The 50 most-cited articles in Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment, 2024

Analogue test structures were fabricated using the Tower Partners Semiconductor Co. CMOS 65 nm ISC process. The purpose was to characterize and qualify this process and to optimize the sensor for the next generation of Monolithic Active Pixels Sensors for high-energy physics. The technology was explored in several variants which differed by: doping levels, pixel geometries and pixel pitches (10–25 μ m). These variants have been tested following exposure to varying levels of irradiation up to 3 MGy and 1 0 16 1 MeV n eq cm −2 . Here the results from prototypes that feature direct analogue output of a 4 × 4 pixel matrix are reported, allowing the systematic and detailed study of charge collection properties. Measurements were taken both using 55 Fe X-ray sources and in beam tests using minimum ionizing particles. The results not only demonstrate the feasibility of using this technology for particle detection but also serve as a reference for future applications and optimizations.

The first loading of gadolinium (Gd) into Super-Kamiokande in 2020 was successful, and the neutron capture efficiency on Gd reached 50%. To further increase the Gd neutron capture efficiency to 75%, 26.1 tons of Gd2(SO4)3⋅8H2O was additionally loaded into Super-Kamiokande (SK) from May 31 to July 4, 2022. As the amount of loaded Gd2(SO4)3⋅8H2O was doubled compared to the first loading, the capacity of the powder dissolving system was doubled. We also developed new batches of gadolinium sulfate with even further reduced radioactive impurities. In addition, a more efficient screening method was devised and implemented to evaluate these new batches of Gd2(SO4)3⋅8H2O. Following the second loading, the Gd concentration in SK was measured to be 333.5±2.5 ppm via an Atomic Absorption Spectrometer (AAS). From the mean neutron capture time constant of neutrons from an Am/Be calibration source, the Gd concentration was independently measured to be 332.7 ± 6.8(sys.) ± 1.1(stat.) ppm, consistent with the AAS result. Furthermore, during the loading the Gd concentration was monitored continually…

We present a mixed-signal ASIC , called ALCOR (A Low-power Chip for Optical sensor Readout), designed for the readout and digitization of signals from Silicon Photomultipliers (SiPMs) in the framework of the dual-radiator RICH (dRICH) detector of the electron–Proton/Ion Collider (ePIC) experiment at the Electron–Ion Collider (EIC). ALCOR features 32 channels arranged in an 8x4 matrix. The amplifier input stage is a low impedance current conveyor based on a regulated common-gate topology. The versatile front-end is able to work with positive or negative input polarity signals and includes four gain settings and two discriminators with 6-bit DAC programmable thresholds. Each channel also incorporates quad-buffered low-power TDCs based on analogue interpolation providing precise timestamping with a 25–50 ps time bin. ALCOR is designed in a 110 nm CMOS technology and the power consumption is about 10–12 mW per channel. The ASIC has been extensively tested in the laboratory standalone and coupled to different SiPM models to assess its functionality and performance. The results have been…

The Timepix4 is an application-specific integrated circuit developed by the Medipix4 collaboration. The chip is a 448 × 512 matrix that can be connected, via bump-bonding, to pixelated sensors of various materials and thicknesses, forming application specific detection systems. Among the Timepix4 operating modes, the data-driven Time-of-Arrival - Time-Over-Threshold is a particularly promising mode for spectral imaging applications: data packets are generated every time the charge created by the incoming radiation goes above a pre-defined threshold, allowing the count of the detected particles and their energy measurement. This article investigates the spectroscopic characteristics of a Timepix4 assembly equipped with a 300 μm Si sensor, using monochromatic X-ray beams in the energy range 8.5 keV–40 keV working at the SYRMEP beamline of the Elettra synchrotron. The accuracy and the energy resolution of the reconstructed energy spectra, together with an energy resolution model, will be presented.

A new development of radiation-resistant silicon sensors is presented. The new sensors exploit the Low-Gain Avalanche Diode (LGAD) technology, with internal multiplication of the charge carriers, in combination with thin substrates, intrinsically less affected by radiation. An innovative design of the gain implant typical of the LGADs has been developed and fabricated, employing the compensation of acceptor and donor dopants to reproduce the effective acceptor doping dose of standard LGAD sensors. At the end of 2022, the Fondazione Bruno Kessler (Italy) delivered the first batch of compensated LGAD sensors on 30μm thick p-type epitaxial substrates. Electrical and transient characterisation of the sensors has been performed before and after irradiation up to 5 ⋅1015 1 MeV equivalent n/cm2. The ultimate goal is to develop and produce compensated LGAD sensors that can efficiently operate above fluences of 1017 1 MeV equivalent n/cm2.

Recent advancements in low-energy rare-event searches rely on the use of cryogenic calorimeters in order to reach extremely low energy thresholds. When attempting to accurately characterize their responses within the region of interest (ROI) these detectors face severe challenges due to the fact that traditional radioactive calibration sources produce signals above the ROI and cannot be used in low background environments. LANTERN, an optical calibration system, can instead be used to accurately study the ROI of cryogenic detectors. It utilizes LED pulses to generate photon signals to perform detector calibration. LANTERN’s current LED matrix allows for a fast characterization of up to 64 calorimeters independently, spanning energies from a few eV to hundreds of keV. Its minimal electronics and optics make it a cost-effective and customizable solution and it will be employed by the BULLKID, NUCLEUS and CRAB experiments.

In this paper, we present our approach to systematically measure numerous performance parameters of microchannel plate photomultiplier tubes . The experimental setups, the analyses and selected results are discussed. Although the techniques used may be different in other locations, the document is intended as a guide for comparable measurements with other types of microchannel plate photomultiplier tubes . Measurements are shown for the following performance parameters: spectral and spatial quantum efficiency , collection efficiency, gain as a function of voltage, position and magnetic field , time resolution, rate capability and lifetime. By using a dedicated 3-axis stepper and an FPGA-based data acquisition system, also inner PMT parameters are measured as a function of the active area, such as relative detection efficiency, dark count rate, time resolution, recoil electron and afterpulse distributions, as well as charge sharing and electronic crosstalk . In addition, some of the parameters are investigated inside a strong magnetic field . For many of these measurements, the…

The optical and radiochemical purification of the scintillating liquid which will fill the detector of the JUNO experiment plays a crucial role in achieving its scientific goals. Given its gigantic mass and dimensions, and an unprecedented target value of about 3 % at 1 MeV in energy resolution, JUNO has set severe requirements on the parameters of its scintillator, such as attenuation length (L at > 20 m at 430 nm), light yield, and content of radioactive contaminants ( 238 U, 232 Th < 10 -15 g/g). To accomplish these needs, the scintillator will be processed using several purification methods, including distillation under vacuum and gas stripping, carried out in two large-scale plants installed at the JUNO site. In this paper, the layout, operating principles, and technical aspects which have driven the design and construction of the distillation and gas stripping plants are reviewed. The distillation is effective in enhancing the optical properties and removing high-boiling radioactive impurities ( 238 U, 232 Th, 40 K), while the stripping process exploits pure water steam and…

An automated quantitative study of the alignment of vertically aligned carbon nanotubes (VA-CNTs) from scanning electron microscopy (SEM) images has been demonstrated. It is based on the fact that the image gradient (directional change in intensity or color) at every pixel in the image contains the information about the anisotropy at that particular pixel i.e., the local alignment is maintained in the orthogonal direction to the gradient. Structure tensor metrics are formulated demonstrating to be able to summarize the distribution of gradient directions within the neighborhood of any pixel within a two-dimensional domain (surface). An image analysis is presented that evaluates the alignment in desired regions of interest (ROIs) in SEM images of VA-CNTs. This method has been exploited to study the alignment of two different kinds of VA-CNTs: one grown via the thermal chemical vapor deposition (T-CVD) method and the second synthesized via the plasma enhanced chemical vapor deposition (PE-CVD) method.

The High Brilliance Neutron Source (HBS) is a High-Current Accelerator-driven Neutron Source (HiCANS) under development at Jülich Centre for Neutron Science - Forschungszentrum Jülich. The unique specifications of the HBS require a neutron target with a high neutron emission able to operate in vacuum with a 70 MeV proton beam with 90 mA peak current and 1.6% duty cycle leading to an average thermal load of 100 kW. A tantalum target of 100 cm 2 irradiated area with an internal cooling structure which removes the heat quite homogeneously, provides a good compromise between low pressure and high heat transfer and ensures an homogeneous protons energy loss was designed and optimized by means of MCNP, CFD and FEM simulations. Such a target was successfully manufactured and its operational capability was demonstrated by operating it under a heat load of 1 kW cm −2 from an electron gun. • High power neutron target for high current accelerator-driven neutron source (HiCANS). • Tantal target for neutron generation at 70 MeV proton beam. • up to 1 kW cm −2 thermal heat dissipation from a…

Liquid argon time projection chambers (TPC) are widely used in neutrino oscillation and dark matter experiments. Detection of scintillation light in liquid argon TPC’s is challenging because of its short wavelength, in the VUV range, and the cryogenic temperatures (∼86 K) at which the sensors must operate. Wavelength shifters (WLS) are typically needed to take advantage of the high Photon Detection Efficiency (PDE) in the visible range of most of photondetectors. The Hamamatsu VUV4 S13370–6075CN SiPMs can directly detect VUV light without the use of WLS, which main benefit is an improved PDE at these short wavelengths, but also the visible light from WLS. The manufacturer (Hamamatsu Photonics K.K.) provides a complete characterization of these devices at room temperature; however, previous studies have indicated a decrease of the PDE at cryogenic temperature for VUV light. In this work, we present the measurement of the PDE of VUV4 SiPMs at cryogenic temperature for different wavelengths in the range [270, 570] nm. A dedicated measurement at 127 nm is also shown.

A compact HOM-damping beam-accelerating rf cavity was developed to mitigate coupled-bunch instabilities in electron storage rings. This cavity operates in the TM020 mode, characterized by a high Q-value and a high shunt impedance. The new HOM-damping mechanism leverages the unique field distributions of the TM020 mode, allowing direct embedding of rf absorbing materials into the cavity body. This novel structure underwent validation through rf simulations and measurements using a model cavity resonating at 508.58 MHz in the TM020 mode with a shunt impedance of 6.8 MΩ and designed to have HOM impedances of less than 0.1 MΩ longitudinally and 0.5 MΩ/m transversely. We also fabricated and tested a prototype cavity, showcasing its HOM-damping efficacy and high-power functionality at 120 kW, generating an accelerating voltage of 900 kV. This prototype operated successfully at full power, confirming the viability of both the damping structure and its high-power application.

For 4H silicon carbide (4H-SiC), the values for the electron–hole pair creation energy ϵ i published in the literature vary significantly. This work presents an experimental determination of ϵ i using 50 μ m 4H-SiC p-n diodes designed for particle detection in high-energy physics. The detector response was measured for α particles between 4 . 2 MeV and 5 . 6 MeV for 4H-SiC and a silicon reference device. Different α energies were obtained by using multiple nuclides and varying the effective air gap between the α source and the detector. The energy deposited in the detectors was determined using a Monte Carlo simulation , taking into account the device cross-sections. A linear fit of the detector response to the deposited energy yields ϵ i = ( 7 . 83 ± 0 . 02 ) eV , which agrees well with the most recent literature. For the 4H-SiC detectors, a linewidth of 28 keV FWHM was achieved, corresponding to an energy resolution of 0.5 %.

As part of the Fukushima Daiichi Nuclear Power Plant (FDNPP) decommissioning, the release of stored treated water began in 2023. We developed a practical tritium monitor to continuously supervise the tritiated water concentration at FDNPP. The monitor contains a flow cell detector comprising plastic scintillator pellets and incorporating simultaneous measurements by three detectors, a veto detector, and lead shielding to reduce the influence of environmental γ rays. The system reached a detection limit of 593 Bq L−1 in 60 min, which is lower than the discharge standard for tritiated water of 1500 Bq L−1.

A new linear Paul trap section has been constructed to replace the existing bunching section of the radiofrequency quadrupole (RFQ) cooler-buncher at the IGISOL radioactive ion beam facility. The cooler-buncher is used to transform a continuous ion beam to temporally short bursts of ions. The new miniaturised cooler-buncher section produces significantly shorter bunches in time, required by the new Multi-Reflection Time-of-Flight Mass Spectrometer. In this article, we report on the longitudinal properties of the ion bunches and compare the results to an analytical model derived for axial distributions of ions confined in a harmonic trap at thermodynamical equilibrium with a heat bath. The new buncher configuration delivers <75ns full-width at half-maximum bunches with a longitudinal emittance of 200 eVns. The bunches have a full-width at half-maximum energy spread of 10 eV. Total transmission efficiency of 45%–65% has been measured from the isotope separator focal plane through the RFQ cooler-buncher, Multi-Reflection Time-of-Flight Mass Spectrometer and JYFLTRAP double Penning trap.

In the high-luminosity era of the Large Hadron Collider, the instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton–proton interactions in a typical bunch crossing. To cope with the resulting increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The innermost part of the ITk will consist of a pixel detector, with an active area of about 13 m 2 . To deal with the changing requirements in terms of radiation hardness, power dissipation and production yield, several silicon sensor technologies equipped with novel ASICs connecting by bump-bonding technique will be employed in the five barrel and endcap layers. As a timeline, it is facing to pre-production of components, sensor, building modules, mechanical structures and services. This contribution presents the status of the ITk-pixel project focusing on the lessons learned and the biggest challenges towards production, from mechanics structures to sensors, and it will summarise the latest results on…