Radiation environment

investigation results obtained

with Liulin-5 experiment in the

human phantom of Matroshka-R

project aboard the International

Space Station

SES 2010, Sofia,

2 - 4 November, 2010

J. Semkovaa, R. Kolevaa, St. Maltcheva, N.

Bankov, V. Benghinb, I. Chernykhb, V.

Shurshakovb, V. Petrovb, S. Drobyshevb

a) Space and Solar-Terrestrial Research Institute ,

Bulgarian Academy of Sciences ,

jsemkova@stil.bas.bg

b) Institute of Biomedical Problems, Russian Academy of Sciences

LIULIN – 5 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 [Semkova, et al.] .

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

We present some results of analysis of the data obtained in 2007- 2009-minimum of 23 Solar Cycle.

Spherical phantom

(MATROSHKA-R)

(Russia & CoI)

Torso phantom

(MATROSHKA)

(ESA & Co-I)

Phantoms on ISS

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. Aim of the experiment – to measure the the time resolved depth distribution of the cosmic radiation doses in the phantom.

Block - diagram of Liulin - 5 connections in the phantom

D2D3

28V

Passive detectors

Detector module of Liulin-5

Stand

D1Electronics of

Liulin - 5

Lay-out of detectors and electronics in the detector module

D1 and D2 operate in coincidence mode to obtain LET. FOV is 81.4 degrees;

Distances: D1-D2=20 mm, D1-D3 = 125 mm, D2-D3 = 105 mm. Detector’s thickness 370 µm. Detector’s diameter 17.2 mm.

Geometry factor for a single detector – 14.6 cm2.sr.

Geometry factor for the D1-D2 telescope coincidence events number is 2.01 cm2.sr .

Positions of D1 and D2 correspond to the depth of BFO.

D3 D1D2

Handle

Electronics

Cable

3450

50

70175

191

Front area of the detectors

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=DxQave.

Основни величини1. Погълната доза D.2. ЛПЕ (LET). L= dE/dl. 3. Качествен фактор Q(L) се прилага за погълнатата доза

в точка, т.е. той служи като тегловен фактор, който зависи само от ЛПЕ в тази точка. Qave = ∫Q(L)D(L)dL/D.

4. Dose equivalent (Дозов еквивалент); H=DxQave.

Parameters provided

Absorbed dose rate in the range 0.4 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(H2O) spectra in the range 0.65 –90 keV/µm.

All events, exceeding the upper energy deposition and/or LET limit, are recorded in the last spectral channel of the respective spectrum.

Measurement modesMeasurement modes

Two measurement modesTwo measurement modes are pre - programmed: are pre - programmed:

Standard -Standard - dose and flux ratesdose and flux rates have a have a time time resolution of 90sresolution of 90s, the , the cycle ofcycle of measurement ofmeasurement of energy deposition spectra and LET spectra is 85 energy deposition spectra and LET spectra is 85 minutesminutes, but may be interrupted by switching to , but may be interrupted by switching to fast modefast mode. .

Fast - dose and flux rates have a time resolution Fast - dose and flux rates have a time resolution of 20 s, of 20 s, the the cycle of energy deposition and LET cycle of energy deposition and LET spectra measurement is 15 min. This mode is spectra measurement is 15 min. This mode is used for measurements in the SAA or during SPE.used for measurements in the SAA or during SPE. Switching from standard to fast mode is made Switching from standard to fast mode is made automatically. automatically.

Phantom

Detector ModuleElectronic Block

Liulin-5 in the spherical phantom

External view of Liulin-5

Two units: a detector

module and an electronic

block.

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

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 and dose rates at 40, 60 and 165

mm depth in the radial channel

5-10 September 2007

Differential fluxes of the energy deposition spectra in 3 detectors;

Dose rate in every detector and dose rates in the equal for all detectors energy deposition range 0.45-10 MeV (0.65 < LET <14 keV/µm).

Absorbed dose depth distributionAbsorbed dose depth distribution 5-10 September 2007

Absorbed doses from particles of 0.65 < LET <14 keV/µm measured at 40, 60 and 165 mm depth .

The total dose at the centre of the phantom is 1.7 times less than at BFO depth. In SAA this decreasing is 2.3.

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

40

80

120

160

200

240

Do

se [

uG

y/d

ay]

Total dose

SAA dose

GCR dose

Comparison with passive LiF TLD Comparison with passive LiF TLD detectors in the spherical phantomdetectors in the spherical phantom

The typical depth-dose curve from TLDs shows decreasing of 5-10% between the values obtained at 40 and 60 mm and decreasing by a factor 1.5-1.6 between the doses measured at 40 mm and 165 mm from the phantom’s surface [Shurshakov, et al., 2008]. .

Good agreement with Good agreement with Liulin-5 data.Liulin-5 data.

Distribution of dose rate in D1 in Distribution of dose rate in D1 in geographic and L-B coordinatesgeographic and L-B coordinates

( (55 February February - 8 April 2008 - 8 April 2008))

DDose rates distribution at 40 mm depth: D1 565 µGy/h. Time resolution 20s in SAA, 90s outside it.

Dependence of flux and dose rate onDependence of flux and dose rate on ISS altitudeISS altitude

At 317-328 km altitude the biggest flux and dose rate at the depth of blood-forming organs of human body are from GCR at high geographic latitudes. The inner radiation belt protons do not penetrate at these depths.

Absorbed dose in the range 0.65 Absorbed dose in the range 0.65 LET LET 90 keV/µm, measured by D1 90 keV/µm, measured by D1

DateDate SAASAA

[µGy/day][µGy/day]

GCRGCR

[µGy/day][µGy/day]

TotalTotal

[µGy/day][µGy/day]

3-10.07. 073-10.07. 07 91.891.8 122.9122.9 214.7214.7

5-10.09. 075-10.09. 07 101.4101.4 128128 229.4229.4

3-13.05.083-13.05.08 67.867.8 123.8123.8 191.6191.6

24.10-01.11.0824.10-01.11.08 84.884.8 130.1130.1 214.9214.9

Absorbed doses at depths of BFO are 35-45% from SAA and 55-65% from GCR .

Сопоставление мощности дозы Сопоставление мощности дозы Люлин-5 и ДБ-8Люлин-5 и ДБ-8

0

1

10

100

1000

07.02.0812:00

07.02.0812:28

07.02.0812:57

07.02.0813:26

07.02.0813:55

07.02.0814:24

07.02.0814:52

07.02.0815:21

07.02.0815:50

07.02.0816:19

07.02.0816:48

Do

se r

ate,

mkG

y/h

P_Liulin, D1

P DB-8 No 1

P DB-8 No 1 10 min

Dependence of dose and flux rates in Dependence of dose and flux rates in SAA on Liulin-5 axis orientationSAA on Liulin-5 axis orientation

In SAA on ascending nodes the Lulin-5 telescope axis (direction with minimum shielding) was oriented to west- towards the maximum proton flux in SAA –maximal dose rates measured;

On descending nodes the Lulin-5 telescope axis was oriented to north- towards the minimum of proton flux in SAA –minimal dose rates measured;

25.10.08 восходящий виток03:12:30

пото

к пр

отон

ов,

см-2s-1

МeV

-1sr

-1

тол

щи

на з

ащи

ты,

гсм

2

Лю

ли

н-5

де

т. №

1

мощность дозы Люлин-5LIULIN-5 det. #1

0,0

20,0

40,0

60,0

80,0

100,0

120,0

140,0

160,0

180,0

200,0

01:41:30 01:43:30 01:45:30 01:47:30 01:49:30 01:51:30

nGy/sec

LIULIN-5 det. #1

30.10.08 нисходящий виток17:00:30

пото

к пр

отон

ов,

см-2

s-1М

eV-1

sr-1

тол

щи

на з

ащи

ты,

g/см

2

Лю

ли

н-5

де

т. №

1

мощность дозы Люлин-5LIULIN-5 det. #1

0,0

20,0

40,0

60,0

80,0

100,0

120,0

140,0

160,0

180,0

200,0

17:36:30 17:38:30 17:40:30 17:42:30 17:44:30 17:46:30 17:48:30 17:50:30

nGy/sec

LIULIN-5 det. #1

LET spectra

Total LET spectrum for 5-10.09.2007

Total LET spectrum for 3-13.05.2008

On the left –LET spectrum in SAA, on right- LET spectrum of GCR.Upper -data for 05-10.09.2007middle -data 03-13.05.2008Bottom –ISS orbits

Q defined by LET spectrumQ defined by LET spectrum

DateDate SAASAA GCRGCR TotalTotalQavQav

0.65 0.65 LET LET 90 90 keV/µm

QavQav

0.65LET 88.1

keV/µm

QavQav

0.65 0.65 LET LET 90 90 keV/µm

QavQav

0.65LET 88.1 keV/µm

QavQav

0.65 0.65 LET LET 90 90 keV/µm

QavQav

0.65LET 88.1 keV/µm

3-10.07. 073-10.07. 07 1.31.3 1.221.22 4.74.766 2.752.75 3.23.2 2.032.03

5-10.09. 075-10.09. 07 1.231.23 1.151.15 4.314.31 2.422.42 2.682.68 1.771.77

3-13.05.083-13.05.08 1.431.43 1.351.35 5.185.18 3.173.17 44 2.542.54

24.10-1.11.0824.10-1.11.08

23-28.02. 0923-28.02. 09

1.31.3

1.331.33

1.191.19

1.331.33

4.144.14

4.894.89

2.592.59

2.92.9

2.832.83

4.234.23

1.91.9

2.592.59

Events in the last spectral channel LET 90 keV/µm are between 0.08-0.17% of all events in the LET spectrum, but they contribute significantly to Qave.

Dose rate of radiation with low and high LET, Dose rate of radiation with low and high LET, measured in D1-D2 telescope for the periodmeasured in D1-D2 telescope for the period

66 February February - 8- 8 April April 2008.2008.

The radiation with low LET presents about 85% of total absorbed dose at the depth of blood forming organs of human body, but its contribution to the dose equivalent is only about 20%. The main part of the dose equivalent (80%) is from high LET particles. For the period 5-10 September 2007 the dose equivalent from particles of LET>10 keV/m comprises 66% of total dose equivalent at the depth of blood forming organs.

LET range Absorbed dose

[Gy/h]

Qav Dose equivalent [Sv/h]

LET <10 keV/m 6.50 1.0 6.50 90keV/m LET

>10 keV/m 1.86 15.19 28.28

90keV/m LET > 0.65 keV/m

8.36 4.15 34.78

Comparison between Liulin-5 and Comparison between Liulin-5 and NASA TEPC data NASA TEPC data at the minimum of at the minimum of

solar cyclesolar cycle The measurements in The measurements in June 2007 - September 2008June 2007 - September 2008

with the NASA TEPC in the US and ESA modules of ISS with the NASA TEPC in the US and ESA modules of ISS [Semones, 2008][Semones, 2008] show that show that about 70% of dose equivalent about 70% of dose equivalent in ISS is from GCR. in ISS is from GCR.

The Liulin-5 results show thatThe Liulin-5 results show that at the minimum of at the minimum of the 23rd solar cycle, the contribution of GCR to the dose the 23rd solar cycle, the contribution of GCR to the dose equivalent inside human body is equivalent inside human body is 75%. 75%.

Both measurements indicate thatBoth measurements indicate that at least 65% of GCR at least 65% of GCR and trapped radiation contribution is from particles with and trapped radiation contribution is from particles with LET > 10 keV/µm.LET > 10 keV/µm.

CONCLUSION (1)

Data obtained in July, 2007 - 2009 show that the dose rates and fluxes measured in the inner radiation belt in SAA are the most intensive and strongly depend on the shielding and attitude of detectors in the phantom. .

The The trapped radiation contributes trapped radiation contributes 3535--4545% and GCR% and GCR contribute 5contribute 555-6-655% to the total absorbed doses at the % to the total absorbed doses at the depths of blood forming organsdepths of blood forming organs of human body. of human body.

The total absorbed dose at the centre of the phantom is at least 1.6 lower than at the depth of blood forming organs and the decreasing of the doses in the radial depth is due to self-shielding of the phantom against trapped protons.

CONCLUSION (2)

At the minimum of the 23rd solar cycle the dose equivalent of GCR and their secondary particles represents 75% of total dose equivalent at the depths of BFO and 65% of the total dose equivalent is from particles with LET > 10 keV/µm.

This shows the importance of measurements of high LET particles and LET spectrum on ISS. Such measurements with active radiation detectors should be planned for the upcoming flights to Mars and Moon to obtain data for radiation doses to future interplanetary missions crew.

Good agreement with the results of other radiation detectors on ISS.

REFERENCESREFERENCES

Semkova J. et al. Adv. Space Res., 45, 2010, No 7, 858-865.

Semones E. Thirteenth WRMISS Workshop, Krakow, Poland, http://wrmiss.org/workshops/thirteenth/Semones_TEPC.pdf, 8-10 September 2008

Shurshakov V. et al. Proceedings of International Conference “Fundamental Space Research”, Sunny Beach, Bulgaria, September 21-28, 2008, 234-238, ISBN 978-954-322-316-9, http://www.stil.bas.bg/FSR/.

ACKNOWLEDGEMENTS Agreement between RAS and BAS on space

research and grant DID-02/8 from the Bulgarian

Science Fund.

NIRS - Japan.

Thanks RKK “Energia” and cosmonauts O.

Kotov, Y. Malenchenko, O. Kononenko and Y.

Lonchakov for the operation of Liulin - 5 aboard

ISS.

Thank you for attention!