Gerhard Stucki, Sandor VörösV

Transcription

1 idgenössisches Justiz- und Polizeidepartement JPD Bundesamt für Metrologie MTAS xperimental k Q,Q0 lectron Beam Quality Correction Factors for the Types NACP02 and PTW34001 Plane-parallel Chambers Gerhard Stucki, Sandor VörösV Federal Office of Metrology

2 xperimental k Q,Q0 lectron Beam Quality Correction Factors for the Types NACP02 and PTW34001 Plane-parallel Chambers 1) Irradiation facilities 2) Primary standard (electron beam) 3) Ionisation chamber calibration 4) Results for k Q,Q Q,Q 0 5) Comparison with TRS 398 6) Conclusions AbsDos 2007 I Gerhard Stucki I I 2

3 1) MTAS Irradiation Facilities lectron accelerator (microtron) M22 lectron energies 5.3 to 22.5 MeV Conventional treatment head 10 photon beams: TPR 20,10 = to electron beams: R 50 = 1.75 to 8.54 g cmg Co irradiation unit ALCYON II AbsDos 2007 I Gerhard Stucki I I 3

4 AbsDos 2007 I Gerhard Stucki I I 4 MTAS microtron M22

5 MTAS Standard Radiation Qualities for High - nergy lectron Beams Nominal electron energy [MeV] Radiation index Q (=R 50 ) [gcm -2 ] z ref [gcm -2 ] AbsDos 2007 I Gerhard Stucki I I 5

6 2) Primary Standard : Chemical Dosimeter (Fricke) Total Absorption xperiment Irradiation experiment: D = F abs m (1) Fricke solution abs = e N e - pencil beam MeV AbsDos 2007 I Gerhard Stucki I I 6

7 2) Primary Standard : Chemical Dosimeter (Fricke) Total Absorption xperiment UV- spectrometer read-out: Fricke solution D F ε Δ A T G ρ = (2) l T e - pencil beam MeV AbsDos 2007 I Gerhard Stucki I I 7

8 2) Primary Standard : Chemical Dosimeter (Fricke) Total Absorption xperiment Irradiation experiment: UV- spectrometer read-out: D = F abs m (1) Fricke solution D F = ε Δ A T G ρ l T (2) abs = e N e - pencil beam MeV (1) + (2) G = Δ A T ε ρ l T m abs (3) AbsDos 2007 I Gerhard Stucki I I 8

9 Total absorption experiment, 6 MeV vessel AbsDos 2007 I Gerhard Stucki I I 9

10 Total absorption experiment, 22 MeV vessel AbsDos 2007 I Gerhard Stucki I I 10

11 Magnetic spectrometer beam exit NMR probe beam entrance AbsDos 2007 I Gerhard Stucki I I 11

12 Corrections 1) abs = e N F T Bremsstrahlung (about 8 22 MeV) Backscattering Fringe field spectrometer nergy losses (entrance- and exit windows, air gap, beam line) AbsDos 2007 I Gerhard Stucki I I 12

13 2) Primary Standard : Chemical Dosimeter (Fricke) Total Absorption xperiment Irradiation experiment: UV- spectrometer read-out: D = F abs m (1) Fricke solution D F = ε Δ A T G ρ l T (2) abs = e N F T e - pencil beam MeV (1) + (2) G = Δ A T ε ρ l T m abs (3) AbsDos 2007 I Gerhard Stucki I I 13

14 1.015 G / <G> versus Beam nergy Measurements June 1999 to March G / <G> [1] Norm lectron nergy [ MeV ] G f() within the given uncertainties AbsDos 2007 I Gerhard Stucki I I 14

15 G / <G> versus Beam nergy Measurements June 1999 to March G / <G> [1] Norm lectron nergy [ MeV ] AbsDos 2007 I Gerhard Stucki I I 15

16 3) Ionisation Chamber Calibration Against Fricke Solution e - Fricke e - IC Monitor Monitor z ref z ref z ref = 0.6 R gcm -2 D F = ΔA ε Gρl (3) D W = N M (4) D, W, Q Q AbsDos 2007 I Gerhard Stucki I I 16

17 NACP02 chamber P bag PMMA holder AbsDos 2007 I Gerhard Stucki I I 17

18 Corrections 2) Fricke solution -> > water -> f e Perturbations / wall effect due to P foil, PMMA holder etc -> f e Temperatue, air pressure, humidity etc. -> Π f i AbsDos 2007 I Gerhard Stucki I I 18

19 3) Ionisation Chamber Calibration Against Fricke Solution D W = ΔA S εgρl S f e (5) e - Monitor z ref = 0.6 R gcm -2 Fricke = ΔA ΔA S T l T l S N e m f f T e (6) G cancels out, since G does not depend on beam energy e - Monitor IC N D,W,Q = ΔA S ΔA T l T 1 l M Πf S Q i N e f f m T e (7) z ref AbsDos 2007 I Gerhard Stucki I I 19

20 4) Results k Q,Q0 lectron Beam Quality Correction Factors Definition of k Q,Q0 (experimental): k = Q, Q 0 N N D D, w, w, Q, Q 0 Definition of k Q,Q0 k Q, Q0 ( s = ( s w, air w, air ) ) Q Q0 (theoretical): ( W ( W air air ) ) Q Q0 p p Q Q0 AbsDos 2007 I Gerhard Stucki I I 20

21 Measurements in 60 Co beam: Primary standard: water calorimeter Measurements in electron beams: Primary standard: chemical dosimeter (total absorption in Fricke solution) No correlations between primary standards u kq = 1 %, (k = 1) u k Q,Q0 = 0.5 %, (k = 1) u kq > u > u kq,q Q,Q0 AbsDos 2007 I Gerhard Stucki I I 21

22 xperimental k Q,Q0 Factors NACP02 (13 chambers) Q 0 = 60 Co k Q [1] TRS 398 <xp> Fit to xp R 50 [g/cm 2 ] u kq = 1 %, (k = 1) AbsDos 2007 I Gerhard Stucki I I 22

23 xperimental k Q,Q0 Factors NACP02 (13 chambers) Q 0 = 60 Co Q 0 = gcm k Q [1] k Q,7.523 [1] TRS 398 <xp> Fit to xp TRS 398 <> Fit R 50 [g/cm 2 ] R 50 [g/cm 2 ] u kq = 1 %, (k = 1) u kq,q0 = 0.5 %, (k = 1) AbsDos 2007 I Gerhard Stucki I I 23

24 xperimental k Factors Q,Q0 NACP02 Chambers, Q 0 =7.523 gcm kq,7.523 [1] chamber to chamber variation: 1.9 % Individual Chambers <> Fit R 50 [g/cm 2 ] AbsDos 2007 I Gerhard Stucki I I 24

25 xperimental k Q,Q0 Factors PTW (18 Chambers) Q 0 = 60 Co kq [1] TRS 398 <xp> Fit to xp R 50 [g/cm 2 ] u kq = 1 %, (k = 1) AbsDos 2007 I Gerhard Stucki I I 25

26 xperimental k Q,Q0 Factors PTW (18 Chambers) Q 0 = 60 Co Q 0 =7.523 gcm kq [1] kq,7.523 [1] TRS 398 <xp> Fit to xp TRS 398 <xp> Fit to xp R 50 [g/cm 2 ] R 50 [g/cm 2 ] u kq = 1 %, (k = 1) u kq,q Q,Q0 = 0.5 %, (k = 1) AbsDos 2007 I Gerhard Stucki I I 26

27 1.08 xperimental k Factors Q,Q0 as a Function of R 50 Individual PTW34001 Chambers, Q 0 =7.523 gcm kq,7.523 [1] chamber to chamber variation: 1.2 % Individual Chambers <xp> Fit to exp R 50 [g/cm 2 ] AbsDos 2007 I Gerhard Stucki I I 27

28 5) Comparison with TRS 398 k Q, Q = ( s w, air ) ( W air 0 ( s ) ( W ) w, air Q 0 air Q ) Q Q 0 p p Q Q 0 Assumptions IAA TRS 398, Appendix II: (W air ) Q :=(W air ) Q0 p Q := p cav p dis p wall p cel and p cav =p dis =p cel :=1 p Q = p wall p wall := 1, in electron beams p wall 1, if Q = 60 Co k = Q,Q 0 (s (s w,air w,air ) ) Q Q 0 k Q = (s (s w,air w,air ) ) 60 Q Co 1 p wall AbsDos 2007 I Gerhard Stucki I I 28

29 0.96 NACP02: k Q Factors, xperiment <> TRS kq [1] TRS 398 <xp> Fit to xp R 50 [g/cm 2 ] u kq = 1 %, (k = 1) <p wall (exp)> = 1.022, σ = p wall (TRS 398, V_12, 5 June 2006) ) = AbsDos 2007 I Gerhard Stucki I I 29

30 1.010 NACP02: k Q,Q0 - exp / k Q,Q0 -TRS398 kq,q0 - exp / k Q,Q0-TRS 398 [1] % xp / IAA 398, Q0=Co-60 xp / TRS 398, Q0=7.523 gcm-2 Linear ( xp / IAA 398, Q0=Co-60) Linear ( xp / TRS 398, Q0=7.523 gcm-2) <>=1.0021, σ= Q 0 = 60 Co AbsDos 2007 I Gerhard Stucki I I 30 R 50 [g/cm 2 ] <>=1.0028, σ= Q 0 = gcm -2

31 PTW : k Q Factors, xperiment <> TRS kq [1] TRS 398 <xp> Fit to xp u kq = 1 %, (k = 1) R 50 [g/cm 2 ] <p wall (exp)> = 1.013, σ = p wall (TRS 398, V_12, AbsDos 2007 I Gerhard Stucki I I 31 V_12, 5 June June 2006) ) = 1.010

32 PTW 34001: k Q,Q0 - exp / k Q,Q0 -TRS xp / IAA 398, Q0=Co-60 xp / TRS 398, Q0=7.523 gcm-2 Linear ( xp / IAA 398, Q0=Co-60) Linear ( xp / TRS 398, Q0=7.523 gcm-2) kq - exp / k Q-TRS 398 [1] % <> = , σ = Q 0 = 60 Co 60 Co AbsDos 2007 I Gerhard Stucki I I 32 R 50 [g/cm 2 ] <> = , σ = Q 0 = gcm -2

33 Conclusions <P Q > (electron beams) : constant (within uncertainty) <k Q,Q0 (exp)> in agreement with k Q,Q 0 NACP02 chamber: <P wall (exp)> = in agreement with p wall (TRS 398 (V_12)) ) = mean ratio k (exp)/k Q,Q0 Q,Q (TRS), Q 0 0 = 60 Co: (σ:( : 0.26 %) mean ratio k (exp)/k Q,Q0 Q,Q (TRS), Q 0 0 = gcm -2 : (σ:( : 0.24 %) chamber to chamber variation: 1.9 %! (TRS 398 (V_12) (V_12)) PTW34001 chamber: <P wall (exp)> = in agreement with p wall (TRS 398 (V_12)) ) = mean ratio k (exp)/k Q,Q0 Q,Q (TRS), Q 0 0 = 60 Co: (σ:( : 0.27 %) mean ratio k (exp)/k Q,Q0 Q,Q (TRS), Q 0 0 = gcm -2 : (σ:( : 0.27 %) chamber to chamber variation: 1.2 %! AbsDos 2007 I Gerhard Stucki I I 33

34 AbsDos 2007 I Gerhard Stucki I I 34 Thank you for your attention!