1. TRACK FORMATION AND ENERGY OF ALPHA PARTICLE
BHABHA ATOMIC RESEARCH CENTRE – INDIA

2. ALPHA INCIDENCES AND TRACK FORMATION a
unetchable
etchable XC XD
ALPHA INCIDENCES AND TRACK FORMATION
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3. TOTAL TRACK ETCH TIME tBC tt tBD XC XD
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4. FACTORS GOVERNING FORMATION OF READABLE TRACKS IN SSNTD
Energy of incident alpha particle
Angle of incidence
Developing the tracks (Etching parameters)
Counting of tracks
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5. BULK ETCH RATE Chemical composition of the detector
Etching conditions – Temperature
Concentration
Duration
Preconditioning of the detector
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6. BHABHA ATOMIC RESEARCH CENTRE – INDIA

7. TRACK ETCH VELOCITY a= 0.16 mm-1 ; b = 2.68 (Andriamanantena and Enge)
BHABHA ATOMIC RESEARCH CENTRE – INDIA

8. K.P. Eappen Design and parametric validation for LR-115
(type –II) based twin cup dosimeter for simultaneous measurements of Rn, Tn and progeny concentrations
K.P. Eappen
Health, Safety & Environment Group
Bhabha Atomic Research Centre
Trombay, Mumbai , India 8

9. Twin cup dosimeter

10. Rn Tn

11. RESPONSE OF LR-115 DETECTOR TO ALPHA PARTICLES IN Rn CUP
6.2 cm
4.1 cm
SSNTD
222 Rn
218 Po
214
Cupwall
RESPONSE OF LR DETECTOR TO ALPHA PARTICLES IN Rn CUP
BHABHA ATOMIC RESEARCH CENTRE – INDIA

12. RESPONSE OF LR-115 DETECTOR TO ALPHA PARTICLES IN Tn CUP
6.2 cm
4.1 cm
SSNTD
220 Rn
216 Po
212 Bi
Cupwall
RESPONSE OF LR DETECTOR TO ALPHA PARTICLES IN Tn CUP
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13. BHABHA ATOMIC RESEARCH CENTRE – INDIA

14. C.F FOR BARE FILM (PER SPECIES): 0.02
CALIBRATION FACTORS THEORETICAL & EXPERIMENTAL (tracks.cm-2 per Bq.d.m-3)
Cup
Radon
Thoron
Theore-tical
Experi-mental
Mem-brane
0.0234
0.021 -
Filter
0.0260
0.023
0.0176
0.019
C.F FOR BARE FILM (PER SPECIES): 0.02
BHABHA ATOMIC RESEARCH CENTRE – INDIA

15. FUNCTIONAL DIAGRAM OF THE DOSIMETER CUP
SSNTD FILM
FUNCTIONAL DIAGRAM OF THE DOSIMETER CUP
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16. BHABHA ATOMIC RESEARCH CENTRE – INDIA

17. Parameters used for computing transmission ratio
0.56 -
Transmission ratio
/C0
2.187 cm
Diffusive length (√(D/l)) ξ
0.093
cm2 s-1
Effective diffusion coefficient Df
4.50
Length of the dosimeter cup L
0.0564
Thickness of filter paper d
0.0126
s-1
Decay constant of 220Rn l
0.10
Diffusion coefficient of 220Rn in air D
1.00
Bq m-3
Thoron concentration at entry point C0
Value
Unit
Details
Term
Parameters used for computing transmission ratio
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18. BHABHA ATOMIC RESEARCH CENTRE – INDIA

19. THORON PROFILE OF INSIDE THE CUP
C is the average concentration of thoron in the cup
C is the concentration of thoron inside the cup at entry point
x    = (D/); D = 0.1 cm2.s-1 (Diffusion coefficient of thoron
in air) and  = s-1 (Decay constant of thoron)
 is the thickness of G.F filter paper; ( cm)
L is the radius of the cup; (6.0 cm)
De is the effective diffusion coefficient of
thoron (0.093 cm2.s-1) through filter paper
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20. BHABHA ATOMIC RESEARCH CENTRE – INDIA

21. BHABHA ATOMIC RESEARCH CENTRE – INDIA

22. BHABHA ATOMIC RESEARCH CENTRE – INDIA

23. Diameters of holes created on LR-115 and Mylar films
r1>100 mm r 2
= 12 m
RESULTANT AREA
Diameters of holes created on LR-115 and Mylar films
BHABHA ATOMIC RESEARCH CENTRE – INDIA

24. BHABHA ATOMIC RESEARCH CENTRE – INDIA
Measurement error with increase in track density
BHABHA ATOMIC RESEARCH CENTRE – INDIA

25. CORRECTION FOR SPARK COUNTER
TT – Tracks by microscope
TS – Tracks by spark counter
BHABHA ATOMIC RESEARCH CENTRE – INDIA

26. MODIFICATIONS separation Optimization of cup dimensions
Pin hole technique for Rn-Tn
separation
Optimization of cup
dimensions
BHABHA ATOMIC RESEARCH CENTRE – INDIA

27. Transmission Fractions of Rn &Tn Through Cellophane Membranes
0.83
98.04 05
0.14
89.30 30
0.17
90.92 25
0.21
92.60 20
0.28
94.35 15
0.42
96.16 10
Thoron
Radon
Transmission, Ci/Co (%)
Cellophane thickness (mm)
BHABHA ATOMIC RESEARCH CENTRE – INDIA

28. BHABHA ATOMIC RESEARCH CENTRE – INDIA
C : Average radon concentration in the compartment volume space
C0: Outside radon concentration
V : Volume of the compartment
A : Area of the hole
J : Radon activity flux at the hole
d : Thickness of the hole
D : Radon diffusion coefficient in air (hole)
l : Radon/Thoron decay constant
BHABHA ATOMIC RESEARCH CENTRE – INDIA

29. BHABHA ATOMIC RESEARCH CENTRE – INDIA
with initial condition
, we can arrive at
BHABHA ATOMIC RESEARCH CENTRE – INDIA

30. BHABHA ATOMIC RESEARCH CENTRE – INDIA
100% response for
95% response for
63% response for
Response time
Transmission factor at 100% response will be
BHABHA ATOMIC RESEARCH CENTRE – INDIA

31. Transmission Fractions of Rn & Tn Through Pin Holes of 2 mm Length
18.76
99.93 10
12.87
99.89 8
7.67
99.80 6
3.56
99.55 4
0.92
99.23 2
Thoron
Radon
Transmission (%)
Dia. of the hole (mm)
BHABHA ATOMIC RESEARCH CENTRE – INDIA

32. Response time for Rn & Tn Through Pin Holes of 2 mm Length3 17 10 27 8 4 48 6
107
422 2
Thoron
Radon
Response time 95% (min.)
Dia. of the hole (mm)
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33. BHABHA ATOMIC RESEARCH CENTRE – INDIA

34. BHABHA ATOMIC RESEARCH CENTRE – INDIA

35. BHABHA ATOMIC RESEARCH CENTRE – INDIA

36. BHABHA ATOMIC RESEARCH CENTRE – INDIA

37. CONTRIBUTION OF TRACKS (tr.cm-2.d-1/Bq.m-3)
0.06
0.04
0.02
Radon
0.079
0.055
0.04 x 0.6 = 0.024
Thoron
Total
Surface
Volume
BHABHA ATOMIC RESEARCH CENTRE – INDIA

38. COMPARISON OF CALIBRATION FACTORS (Tr.cm-2.d-1/Bq.m-3)
0.079
0.019
Thoron Cup
0.06
0.02
Radon Cup
Hemi-
spherical
Cylindrical
Cup shape
BHABHA ATOMIC RESEARCH CENTRE – INDIA

39. DESIGN PARAMETERS Radon Cup Thoron Cup 75 cm2 Filter area 6.0 cm
Radius of the cup
Spherical
Shape
Thoron Cup
2 mm
Pin hole length
1 mm
Pin hole radius
4.6 cm
Radon Cup
BHABHA ATOMIC RESEARCH CENTRE – INDIA

40. BHABHA ATOMIC RESEARCH CENTRE – INDIA
DOSIMETER DESIGN
Bare SSNTD
Tn cup
Rn cup
16:32 00
BHABHA ATOMIC RESEARCH CENTRE – INDIA

41. Conclusions……. 1. Calibration factors for dosimeter cups depends on:
cup dimensions
track development protocols
track reading methods
2. Pin holes against filters are better options for separating Rn and Tn in cup dosimeters.
3. Computation of response time enables designing dosimeters with desired exposure period.
4. Optimization of dosimeter dimensions is possible with parametric studies.
BHABHA ATOMIC RESEARCH CENTRE – INDIA

42. B A R C
………….THANK YOU

43. For further reading……………..
Eappen K.P, Sahoo B.K, Ramachandran T.V, Mayya Y.S
Calibration factor for thoron estimation in cup dosimeter. Accepted for publication in journal Radiation Measurements. Radiation. Meas. 43 S (2008).
K.P. Eappen
Factors Affecting the Registration and Counting of Alpha tracks in Solid State Nuclear Track Detectors. Accepted for publication in Indian journal of Physics (2008)
K.P. Eappen, Y.S. Mayya, R.L. Patnayak, H.S. Kushwaha.
Estimation of radon progeny equilibrium factors and their uncertainty bounds using solid state nuclear track detectors. Radiation. Meas. 41 (3), 342 – 348 (2005).
K.P. Eappen, Y. S. Mayya
Calibration factors for LR –115 (Type-II) based radon thoron discriminating dosimeter. Radiation Meas., 38, 5 –1 7 (2004).
Y.S Mayya, K.P Eappen, K.S. V. Nambi
Methodology for Mixed Field Inhalation Dosimetry in Monazite areas using a Twin-cup Dosemeter with Three Track Detectors., RPD, Vol.77, No.3, pp (1998)
BHABHA ATOMIC RESEARCH CENTRE – INDIA