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

ALPHA INCIDENCES AND TRACK FORMATION 0 1 2 3 4 a unetchable etchable XC XD ALPHA INCIDENCES AND TRACK FORMATION BHABHA ATOMIC RESEARCH CENTRE – INDIA

TOTAL TRACK ETCH TIME tBC tt tBD XC XD BHABHA ATOMIC RESEARCH CENTRE – INDIA

FACTORS GOVERNING FORMATION OF READABLE TRACKS IN SSNTD Energy of incident alpha particle Angle of incidence Developing the tracks (Etching parameters) Counting of tracks BHABHA ATOMIC RESEARCH CENTRE – INDIA

BULK ETCH RATE Chemical composition of the detector Etching conditions – Temperature Concentration Duration Preconditioning of the detector BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

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

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-400 085, India 8

Twin cup dosimeter

Rn Tn

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-115 DETECTOR TO ALPHA PARTICLES IN Rn CUP BHABHA ATOMIC RESEARCH CENTRE – INDIA

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-115 DETECTOR TO ALPHA PARTICLES IN Tn CUP BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

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

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

BHABHA ATOMIC RESEARCH CENTRE – INDIA

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 BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

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  = 0.0126 s-1 (Decay constant of thoron)  is the thickness of G.F filter paper; ( 0.0564 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 BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

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

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

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

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

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

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

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

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

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

Response time for Rn & Tn Through Pin Holes of 2 mm Length 3 17 10 27 8 4 48 6 107 422 2 Thoron Radon Response time 95% (min.) Dia. of the hole (mm) BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

BHABHA ATOMIC RESEARCH CENTRE – INDIA

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

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

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

BHABHA ATOMIC RESEARCH CENTRE – INDIA DOSIMETER DESIGN Bare SSNTD Tn cup Rn cup 05.09.08 16:32 00 BHABHA ATOMIC RESEARCH CENTRE – INDIA

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

B A R C ………….THANK YOU eappen@barc.gov.in

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 S418 - 421(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 177-184 (1998) BHABHA ATOMIC RESEARCH CENTRE – INDIA