Transcript No Slide Title

SPACE RADIATION DOSIMETRY
S. Deme, KFKI AEKI, Hungary
3rd ISOE EUROPEAN WORKSHOP
Portoroz, Slovenia 17-19 April 2002
Space radiation
• Galactic 98% ions
87% protons
12% alpha p.
1% heavier (Fe)
2% electrons
• Solar ~ protons
(minimum - maximum activity, flares)
• Secondary neutrons (up to 200 MeV)
- albedo
- interactions with spacecraft materials
Magnetosphere of the Earth and its
influence on solar radiation
Magnetic field of the Earth
LEO space radiation
Magnetic shield
Pole
Equator
Dose rate
Pole
Dose rate [mSv/year]
Annual dose – aeroplanes (average)
10
8
6
4
2
0
0
2
4
6
8
10
Height [km]
12
14
16
LEO space radiation
Galactic (constant) + solar (time dependent) particle radiation
Van Allen belt (inner)
Westward - protons <600 MeV
SAA (South - 30°)
Eastward - electrons <7 MeV
Dose rate [mSv/year]
Annual dose – orbital stations (average)
800
Space Shuttle
600
400
200
0
350
Space stations
400
450
Height [km]
500
charged particles
secondary
neutrons
Irradiation geometry
Personal dosimetry
• Area dosimeters + calculations
- proportional counters (LET spectra)
- silicon telescopes (LET spectra)
- Bonner spheres (depth dose, neutrons)
- phantom measurements
• Personal dosimeters
- TLDs (ground/on-board readout)
- PNTDs
- Bubble detectors
- silicon dosimeters
Ground
exposure
T0
T0+
T>T0
dose
rate 
T1
Shielding
thickness
Dislocation of dosimeters, T2
Exposure
On-board
measurement
T3
Salyut-6, 1980
B. Farkas
Space Shuttle
1984
S. Ride
15
heavy shield
light shield
Altitude
10
400
300
200
5
100
0
0
0
50
100
150
Time [MET]
200
Altitude [km]
Dose rate [µGy/h]
TLD data vs. readout time
Mir
1996
T. Reiter
On board TLD reader, Mir version
TLD data (1 h readout period)
Dose [µGy]
90
80
70
60
50
40
30
20
10
0
5
3 Days
1
4
7
10
13
Hours
16
1
19
22
SAA dose vs. longitude
70
Gaussian fit
Dose [μGy]
60
measured data
50
EVA crossings
40
30
20
10
0
-100
-80
-60
-40
-20
Longitude [degrees]
0
20
International Space Station, 2001, J. Voss
Extravehicular activity (EVA)
Location of TLDs
during EVA
(NASA)
Location of
TLDs during
EVA (Russian)
EVA dose
Dose rate [µGy/h]
50
EVA
Bgr
40
30
EVA dose
282 µGy
20
Bgr. dose
84 µGy
10
0
0
2
4
6
Time [h]
8
10
12
Gradient of dose at the surface of
space station MIR
absorbed dose [Gy]
7
measurement
calculation
6
electrons
5
4
3
protons
2
1
0
0
1
2
depth [mm]
3
4
Effective dose [Sv]
Career limit vs. age at exposure
(10 y duration)
3
males
2
females
1
0
25
30
35
40
45
Age at exposure [years]
50
55
Space missions
Low Earth Orbit (LEO)
• Earth’s magnetosphere
• 90 days to 180 days
Interplanetary space
•
•
•
•
outside the Earth's magnetic field
Solar Particle Events (SPEs)
several years
countermeasures are necessary
Conclusions