Using a Focused X-Ray Beam for Mapping Sensitivity of a Single Crystal CVD Diamond Detector

This paper presents an in-depth mapping sensitivity study using a focused X-ray beam produced by an X-ray tube and applied to a low purity single crystal diamond sample designated as VS-Ti/Au. More specifically, the study shows the effect of changing the beam size, step displacement, bias polarity, annealing of the device as well as the dose rate (tube current) on the current response of these maps. In addition, the current response of the mapping sensitivity as a function of the bias voltage, and the photocurrent pulse shapes at different points (positions within the sample) as a function of time are also presented in this paper. It is worth highlighting that during the investigations of this paper a chemical vapour deposition (CVD) grown understudy sample was selected due to its special features such as: thin nitrogen lines and substrate area (which can be observed by X-ray mapping). Moreover, the investigations included in this paper illustrate two methods which were utilized to measure the spot diameter (a crucial parameter for sensitivity mapping) when moving the detector in the x–y direction. The first method applies a fluorescent paper and a video camera, while the second method applies stepping over an edge of a silicon PIN diode. The results of applying these two methods showed similar trends of spot diameter (i.e. the intensity increase with the increase of the dose rate), however, the second method (silicon PIN diode) resulted-in higher values. The obtained results provide key insights into the behaviour of single crystal CVD diamond detector under X-ray exposure. This is especially important as X-ray exposure sees use in radiotherapeutic applications, small field and online dosimetry, along with medical imaging and beam monitoring in both accelerators and synchrotron radiation facilities.