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Empirical data in proton therapy indicate that relative biological effectiveness (RBE) is not constant, and it is directly related to the linear energy transfer (LET). The experimental assessment of LET with high resolution would be a powerful tool for minimizing the LET hot spots in intensity-modulated proton therapy, RBE- or LET-guided evaluation and optimization to achieve biologically optimized proton plans, verifying the theoretical predictions of variable proton RBE models, and so on. This could impact clinical outcomes by reducing toxicities in organs at risk.

During the prototyping phase of the new ATLAS Inner-Tracker (ITk) strip sensors, a degradation of the device breakdown voltage at high humidity was observed. Although the degradation was temporary, showing a fast recovery in dry conditions, the study of the influence of humidity on the sensor performance was critical to establish counter-measures and handling protocols during production testing in order to ensure the proper performance of the upgraded detector. The work presented here has the objective to study for the first time the breakdown voltage deterioration in presence of ambient humidity of ATLAS ITk production-layout strip sensors with different surface properties, before and after proton, neutron and gamma irradiations. A study of the humidity sensitivity of miniature ATLAS ITk strip sensors, before and after proton irradiations, is also presented to compare the sensitivity of devices with different sizes. The sensors were also exposed for several days to high humidity with the aim to recreate and evaluate the influence of the detector integration environment expected during the Large Hadron Collider (LHC) Long Shutdown 3 (LS3) in 2026, where the sensors will be exposed to ambient humidity for prolonged times.

New silicon 3-D-microdetectors have been developed to perform microdosimetry measurements for applications in hadron therapy. In this work, the charge collection efficiency (CCE) of an improved second generation of microdetectors having two different thicknesses (10 and 20 \mu \text{m} ) and a diameter of 25 \mu \text{m} has been studied by means of the ion beam induced charge (IBIC) technique. New methods to study the active volume and the CCE of microdosimeters are proposed and verified here. The results show that, for this new generation of microdetectors, the CCE is 100% for radial distances up to 10.2 \mu \text{m} from the center of the device, and it rapidly decays between 10.2 \mu \text{m} and the detector edge. The characterization of the CCE conducted here will allow us to completely explain the energy spectra obtained during the microdosimetry studies performed in clinical centers.

New silicon 3-D-microdetectors have been developed to perform microdosimetry measurements for applications in hadron therapy. In this work, the charge collection efficiency (CCE) of an improved second generation of microdetectors having two different thicknesses (10 and 20 \mu \text{m} ) and a diameter of 25 \mu \text{m} has been studied by means of the ion beam induced charge (IBIC) technique. New methods to study the active volume and the CCE of microdosimeters are proposed and verified here. The results show that, for this new generation of microdetectors, the CCE is 100% for radial distances up to 10.2 \mu \text{m} from the center of the device, and it rapidly decays between 10.2 \mu \text{m} and the detector edge. The characterization of the CCE conducted here will allow us to completely explain the energy spectra obtained during the microdosimetry studies performed in clinical centers.

Microdosimetry has been traditionally performed through gaseous proportional counters, although in recent years different solid-state microdosimeters have been proposed and constructed for this task. In this paper, we analyze the response of solid-state devices of micrometric size with no intrinsic gain developed by CNM-CSIC (Spain). There are two major aspects of the operation of these devices that affect the reconstruction of the probability distributions and momenta of stochastic quantities related to microdosimetry. For micrometric volumes, the drift and diffusion of the charge carriers gives rise to a partial charge collection efficiency in the peripheral region of the depleted volume. This effect produces a perturbation of the reconstructed pulse height (i.e. imparted energy) distributions with respect to the actual microdosimetric distributions. The relevance of this deviation depends on the size, geometry and operating conditions of the device. On the other hand, the electronic noise from the single-event readout set-up poses a limit on the minimum detectable lineal energy when the microdosimeter size is reduced. This article addresses these issues to provide a framework on the physical constraints for the design and operation of solid-state microdosimeters.

The present overview describes the evolution of new microdosimeters developed in the National Microelectronics Center in Spain (IMB-CNM, CSIC), ranging from the first ultra-thin 3D diodes (U3DTHINs) to the advanced 3D-cylindrical microdetectors, which have been developed over the last 10 years. In this work, we summarize the design, main manufacture processes, and electrical characterization of these devices. These sensors were specifically customized for use in particle therapy and overcame some of the technological challenges in this domain, namely the low noise capability, well-defined sensitive volume, high spatial resolution, and pile-up robustness. Likewise, both architectures reduce the loss of charge carriers due to trapping effects, the charge collection time, and the voltage required for full depletion compared to planar silicon detectors. In particular, a 3D‒cylindrical architecture with electrodes inserted into the silicon bulk and with a very well‒delimited sensitive volume (SV) mimicked a cell array with shapes and sizes similar to those of mammalian cells for the first time. Experimental tests of the carbon beamlines at the Grand Accélérateur National d’Lourds (GANIL, France) and Centro Nazionale Adroterapia Oncologica (CNAO, Italy) showed the feasibility of the U3DTHINs in hadron therapy beams and the good performance of the 3D‒cylindrical microdetectors for assessing linear energy distributions of clinical beams, with clinical fluence rates of 5 × 107 s−1cm−2 without saturation. The dose-averaged lineal energies showed a generally good agreement with Monte Carlo simulations. The results indicated that these devices can be used to characterize the microdosimetric properties in hadron therapy, even though the charge collection efficiency (CCE) and electronic noise may pose limitations on their performance, which is studied and discussed herein. In the last 3D‒cylindrical microdetector generation, we considerably improved the CCE due to the microfabric

Microdosimetry has been traditionally performed through gaseous proportional counters, although in recent years different solid-state microdosimeters have been proposed and constructed for this task. In this paper, we analyze the response of solid-state devices of micrometric size with no intrinsic gain developed by CNM-CSIC (Spain). There are two major aspects of the operation of these devices that affect the reconstruction of the probability distributions and momenta of stochastic quantities related to microdosimetry. For micrometric volumes, the drift and diffusion of the charge carriers gives rise to a partial charge collection efficiency in the peripheral region of the depleted volume. This effect produces a perturbation of the reconstructed pulse height (i.e. imparted energy) distributions with respect to the actual microdosimetric distributions. The relevance of this deviation depends on the size, geometry and operating conditions of the device. On the other hand, the electronic noise from the single-event readout set-up poses a limit on the minimum detectable lineal energy when the microdosimeter size is reduced. This article addresses these issues to provide a framework on the physical constraints for the design and operation of solid-state microdosimeters.

The present overview describes the evolution of new microdosimeters developed in the National Microelectronics Center in Spain (IMB-CNM, CSIC), ranging from the first ultra-thin 3D diodes (U3DTHINs) to the advanced 3D-cylindrical microdetectors, which have been developed over the last 10 years. In this work, we summarize the design, main manufacture processes, and electrical characterization of these devices. These sensors were specifically customized for use in particle therapy and overcame some of the technological challenges in this domain, namely the low noise capability, well-defined sensitive volume, high spatial resolution, and pile-up robustness. Likewise, both architectures reduce the loss of charge carriers due to trapping effects, the charge collection time, and the voltage required for full depletion compared to planar silicon detectors. In particular, a 3D‒cylindrical architecture with electrodes inserted into the silicon bulk and with a very well‒delimited sensitive volume (SV) mimicked a cell array with shapes and sizes similar to those of mammalian cells for the first time. Experimental tests of the carbon beamlines at the Grand Accélérateur National d’Lourds (GANIL, France) and Centro Nazionale Adroterapia Oncologica (CNAO, Italy) showed the feasibility of the U3DTHINs in hadron therapy beams and the good performance of the 3D‒cylindrical microdetectors for assessing linear energy distributions of clinical beams, with clinical fluence rates of 5 × 107 s−1cm−2 without saturation. The dose-averaged lineal energies showed a generally good agreement with Monte Carlo simulations. The results indicated that these devices can be used to characterize the microdosimetric properties in hadron therapy, even though the charge collection efficiency (CCE) and electronic noise may pose limitations on their performance, which is studied and discussed herein. In the last 3D‒cylindrical microdetector generation, we considerably improv

The planned High Luminosity Large Hadron Collider is being designed to maximise the physics potential of the LHC with 10 years of operation at instantaneous luminosities of 7.5×10 34 cm ¿2 s ¿1 . A consequence of this increased luminosity is the expected radiation damage requiring the tracking detectors to withstand hadron fluence to over 1×10 15 1 MeV neutron equivalent per cm 2 in the ATLAS Strips system. Fast readout electronics, deploying 130 nm CMOS front-end electronics are glued on top of a silicon sensor to make a module. The radiation hard n-in-p micro-strip sensors used have been developed by the ATLAS ITk Strip Sensor collaboration and produced by Hamamatsu Photonics. A series of tests were performed at the DESY-II test beam facility to investigate the detailed performance of a strip module with both 2.5 cm and 5 cm length strips before irradiation. The DURANTA telescope was used to obtain a pointing resolution of 2 ¿m, with an additional pixel layer installed to improve timing resolution to ~25 ns. Results show that prior to irradiation a wide range of thresholds (0.5¿2.0 fC) meet the requirements of a noise occupancy less than 1×10 ¿3 and a hit efficiency greater than 99%. © 2018

[Introduction] Use of solid-state sensors for measuring microdosimetric quantities has been increasing recently due to advantages such as its size, portability and its lack of high voltage biasing to work properly. However, these devices do not lack drawbacks; drift and diffusion phenomena affect partial charge collection, modifying the microdosimetric spectra depending on the geometry of the site, operation conditions and readout electronic noise. [Methods] Drift and diffusion processes are very relevant when micrometric active sites are considered. A perturbation in the pulse height detected spectrum respect to the ideal imparted energy within the considered site geometry is produced. Effects in silicon micro-dosimeters built by IMB-INM (CSIC, Spain) were evaluated. To parametrize the charge collection effi ciency an IBIC test at CNA (Seville, Spain) was performed and results were compared with TCAD simulations. The device model used together with FLUKA Monte Carlo simulations has been compared with experimental micro-dosimetric spectra of a clinical 12C ion beam at Fondazione CNAO (Pavia, Italy). [Results] Smeared Monte Carlo spectra reproduce the main features of the experimental spectra taken with the silicon microdosimeters affected by partial charge collection events. The perturbation on the frequency and dose averaged lineal energy as a function of micro-dosimeter size was evaluated. Additionally, the minimum detectable lineal energy for no intrinsic gain devices was evaluated considering a general model of readout electronics as a function of the fl uence averaged mass thickness of solid-state micro-dosimeters. [Conclusions] Solid-state devices can be employed to measure microdosimetric spectra, but large collection and electronic noise pose limitations on their performance. The perturbation on the microdosimetric spectra has been evaluated in this work to set a general benchmark for the expected performance of a micro-dosimeter depending on geometry and se