[Dosimetric characteristics of a californium neutron source]

The spectrum of energy linear transmission (ELT) and a coefficient of neutron quality were measured in the air in the clinical use of sources by means of a set of low efficacy Geiger counters to find a solution to a problem of the standardization of working conditions for persons dealing with 252Cf sources. The ELT mean values LN = 27 +/- 3 keV/micron and LD = 51 +/- 5 KeV/micron and a coefficient of quality Q = 8.9 +/- 1.0 were obtained in measurements with sources in the air. Values obtained in measurements on a patient receiving interstitial therapy with the use of 252Cf were as follows: 33 +/- 5; 57 +/- 8 keV/micron and 9.3 +/- 1.3 respectively. The value Q-7 is recommended for the evaluation of an equivalent dose of mixed 252Cf gamma-neutron radiation. Using 237Np track detectors for various distances and azimuthal angles which are of the main interest to the therapeutic use of 252Cf neutron sources, spatial distribution of the specific standard rate of neutrons was measured in the air (in geometry without scattering) and in the water phantom (in geometry with maximum scattering and accumulation). The results obtained made it possible to deduce regularities of neutron field formation in the vicinity of a single source and to evaluate the reliability of data obtained with calculation methods. They can be used for the planning of application, interstitial and intracavitary tumor therapy, for a neutron activation analysis and radiography.