Lab Work on Dosimetry

The Lab Work on Dosimetry forms the concepts of basic dosimetric quantities and their relationship. The quantitative effects produced by nuclear radiation in a substance are investigated, relations between activity of radioactive substance and dose created by it are established. Practical skills of work with measuring devices used in dosimetric control are formed.
On the example of a specially designed training dosimeter, the technique of measuring dosimetric quantities and methods of registration of ionizing radiation with the help of various detectors is studied.
As detectors of ionizing radiation in the Lab Work uses a set of sensors, including: tube (gas-discharge counter) Geiger; mica high-sensitivity detector, registering with high efficiency as γ-radiation, and α - and β-particles; as well as a set of scintillation crystals, leading to the composition of scintillation dosimeter, which can also operate in the mode of the spectrometer of nuclear radiation.
With the help of these devices, quantitative measurements of dosimetric quantities are carried out, and the influence of radiation protection from different materials on the amount of doses from different types of radioactive sources is experimentally measured. With the help of special techniques, theoretical calculations are also made, which are compared with the experimentally obtained results.

Requirements for access to the workshop:

• Before the beginning of the Lab Work, students should be familiar with safety when working with radioactive isotopes and sign in a special journal.
• To perform practical tasks, you need initial knowledge of the course "Nuclear physics", namely , to have an idea of the existing types of ionizing radiation (α, β, γ - radiation) and their distinctive features.
• To analyze the results of experiments, it is recommended to have initial data from The course "fundamentals of mathematical statistics" on the processing of experimental data, calculation of measurement errors and the least squares method for approximation of dependencies.
The list of laboratory works
1) Familiarity with the basic principles of the dosimeter-radiometer on the example of the dosimeter training model, familiarity with the program for obtaining and processing experimental data. The main methods of registration of ionizing radiation of different types with interchangeable detectors: gas-discharge counter Geiger and mica sensitive detector. Determination sensitivity of sensors to different types of radiation.

2) Radiation source in the point approximation. Determination of absolute activity of available isotopes. Verification of the law of "inverse squares" for calculating the dose from a point source, radiation protection from the source by "distance". Theoretical calculation of dose from ionizing radiation source in point approximation.

3) Research of ionizing radiation detectors. Schemes for inclusion of Geiger counters in the counting device circuit, study of the counting characteristics of detectors and study of the dependence the counting rate on the supply voltage. Investigation the dependence of the speed and efficiency of the account on the type of ionizing radiation source. Determination of the coefficient of sensitivity of the sensors by the reference isotopes.

4) Estimation of the half-life and absolute activity of the long-lived isotope 40K as part of a complex chemical compound KCl (potassium chloride), calibration of the dosimeter for study of food contamination.

5) Quantitative estimation of the effect of biological radiation on the body. Equivalent dose. Units of measurement used in dosimetry. Protection from ionizing radiation. Maximum permissible levels of ionizing radiation in accordance with radiation safety standards.

6) Introduction in scintillation methods of dosimetry. Scintillation dosimeter: device, operating principle, calibration and switching circuit. Qualitative and quantitative processing of radiation spectra from different isotopes.