TRACK FORMATION AND ENERGY OF ALPHA PARTICLE

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TRACK FORMATION AND ENERGY OF ALPHA PARTICLE
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ALPHA INCIDENCES AND TRACK FORMATION
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TOTAL TRACK ETCH TIME
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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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• BULK ETCH RATE
• Chemical composition of the detector
• Etching conditions Temperature
• 
  Concentration
• 
  Duration
• Preconditioning of the detector

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TRACK ETCH VELOCITY
a 0.16 mm-1 b 2.68 (Andriamanantena and Enge)
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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
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Rn

Tn
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RESPONSE OF LR-115 DETECTOR TO ALPHA
PARTICLES IN Rn CUP
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RESPONSE OF LR-115 DETECTOR TO ALPHA
PARTICLES IN Tn CUP
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CALIBRATION FACTORS THEORETICAL
EXPERIMENTAL(tracks.cm-2 per Bq.d.m-3)
Cup Radon Radon Thoron Thoron
Cup Theore-tical Experi-mental 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
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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
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Diameters of holes created on LR-115 and Mylar
films
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Measurement error with increase in track density
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MODIFICATIONS

• Pin hole technique for Rn-Tn
• separation
• Optimization of cup
• dimensions

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Transmission Fractions of Rn Tn Through
Cellophane Membranes
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Transmission Fractions of Rn Tn Through Pin
Holes of 2 mm Length
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Response time for Rn Tn Through Pin Holes of 2
mm Length
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CONTRIBUTION OF TRACKS(tr.cm-2.d-1/Bq.m-3)
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COMPARISON OF CALIBRATION FACTORS(Tr.cm-2.d-1/B
q.m-3)
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DESIGN PARAMETERS
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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.

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B A R C
.THANK YOU eappen_at_barc.gov.in
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For further reading..
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