Physics research is constantly pursuing more efficient silicon detectors, often trying to develop complex and optimized geometries, thus leading to non-trivial engineering challenges. Although ...critical for this optimization, there are few silicon tile mechanical data available in the literature. In an attempt to partially fill this gap, the present work details various mechanical-related aspects of spaceborne silicon detectors. Specifically, this study concerns three experimental campaigns with different objectives: a mechanical characterization of the material constituting the detector (in terms of density, elastic, and failure properties), an analysis of the adhesive effect on the loads, and a wirebond vibrational endurance campaign performed on three different unpotted samples. By collecting and discussing the experimental results, this work aims to fulfill its purpose of providing insight into the mechanical problems associated with this specific application and procuring input data of paramount importance. For the study to be complete, the perspective taken is broader than mere silicon analysis and embraces all related aspects; i.e., the detector–structure adhesive interface and the structural integrity of wirebonds. In summary, this paper presents experimental data on the material properties of silicon detectors, the impact of the adhesive on the gluing stiffness, and unpotted wirebond vibrational endurance. At the same time, the discussion of the results furnishes an all-encompassing view of the design-associated criticalities in experiments where silicon detectors are employed.
Hydrogenated amorphous silicon (a-Si:H) can be produced by plasma-enhanced chemical vapor deposition (PECVD) of SiH4 (silane) mixed with hydrogen. The resulting material shows outstanding radiation ...hardness properties and can be deposited on a wide variety of substrates. Devices employing a-Si:H technologies have been used to detect many different kinds of radiation, namely, minimum ionizing particles (MIPs), X-rays, neutrons, and ions, as well as low-energy protons and alphas. However, the detection of MIPs using planar a-Si:H diodes has proven difficult due to their unsatisfactory S/N ratio arising from a combination of high leakage current, high capacitance, and limited charge collection efficiency (50% at best for a 30 µm planar diode). To overcome these limitations, the 3D-SiAm collaboration proposes employing a 3D detector geometry. The use of vertical electrodes allows for a small collection distance to be maintained while preserving a large detector thickness for charge generation. The depletion voltage in this configuration can be kept below 400 V with a consequent reduction in the leakage current. In this paper, following a detailed description of the fabrication process, the results of the tests performed on the planar p-i-n structures made with ion implantation of the dopants and with carrier selective contacts are illustrated.
In this paper, by means of high-resolution photoemission, soft X-ray absorption and atomic force microscopy, we investigate, for the first time, the mechanisms of damaging, induced by neutron source, ...and recovering (after annealing) of p-i-n detector devices based on hydrogenated amorphous silicon (a-Si:H). This investigation will be performed by mean of high-resolution photoemission, soft X-Ray absorption and atomic force microscopy. Due to dangling bonds, the amorphous silicon is a highly defective material. However, by hydrogenation it is possible to reduce the density of the defect by several orders of magnitude, using hydrogenation and this will allow its usage in radiation detector devices. The investigation of the damage induced by exposure to high energy irradiation and its microscopic origin is fundamental since the amount of defects determine the electronic properties of the a-Si:H. The comparison of the spectroscopic results on bare and irradiated samples shows an increased degree of disorder and a strong reduction of the Si-H bonds after irradiation. After annealing we observe a partial recovering of the Si-H bonds, reducing the disorder in the Si (possibly due to the lowering of the radiation-induced dangling bonds). Moreover, effects in the uppermost coating are also observed by spectroscopies.
Silicon trackers technology, developed in the last century for accelerator based experiments, is currently used in several space-borne astro-particle experiments. The challenge is not only in the ...design and construction of the detector itself, but also in fulfilling the special requirements imposed by the launch process and the hostile running environment in space. In particular, the silicon trackers for DAMPE and LIMADOU experiments designed, assembled and tested under INFN Perugia leadership, have been successfully launched in space: DAMPE in December 2015 and LIMADOU in February 2018 and they are currently taking data. In this contribution, we report on the design and assembly of both trackers and the results from the construction.
•The silicon ladders were built with reliable assembly and calibration method.•Quality control of single component is mandatory.•The trackers for DAMPE and LIMADOU/HEPD were tested in space conditions.
PURPOSESmall photon beams used in radiotherapy techniques have inherent characteristics of charge particle disequilibrium and high-dose gradient making accurate dosimetry for such fields very ...challenging. By means of a 3D manufacturing technique, it is possible to create arrays of pixels with a very small sensitive volume for radiotherapy dosimetry. We investigate the impact of 3D pixels size on absorbed dose sensitivity, linearity of response with dose rate, reproducibility and beam profile measurements. METHODSDiamond detectors with different pixel sizes have been produced in the 3DOSE experiment framework. To investigate the pixels size impact, they were tested using an Elekta Synergy LINAC. Dose rate dependence, absorbed dose sensitivity, reproducibility and beam profile measurement accuracy have been investigated and compared with PTW 60019 and IBA SFD reference dosimeters. RESULTSAll of the 3D pixels had a linear and reproducible response to the dose rate. The sensitivity of a pixel decreases with its size, although even the smallest pixel has a high absorbed dose sensitivity (15 nC/Gy). The penumbra width measured with the smallest pixel size was consistent with the PTW microDiamond and differed by 0.2 mm from the IBA SFD diode. CONCLUSIONSThe study demonstrates that variation in pixel size do not affect the linearity of response with dose rate and the reproducibility of response. Due to the 3D geometry, the absorbed dose sensitivity of the detector remains high even for the smallest pixel, furthermore the pixel size was demonstrated to be of fundamental importance in the measurement of beam profiles.
. Microbeam radiation therapy (MRT) is an alternative emerging radiotherapy treatment modality which has demonstrated effective radioresistant tumour control while sparing surrounding healthy tissue ...in preclinical trials. This apparent selectivity is achieved through MRT combining ultra-high dose rates with micron-scale spatial fractionation of the delivered x-ray treatment field. Quality assurance dosimetry for MRT must therefore overcome a significant challenge, as detectors require both a high dynamic range and a high spatial resolution to perform accurately.
. In this work, a series of radiation hard a-Si:H diodes, with different thicknesses and carrier selective contact configurations, have been characterised for x-ray dosimetry and real-time beam monitoring applications in extremely high flux beamlines utilised for MRT at the Australian Synchrotron.
. These devices displayed superior radiation hardness under constant high dose-rate irradiations on the order of 6000 Gy s
, with a variation in response of 10% over a delivered dose range of approximately 600 kGy. Dose linearity of each detector to x-rays with a peak energy of 117 keV is reported, with sensitivities ranging from (2.74 ± 0.02) nC/Gy to (4.96 ± 0.02) nC/Gy. For detectors with 0.8
m thick active a-Si:H layer, their operation in an edge-on orientation allows for the reconstruction of micron-size beam profiles (microbeams). The microbeams, with a nominal full-width-half-max of 50
m and a peak-to-peak separation of 400
m, were reconstructed with extreme accuracy. The full-width-half-max was observed as 55 ± 1
m. Evaluation of the peak-to-valley dose ratio and dose-rate dependence of the devices, as well as an x-ray induced charge (XBIC) map of a single pixel is also reported.
. These devices based on novel a-Si:H technology possess a unique combination of accurate dosimetric performance and radiation resistance, making them an ideal candidate for x-ray dosimetry in high dose-rate environments such as FLASH and MRT.
Hydrogenated amorphous silicon (a-Si:H) is a material having an intrinsically high radiation hardness that can be deposited on flexible substrates such as polyimide (PI). For these properties, a-Si:H ...can be used for the production of flexible sensors. a-Si:H sensors can be successfully utilized in dosimetry, beam monitoring for particle physics (X-ray, electron, gamma ray, and proton detection) and radiotherapy, radiation flux measurement for space applications (study of solar energetic particles and stellar events), and neutron flux measurements. In this article, we have studied the dosimetric X-ray response of n-i-p diodes deposited on PI. We measured the linearity of the photocurrent response to X-rays versus dose rate from which we have extracted the dosimetric X-ray sensitivity at various bias voltages. In particular, low bias voltage operation has been studied to assess the high energy efficiency of these kinds of sensors. A measurement of stability of X-ray response versus time has been shown. The effect of detectors annealing has been studied. Operation under bending at various bending radii is also shown.
Silicon photomultipliers are commonly used to detect the passage of radiation in matter via the collection of photons produced by the ionizing radiation in converting materials. We investigated the ...possibility of direct detection of high-intensity X-ray fluxes using the measurement of the current produced by silicon photomultipliers directly exposed to the X-ray beam, in absence of any converter material. We have analyzed the response of different devices directly exposed to the radiation produced by an X-ray tube. The signal-to-noise ratio of the response confirms that the current produced during the irradiation provides information on the X-ray flux intensity. We parametrize the current response of SiPM devices as function of the X-ray flux intensity. We verify that the parametrization is accurate down to the % level and we study the linearity of the response to investigate the prospects for possible applications in real-time X-ray beam monitoring and beam spatial profiling.
Oncological hadrontherapy is a novel technique for cancer treatment that improves over conventional radiotherapy by having higher effectiveness and spatial selectivity. The FOOT (FragmentatiOn Of ...Target) experiment studies the nuclear fragmentation caused by the interactions of charged particle beams with patient tissues in Charged Particle Therapy. Among the several FOOT detectors, the silicon Microstrip Detector is part of the charged-ions-tracking magnetic spectrometer. The detector consists of three x-y planes of two silicon microstrip detectors arranged orthogonally between each other to enable tracking capabilities. Ten analog buffer chips and five ADCs read out each detector. A Field-Programmable Gate Array collects the output of the ADCs of an x-y plane, possibly processes the data, and forms a packet to be sent to the experiment central data acquisition. This data acquisition system shall withstand the trigger rate and detector's throughput at any time. In this work, we discuss the architecture of the data acquisition system-in particular of the silicon microstrip detector one-and the first results obtained from the x-y plane's prototype.
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