Nuclear Tracks Sup. P.J.Apel 4/4/20101

 A solid-state nuclear track detector or SSNTD (also known as an etched track detector or a dielectric track detector, DTD) is a sample of a solid material (photographic emulsion, crystal, glass or plastic) exposed to nuclear radiation (neutrons or charged particles, occasionally also gamma rays), etched, and examined microscopically.emulsionnuclear radiationneutronscharged particlesgamma rays etched Solid-state nuclear track detector  The tracks of nuclear particles are etched faster than the bulk material, and the size and shape of these tracks yield information about the mass, charge, energy and direction of motion of the particles.  If the particles enter the surface at normal incidence, the pits are circular; otherwise the ellipticity and orientation of the elliptical pit mouth indicate the direction of incidence.ellipticity 4/4/20102

Charged particles which penetrate a solid, can lose their energy via various interaction types, such as Excitation and ionization of target electrons (electronic energy loss) Projectile excitation and ionization Electron capture Elastic collisions with target atoms (nuclear energy loss) Electromagnetic radiation(Bremsstrahlung, Cherenkov effect) 4/4/20103

The energy loss depending on the specific energy of the incoming ion is displayed in fig. (1) for a uranium ion passing through polyimide, calculated using the SRIMo 3 code. It is a characteristic of fast ions that the maximum of the irradiated electronic energy loss occurs shortly before the particle is stopped, because their interaction cross section for these processes increases with decreasing velocity. a b 4/4/20104

The electronic energy loss can be described by the Bethe-Bloch formula where e elementary charge Z eff effective charge of the projectile Z t atomic number N number of target atoms per unit volume m e electron mass v velocity of the ion I ionization energy β v/c δ relativistic correction U correction taking in to account screening of inner electrons 4/4/20105

The reasons for the widespread use of SSNTD include: The basic simplicity of its methodology The low cost of its materials The great versatility of its possible applications The small geometry of the detectors Their ability in certain cases to preserve their track record for almost infinite length of time Their rigidness 4/4/20106

The basic principles of SSNTD technique When heavy charged particles [proton upward] traverse a dielectric medium, they are able to leave long lived trials of damage that may be observed either directly by transmission electron microscope [TEM] provided that the detector is thick enough, viz. some  m across or under ordinary optical microscope after suitable enlargement by etching the medium. 4/4/20107

8 They fall in two distinct categories: 1) Polymetric or plastic detectors: These are widely used not only for radiation monitoring and measurement, but also in may other fields involving nuclear physics and radioactivity. 2) Natural minerals crystals (and glasses): That have imprinted within them, a record of their radiation (and thermal) history over the icons. These find their greatest application in fields such as geology, planetary sciences [especially lunar and meteoritic samples], oil exploration etc. 4/4/2010

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Figure: Chemical Etching of SSNTD 4/4/201010

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Track Evaluation Methods: 1) Manual (Ocular) Counting: Manual [or more accurately, ocular: eye] counting denotes non-automatic counting of etched tracks generally using an optical microscope, with a moving stage, and two eye pieces Figure: Track analysis of charged particle on SSNTD after chemical etching 4/4/201013

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Measurements and Applications: 1. Earth and Planetary Sciences Radon Measurements: Radon measurements are one of the most widely used application of SSNTDs today. Radon is naturally occurring radioactive gas that constitutes both a hazard e.g. Lung Cancer, and a helpful resource – e.g. means for uranium exploration and tentatively for earthquake prediction. 4/4/201015

Figure: Measurements of radon exhalation rate from granites using SSNTD with sealed vessel. 4/4/201016

2. Fission Track Dating 3. Planetary Science b) Meteoritic Samples: a) Lunar Samples 1) Age determination 2) Cooling-down of the early solar system 3) Determination of pre-atmospheric size of meteorites 4) Cosmic Ray Measurements: Particle Identification 4/4/201017

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