solid state detector, Study notes of Applied Chemistry

Download solid state detector and more Study notes Applied Chemistry in PDF only on Docsity! Objective of experiment: In this experiment we need to study etching characteristics of SSNTD. We observe effect of duration of etching on tracks formed on detector Radioactive elements emit different kinds of radiations. These radiations may be alpha particles, beta particles or electromagnetic gamma rays. Solidstate nuclear track detector is also used to detect nuclear radiations. . Solid state nuclear track detector (SSNTD): Fast moving charged particles are known to produce trails of atomic disorder in an immense variety of dielectric solids and some other materials. These dielectric solids include crystals, glasses, and high polymers, and other materials used, include intermetallics, certain metals and amorphous metals, oxide conductors and superconductors. Tracks produced by radiations from nucleus are known as nuclear tracks. Nuclear tracks have found many applications in different branches of science. A solid-state nuclear track detector or SSNTD is also known as an etched track detector or a dielectric track detector DTD. When it is uncovered to nuclear radiation i.e. neutrons or charged particles, intermittently as well gamma rays , is etched, and inspected microscopically which give information about the radiation WORKING: When a heavily ionized particle falls on SSNTD, it penetrates inside it. During the process particle strikes with the atoms of lattice of SSNTD and may knock out them from their lattice sites. Depending on particle’s energy, it may penetrate deep inside SSNTD and having some decrease in energy. Therefore track continuous inside the detector also in form of cone. These tracks are used to extract valuable information about the radiation incident on detector. SSNTDs fall in two distinct categories: 1) Polymeric or plastic detectors: These are widely used for radiation monitoring 2) Natural minerals crystals (and glasses): This kind of SSNTD has greatest application in fields such as geology, planetary sciences [especially lunar and meteoritic samples], oil exploration etc. The most widely used SSNTDs today are plastic, which unlike mineral crystal do not require special preparation such as grinding and polishing. They are also much more sensitive than crystals and glasses. Tracks visualization: Due to irradiation of radiation tracks are formed on SSNTD. These tracks are of very small size and of order of 10nm. To make these tracks visible, they are passed through a process called etching. In etching 6 Molar solution of NaOH is used and SSNTD is placed in it for irradiation. This process make the tracks formed by radiation larger in size and after some time their size become of the order of micrometer .Size of tracks depends on duration of etching. In this experiment we study etching characteristics of SSNTD detector. Tracks evaluations: Many methods are used to evaluate tracks so that valuable information about the radiation is obtained. 1 . Manual (Ocular) Counting: Manual or more accurately, ocular (with eye)counting denotes non- automatic counting of etched tracks generally using an optical microscope, with a moving stage, and two eye pieces. But there is a problem with this method that some of tacks may be repeated in counting and some may be left. 2.There are also spark counting and automatic track evaluation. By these methods we can also count tracks of pits. From data taken track density is found. Track densities are expressed either in relative terms or in absolute terms which is converted after calibrating into a dose or radon concentration by dividing by the time of exposure. MATERIALS AND METHODS: In this experiment we used SSNTD strips which were already passed through the process of etching and irradiation from two different radiation sources and microscope. Procedure: 9 8 8 4 4 10 8 5 5 4 9 9 6 7 4 8 8 10 5 3 7 7 5 5 2 Avg= 8.2µm =7.9µm 6.6µm 4.7µm 3.6µm Table of data taken for Fission fragments particles emitted from Californium 252 , scale is in micrometer Etching time 10.5hrs 8.5 hrs 6.5hrs 4.5hrs 2.5hrs 17 14 11 9 11 16 15 10 8 14 16 11 12 7 11 17 12 13 6 12 18 11 12 8 13 16 11 13 9 11 16 11 11 8 12 17 11 12 7 11 15 12 10 9 13 15 13 9 8 11 16.3µm 12.1µm 10.1µm 7.9µm 11.9µm Diameter of tracks measured for ten different tracks randomly in micrometer Table of data taken for alpha particles emitted from Californium 252 , scale is in micrometer Diameter measured in micrometer For ten different tracks for each track Etching time 10.5hrs 8.5 hrs 6.5hrs 4.5hrs 2.5hrs 8 7 5 3 5 6 6 4 2 4 7 5 5 3 3 5 5 5 2 4 6 6 3 3 5 7 7 4 4 5 6 6 5 3 5 7 7 5 3 4 8 6 4 3 3 7 5 5 3 4 6.7µm 6.0µm 4.5µm 2.9µm 3.8µm Vb=DF.F/2t =16.3/2(10.5) =2.1×10-10m/s X=Dα/DF.F =6.7/16.3 =0.41 VT=Vb(1+x2)/ (1-x2) = 2.9×10-10m/s Efficiency =1-Vb/Vt =0.28