Organic scintillators are widely used for fast neutron detection and spectroscopy. Several effects complicate the interpretation of results from detectors based upon these materials. First, fast neutrons will often leave a detector before depositing all of their energy within it. Second, fast neutrons will typically scatter several times within a detector, and there is a non-proportional relationship between the energy of, and the scintillation light produced by, each individual scatter; therefore, there is not a deterministic relationship between the scintillation light observed and the neutron energy deposited. Here we demonstrate a hardware technique for reducing both of these effects. Use of a segmented detector allows for the event-by-event correction of the light yield non-proportionality and for the preferential selection of events with near-complete energy deposition, since these will typically have high segment multiplicities.
A novel large volume spherical proportional counter, recently developed, is used for neutron measurements. Gas mixtures of $N_{2}$ with $C_{2}H_{6}$ and pure $N_{2}$ are studied for thermal and fast neutron detection, providing a new way for the neutron spectroscopy. The neutrons are detected via the ${}^{14}N(n, p)C^{14}$ and ${}^{14}N(n, α)B^{11}$ reactions. Here we provide studies of the optimum gas mixture, the gas pressure and the most appropriate high voltage supply on the sensor of the detector in order to achieve the maximum amplification and better resolution. The detector is tested f…
Neutron detection provides an effective method to detect, locate, and characterize sources of interest to nuclear security applications. Current neutron imaging systems based on double-scatter kinematic reconstruction provide good signal vs. background discrimination and spectral capability, but suffer from poor sensitivity due to geometrical constraints. This weakness can be overcome if both neutron-proton scattering interactions are detected and resolved within one large contiguous active detector volume. We describe here a maximum likelihood approach to event reconstruction in a single-volu…
Neutron correlation spectroscopy can exceed direct spectroscopy in the incoming beam intensity by up to two orders of magnitude at the same energy resolution. However, the propagation of the counting noise in the correlation algorithm of data reduction is disadvantageous for the lowest intensity parts of the observed spectrum. To mitigate this effect at pulsed neutron sources we propose two dimensional time-of-flight recording of each neutron detection event: with respect to both the neutron source pulses and to the rotation phase of the pseudo-random beam modulation statistical chopper. We ha…
The spherical proportional counter is a large volume gaseous detector which finds application in several fields, including direct Dark Matter searches. When the detector is filled with nitrogen it becomes an effective neutron spectrometer thanks to the $^{14}$N(n,$\mathrmα$)$^{11}$B and $^{14}$N(n,p)$^{14}$C reactions. Nitrogen, however, is a challenging operating gas for proportional counters and requires a high electric field strength to gas pressure ratio. Benefiting from the latest advances in spherical proportional counter instrumentation and simulation techniques, we report first neutron…
We have experimentally characterized the light-output response of a deuterated trans-stilbene (stilbene-d12) crystal to quasi-monoenergetic neutrons in the 0.8 to 4.4 MeV energy range. These data allowed us to perform neutron spectroscopy measurements of a DT 14.1 MeV source and a PuBe-239 source by unfolding the impinging neutron spectrum from the measured light-output response. The stilbene-d12 outperforms a H1-stilbene of similar size when comparing the shape of the unfolded spectra and the reference ones. These results confirm the viability of non-hygroscopic stilbene-d12 crystal for direc…
In the frame of direct dark matter search, the fast neutrons producing elastic collisions are the ultimate background. The MIMAC (MIcro-tpc MAtrix Chambers) project has developed a directional detector providing the directional signature to discriminate them based on 3D nuclear tracks reconstruction. The MIMAC team of the LPSC has adapted one MIMAC chamber as a portable fast neutron spectrometer, the Mimac-FastN detector, having a very large neutron energy range (10 keV - 600 MeV) with different gas mixtures and pressures. The present paper shows its main features and functionality and demonst…
A novel concept for detection and spectroscopy of gamma rays, and detection of thermal neutrons based on codoped lanthanum fluoride nanocrystals containing gadolinium is presented.The trends of colloidal synthesis of the mentioned material, LaF3 co-doped with Ce as the activator, Yb as the wavelength-shifter and Gd as the neutron captor, is reported. Nanocrystals of the mentioned material were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), optical absorption, and photoluminescence spectroscopy. Gamma detection and i…
Neutron spectroscopy is an invaluable tool for many scientific and industrial applications, including underground Dark Matter searches. Neutron-induced backgrounds produced by cosmic ray muons and the cavern radioactivity can mimic the expected Dark Matter signal. However, existing neutron detection methods have several drawbacks and limitations, thus measurements remain elusive. A promising new approach to neutron spectroscopy is the use of a nitrogen-filled spherical proportional counter that exploits the $^{14}$N(n,$α$)$^{11}$B and $^{14}$N(n, p)$^{14}$C reactions. This is a safe, inexpensi…
Precise in-situ measurements of the neutron flux in underground laboratories is crucial for direct dark matter searches, as neutron induced backgrounds can mimic the typical dark matter signal. The development of a novel neutron spectroscopy technique using Spherical Proportional Counters is investigated. The detector is operated with nitrogen and is sensitive to both fast and thermal neutrons through the $^{14}$N(n, $α$)$^{11}$B and $^{14}$N(n, p)$^{14}$C reactions. This method holds potential to be a safe, inexpensive, effective, and reliable alternative to $^3$He-based detectors. Measuremen…
The article by Fernandez et al argues that, because of advances made in laser-produced neutron pulses, it should now be possible to measure temperature in samples loaded to elevated pressures, by neutron resonance spectrometry with neutrons accelerated using a single sub-picosecond laser pulse in the 300J range. We point out that the configuration used for neutron source and detector would require an infeasibly large sample, potentially requiring tens of megajoules of laser energy to drive the sample. The laser-driven neutron technology is thus not yet mature enough to consider for new facilit…
A new double time-of-flight (dTOF) neutron spectroscopy technique has been developed for pulsed broad spectrum sources with a duty cycle that results in frame overlap, where fast neutrons from a given pulse overtake slower neutrons from previous pulses. Using a tunable beam at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory, neutrons were produced via thick-target breakup of 16 MeV deuterons on a beryllium target in the cyclotron vault. The breakup spectral shape was deduced from a dTOF measurement using an array of EJ-309 organic liquid scintillators. Simulation of the neutron …
We present two new types of spectroscopy methods for cold and ultra-cold neutrons. The first method, which uses the \RB drift effect to disperse charged particles in a uniformly curved magnetic field, allows to study neutron $β$-decay. We aim for a precision on the 10$^{-4}$ level. The second method that we refer to as gravity resonance spectroscopy (GRS) allows to test Newton's gravity law at short distances. At the level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, limits on dark energy chameleon fields are improved by several order…
An instrument and software algorithm is described for the purpose of characterization of large single crystals at the Alignment Facility (ALF) of the ISIS spallation neutron source. We describe a method for both characterizing the quality of the sample and also aligning it in a particular scattering plane. We present a software package written for this instrument and demonstrate its utility by way of an example of the structural characterization of large singles crystals of Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$. We suggest extensions and modifications of characterization instruments for future impro…
We present the concept of a novel time-focusing technique for neutron spectrometers, which allows to disentangle time-focusing from beam divergence. The core of this approach is a double rotating-crystal monochromator that can be used to extract a larger wavelength band from a white beam, thus providing a higher flux at the sample compared to standard time-of-flight instruments, yet preserving energy resolution and beam collimation. The performances of a spectrometer based on this approach are quantitatively discussed in terms of possible incident wavelengths, flux at the sample and $(Q,E)$-re…
Following significant instrument upgrades and parallel methodological developments over the past decade, the TOSCA neutron spectrometer at the ISIS Pulsed Neutron & Muon Source in the United Kingdom has developed a rich and growing scientific community spanning a broad range of non-traditional areas of neutron science, including chemical catalysis, gas adsorption & storage, and new materials for energy and sustainability. High-pressure science, however, has seen little to no representation to date owing to previous limitations in capability. Herein, we explore for the first time the viability …
This manuscript outlines a concept that would leverage the existing proton accelerator at the Spallation Neutron Source of Oak Ridge National Laboratory to enable transformative science via one world-class facility serving two missions: Single Event Effects (SEE) and Muon Spectroscopy ($μ$SR). The $μ$SR portion would deliver the world's highest flux and highest resolution pulsed muon beams for materials characterization purposes, with precision and capabilities well beyond comparable facilities. The SEE capabilities deliver neutron, proton and muon beams for aerospace industries that are facin…
We propose a Modulation of intensity with zero effort (MIEZE) set-up for high-resolution neutron spectroscopy at momentum transfers up to 3Å$^{-1}$,energy transfers up to ~ 20 meV, and an energy resolution in the $μ$eV-range using both thermal and cold neutrons. MIEZE has two prominent advantages compared to classical neutron spin-echo. The first one is the possibility to investigate spin-depolarizing samples or samples in strong magnetic fields without loss of signal amplitude and intensity. This allows for the study of spin fluctuations in ferromagnets, and facilitates the study of samples w…
Characterisation of a Thick Pixelated Silicon Detector for Electron Spectroscopy of Neutron Beta Decay
Heinz Maier-Leibnitz Zentrum (MLZ), Technical University of Munich（海因茨·迈尔-莱布尼茨中心，慕尼黑工业大学）；Technical University of Munich, School of Natural Sciences（慕尼黑工业大学自然科学院）
Samples of two characteristic semiconductor sensor materials, silicon and germanium, have been irradiated with neutrons produced at the RP-10 Nuclear Research Reactor at 4.5 MW. Their radionuclides photon spectra have been measured with high resolution gamma spectroscopy, quantifying four radioisotopes ($^{28}$Al, $^{29}$Al for Si and $^{75}$Ge and $^{77}$Ge for Ge). We have compared the radionuclides production and their emission spectrum data with Monte Carlo simulation results from FLUKA. Thus we have tested FLUKA's low energy neutron library (ENDF/B-VIIR) and decay photon scoring with resp…
The photoneutron source (PNS, phase 1), an electron linear accelerator (linac)-based pulsed neutron facility that uses the time-of-flight (TOF) technique, was constructed for the acquisition of nuclear data from the thorium molten salt reactor(TMSR) at the Shanghai Institute of Applied Physics (SINAP). The neutron detector signal, with the information on the pulse arrival time, pulse shape, and pulse height, was recorded by using a waveform digitizer (WFD). By using the pulse height and pulse-shape discrimination (PSD) analysis to identify neutrons and $γ$-rays, the neutron TOF spectrum was ob…
Recent progress in neutron spin-echo spectroscopy by means of longitudinal Modulation of IntEnsity with Zero Effort (MIEZE) is reviewed. Key technical characteristics are summarized which highlight that the parameter range accessible in momentum and energy, as well as its limitations, are extremely well understood and controlled. Typical experimental data comprising quasi-elastic and inelastic scattering are presented, featuring magneto-elastic coupling and crystal field excitations in Ho2Ti2O7, the skyrmion lattice to paramagnetic transition under applied magnetic field in MnSi, ferromagnetic…
In this article we report on the design, manufacture and testing of a high-pressure cell for doing simultaneous dielectric and neutron spectroscopy. This cell is a unique tool for studying dynamics on different timescales, from kilo- to picoseconds, covering universal features such as the alpha relaxation and fast vibrations at the same time. The cell, constructed in cylindrical geometry, is made in high-strength aluminum alloy and operates up to 500 MPa in a temperature range between roughly 2 and 320 K. In order to measure the scattered neutron intensity and the sample capacitance simultaneo…
The generation of high frequency oscillatory magnetic fields represents a fundamental component underlying the successful implementation of neutron resonant spin-echo spectrometers, a class of instrumentation critical for the high-resolution extraction of dynamical excitations (structural and magnetic) in materials. In this paper, the setup of the resonant circuits at the longitudinal resonant spin-echo spectrometer RESEDA is described in comprehensive technical detail. We demonstrate that these circuits are capable of functioning at frequencies up to 3.6 MHz and over a broad bandwidth down to…
Recently, a new neutron spectroscopy for the dynamics in complex (bio-) systems has been proposed [A. Benedetto, and G. J. Kearley, Sci. Rep. 6, 34266, (2016)]. This spectroscopy is ideal where only the overall relaxation time in a parameterless way is required, for example in complex systems, because only the elastic-scattering intensity as a function of the energy resolution is required. This has been termed "Elastic Scattering Spectroscopy" (ESS). It is based on the inflection points in the elastic-scattering intensity at the energy-resolution value corresponding to the overall system relax…
Detailed characterization of the newly available plastic scintillator (EJ-299-33A) having the pulse shape discrimination (PSD) property has been carried out in case of a large-sized detector (5 in.$\times$5 in.). The pulse height response of the scintillator for nearly mono-energetic neutrons has been reported in case of neutron energies E$_n$ =3, 6 and 9 MeV. Important properties (figure-of-merit (FOM), time resolution, detection efficiency) of the detector has been compared with a commonly used liquid organic scintillator based detector of the same size coupled to the same PMT for uniformity…
We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a $|B_0|=1~\text{μT}$ magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCN of different energies, and also permits an improved determination of the vertical mag…
Large acceptance spectrometers at in-flight RI separators have played significant roles in investigating the structure of exotic nuclei. Such spectrometers are in particular useful for probing unbound states of exotic nuclei, using invariant mass spectroscopy with reactions at intermediate and high energies. We discuss here the key characteristic features of such spectrometers, by introducing the recently commissioned SAMURAI facility at the RIBF, RIKEN. We also explore the issue of cross talk in the detection of multiple neutrons, which has become crucial for exploring further unbound states …
The Multi-Grid detector technology has evolved from the proof-of-principle and characterisation stages. Here we report on the performance of the Multi-Grid detector, the MG.CNCS prototype, which has been installed and tested at the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a side-by-side comparison to the performance of $^3$He detectors on an operational instrument. The demonstrator has an active area of 0.2 m$^2$. It is specifically tailored to the specifications of CNCS. The detector was installed in June 2016 and has operated since then, collecting neutron scattering …
Research efforts ranging from studies of solid helium to searches for a neutron electric dipole moment require isotopically purified helium with a ratio of 3He to 4He at levels below that which can be measured using traditional mass spectroscopy techniques. We demonstrate an approach to such a measurement using accelerator mass spectroscopy, reaching the 10e-14 level of sensitivity, several orders of magnitude more sensitive than other techniques. Measurements of 3He/4He in samples relevant to the measurement of the neutron lifetime indicate the need for substantial corrections. We also argue …
For ultracold neutrons with a kinetic energy below 10 neV, strong scattering, characterized by $2πl_{c} / λ\leq 1$, can be obtained in metamaterials of C and $^7$Li. Here $l_{c}$ and $λ$ are the coherent scattering mean free path and the neutron wavelength, respectively. UCN interferometry and high-resolution spectroscopy (nano-electronvolt to pico-electronvolt resolution) in parallel waveguide arrays of neutronic metamaterials are given as examples of new experimental possibilities.
