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Nuclear matrix element (NME M0ν) for neutrinoless double beta decay (DBD) of X Z A → X Z + 2 A with A and Z being the mass and atomic numbers is shown for the first time to be experimentally studied by measuring electromagnetic transition rates from the isobaric analogue state (IAS) of X Z A to low-lying states in the intermediate nucleus of X Z + 1 A. NMEs for electric dipole and magnetic dipole transitions from IAS are used to evaluate vector dipole and Gamow-Teller NMEs associated with DBD and the effective weak couplings to help theoretical model calculations of the DBD NME. The IAS gamma transition rates and the cross sections are evaluated for DBD nuclei to show that the IAS gamma experiments are quite feasible and realistic. [ABSTRACT FROM AUTHOR]

The MAJORANA DEMONSTRATOR is a neutrinoless double-beta decay (0νββ) experiment containing ~30 kg of p-type point-contact germanium detectors enriched to 88% in 76Ge and ~14 kg of natural germanium detectors. The detectors are housed in two electroformed copper cryostats and surrounded by a graded passive shield with an active muon veto. An extensive radioassay campaign was performed prior to installation to insure the use of ultra-clean materials. The DEMONSTRATOR achieved one of the lowest background rates in the region of the 0νββ Q-value, 15.7±1.4 cts/(FWHM t y) from the low-background configuration spanning most of the 64.5 kg-yr active exposure. Nevertheless this background rate is a factor of five higher than the projected background rate. This discrepancy arises from an excess of events from the 232Th decay chain. Background-model fits aim to explain the deviation from assay-based projections, potentially determine the source(s) of observed backgrounds, and allow a precise measurement of the two-neutrino double-beta decay half-life. The fits agree with earlier simulation studies, which indicate the origin of the 232Th excess is not from a near-detector component and have informed design decisions for the next-generation LEGEND experiment. Recent findings have narrowed the suspected locations for the excess activity, motivating a final simulation and assay campaign to complete the background model. [ABSTRACT FROM AUTHOR]

Non-inductive plasma start-up is required for a spherical tokamak fusion reactor. Start-up using lower-hybrid current drive has been studied at the TST-2 spherical tokamak. Recently, equilibrium reconstruction based on the extended MHD model was developed to describe the fast electron current dominated equilibrium more accurately. The new equilibrium was applied to a coupled ray-tracing and Fokker-Planck solver based current drive simulation. The simulated total plasma current was within a factor of two of the outer-midplane launch experimental result, but overestimated the experiment by a factor of three for the top launch case. The measured x-ray radiation was substantially greater for the top launch case compared to the outer-midplane launch case despite the similar plasma current. This may indicate that current drive is affected appreciably by the rf induced transport that is a finite-orbit effect neglected in the present current drive simulation. [ABSTRACT FROM AUTHOR]

Non-inductive plasma start-up using lower-hybrid waves (LHW) has been studied on the TST-2 spherical tokamak. Two different LHW launching scenario has been investigated using the outer-midplane antenna and the top antenna. According to the numerical calculation, plasma current is driven near the plasma edge and the orbit losses of fast electrons is thought to limit the current drive efficiency in these two scenarios. The off-midplane launch scenario was investigated for improved current drive closer to the magnetic axis using ray-tracing and Fokker-Planck code. The current drive simulation showed that plasma current twice as high as presently achieved may be obtained by the off-midplane launch scenario. The driven current was found to be robust against variation of density and temperature. Finally, substantial synergistic improvement may be obtained by simultaneous injection of both the outer-midplane and off-midplane launch. A new off-midplane antenna was fabricated and installed in TST-2. [ABSTRACT FROM AUTHOR]

Ordinary µ capture is useful for probing the neutrino nuclear responses for double beta decay especially in the β+ side region. The aim of this study is to measure the prompt and delayed gamma rays from NatMo (µ,xnv) and 100Mo (µ,xnv) reactions and calculate the relative capture strength, β(µ,E) using the Proton-Neutron Emission Model (PNEM). Experimental data of NatMo and 100Mo targets irradiated by negative µ at MuSIC Facility, Osaka University are analysed and the production rates, and the mass distribution were obtained. The experimental data was compared with the mass distribution calculation using PNEM to get the β(µ,E). The giant resonance (GR) like distribution was observed with the first GR peak around 12 MeV. [ABSTRACT FROM AUTHOR]

Plasma start-up experiments using the lower hybrid wave (LHW) were performed on the TST-2 spherical tokamak. Two capacitively-coupled combline antennas (outboard-launch and top-launch) are presently being used. Bottom-launch can be simulated using the top-launch antenna with reversed toroidal field. The unexpectedly good result of the simulated bottom-launch case was investigated by a combined ray-tracing and Fokker-Planck analysis. In the case of simulated bottom-launch the parallel index of refraction (n||) downshifts initially, but because of the plateau formed by the upshifted n|| LHW after reflecting from the cut-off layer at the bottom of the plasma, strong absorption of the low n|| LHW occurs during the first pass through the plasma, generating a distribution function which extends to very high energies. [ABSTRACT FROM AUTHOR]

The existence of the neutrinoless double beta (0νββ) decay is one of the most intriguing open questions in the neutrino physics field. Despite many large-scale experiments have aimed to measure the reaction for decades, it has not yet been observed. Therefore, accurate theoretical calculations on 0νββ are crucial. To describe the double beta decay processes reliably one needs a possibility to test the involved virtual transitions against experimental data. In this work we manifest how to utilise the charge-exchange and ordinary muon capture (OMC) data in the study of 0νββ decay. [ABSTRACT FROM AUTHOR]

Nuclear matrix elements (NMEs) for GT (Gamow Teller), spin dipole (SD) and higher multipole transitions are associated with double beta decays and astro neutrino nuclear interactions. They are reduced with respect to quasi-particle (QP) NMEs by a factor k ≈ 0.2-0.3. The reduction coefficient k is discussed in terms of the nucleonic spin isospin correlations and the non-nucleonic nuclear medium effects. The latter may be incorporated by the effective (quenching) factor ge f f A /gf ree A . The SD NMEs derived from the (3He,t) charge exchange reactions (CERs) are consistent with the empirical NMEs M(SD) based on the quasi-particle model with the empirical effective SD coupling constant k. The SD NMEs derived from CERs are reduced uniformly in the wide momentum range of q ≈20-100 MeV/c. Impacts of the universal reduction(quenching) on NMEs for neutrino-less DBDs and low and medium energy astro neutrinos are discussed. [ABSTRACT FROM AUTHOR]

Solar neutrinos interact within double-beta decay (ββ) detectors and contribute to backgrounds for ββ experiments. Background contributions due to charge-current solar neutrino interactions with ββ nuclei of 76Ge, 82Se, 100Mo, 130Te, 136Xe, and 150Nd are evaluated. They are shown to be significant for future high-sensitivity ββ 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 ββ experiments. [ABSTRACT FROM AUTHOR]

Non-inductive plasma current start-up, ramp-up and sustainment by waves in the lower hybrid wave (LHW) frequency range at 200 MHz were investigated on the TST-2 spherical tokamak (R0 ≤ 0.38m, a ≤ 0.25m, Bt0 ≤ 0.3T, Ip ≤ 0.14MA). Experimental results obtained using three types of antenna were compared. Both the highest plasma current (Ip = 18kA) and the highest current drive figure of merit ηCD ≡ neIpR0/PRF = 1.4×1017 A/W/m² were achieved using the capacitively-coupled combline (CCC) antenna, designed to excite the LHW with a sharp and highly directional wavenumber spectrum. For Ip greater than about 5 kA, high energy electrons accelerated by the LHW become the dominant carrier of plasma current. The low value of ηCD observed so far are believed to be caused by a rapid loss of energetic electrons and parasitic losses of the LHW energy in the plasma periphery. ηCD is expected to improve by an order of magnitude by increasing the plasma current to improve energetic electron confinement. In addition, edge power losses are expected to be reduced by increasing the toroidal magnetic field to improve wave accessibility to the plasma core, and by launching the LHW from the inboard upper region of the torus to achieve better single-pass absorption. [ABSTRACT FROM AUTHOR]

Neutrino nuclear responses for neutrino-less double beta decays (0νββ DBD) are studied by muon, photon and nuclear charge exchange reactions (CER) and β-EC transitions. These experimental responses with low and medium momentum transfers are used to evaluate 0νββ nuclear matrix elements and the solar neutrino interactions with atoms and nuclei of DBD detectors. Gamma-ray measurements from residual RI nuclei produced by (µ, ν µxn) reactions on 100Mo shows a giant resonance around 12-15 MeV for µ− capture strength. Single β Gamow-Teller (GT) and spin-dipole (SD) strengths are reduced with respect to pnQRPA calculations by gAeff ≈0.5−0.6gA, suggesting considerable reductions of the axial vector responses for DBD. Solar neutrino nuclear interactions with nuclei of the DBD isotopes and atoms of liquid scintillators used for DBD experiments are shown to be the serious backgrounds at the ROI (region of interest) of 0νββ. [ABSTRACT FROM AUTHOR]

The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, modular, HPGe detector array with a mass of 44-kg (29 kg 76Ge and 15 kg natGe) to search for neutrinoless double beta decay in 76 Ge. The next generation of tonne-scale Ge-based neutrinoless double beta decay searches will probe the neutrino mass scale in the inverted-hierarchy region. The MAJORANA DEMONSTRATOR is envisioned to demonstrate a path forward to achieve a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value of 2039 keV. The MAJORANA DEMONSTRATOR follows a modular implementation to be easily scalable to the next generation experiment. First, the prototype module was assembled; it has been continuously taking data from July 2014 to June 2015. Second, Module 1 with more than half of the total enriched detectors and some natural detectors has been assembled and it is being commissioned. Finally, the assembly of Module 2, which will complete MAJORANA DEMONSTRATOR, is already in progress. [ABSTRACT FROM AUTHOR]

The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, 40- kg modular HPGe detector array to search for neutrinoless double beta decay in 76Ge. In view of the next generation of tonne-scale Ge-based 0νβ β-decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. The background rejection techniques to be applied to the data include cuts based on data reduction, pulse shape analysis, event coincidences, and time correlations. The Point Contact design of the DEMONSTRATOR's germanium detectors allows for significant reduction of gamma background. [ABSTRACT FROM AUTHOR]

The Majorana Demonstrator is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta decay (0νββ) in 76Ge. Such an experiment would require backgrounds of less than 1 count/tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the ββ decay. Designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. This paper will discuss the Majorana collaboration's solutions to some of these challenges. [ABSTRACT FROM AUTHOR]

The MAJORANA DEMONSTRATOR neutrinoless double beta-decay experiment is currently under construction at the Sanford Underground Research Facility in South Dakota, USA. An overview and status of the experiment are given. [ABSTRACT FROM AUTHOR]

A new type of traveling wave antenna which excites the lower hybrid wave directly was developed. This antenna is similar to the inductively-coupled combline antenna in that only the first element of the antenna array is excited externally, and subsequent elements are excited passively by mutual coupling between adjacent elements. The main difference is that whereas the inductively-coupled combline antenna makes use of mutual inductance, the presently proposed antenna makes use of mutual capacitance. The radiating elements are located at the voltage maximum, and the electric field induced in the plasma is in the toroidal direction rather than the poloidal direction, matching the polarization of the lower hybrid wave. Optimization studies were carried out to obtain a band-pass characteristic centered around 200 MHz, and a unidirectional wavenumber spectrum with the parallel index of refraction corresponding to approximately 5. Plasma current ramp-up to 2 kA has been achieved on the TST-2 spherical tokamak with 12 kW of RF power at 200 MHz during the initial experimental period using this antenna. Further optimization studies are being performed. [ABSTRACT FROM AUTHOR]

Nuclear matrix elements M0v for neutrino less double beta decays (Ovßß) are crucial for neutrino studies in 0vßß experiments. The neutrino mass to be studied is sensitive to M0v, while theoretical calculations for M0v are hard. Thus experimental studies of nuclear structures and single ß matrix elements Mβ associated with Ovßß are useful to confirm and help the theoretical calculations. This reports briefly experimental methods and recent charge exchange reaction studies for Mβ. The single ß elements for M-(2-) associated with M0v(2-), which is the major component of M0v, are found to be reduced (quenched) much by the spin isospin correlation and the nuclear medium (non-nucleonic isobar) effect. The present result suggests that the spin isospin components of M0v is fairly reduced (quenched). [ABSTRACT FROM AUTHOR]

We consider a measurement of isobaric analog states (IAS) of 76As in 76Se as a method for measuring the Gamow-Teller (GT) strength important to constrain and possibly help normalize calculations of double beta (ββ) decay matrix elements. We show that photo-nuclear reactions via IAS can provide valuable information about the parent and daughter states of ββ-decay not currently available from measurements of charge exchange reactions. Several experiments have been proposed at the HI□ Sfacility at the Triangle Nuclear Research Laboratory in Durham, NC, the first of which will measure the lowest 1-, 1+ and 2+ IAS in 76Se. [ABSTRACT FROM AUTHOR]

Plasma current start-up experiments using the lower hybrid wave (LHW) excited by a new dielectric loaded waveguide array antenna are planned on TST-2. The wave excitation efficiency of this antenna is investigated using a versatile FEM solver package, COMSOL. Propagation and absorption of the LHW are calculated by iterating between the TORLH full wave code and the CQL3D Fokker-Planck code. Wave absorption is very weak for Maxwellian plasma, but becomes stronger as the quasilinear deformation of the distribution function develops. [ABSTRACT FROM AUTHOR]

Noninductive plasma current (Ip) start-up experiments using RF power in the lower hybrid frequency range are being conducted on the TST-2 spherical tokamak. The lower hybrid wave (LHW) has demonstrated efficient current drive in conventional tokamaks. However, in spherical tokamak (ST) plasmas with very high dielectric constants (;[variant_greek_epsilon]∼ωpe2/Ωe2>1), accessibility of the LHW to the plasma core is severely limited. Our approach is to keep the plasma density low (such that [variant_greek_epsilon]∼1) during Ip ramp-up. Once Ip reaches a level sufficiently high for neutral beam current drive, plasma can be densified and transformed into an advanced tokamak plasma dominated by the self-driven bootstrap current. Initial plasma start-up experiments were performed on TST-2 using a combline antenna which excites a traveling fast wave. After formation of toroidal flux surfaces, RF power and vertical field were ramped up to increase Ip. Up to 12 kA of Ip has been obtained by this method. Soft X-ray measurements indicate that the electron temperature increases as Ip increases, and hard X-ray spectroscopy indicates that energetic electrons build up as Ip is ramped up. [ABSTRACT FROM AUTHOR]

The phased-array antenna system for Electron Cyclotron/Bernstein Wave Heating and Current Drive experiments has been developed in the QUEST. The antenna was designed to excite a pure O-mode wave in the oblique injection for the O-X-B mode conversion experiments, and its good performances were confirmed at a low power level. The plasma current (<∼15 kA) with an aspect ratio of 1.5 was started up and sustained by only RF injection in the low-density operations. The long pulse discharge of 10 kA was also attained for 37 s. The new density window to sustain the plasma current was observed in the high-density plasmas. The single-null divertor configuration with the high plasma current (<∼25 kA) was attained in the 17 s plasma sustainment. [ABSTRACT FROM AUTHOR]

Neutrinos are key particles for particle and astro-nuclear physics. Majorana neutrino masses and phases, solar and supernova neutrino productions and oscillations, and neutrino nuclear synthesis and fundamental weak interactions are well studied in nuclei as femto laboratories. Here neutrino nuclear responses are crucial for the neutrino studies. This reports briefly experimental studies of neutrino nuclear responses, charge exchange reactions on Ga to study nuclear responses for solar and 51Cr neutrinos, and β+ neutrino responses for ββ-ν matrix elements and astro ν interactions by photon and muon probes. [ABSTRACT FROM AUTHOR]

The Majorana collaboration is actively pursuing research and development aimed at a tonne-scale 76Ge neutrinoless double-beta decay (ββ(0ν)-decay) experiment. The current, primary focus is the construction of the Majorana Demonstrator experiment, an R&D effort that will field approximately 40 kg of germanium detectors with mixed enrichment levels. This article provides a status update on the construction of the Demonstrator. [ABSTRACT FROM AUTHOR]

Fundamental properties of neutrinos and neutrino nuclear interactions are of great interest from particle and astro-nuclear physics view points. They are well studied in nuclear femto laboratories, where neutrino nuclear responses are crucial. Neutrino masses and neutrino natures are studied by neutrino-less double beta decays (0νββ) in nuclei. Here neutrino nuclear responses are required to extract neutrino properties from 0νββ rates. Neutrino nuclear responses are sensitive to nuclear spin isospin correlations and nuclear structures. They are experimentally studied by nuclear probes for charge exchange nuclear reactions, photon EM probes for photo-nuclear reactions, and lepton probes for muon and neutrino capture reactions. [ABSTRACT FROM AUTHOR]

Plasma current start-up and formation of the ST configuration without the use of the central solenoid is a critical issue in ST research. In the TST-2 spherical tokamak (R = 0.38 m, a = 0.25 m), sustainment of an ECRF (2.45 GHz) produced ST plasma by low frequency (21 MHz) RF power alone was demonstrated. Since direct RF current drive can be ruled out, this result implies that the ST configuration is sustained entirely by pressure-driven currents. The Grad-Shafranov equilibrium was generalized to take into account the open field line region with finite plasma current and pressure (truncated equilibrium). In addition to the precessional current of trapped particles, Pfirsch-Schlüter current flowing along the open field line (and partially returning through the vacuum vessel) contributes to the toroidal plasma current. Three phases of plasma start-up are analyzed: (i) the current formation phase, (ii) the current jump phase, and (iii) the current sustainment phase. In the current formation phase, the plasma current is formed and increases slowly, roughly proportional to the stored energy. Closed flux surfaces do not exist and the current density profile is peaked on the outboard side. Once the plasma current increases beyond a critical value (approximately equal to the level necessary to satisfy the major radial force balance), the plasma current increases rapidly (current jump). Closed flux surfaces appear not at the beginning, but at the end of the current jump. In the sustainment phase, plasma has a high poloidal beta, βp = O(1). The equilibrium is characterized by the hollowness of the current density profile, which also determines the fraction of the plasma current inside the last closed flux surface. The plasma equilibrium does not differ greatly between EC-sustained and RF-sustained plasmas. However, RF-sustained plasmas are more turbulent, with larger fluctuation levels over a wide frequency band (0–20 kHz), and in many cases MHD activity in the 5–10 kHz frequency band increases rapidly and terminates the discharge. [ABSTRACT FROM AUTHOR]

HHFW experiments on TST-2 and UTST were performed. In the TST-2 HHFW experiment, the pickup probe mounted on the inboard wall detected the same PDI lower sideband peak as probes on the outboard side. Since the frequency difference from the pump wave corresponds to the ion cyclotron frequency on the low field side, the lower sideband wave is believed to be generated at the plasma edge on the low field side, and propagated to the high field side. This component may be the FW. In the UTST HHFW experiment, direct measurements of the RF fields in the plasma were made successfully. [ABSTRACT FROM AUTHOR]

The MOON project aims at spectroscopic 0vββ studies with the v-mass sensitivity of 100–30 meV by measuring two beta rays from 100Mo and/or 82Se. The detector is a compact super-module of multi-layer PL scintillator plates. R&D works made by the pro to-type MOON-1 and the small PL plate show the possible energy resolution of around σ∼2.2%, as required for the mass sensitivity. Nuclear matrix elements M2v for 2vββ are shown to be given by the sum ΣLMk of the 2vββ matrix elements Mk through intermediate quasi-particle states in the Fermi-surface, where Mi is obtained experimentally by using the GT(Jπ = 1+) matrix elements of Mi(k) and Mf(k) for the successive single-β transitions through the k-th intermediate state. [ABSTRACT FROM AUTHOR]

The coherent contribution of all neutrons in neutrino nucleus scattering due to the neutral current is examined considering the boron solar neutrinos. These neutrinos could potentially become a source of background in the future dark matter searches aiming at nucleon cross sections in the region well below the 10-10 pb, i.e a few events per ton per year. [ABSTRACT FROM AUTHOR]

Measurements of radon and thoron exhalation rates have been done using the radon and thoron exhalation rate measuring instrument adopting the accumulation method. We obtained the 111 data in the 40 sites of the 14 prefectures in Japan. The arithmetic average value of the radon and thoron exhalation rates by all 111 data were obtained to be 8.6 mBq·m-2·s-1 and 0.80 Bq·m-2·s-1, respectively, and we have reported the radon and thoron exhalation rates in relation to the geological features. The relation between the exhalation rate and geology was shown that the exhalation rate had an increasing tendency in order of basic rock, neutral rock and acidic rock. We made the nationwide exhalation-rate map using the survey data of exhalation-rate of radon and thoron and the geological distribution map. [ABSTRACT FROM AUTHOR]