NEXT Collaboration(Mistry, K. et al), Carcel, S., Lopez-March, N., Martin-Albo, J., Novella, P., Querol, M., et al. (2024). Design, characterization and installation of the NEXT-100 cathode and electroluminescence regions. J. Instrum., 19(2), P02007–36pp.
Abstract: NEXT -100 is currently being constructed at the Laboratorio Subterraneo de Canfranc in the Spanish Pyrenees and will search for neutrinoless double beta decay using a high-pressure gaseous time projection chamber (TPC) with 100 kg of xenon. Charge amplification is carried out via electroluminescence (EL) which is the process of accelerating electrons in a high electric field region causing secondary scintillation of the medium proportional to the initial charge. The NEXT -100 EL and cathode regions are made from tensioned hexagonal meshes of 1 m diameter. This paper describes the design, characterization, and installation of these parts for NEXT -100. Simulations of the electric field are performed to model the drift and amplification of ionization electrons produced in the detector under various EL region alignments and rotations. Measurements of the electrostatic breakdown voltage in air characterize performance under high voltage conditions and identify breakdown points. The electrostatic deflection of the mesh is quantified and fit to a first -pr inciples mechanical model. Measurements were performed with both a standalone test EL region and with the NEXT-100 EL region before its installation in the detector. Finally, we describe the parts as installed in NEXT-100, following their deployment in Summer 2023.
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Brzezinski, K., Oliver, J. F., Gillam, J., & Rafecas, M. (2014). Study of a high-resolution PET system using a Silicon detector probe. Phys. Med. Biol., 59(20), 6117–6140.
Abstract: A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 x 52 array of 1 x 1 x 1 mm(3) pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image resolution for two probe positions. A homogeneous source distribution with hot and cold regions was used to demonstrate that the localized improvement in resolution does not come at the expense of the overall quality of the image. Since the improvement is constrained to an area close to the probe, breast imaging is proposed as a potential application for the novel geometry. In this sense, a simplified breast phantom, adjacent to heart and torso compartments, was simulated and the effect of the probe on lesion detectability, through measurements of the local contrast recovery coefficient-to-noise ratio (CNR), was observed. The list-mode ML-EM algorithm was used for image reconstruction in all cases. As expected, the point spread function of the PET-probe system was found to be non-isotropic and vary with position, offering improvement in specific regions. Increase in resolution, of factors of up to 2, was observed in the region close to the probe. Images of the resolution phantom showed visible improvement in resolution when including the probe in the simulations. The image quality study demonstrated that contrast and spill-over ratio in other areas of the FOV were not sacrificed for this enhancement. The CNR study performed on the breast phantom indicates increased lesion detectability provided by the probe.
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AGATA Collaboration, Doncel, M., Recchia, F., Quintana, B., Gadea, A., & Farnea, E. (2010). Experimental test of the background rejection, through imaging capability, of a highly segmented AGATA germanium detector. Nucl. Instrum. Methods Phys. Res. A, 622(3), 614–618.
Abstract: The development of highly segmented germanium detectors as well as the algorithms to identify the position of the interaction within the crystal opens the possibility to locate the gamma-ray source using Compton imaging algorithms. While the Compton-suppression shield, coupled to the germanium detector in conventional arrays, works also as an active filter against the gamma rays originated outside the target, the new generation of position sensitive gamma-ray detector arrays has to fully rely on tracking capabilities for this purpose. In specific experimental conditions, as the ones foreseen at radioactive beam facilities, the ability to discriminate background radiation improves the sensitivity of the gamma spectrometer. In this work we present the results of a measurement performed at the Laboratori Nazionali di Legnaro (LNL) aiming the evaluation of the AGATA detector capabilities to discriminate the origin of the gamma rays on an event-by-event basis. It will be shown that, exploiting the Compton scattering formula, it is possible to track back gamma rays coming from different positions, assigning them to specific emitting locations. These imaging capabilities are quantified for a single crystal AGATA detector.
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Labiche, M. et al, Caballero, L., & Rubio, B. (2010). TIARA: A large solid angle silicon array for direct reaction studies with radioactive beams. Nucl. Instrum. Methods Phys. Res. A, 614(3), 439–448.
Abstract: A compact, quasi-4 pi position sensitive silicon array. TIARA, designed to study direct reactions induced by radioactive beams in inverse kinematics is described here. The Transfer and Inelastic All-angle Reaction Array (TIARA) consists of 8 resistive charge division detectors forming an octagonal barrel around the target and a set of double-sided silicon-strip annular detectors positioned at each end of the barrel. The detector was coupled to the gamma-ray array EXOGAM and the spectrometer VAMOS at the GANIL Laboratory to demonstrate the potential of such an apparatus with radioactive beams. The N-14(d,p)N-15 reaction, well known in direct kinematics, has been carried out in inverse kinematics for that purpose. The observation of the N-15 ground state and excited states at 7.16 and 7.86 MeV is presented here as well as the comparison of the measured proton angular distributions with DWBA calculations. Transferred l-values are in very good agreement with both theoretical calculations and previous experimental results obtained in direct kinematics.
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Miñano, M. (2011). Radiation Hard Silicon Strips Detectors for the SLHC. IEEE Trans. Nucl. Sci., 58(3), 1135–1140.
Abstract: While the Large Hadron Collider (LHC) began taking data in 2009, scenarios for a machine upgrade to achieve a much higher luminosity are being developed. In the current planning, it is foreseen to increase the luminosity of the LHC at CERN around 2018. As radiation damage scales with integrated luminosity, the particle physics experiments will need to be equipped with a new generation of radiation hard detectors. This article reports on the status of the R&D projects on radiation hard silicon strips detectors for particle physics, linked to the Large Hadron Collider Upgrade, super-LHC (sLHC) of the ATLAS microstrip detector. The primary focus of this report is on measuring the radiation hardness of the silicon materials and the detectors under study. This involves designing silicon detectors, irradiating them to the sLHC radiation levels and studying their performance as particle detectors. The most promising silicon detector for the different radiation levels in the different regions of the ATLAS microstrip detector will be presented. Important challenges related to engineering layout, powering, cooling and reading out a very large strip detector are presented. Ideas on possible schemes for the layout and support mechanics will be shown.
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Herrero-Garcia, J., Schwetz, T., & Zupan, J. (2012). On the annual modulation signal in dark matter direct detection. J. Cosmol. Astropart. Phys., 03(3), 005–28pp.
Abstract: We derive constraints on the annual modulation signal in Dark Matter (DM) direct detection experiments in terms of the unmodulated event rate. A general bound independent of the details of the DM distribution follows from the assumption that the motion of the earth around the sun is the only source of time variation. The bound is valid for a very general class of particle physics models and also holds in the presence of an unknown unmodulated background. More stringent bounds are obtained, if modest assumptions on symmetry properties of the DM halo are adopted. We illustrate the bounds by applying them to the annual modulation signals reported by the DAMA and CoGeNT experiments in the framework of spin-independent elastic scattering. While the DAMA signal satisfies our bounds, severe restrictions on the DM mass can be set for CoGeNT.
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Egea Canet, F. J. et al, Gadea, A., & Huyuk, T. (2015). A New Front-End High-Resolution Sampling Board for the New-Generation Electronics of EXOGAM2 and NEDA Detectors. IEEE Trans. Nucl. Sci., 62(3), 1056–1062.
Abstract: This paper presents the final design and results of the FADC Mezzanine for the EXOGAM (EXOtic GAMma array spectrometer) and NEDA (Neutron Detector Array) detectors. The measurements performed include those of studying the effective number of bits, the energy resolution using HP-Ge detectors, as well as timing histograms and discrimination performance. Finally, the conclusion shows how a common digitizing device has been integrated in the experimental environment of two very different detectors which combine both low-noise acquisition and fast sampling rates. Not only the integration fulfilled the expected specifications on both systems, but it also showed how a study of synergy between detectors could lead to the reduction of resources and time by applying a common strategy.
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Egea Canet, F. J. et al, Gadea, A., & Huyuk, T. (2015). Digital Front-End Electronics for the Neutron Detector NEDA. IEEE Trans. Nucl. Sci., 62(3), 1063–1069.
Abstract: This paper presents the design of the NEDA (Neutron Detector Array) electronics, a first attempt to involve the use of digital electronics in large neutron detector arrays. Starting from the front-end modules attached to the PMTs (PhotoMultiplier Tubes) and ending up with the data processing workstations, a comprehensive electronic system capable of dealing with the acquisition and pre-processing of the neutron array is detailed. Among the electronic modules required, we emphasize the front-end analog processing, the digitalization, digital pre-processing and communications firmware, as well as the integration of the GTS (Global Trigger and Synchronization) system, already used successfully in AGATA (Advanced Gamma Tracking Array). The NEDA array will be available for measurements in 2016.
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Bertone, G., Bozorgnia, N., Kim, J. S., Liem, S., McCabe, C., Otten, S., et al. (2018). Identifying WIMP dark matter from particle and astroparticle data. J. Cosmol. Astropart. Phys., 03(3), 026–42pp.
Abstract: One of the most promising strategies to identify the nature of dark matter consists in the search for new particles at accelerators and with so-called direct detection experiments. Working within the framework of simplified models, and making use of machine learning tools to speed up statistical inference, we address the question of what we can learn about dark matter from a detection at the LHC and a forthcoming direct detection experiment. We show that with a combination of accelerator and direct detection data, it is possible to identify newly discovered particles as dark matter, by reconstructing their relic density assuming they are weakly interacting massive particles (WIMPs) thermally produced in the early Universe, and demonstrating that it is consistent with the measured dark matter abundance. An inconsistency between these two quantities would instead point either towards additional physics in the dark sector, or towards a non-standard cosmology, with a thermal history substantially different from that of the standard cosmological model.
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Caputo, A., Regis, M., Taoso, M., & Witte, S. J. (2019). Detecting the stimulated decay of axions at radio frequencies. J. Cosmol. Astropart. Phys., 03(3), 027–22pp.
Abstract: Assuming axion-like particles account for the entirety of the dark matter in the Universe, we study the possibility of detecting their decay into photons at radio frequencies. We discuss different astrophysical targets, such as dwarf spheroidal galaxies, the Galactic Center and halo, and galaxy clusters. The presence of an ambient radiation field leads to a stimulated enhancement of the decay rate; depending on the environment and the mass of the axion, the effect of stimulated emission may amplify the photon flux by serval orders of magnitude. For axion-photon couplings allowed by astrophysical and laboratory constraints (and possibly favored by stellar cooling), we find the signal to be within the reach of next-generation radio telescopes such as the Square Kilometer Array.
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