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 An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Altho ...

, crystal, glass or plastic) exposed to

nuclear radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...

(

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

s or

charged particle In physics, a charged particle is a particle with an electric charge. It may be an ion, such as a molecule or atom with a surplus or deficit of electrons relative to protons. It can also be an electron or a proton, or another elementary pa ...

s, occasionally also

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

s), etched, and examined microscopically. 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. The main advantages over other radiation detectors are the detailed information available on individual particles, the persistence of the tracks allowing measurements to be made over long periods of time, and the simple, cheap and robust construction of the detector. The basis of SSNTDs is that charged particles damage the detector within nanometers along the track in such a way that the track can be etched many times faster than the undamaged material. Etching, typically for several hours, enlarges the damage to conical pits of micrometer dimensions, that can be observed with a microscope. For a given type of particle, the length of the track gives the energy of the particle. The charge can be determined from the etch rate of the track compared to that of the bulk. If the particles enter the surface at normal incidence, the pits are circular; otherwise the

ellipticity Flattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid) respectively. Other terms used are ellipticity, or oblateness. The usual notation for flattening is ...

and orientation of the elliptical pit mouth indicate the direction of incidence. SSNTDs are commonly used to study

cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

s, long-lived

radioactive element A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfe ...

radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...

concentration in houses, and the age of geological samples. A material commonly used in SSNTDs is polyallyl diglycol carbonate (PADC), also known as Tastrak,

CR-39 Poly(allyl diglycol carbonate) (PADC) is a plastic commonly used in the manufacture of eyeglass lenses alongside the material PMMA (polymethyl methacrylate). The monomer is allyl diglycol carbonate (ADC). The term CR-39 technically refers to the ...

and CR39. It is a clear, colorless, rigid plastic with the chemical formula C₁₂H₁₈O₇. Etching to expose radiation damage is typically performed using solutions of caustic alkalis such as sodium hydroxide, often at elevated temperatures for several hours.

External links

* Gregory Choppin,

Jan-Olov Liljenzin Jan-Olov Liljenzin (1936-2019) was a Swedish chemist and professor in nuclear chemistry. Liljenzin was professor at University of Oslo, Nuclear Chemistry, Norway 1986-1989, and at Chalmers University of Technology Chalmers University of Techno ...

, Jan Rydberg Radiochemistry and Nuclear Chemistry
Chapter 8, "Detection and Measurement Techniques"
{dead link, date=May 2018 , bot=InternetArchiveBot , fix-attempted=yes Nuclear physics Particle detectors

See also

External links