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. Althoug ...
, 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 particles, 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 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; transfer ...
s,
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 C
12H
18O
7. Etching to expose radiation damage is typically performed using solutions of caustic alkalis such as
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
, often at elevated temperatures for several hours.
See also
*nuclear track detectors that are not solid state
**
cloud chamber
**
bubble chamber
*solid-state (semiconductor) nuclear detectors that do not record tracks
**
surface-barrier detector
**
silicon drift detector Silicon drift detectors (SDDs) are X-ray radiation detectors used in x-ray spectrometry ( XRF and EDS) and electron microscopy. Their chief characteristics compared with other X-ray detectors are:
*high count rates
*comparatively high energy resolu ...
**
lithium-drifted silicon detector - Si(Li)
**
intrinsic detector
In science and engineering, an intrinsic property is a property of a specified subject that exists itself or within the subject. An extrinsic property is not essential or inherent to the subject that is being characterized. For example, mass ...
*
ion track
External links
* Gregory Choppin,
Jan-Olov Liljenzin
Jan-Olov Liljenzin (1936-2019) was a Swedish language, 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, Nuclear Chemi ...
, 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