SU-E-T-65: On the Dose Response Function and the Energy Dependence of a Novel Synthetic Single Crystal Diamond Detector

Abstract

Purpose: To characterize the dose response function K(x) and to analyze the dependence on changing photon spectra of a novel synthetic single crystal diamond prototype detector (microDiamond, T60019, PTW‐Freiburg). Methods: The K(x) of the microDiamond was examined by scanning a narrow photon field, with the detector symmetry axis arranged towards the photon source, at 6 and 15 MV. The same dose profiles were scanned with a Si diode, for which the K(x) is already known, to obtain D(x). In a search process, the D(x) were numerically convolved with normalized one‐dimensional Gaussian kernels K(x) of varying o. The best fit between the convolution product D(x)*, K(x) and the measured profile M(x) of the microDiamond was used to determine σ. Furthermore, profiles were compared with ion‐chamber (PTW Semiflex 31010) measurements at different field sizes and depths to study its spatial resolution, output factor and out‐of‐field measurement characteristics. The EPOM was determined by comparing the PDDs against those obtained with a Roos chamber. Results: The optimal σ of K(x) of the microDiamond was found to be 1.14 mm, which is comparable to the detector dimensions (radius = 1.1 mm). The microDiamond profiles agree well with the ion‐chamber measurements within regions where the volume effect of the ion‐chamber can be neglected. At 10 cm depth and for field sizes between 4×4 cm2 and 20×20 cm2 the output factors measured with the microDiamond and ion‐chamber agree better than 1% thus setting a limit for a possible energy dependence of the detector. This is underpinned by the good agreement of the out‐of field doses between ion‐chamber and microDiamond. The vendor specified EPOM was also verified (1.3 mm below the surface). Conclusion: Our study indicates that the characteristics of the microDiamond detector are well suited for accurate dosimetry within the investigated field sizes and depth limits.