Decay Detector Research Articles

New lower background and higher rate technique for anti-neutrino detection using Tungsten 183 Isotope

Low energy anti-neutrinos detected from reactors or other sources have typically used the conversion of an anti-neutrino on Hydrogen, producing a positron and a free neutron. This neutron is subsequently captured on a secondary element with a large neutron capture cross-section such as gadolinium or cadmium. With most neutron captures on gadolinium, it is possible to get two or three delayed gamma signals of known energy to occur. Modern experiments can make measurements with timing on the order of 25 ns. Fast electronics like these allow for the possibility of accessing the very fast signals from the nuclear de-excitation of a heavy nucleus following the prompt positron signal, rather than relying on traditional IBD techniques. We have found an isotope of tungsten, 183W that produces tantalum in the ground state at 2.094 MeV or the first excited state at 2.167 MeV. The excited state of 183Ta* emits a signature secondary gamma pulse of 73 keV with a 106 ns half-life. This offers a new delayed coincidence technique that can be used to identify anti-neutrinos with lower background noise. This allows for less shielding than required for modern inverse beta decay detectors.

Radionuclide metrology: confidence in radioactivity measurements

Radionuclides, whether naturally occurring or artificially produced, are readily detected through their particle and photon emissions following nuclear decay. Radioanalytical techniques use the radiation as a looking glass into the composition of materials, thus providing valuable information to various scientific disciplines. Absolute quantification of the measurand often relies on accurate knowledge of nuclear decay data and detector calibrations traceable to the SI units. Behind the scenes of the radioanalytical world, there is a small community of radionuclide metrologists who provide the vital tools to convert detection rates into activity values. They perform highly accurate primary standardisations of activity to establish the SI-derived unit becquerel for the most relevant radionuclides, and demonstrate international equivalence of their standards through key comparisons. The trustworthiness of their metrological work crucially depends on painstaking scrutiny of their methods and the elaboration of comprehensive uncertainty budgets. Through meticulous methodology, rigorous data analysis, performance of reference measurements, technological innovation, education and training, and organisation of proficiency tests, they help the user community to achieve confidence in measurements for policy support, science, and trade. The author dedicates the George Hevesy Medal Award 2020 to the current and previous generations of radionuclide metrologists who have devoted their professional lives to this noble endeavour.

Secondary scintillation yield in pure krypton

The absolute secondary scintillation yield is of paramount importance for modelling dual-phase or high-pressure gas detectors, to be used in contemporary and in future rare event detection experiments. In addition, the search for neutrinoless double electron capture complements the search for neutrinoless double beta decay and has been measured for 124Xe in several Dark Matter and Double Beta decay detectors, operating at present. Krypton presents itself as an interesting candidate for double electron capture detection experiments. We have studied the krypton secondary scintillation yield, at room temperature, as a function of electric field in the gas scintillation gap. A large area avalanche photodiode has been used to allow the simultaneous detection of the scintillation pulses as well as the direct interaction of x-rays, the latter being used as a reference for the calculation of the number of charge carriers produced by the scintillation pulses and, thus, the determination of the number of photons impinging the photodiode. An amplification parameter of 113 photons per kV per drifting electron and a scintillation threshold of 2.7 Td (0.7 kVcm−1bar−1 at 293 K) was obtained, in good agreement with the simulation data reported in the literature. On the other hand, the ionisation threshold in krypton was found to be around 13.5 Td (3.4 kVcm−1bar−1), less than what had been obtained by the most recent simulation work-package. The krypton amplification parameter is about 80% and 140% of those measured for xenon and argon, respectively.

Measurement of proton quenching in a plastic scintillator detector

The non-linear energy response of the plastic scintillator EJ-260 is measured with the MicroCHANDLER detector, using neutron beams of energy 5 to 27 MeV at the Triangle Universities Nuclear Laboratory. The first and second order Birks' constants are extracted from the data, and found to be kB = (8.70 ± 0.93)× 10−3 g/cm2/MeV and kC = (1.42 ± 1.00) × 10−5 (g/cm2/MeV)2. This result covers a unique energy range that is of direct relevance for fast neutron backgrounds in reactor inverse beta decay detectors. These measurements will improve the energy non-linearity modeling of plastic scintillator detectors. In particular, the updated energy response model will lead to an improvement of fast neutron modeling for detectors based on the CHANDLER reactor neutrino detector technology.

Measurement of the scintillation and ionization response of liquid xenon at MeV energies in the EXO-200 experiment

Liquid xenon (LXe) is employed in a number of current and future detectors for rare event searches. We use the EXO-200 experimental data to measure the absolute scintillation and ionization yields generated by $\gamma$ interactions from $^{228}$Th (2615~keV), $^{226}$Ra (1764~keV) and $^{60}$Co (1332~keV and 1173~keV) calibration sources, over a range of electric fields. The $W$-value that defines the recombination-independent energy scale is measured to be $11.5~\pm~0.5$~(syst.)~$\pm~0.1$~(stat.) eV. These data are also used to measure the recombination fluctuations in the number of electrons and photons produced by the calibration sources at the MeV-scale, which deviate from extrapolations of lower-energy data. Additionally, a semi-empirical model for the energy resolution of the detector is developed, which is used to constrain the recombination efficiency, i.e., the fraction of recombined electrons that result in the emission of a detectable photon. Detailed measurements of the absolute charge and light yields for MeV-scale electron recoils are important for predicting the performance of future neutrinoless double beta decay detectors.

Fast inference using FPGAs for DUNE data reconstruction

The Deep Underground Neutrino Experiment (DUNE) will be a world-class neutrino observatory and nucleon decay detector aiming to address some of the most fundamental questions in particle physics. With a modular liquid argon time-projection chamber (LArTPC) of 40 kt fiducial mass, the DUNE far detector will be able to reconstruct neutrino interactions with an unprecedented resolution. With no triggering and no zero suppression or compression, the total raw data volume would be of order 145 EB/year. Consequently, fast and affordable reconstruction methods are needed. Several state-of-theart methods are focused on machine learning (ML) approaches to identify the signal within the raw data or to classify the neutrino interaction during the reconstruction. One of the main advantages of using those techniques is that they will reduce the computational cost and time compared to classical strategies. Our plan aims to go a bit further and test the implementation of those techniques on an accelerator board. In this work, we present the accelerator board used, a commercial off-the-shelf (COTS) hardware for fast deep learning (DL) inference based on an FPGA, and the experimental results obtained outperforming more traditional processing units. The FPGA-based approach is planned to be eventually used for online reconstruction.

Experimental and numerical investigations of the Czochralski growth of Li2MoO4 crystals for heat-scintillation cryogenic bolometers

Abstract A new technology for the mass production of lithium molybdate (Li2MoO4) crystals needed for the realization of the cryogenic neutrinoless double-beta decay detectors is under development within the framework of the CLYMENE project. Crystals with 4 and 5 cm in diameter were grown in two different Czochralski configurations. The first configuration, based on inductive heating of a RF coil coupled with a platinum crucible, was used to grow crystals of 4 cm in diameter. Bolometric tests performed with two samples cut from a 230 g crystal have shown less performances of the large sample (158 g), which had a cleavage, as compared to the small non-cracked sample (13.5 g). Numerical modeling was applied to investigate the temperature field in the furnace, the melt convection and thermo-elastic stresses in the crystal. Numerical results reveal 30% higher thermal stress at the bottom part of the ingot in the case of a concave shape of the crystal tail (experimental case) as compared to the case of a convex shaped tail. This could explain why the fracture started at the bottom part of the 230 g crystal boule, and highlights the importance of the crystal shape in the last stage of growth process. The furnace configuration used to grow 5 cm-diameter crystals was numerically optimized in order to reduce the thermal stress in the crystals. The first kg-mass Li2MoO4 ingot grown in the optimized configuration exhibit regular shape and good structural quality.

Nuclear response to supernova neutrino spectra

In current probes searching for rare event processes, appropriate nuclear targets are employed (in the COBRA double-beta decay detector the CdZnTe semiconductor is used). In this work the response of such detectors to various low-energy neutrino spectra is explored starting from state-by-state calculations of the neutrino-nucleus reactions cross sections obtained by using the quasi particle random phase approximation (QRPA) based on realistic two-body residual interactions. As a concrete example, we examine the response of 64Zn isotope to low energy supernova neutrinos.

Studying supernova neutrinos through nuclear structure calculations

Differential and integrated cross section calculations are performed in the context of the quasi particle random phase approximation (QRPA) by utilizing realistic two- nucleon forces, for the 64,66 Zn isotopes, contents of the COBRA double beta decay detector. For these isotopes the response to supernova neutrinos is of current inter- est. The response of the 66 Zn isotope to the energy-spectra of supernova neutrinos is also explored by convoluting the original results for the differential cross sections by employing: (i) a two-parameter Fermi-Dirac (FD) and (ii) a Power-Law (PL) neutrino energy distribution. Such folded cross sections are useful in low-energy astrophysical-neutrino detection in underground terrestrial experiments.

Decay detection in Norway spruce (Picea abies) with the Rotfinder instrument

Wood decay limits the function of Norway spruce (Picea abies (L.) H.Karst.) for wood production and in protection forests (i.e. forests protecting against natural hazards). Therefore, more detailed knowledge about the presence and extent of decay in living trees is highly relevant for both the timber industry and risk management strategies. However, decay detection in living Norway spruce trees is not sufficiently possible by visual methods. One possibility to overcome this problem are indirect, non- or least-destructive measurement devices such as the decay detector Rotfinder. Yet, the influence of climatic variables on the reliability of decay detection determined with the Rotfinder is not sufficiently known. Therefore, we assessed the influences of several climatic variables on the Rotfinder values continuously over one year at the same measuring position. Additionally, we determined a threshold value for decay detection in single Norway spruce trees in Central Europe. Regardless of the temperature, Rotfinder values measured over one year were mainly influenced by internal decay status, i.e. damage degree, which explained about 85% of the variation based on a generalized linear mixed effects model in this temperature range (about 6–27 °C). Together with fluctuations in air temperature, about 87% of the variation in Rotfinder values could be accounted for. For decay detection in single Norway spruce trees, a maximum threshold value of about 11,000 Rotfinder units (RU) was identified, equivalent to about 36% of the Rotfinder values measured for intact trees. Our results indicate that the Rotfinder can be used successfully for decay detection in single Norway spruce trees under Central European conditions.

Radon mitigation during the installation of the CUORE 0νββ decay detector

CUORE—the Cryogenic Underground Observatory for Rare Events—is an experiment searching for the neutrinoless double-beta (0νββ) decay of 130Te with an array of 988 TeO2 crystals operated as bolometers at ∼10 mK in a large dilution refrigerator. With this detector, we aim for a 130Te 0νββ decay half-life sensitivity of 9×1025 y with 5 y of live time, and a background index of ≲ 10−2 counts/keV/kg/y. Making an effort to maintain radiopurity by minimizing the bolometers' exposure to radon gas during their installation in the cryostat, we perform all operations inside a dedicated cleanroom environment with a controlled radon-reduced atmosphere. In this paper, we discuss the design and performance of the CUORE Radon Abatement System and cleanroom, as well as a system to monitor the radon level in real time.

Photoelectric Solar Power Revisited

Dr. Gavin Bell is a Reader in the Department of Physics at the University of Warwick, UK. His research interests combine epitaxy and nano-materials growth with surface/interface science. He works on semiconductors and thin-film magnetic/topological materials for spintronics, photocathodes, and low-dimensional materials. Dr. Yorck Ramachers is a Reader in the Department of Physics at the University of Warwick, UK. His research focuses on neutrino physics and particle physics instrumentation. He works on neutrinoless double beta decay and general detector development for future neutrino physics projects.

Solar neutrino interactions with the double- β decay nuclei Se82, Mo100 , and Nd150

Solar neutrinos interact within double-beta decay (\BB) detectors and contribute to backgrounds for \BB\ experiments. Background contributions due to solar neutrino interactions with \BB\ nuclei of $^{82}$Se, $^{100}$Mo, and $^{150}$Nd are evaluated. They are shown to be significant for future high-sensitivity \BB\ experiments that may search for Majorana neutrino masses in the inverted-hierarchy mass region. The impact of solar neutrino backgrounds and their reduction are discussed for future \BB\ experiments.

Comparative evaluation of acoustic techniques for detection of damages in historical wood

Abstract This study assesses the suitability and sensitivity of select acoustic devices (Arborsonic Decay Detector, Fakopp Ultrasonic Timer with two types of sensors–TD45 and US10, and Fakopp 2D) for identification of damage in seven approximately 315 year old fir joining beams acquired during the reconstruction of the Baroque truss in the St. Mary of the Assumption Church in Vranov nad Dyji, Czech Republic. The particular acoustic devices did not always provide similar results. However, brown rot and other inner damages in fir beams, located closer to their endings situated on masonry and connected with rafters, were determined with all acoustic devices. The possibility of indirect prediction of the strength, elasticity and hardness of the historical wood by means of the acoustic method was verified by correlation analyses, however, not seldom without higher significance. Generally, the results obtained indicate that it is not possible to fully rely on in situ acoustic methods for inspection of defects in wooden elements of historical structures, and therefore they should be combined with visual inspection and some other instrumental method(s).

Minimal nonsupersymmetricSO(10)model: Gauge coupling unification, proton decay, and fermion masses

We present a minimal renormalizable non-supersymmetric SO(10) grand unified model with a symmetry breaking sector consisting of Higgs fields in the 54_H + 126_H + 10_H representations. This model admits a single intermediate scale associated with Pati-Salam symmetry along with a discrete parity. Spontaneous symmetry breaking, the unification of gauge couplings and proton lifetime estimates are studied in detail in this framework. Including threshold corrections self-consistently, obtained from a full analysis of the Higgs potential, we show that the model is compatible with the current experimental bound on proton lifetime. The model generally predicts an upper bound of few times 10^{35} yrs for proton lifetime, which is not too far from the present Super-Kamiokande limit of \tau_p \gtrsim 1.29 \times 10^{34} yrs. With the help of a Pecci-Quinn symmetry and the resulting axion, the model provides a suitable dark matter candidate while also solving the strong CP problem. The intermediate scale, M_I \approx (10^{13}-10^{14}) GeV which is also the B-L scale, is of the right order for the right-handed neutrino mass which enables a successful description of light neutrino masses and oscillations. The Yukawa sector of the model consists of only two matrices in family space and leads to a predictive scenario for quark and lepton masses and mixings. The branching ratios for proton decay are calculable with the leading modes being p \rightarrow e^+ \pi^0 and p \rightarrow \overline{\nu} \pi^+. Even though the model predicts no new physics within the reach of LHC, the next generation proton decay detectors and axion search experiments have the capability to pass verdict on this minimal scenario.

Nuclear structure of 37, 38Si investigated by decay spectroscopy of 37, 38Al

We present a study on the β decays of the neutron-rich isotopes 37Al and 38Al, produced by projectile fragmentation of a 48Ca beam with an energy E = 345 A MeV at the RIKEN Nishina Center. The half-lives of 37Al and 38Al have been measured to 11.5(4)ms and 9.0(7)ms, respectively, using the CAITEN implantation and decay detector setup. The level schemes for 37Si and 38Si were deduced by employing γ-γ coincidence spectroscopy following the event-by-event identification of the implanted nuclei. Comparison to large scale nuclear shell model calculations allowed for a tentative assignment of spin and parity of the populated states. The data indicate that the classical shell gap at magic neutron number N = 28 between the νf7/2 and νp3/2 orbits gets reduced by 0.3 MeV in this region leading to low-energy states with intruder configuration in 37Si.

Searches for a sterile-neutrino admixture in detecting tritium decays in a proportional counter: New possibilities

We propose an experiment intended for search for an admixture of sterile neutrino with mass m$_s$ in the range of 1-8 keV that may be detected as specific distortion of the electron energy spectrum during tritium decay. The distortion is spread over large part of the spectrum so to reveal it one can use a detector with relatively poor (near 10-15%) energy resolution. A classic proportional counter is a simple natural choice for a tritium $\beta$-decay detector. The method we are proposing is original in two respects. First, the counter is produced as a whole from fully-fused quartz tube allowing to measure current pulse directly from anode while providing high stability for a long time. Second, a modern digital acquisition technique can be used in measurements at ultrahigh count rate - up to 10$^6$ Hz. As a result an energy spectrum of tritium electrons containing up to 10$^{12}$ counts may be collected in a month of live time measurements. Due to high statistics an upper limit down to 10$^{-3}$..10$^{-5}$ can be put on sterile neutrino mixing at 95% CL for m$_s$ in the range of 1-8 keV, that will be 1..2 orders of magnitude better then bounds published up to now.

VLIV POVRCHOVÉ ÚPRAVY NA RYCHLOST ŠÍŘENÍ ULTRAZVUKU VE DŘEVĚ

Non-destructive diagnostic methods are very useful for monumental buildings. This paper deals with one of these technique, namely with ultrasound testing and influence of surface finishing on ultrasound velocity measured by means of device the Arborsonic Decay Detector. Surface finishing (Primalex – thick synthetic film of the surface finishing, Luxol – Extra – thin synthetic film of the surface finishing and Impranal Profi SL – thick acryl film the surface finishing) were selected and tested in this research. The transmittion time was measured and velocity was converted from it. This was compared before and after application of surface finishing.

A convenient approach to 10−12 g/g ICP-MS limits for Th and U in aurubis electrolytic NA-ESN brand copper

Inductively coupled plasma mass spectroscopy is a powerful technique for measuring trace levels of radioactive contaminants, specifically Th and U, in materials for use in construction of low-background rare-event detectors such as double beta decay and dark matter detectors. I describe here a technique for measuring Th and U contamination in copper using direct acid digestion and dilution, without further chemical processing, achieving results comparable to previous work which utilized more complex chemical pre-concentration techniques. A convenient research-oriented analysis environment is described as well. Results are presented for measurements of three samples from the production line of electrolytically-purified, LME (London Metal Exchange) grade A, NA-ESN Aurubis copper. Purified samples showed levels consistent with zero contamination for both elements, while weak but inconclusive indications of contamination were present for the un-purified anode copper. The best limits achieved are near $1\cdot 10^{-12}$~g/g (95% CL) for both Th and U measured for copper from the cathode of the purification process.

Atomic shell structure from the Single-Exponential Decay Detector.

The density of atomic systems is analysed via the Single-Exponential Decay Detector (SEDD). SEDD is a scalar field designed to explore mathematical, rather than physical, properties of electron density. Nevertheless, it has been shown that SEDD can serve as a descriptor of bonding patterns in molecules as well as an indicator of atomic shells [P. de Silva, J. Korchowiec, and T. A. Wesolowski, ChemPhysChem 13, 3462 (2012)]. In this work, a more detailed analysis of atomic shells is done for atoms in the Li-Xe series. Shell populations based on SEDD agree with the Aufbau principle even better than those obtained from the Electron Localization Function, which is a popular indicator of electron localization. A link between SEDD and the local wave vector is given, which provides a physical interpretation of SEDD.