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NMi, Van Swinden Laboratorium,
Eduard van Dijk
The primary air kerma standards for 60Co and 137Csin the Netherlands
10 May 2007 Eduard van Dijk
10 May 2007 Eduard van Dijk 2
Content
• Kwall determination by extrapolation measurements• Kwall determination by Monte Carlo calculation• Results NMi 60C0• Results NMi 137Cs (preliminary)
The primary air kerma standards for 60Co and 137Csin the Netherlands
10 May 2007 Eduard van Dijk 3
Kair(p) : Kerma to air = E / mair (J/kg) at point p
The primary air kerma standard
Photon beam
P
air
100 cm
60Co
10 May 2007 Eduard van Dijk 4
Kair(p) : Kerma to air = E / mair (J/kg) at point p
The primary air kerma standard
Carbon spherePhoton beam
P
air
R
100 cm
10 May 2007 Eduard van Dijk 5
The primary air kerma standard
Photon beam Carbon sphere
P
air
Kair(p) : Kerma to air = E / mair (J/kg) at point p
10 May 2007 Eduard van Dijk 6
air
Carbon sphere
The primary air kerma standard
Photon beam
Air volume (i)P
( ) kcarbonattsckSene
WV
iKa i
C
air
air
Cair
Π+⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛ −
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛ −
=
−
...... ρρ
μρ
10 May 2007 Eduard van Dijk 7
air
Photon beam Carbon sphere
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 8
air
Photon beam Carbon sphere
1 2 3 4 5 6
mm carbon buildup
Ion.current
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 9
air
Photon beam Carbon sphere
1 2 3 4 5 6
mm carbon buildup
Ion.current
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 10
air
Photon beam Carbon sphere
1 2 3 4 5 6
mm carbon buildup
Ion.current
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 11
air
Photon beam Carbon sphere
1 2 3 4 5 6
mm carbon buildup
Ion.current
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 12
air
Photon beam Carbon sphere
1 2 3 4 5 6
mm carbon buildup
Ion.current
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 13
air
Photon beam Carbon sphere
1 2 3 4 5 6
mm carbon buildup
Ion.current
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 14
air
Photon beam Carbon sphere
1 2 3 4 5 6
mm carbon buildup
Kwall
Correction for attenuation and scatter
Ion. current
10 May 2007 Eduard van Dijk 15
air
1 2 3 4 5 6
mm carbon buildup
Kwall
Cep
Mean center of electron production
10 May 2007 Eduard van Dijk 16
air
1 2 3 4 5 6
mm carbon buildup
Kwall
Cep
Mean center of electron production
Kcep
Air volume (i)
10 May 2007 Eduard van Dijk 17
Central electrodeChamber wall 4mm
5cm3 air volume
( )EEE
kiii
ii
1,0,
0,sc +∑
∑=
Si
hvhv
hv’
hv’Ei,1
Stemholder
Graphite Air
Ei,0e-
e-Ei,0
MC PENELOPE simulation of attenuation and scatter
EeEkii
iis ii
0,
0,att ∑
∑ ⋅=
μ
Kwall = Katt . Ksc
5 cm3 spherical standard
10 May 2007 Eduard van Dijk 18
radiaal
Radial orientation calculated with: 3mm, 4mm, 5mm and 6mm wall thickness
MC calculation of attenuation and scatter
100 cm from source reference point
Photon beam
2.5 cm3 cylindrical standard
10 May 2007 Eduard van Dijk 19
axiaal
Axiaal orientation calculated with: 3mm, 4mm, 5mm and 6mm wall thickness
MC calculation of attenuation and scatter
100 cm from source reference point
Photon beam
2.5 cm3 cylindrical standard
10 May 2007 Eduard van Dijk 20
Oblique (45o)
Oblique orientation calculated with: 3mm, 4mm, 5mm and 6mm wall thickness
MC calculation of attenuation and scatter
100 cm from source reference point
Photon beam
2.5 cm3 cylindrical standard
10 May 2007 Eduard van Dijk 21
Gammatron3 60Co radiator head
60Co source holder
Set diaphragm
5 cm3 NMi standard
Beam sharpener
10 May 2007 Eduard van Dijk 22
Diaphragm and beamsharpener Gammatron3
10 May 2007 Eduard van Dijk 23
Rotating source drum
Beam sharpener
Diaphragm
60Co source
Light mirror
Uranium
Tungsten
Stainless steelLead
Beam limiter
MC simulation Gammatron3 radiation head
60Co beam
10 May 2007 Eduard van Dijk 24
Results 60Co measurements and calculations
2.5 cm3
3 mm4 mm5 mm6 mm
774.11772.64769.66767.07
Standard Orientation Wall thickness Kwall Imeasured (pA) K (Gy/h)
2.5 cm3
2.5 cm3
3 mm4 mm5 mm6 mm
5 cm3
Standard Orientation Wall thickness Kwall Imeasured (pA) K (Gy/h)
Standard Orientation Wall thickness Kwall Imeasured (pA) K (Gy/h)
Standard Orientation Wall thickness Kwall Imeasured (pA) K (Gy/h)
4 mm
1.04911.05101.05451.0563
3 mm4 mm5 mm6 mm
34.10934.10434.08834.030
802.06798.04794.38790.72
1.01111.01511.01931.0232
34.05834.02434.00633.979
-790.30784.11778.50
-1.02551.03451.0409
-34.03734.06534.033
1.0214 1581.12 34.019
10 May 2007 Eduard van Dijk 25
Results 60Co measurements and calculations
2.5 cm3
3 mm4 mm5 mm6 mm
Standard Orientation Wall thickness
2.5 cm3
2.5 cm3
3 mm4 mm5 mm6 mm
5 cm3
Standard Orientation Wall thickness
Standard Orientation Wall thickness
Standard Orientation Wall thickness
4 mm
3 mm4 mm5 mm6 mm
Average: 34.083 Gy/h st.dev. 0.1%
Average: 34.045 Gy/h st.dev. 0.1%
Average: 34.017 Gy/h st.dev. 0.1%
34.019 Gy/h st.dev. 0.1%
10 May 2007 Eduard van Dijk 26
2.5 cm3 4 mm
5 cm3 4 mm
Ratio 5 cm3 and 2.5 cm3 = 1.0002,
with an expanded uncertainty of 0.36 % (coverage factor k = 2).
10 May 2007 Eduard van Dijk 27
10 May 2007 Eduard van Dijk 28
10 May 2007 Eduard van Dijk 29
100 cm
137Cs source
Lead shieldingPhase space determination
Tungsten diaphragm
10 May 2007 Eduard van Dijk 30
Results 137Cs measurements and calculations
2.5 cm3
3 mm4 mm5 mm6 mm
Standard Orientation Wall thickness
2.5 cm3
2.5 cm3
3 mm4 mm5 mm6 mm
Standard Orientation Wall thickness
Standard Orientation Wall thickness
3 mm4 mm5 mm6 mm
Average: 21.441 Gy/h st.dev. 0.1%
Average: 21.396 Gy/h st.dev. 0.1%
Average: 21.462 Gy/h st.dev. 0.1%
Average 137Cs 2.5 cm3 = 21.433 Gy/h (1m STP)
with an expanded uncertainty of 0.60 % (coverage factor k = 2).