Tumour control is performed in particle therapy using particles and ions, whose high irradiation precision enhances the effectiveness of the treatment, while sparing the healthy tissue surrounding ...the target volume. Dose range monitoring devices using photons and charged particles produced by the beam interacting with the patient's body have already been proposed, but no attempt has been made yet to exploit the detection of the abundant neutron component. Since neutrons can release a significant dose far away from the tumour region, precise measurements of their flux, production energy and angle distributions are eagerly sought in order to improve the treatment planning system (TPS) software. It will thus be possible to predict not only the normal tissue toxicity in the target region, but also the risk of late complications in the whole body. The aforementioned issues underline the importance of an experimental effort devoted to the precise characterisation of neutron production, aimed at the measurement of their abundance, emission point and production energy. The technical challenges posed by a neutron detector aimed at high detection efficiency and good backtracking precision are addressed within the MONDO (monitor for neutron dose in hadrontherapy) project, whose main goal is to develop a tracking detector that can target fast and ultrafast neutrons. A full reconstruction of two consecutive elastic scattering interactions undergone by the neutrons inside the detector material will be used to measure their energy and direction. The preliminary results of an MC simulation performed using the FLUKA software are presented here, together with the DSiPM (digital SiPM) readout implementation. New detector readout implementations specifically tailored to the MONDO tracker are also discussed, and the neutron detection efficiency attainable with the proposed neutron tracking strategy are reported.
The search for a novel technology, which is able to detect and reconstruct nuclear recoil events in the keV energy range, has become increasingly important now that vast regions of high mass ...weakly-interacting-massive-particle-like dark matter candidates have been excluded. Gaseous time projection chambers (TPC) with optical readout are very promising candidates combining the complete event information provided by the TPC technique with the high sensitivity and granularity of the latest generation light sensors. A TPC with an amplification at the anode, obtained with gas electron multipliers (GEMs), was tested at the Laboratori Nazionali di Frascati. Photons and neutrons from radioactive sources were employed to induce recoiling nuclei and electrons with kinetic energy in the range 1-100 keV. A He-CF4 (60/40) gas mixture was used at atmospheric pressure and the light produced during the multiplication in the GEM channels was acquired by a high-position resolution and low-noise complementary metal-oxide semiconductor camera and a photomultiplier. A multi-stage pattern recognition algorithm based on an advanced clustering technique is presented here. A number of cluster-shaped observables are used to identify nuclear recoils induced by neutrons, which originated from a AmBe source against x-ray 55Fe photoelectrons. An efficiency of 18% to detect nuclear recoils with an energy of about 6 keV is reached, while suppressing 96% of the 55Fe photoelectrons, making this optical read-out gas TPC a very promising candidate for future investigations of ultra-rare events such as directional direct dark matter searches.
The MOnitor for Neutron Dose in hadrOntherapy (MONDO) project addresses the technical challenges posed by a neutron tracker detector aiming for a high detection efficiency and a good backtracking ...precision. The project aims to develop a tracking device capable of fully reconstructing the four momentum of fast and ultrafast secondary neutrons produced, e.g., in particle therapy (PT) treatments or in other physical processes. The MONDO tracker uses, as active material, squared scintillating fibers readout by dedicated CMOS-based digital single-photon avalanche diode (SPAD) array sensors. The expected light output, when operating in neutron monitoring applications, was experimentally evaluated in order to optimize the design of the MONDO detector readout. A small detector prototype (4 × 4 × 4.8 cm) has been built and tested at a test beam facility. The detection capabilities have been measured using a traditional photomultiplier (PMT) and a particle beam of 450-MeV electrons crossing a single layer of fibers. The observed number of photoelectrons in this case is (7.2 ± 1.4). A detector prototype was also tested with an SPAD-based SBAM (SPAD-Based Acquisition readout for MONDO experiment) sensor (SPADnet-I) to study the tracking performances. SBAM is a novel sensor developed to match the need of high single-photon detection efficiency and high spatial resolution and compactness. The sensor expected performance is discussed in view of an operation tailored for PT applications. In this contribution, we also report the results of a simulation performed to optimize the full MONDO detector layout.
Combined readout of a triple-GEM detector Antochi, V.C.; Baracchini, E.; Cavoto, G. ...
Journal of instrumentation,
05/2018, Letnik:
13, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Optical readout of GEM based devices by means of high granularity and low noise CMOS sensors allows to obtain very interesting tracking performance. Space resolution of the order of tens of μm were ...measured on the GEM plane along with an energy resolution of 20%÷30%. The main limitation of CMOS sensors is represented by their poor information about time structure of the event. In this paper, the use of a concurrent light readout by means of a suitable photomultiplier and the acquisition of the electric signal induced on the GEM electrode are exploited to provide the necessary timing informations. The analysis of the PMT waveform allows a 3D reconstruction of each single clusters with a resolution on z of 100 μm. Moreover, from the PMT signals it is possible to obtain a fast reconstruction of the energy released within the detector with a resolution of the order of 25% even in the tens of keV range useful, for example, for triggering purpose.
The performance and long term stability of an optically readout Time Projection Chamber with an electron amplification structure based on three Gas Electron Multipliers was studied. He/CF4 based gas ...mixtures were used in two different proportions (60/40 and 70/30) in a CYGNO prototype with 7 litres sensitive volume. With electrical configurations providing very similar electron gains, an almost full detection efficiency in the whole detector volume was found with both mixtures, while a light yield about 20% larger for the 60/40 was found. The electrostatic stability was tested by monitoring voltages and currents during 25 days. The detector worked in very stable and safe condition for the whole period. In the presence of less CF4, a larger probability of unstable events was clearly detected.
Time Projection Chambers (TPCs) working in combination with Gas Electron Multipliers (GEMs) produce a very sensitive detector capable of observing low energy events. This is achieved by capturing ...photons generated during the GEM electron multiplication process by means of a high-resolution camera. The CYGNO experiment has recently developed a TPC Triple GEM detector coupled to a low noise and high spatial resolution CMOS sensor. For the image analysis, an algorithm based on an adapted version of the well-known DBSCAN was implemented, called iDBSCAN. In this paper a description of the iDBSCAN algorithm is given, including test and validation of its parameters, and a comparison with DBSCAN itself and a widely used algorithm known as Nearest Neighbor Clustering (NNC). The results show that the adapted version of DBSCAN is capable of providing full signal detection efficiency and very good energy resolution while improving the detector background rejection.
The CYGNO project has the goal to use a gaseous TPC with optical readout to detect dark matter and solar neutrinos with low energy threshold and directionality. The CYGNO demonstrator will consist of ...1 m3 volume filled with He:CF4 gas mixture at atmospheric pressure. Optical readout with high granularity CMOS sensors, combined with fast light detectors, will provide a detailed reconstruction of the event topology. This will allow to discriminate the nuclear recoil signal from the background, mainly represented by low energy electron recoils induced by radioactivity. Thanks to the high reconstruction efficiency, CYGNO will be sensitive to low mass dark matter, and will have the potential to overcome the neutrino floor, that ultimately limits non-directional dark matter searches.
CYGNO is a project realising a cubic meter demonstrator to study the scalability of the performance of the optical approach for the readout of large-volume, GEM-equipped TPC. This is part of the ...CYGNUS proto-collaboration which aims at constructing a network of underground observatories for directional Dark Matter search. The combined use of high-granularity sCMOS and fast sensors for reading out the light produced in GEM channels during the multiplication processes was shown to allow on one hand to reconstruct 3D direction of the tracks, offering accurate energy measurements and sensitivity to the source directionality and, on the other hand, a high particle identification capability very useful to distinguish nuclear recoils. Results of the performed R&D and future steps toward a 30-100 cubic meter experiment will be presented.
The performance of the muon identification in LHCb is extracted from data using muons and hadrons produced in J/psi arrow right mu super(+) mu super(-) , Lambda super(0) arrow right ppi super(-) and ...D* super(+) arrow right pi super(+)D super(0)(K super(-)pi super(+)) decays. The muon identification procedure is based on the pattern of hits in the muon chambers. A momentum dependent binary requirement is used to reduce the probability of hadrons to be misidentified as muons to the level of 1%, keeping the muon efficiency in the range of 95-98%. As further refinement, a likelihood is built for the muon and non-muon hypotheses. Adding a requirement on this likelihood that provides a total muon efficiency at the level of 93%, the hadron misidentification probabilities are below 0.6%.
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