Detector radiation damage

The total energy, E, is obtained from the total charge accumulated in both sections of the anode. The second part of the ionization chamber, which measures the energy E - AE, can be replaced by an SBD [3.167], and the first part, which measures the energy loss AE, by a transmission SBD [3.168, 3.169]. When SBDs are used to measure heavy ions, radiation damage of the detector by the ions must be taken into account. 

Since tracks caused by radiation damage are very stable, they can be investigated after very long periods of time. Many minerals contain a record of damage by fission products or cosmic rays that has been conserved over millions of years. This makes track detectors very valuable for geochemistry and space science. 

When quartz or other suitable mineral detector is deposited into a matrix of minerals containing the radioactive nuclides of the U, U, and Th decay series, and the detector mineral is subject to radiation damage. If the grain had been cleared of all memory of radiation damage prior to deposition, then the extent of damage is a function of the time the detector mineral has been immersed in the radiation-producing matrix. 

When charged particles, e.g. a particles, impinge on certain types of plastic materials like polycarbonate or cellulose nitrate, they cause radiation damage tracks in the material. The tracks can be made visually detectable through chemical or electrochemical etching procedures. The visible tracks can be counted using a microscope, microfilm reader or automatic image analyzers. The number of tracks is used to calculate the total amount of radiation to which the detector material was exposed. 

A solid-state nuclear track detector is a piece of special plastic which is exposed as the sensitive element in a radon monitor. The alpha radiation from Rn and RnD, which penetrates the surface of the plastic, causes radiation damage along the entrance path, as shown in the schematic in Fig. 9.26. Chemical etching of the plastic after exposure... 

At synchrotron sources, attenuators such as graphite, aluminium or synthetic-diamond foils can be inserted into the primary beam path to reduce the heat load on an optical element, to prevent saturation of the X-ray detector, or to reduce the rate of radiation damage to the sample. 

These experiments confirmed reduced exposure times and reductions in the relative amount of radiation damage over that on a conventional source (Fourme 1978, 1979 Kahn et al 1982a). In the Soviet Union on the VEPP-3 ring some preliminary data were collected by Mokulskaya (1981) using an electronic area detector in an attempt to optimise the anomalous dispersion of a platinum derivative of pea lectin crystals. 

Alternatively, native protein crystal data sets measured at wavelengths as short as 0.33 A (i.e. utilising the K edge of the barium in an image plate as detector) would also be free of absorption errors and with greatly reduced random errors. This latter arises due to the ability to have prolonged exposure times and repeated measurements before the protein crystal suffers radiation damage. Hence, unprecedented data... 

Lil(Eu). Lil(Eu) is an efficient thermal-neutron detector through the reaction jLKn, a)jH. The alpha particle and the triton, both charged particles, produce the scintillations. Lil has a density of 4.06 X 10 kg/m, decay time of about 1.1 /i,s, and emission spectrum peaking at 470 nm. Its conversion efficiency is about one-third of that for Nal. It is very hygroscopic and is subject to radiation damage as a result of exposure to neutrons. 

The fabrication and operation of a semiconductor detector are based on the premise that one starts with a perfect crystal containing a known amount of impurities. Even if this is true at the beginning, a semiconductor detector will suffer damage after being exposed to radiation. The principal type of radiation damage is caused by the collision of an incident particle with an atom. As a result of the collision, the atom may be displaced into an interstitial position, thus creating an interstitial-vacancy pair known as the Frenkel defect. A recoiling... 

High energy particles not only cause ionization in the detector crystal but may displace some detector atoms from the crystal lattice. Radiation damage decreases with applied bias and increases with the particle mass. Such radiation damage to the crystals limits the lifetime of the detectors. The threshold dose (in particles/cm ) is about 10 for fission fragments, 10 for a, 10 for p, 10 for fast neutrons, and 10 for e . Radiation damage can usually be removed if the detector can be annealed at 200°C. 

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