Dosimetry of mixed radiation field at the Kraków cyclotron using lithium fluoride TL detectors

The AIC-144 isochronous cyclotron at the Institute of Nuclear Physics (IFJ) in Kraków can be used for acceleration of light ions. Protons can be accelerated to maximum energy of 60 MeV in the form of a focused ion beam. In October 2009 the AIC-144 isochronous cyclotron at the IFJ was dedicated to the Kraków Centre for Hadron Radiotherapy. Then, the cyclotron was modernized and adapted for proton radiotherapy of eye cancer. The aim of our work was to validate suitability of different thermoluminescent (TL) detector types for dosimetry of a mixed radiation field at the cyclotron unit. LiF:Mg,Ti and LiF:Mg,Cu,P detectors are well known standards of TL dosimetry; however, several of their properties are significantly different. In this study four types of LiF-based TL detectors were used to measure spatial dose distribution of a mixed radiation field in the Cyclotron Hall during operation of the machine. A program named the MapFly was developed in order to visualize radiation levels in the Cyclotron Hall in 2D and 3D.