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This work aims at describing a dose-measurement system based on a high-quality single-crystal synthetic diamond coupled to specifically-designed front-end electronics and timing circuitry. By exploiting the pulsed nature of radiation sourced by LINACs, the electronics performs a synchronous detection of charge-carriers generated by the diamond detector on which pulsed X-rays impinge. Synchronous detection would assure superior level of accuracy, sensitivity, and dynamics in comparison to conventional continuous-integration solutions, since the measurements are affected by environmental noise to a lesser extent. In addition, preliminary characterization described in this paper highlights the feasibility of a measurement system capable of providing information on the dose delivered at the level of a single X-ray pulse. In this context, the proposed system would be able to respond to the specific needs of accurate dose diagnostics for modern radiotherapy treatments where radiation-dose is characterized by a complex shaped distribution and steep gradients.

In this work we analyze the behavior of pressure sensors based on membranes of chemically very inert materials and robust to atmospheric agents with non-neutral pH. The selected material for cheapness and chemical stability for the manufacture of low-cost pressure sensors is Silicon Carbide, even if a special section is dedicated to diamond membranes pressure sensors because of its unique chemical inertness. Considering also the electromagnetic noise as an aggressive element of the measurement environment, the low-cost reproduction via sensor - optical fiber coupling of a low-finesse Fabry-Perot interferometer was chosen as the reading setup. SiC membranes are realized by nanosecond LASER processing while those in diamond are made by CVD deposition and microelectronic etching techniques.

Pressure sensors based on diamond membranes were designed and tested for gas pressure measurement up to 6.8 MPa. The diamond film (2” diameter, 6 μm thickness)—grown by microwave plasma chemical vapor deposition on a silicon substrate—was a starting material to produce an array of membranes with different diameters in the 130–400 μm range, in order to optimize the sensor performance. Each 5 mm × 5 mm sensing element was obtained by subsequent silicon slicing. The fixed film thickness, full-scale pressure range, and sensor sensitivity were established by a proper design of the diameter of diamond membrane which represents the sensing element for differential pressure measurement. The pressure-induced deflection of the membrane was optically measured using a Fabry-Pérot interferometer formed by a single mode optical fiber front surface and the deflecting diamond film surface. The optical response of the system was numerically simulated using geometry and the elastic properties of the diamond diaphragm, and was compared with the experiments. Depending on the diamond membrane’s diameter, the fabricated sensors displayed a good modulation depth of response over different full-scale ranges, from 3 to 300 bar. In view of the excellent mechanical, thermal, and chemical properties of diamond, such pressure sensors could be useful for performance in a harsh environment.

Thin polycrystalline diamond films chemically vapor deposited on thinned silicon substrates were used as membranes for pressure sensor fabrication by means of selective chemical etching of silicon. The sensing element is based on a simple low-finesse Fabry&ndash, P&eacute, rot (FP) interferometer. The FP cavity is defined by the end-face of a single mode fiber and the diamond diaphragm surface. Hence, pressure is evaluated by measuring the cavity length by an optoelectronic system coupled to the single mode fiber. Exploiting the excellent properties of Chemical Vapor Deposition (CVD) diamond, in terms of high hardness, low thermal expansion, and ultra-high thermal conductivity, the realized sensors have been characterized up to 16.5 MPa at room temperature. Preliminary characterizations demonstrate the feasibility of such diamond-on-Si membrane structure for pressure transduction. The proposed sensing system represents a valid alternative to conventional solutions, overcoming the drawback related to electromagnetic interference on the acquired weak signals generated by standard piezoelectric sensors.