS-122 and 119. The heavy shielded 3th

detector response is very smalldetector response is very small

STS-122 docked

D1

D2

D3

STS - 123 docked

Comparison of the dose rates in SAA from Comparison of the dose rates in SAA from different instruments on ISS close to STS-123different instruments on ISS close to STS-123

dockingdocking•TEPC (NASA-TEPC (NASA-JSFC) – in US JSFC) – in US Lab. ModuleLab. Module

•D3DE (STIL-D3DE (STIL-BAS)-outside BAS)-outside ESA Columbus ESA Columbus ModuleModule

•Liulin-5 (STIL-Liulin-5 (STIL-BAS)– in PIERS BAS)– in PIERS of Russian of Russian Service ModuleService Module

Thanks Dr. E. Semones for the TEPC and Prof. Dachev for R3DE dataThanks Dr. E. Semones for the TEPC and Prof. Dachev for R3DE data

CONCLUSIONS (1)

Data obtained in July, 2007- March, 2009 show that the dose rates and fluxes measured in SAA are the most intensive and strongly depend on the shielding of detectors in the phantom and ISS orbital ISS orbital parameters. parameters.

During July 2007-April 2008 in SAA the absorbed doses at the center of the phantom are 2.5 - 3 times lower than at 40-60 mm distance from the surface. The total absorbed dose from all space radiation sources at 165 mm depth in the phantom is 1.6-2 times less than that at 40 mm.

CONCLUSIONS (2)

The results are indicative for the GCR heavy charged particles and SAA protons contribution to the average quality factor and dose equivalent in the phantom.

At the minimum of the solar cycle the dose equivalent from GCR is more than 80% of total dose equivalent at the depth of the blood-forming organs. The rest dose equivalent is due to the trapped radiation.

The results of radiation investigations with phantoms in space to be taken into account in planning of future exploratory manned missions.

FUTURE WORKS (1)

Additional analysis for estimating the Additional analysis for estimating the contribution of the radiation with LET (H2O) < contribution of the radiation with LET (H2O) < 0.65 keV/0.65 keV/m and with LET (H2O) m and with LET (H2O) 90 keV/ 90 keV/m to m to the LET spectra and radiation quantities of the the LET spectra and radiation quantities of the GCR and trapped particles, including GCR and trapped particles, including comparisons with models of the radiation comparisons with models of the radiation environment, shielding conditions for Liulin-5 environment, shielding conditions for Liulin-5 detectors and with data from other dosemeters detectors and with data from other dosemeters of MATROSHKA-R experiment.of MATROSHKA-R experiment.

The Liulin-5 experiment continues on ISS.

FUTURE WORKS (2)

A new experiment for radiation research with a new charged particle telescope Liulin-F will be flown onboard the Phobos-Soil space mission (Launch expected October 2009). Measurement parameters similar to Liulin-5 .

Measurements of radiation conditions during the cruise phase, on Mars’s orbit and on the surface of Phobos are planned. Objectives:

Radiation doses received by the components of spacecraft.

Verification the radiation environment models and assessment of radiation risk to the crewmembers of future exploratory flights.

ACKNOWLEDGEMENTS

Agreement between RAS and BAS on space

research and grant HZ-1505/2005 from the

Bulgarian Ministry of Education and Science.

Thanks the cosmonauts O. Kotov, Y.

Malenchenko, O. Kononenko and Y. Lonchakov for

the operation of Liulin - 5 aboard ISS.

Thank you for attention!