This paper reports on the fabrication, simulation, and charge collection characteristics of a new generation of cylindrical silicon microdosimeters fabricated on SOI wafers. The devices consist of an array of p + electrodes surrounded by trench n + electrodes creating well defined, cylindrical sensitive volumes. A first batch of microsensors with 5.4 µm active thickness has been successfully fabricated. The devices are fully functional with good diode behavior and a depletion voltage of only 3 V. Their charge collection characteristics have been investigated using the IBIC technique with protons and alpha particles. The IBIC maps show a 100% yield of active cells in a microdosimeter array and full charge collection efficiency in the active area of the unit microsensors. These devices constitute an step forward in the current status of microdosimeters based on silicon technologies.

In this work, we propose a solid-state-detector for use in radiation microdosimetry. This device improves the performance of existing dosimeters using customized 3D-cylindrical microstructures etched inside silicon. The microdosimeter consists of an array of micro-sensors that have 3Dcylindrical electrodes of 15 lm diameter and a depth of 5 lm within a silicon membrane, resulting in a well-defined micrometric radiation sensitive volume. These microdetectors have been characterized using an 241 Am source to assess their performance as radiation detectors in a high-LET environment. This letter demonstrates the capability of this microdetector to be used to measure dose and LET in hadrontherapy centers for treatment plan verification as part of their patient-specific quality control program. V

The commissioning of an ion beam for hadrontherapy requires the evaluation of the biologically weighted effective dose that results from the microdosimetric properties of the therapy beam. The spectra of the energy imparted at cellular and sub-cellular scales are fundamental to the determination of the biological effect of the beam. These magnitudes are related to the microdosimetric distributions of the ion beam at different points along the beam path. This work is dedicated to the measurement of microdosimetric spectra at several depths in the central axis of a (12)C beam with an energy of 94.98 AMeV using a novel 3D ultrathin silicon diode detector. Data is compared with Monte Carlo calculations providing an excellent agreement (deviations are less than 2% for the most probable lineal energy value) up to the Bragg peak. The results show the feasibility to determine with high precision the lineal energy transfer spectrum of a hadrontherapy beam with these silicon devices.

We describe the design, fabrication process and characterization of a thermal neutron detector based on ultra-thin silicon PIN diodes with 3D electrodes and a 10 B 4 C neutron converter layer. The sensors were fabricated on SOI silicon with an active thickness of 20 µm which allows for a low gamma sensitivity, while the 3D structure of the electrodes results in a lower capacitance that in the equivalent planar sensor. The 2.7 µm 10 B 4 C converter layer was deposited through RF magnetron sputtering on a whole silicon wafer, opening the path for mass-production. The detectors were tested in a thermal neutron beam at the nuclear reactor at the Instituto Superior Técnico in Lisbon and their intrinsic detection efficiency for themal neutrons and the gamma sensitivity as a function of the energy threshold were obtained.

In this paper we present the design and performance of a perforated thermal neutron silicon detector with a 6 LiF neutron converter. This device was manufactured within the REWARD project workplace whose aim is to develop and enhance technologies for the detection of nuclear and radiological materials. The sensor perforated structure results in a higher efficiency than that obtained with an equivalent planar sensor. The detectors were tested in a thermal neutron beam at the nuclear reactor at the Instituto Superior Técnico in Lisbon and the intrinsic detection efficiency for thermal neutrons and the gamma sensitivity were obtained. The Geant4 Monte Carlo code was used to simulate the experimental conditions, i.e. thermal neutron beam and the whole detector geometry. An intrinsic thermal neutron detection efficiency of 8.6% ± 0.4% with a discrimination setting of 450 keV was measured.

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