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arXiv2013

Phase inversion and collapse of the cross-spectral function

Cross-spectral analysis is a mathematical tool for extracting the power spectral density of a correlated signal from two time series in the presence of uncorrelated interfering signals. We demonstrate and explain a set of conditions where the detection of the desired signal using cross-spectral fails partially or entirely in the presence of a second uncorrelated signal. Not understanding when and how this effect occurs can lead to dramatic underreporting of the desired signal. Theoretical, simulated and experimental demonstrations of this effect as well as mitigating methods are presented.

physics.ins-det↗
arXiv2013

A large-area single photon sensor employing wavelength-shifting and light-guiding technology

Large-scale underground water-Cherenkov neutrino observatories rely on single photon sensors whose sensitive area for Cherenkov photons one wants to maximise. Low dark noise rates and dense module spacing will thereby allow to substantially decrease the energy threshold in future projects. We describe a feasibility study of a novel type of single photon sensor that employs organic wavelength-shifting material (WLS) to capture Cherenkov photons and guide them to a PMT readout. Different WLS materials have been tested in lab measurements as candidates for use in such a sensor and photon capture efficiencies as high as 50 % have been achieved. Based on these findings we estimate that the effective photosensitive area of a prototype built with existing technology can easily exceed that of modules currently used e. g. in IceCube. Additionally, the dark noise rate of such a module can be exceptionally low in the order of 10 Hz. This is of special importance when targeting low-energy neutrinos that yield only few photons that need to be distinguished from noise hits.

astro-ph.IM↗
arXiv2013

Effects of upward-going cosmic muons on density radiography of volcanoes

Muon tomography aims at deriving the density structure of geological bodies from their screening attenuation produced on the natural cosmic muons flux. Because of their open-sky exposure, muons telescopes are subject to noise fluxes with large intensities relative to the tiny flux of interest. A recognized source of noise flux comes from fake tracks caused by particles that fortuitously trigger the telescope detectors at the same time. Such a flux may be reduced by using multiple-detector telescopes so that fortuitous events become very unlikely. In the present study, we report on a different type of noise flux caused by upward-going muons crossing the detectors from the rear side. We describe field experiments on La Soufriére of Guadeloupe and Mount Etna, and give details on the high-resolution clocking system and the statistical procedure necessary to detect upward-going muons. We analyse several data sets acquired either in calibration or in volcano tomography situation. All data sets are shown clearly biased by upward-going noise flux whose intensity may amount to 50% of the measured total flux in given directions. Biases produced on density radiographies by this kind of flux are quantified and correction procedures are detailed. Examples for La Soufriére and Mount Etna are given.

physics.ins-det↗
arXiv2013

Imaging of weak phase objects with a Zernike phase plate

Analysis of the imaging of some simple distributions of object phase by a phase plate of Zernike type shows that sharp transitions in the object phase are well transmitted. The low-frequency components of the complete object function are attenuated by the plate. The behaviour can be characterised by a cut-on parameter defined as the product of the cut-on frequency of the plate and a characteristic dimension of the object. When this parameter exceeds a value of the order of unity, a sharp boundary in the object is imaged by a Zernike plate as a dark lining inside the boundary with a white outline or halo outside the boundary, in agreement with reported observations. The maximum diameter of objects that can be imaged accurately is inversely proportional to the diameter of the hole for beam transmission in the phase plate.

physics.ins-det↗
arXiv2013

The OscSNS White Paper

There exists a need to address and resolve the growing evidence for short-baseline neutrino oscillations and the possible existence of sterile neutrinos. Such non-standard particles require a mass of $\sim 1$ eV/c$^2$, far above the mass scale associated with active neutrinos, and were first invoked to explain the LSND $\bar ν_μ\rightarrow \bar ν_e$ appearance signal. More recently, the MiniBooNE experiment has reported a $2.8 σ$ excess of events in antineutrino mode consistent with neutrino oscillations and with the LSND antineutrino appearance signal. MiniBooNE also observed a $3.4 σ$ excess of events in their neutrino mode data. Lower than expected neutrino-induced event rates using calibrated radioactive sources and nuclear reactors can also be explained by the existence of sterile neutrinos. Fits to the world's neutrino and antineutrino data are consistent with sterile neutrinos at this $\sim 1$ eV/c$^2$ mass scale, although there is some tension between measurements from disappearance and appearance experiments. In addition to resolving this potential major extension of the Standard Model, the existence of sterile neutrinos will impact design and planning for all future neutrino experiments. It should be an extremely high priority to conclusively establish if such unexpected light sterile neutrinos exist. The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, built to usher in a new era in neutron research, provides a unique opportunity for US science to perform a definitive world-class search for sterile neutrinos.

physics.ins-det↗
arXiv2013

Neutrino mass hierarchy determination and other physics potential of medium-baseline reactor neutrino oscillation experiments

Medium-baseline reactor neutrino oscillation experiments (MBRO) have been proposed to determine the neutrino mass hierarchy (MH) and to make precise measurements of the neutrino oscillation parameters. With sufficient statistics, better than ~3%/\sqrt{E} energy resolution and well understood energy non-linearity, MH can be determined by analyzing oscillation signals driven by the atmospheric mass-squared difference in the survival spectrum of reactor antineutrinos. With such high performance MBRO detectors, oscillation parameters, such as \sin^22θ_{12}, Δm^2_{21}, and Δm^2_{32}, can be measured to sub-percent level, which enables a future test of the PMNS matrix unitarity to ~1% level and helps the forthcoming neutrinoless double beta decay experiments to constrain the allowed values. Combined with results from the next generation long-baseline beam neutrino and atmospheric neutrino oscillation experiments, the MH determination sensitivity can reach higher levels. In addition to the neutrino oscillation physics, MBRO detectors can also be utilized to study geoneutrinos, astrophysical neutrinos and proton decay. We propose to start a U.S. R&D program to identify, quantify and fulfill the key challenges essential for the success of MBRO experiments.

hep-ex↗
arXiv2013

An Information-Theoretical Approach to Image Resolution Applied to Neutron Imaging Detectors based upon Individual Discriminator Signals

1D or 2D neutron imaging detectors with individual wire or strip readout using discriminators have the advantage of being able to treat several neutron impacts partially overlapping in time, hence reducing global dead time. A single neutron impact usually gives rise to several discriminator signals. In this paper, we introduce an information-theoretical definition of image resolution. Two point-like spots of neutron impacts with a given distance between them act as a source of information (each neutron hit belongs to one spot or the other), and the detector plus signal treatment is regarded as an imperfect communication channel that transmits this information. The maximal mutual information obtained from this channel as a function of the distance between the spots allows to define a calibration-independent measure of resolution. We then apply this measure to quantify the power of resolution of different algorithms treating these individual discriminator signals which can be implemented in firmware. The method is then applied to different detectors existing at the ILL. Center-of-gravity methods usually improve the resolution over best-wire algorithms which are the standard way of treating these signals.

physics.ins-det↗
arXiv2013

Numerical simulation of non-steady state neutron kinetics of the TRIGA Mark II reactor Vienna

This paper presents an algorithm for numerical simulations of non-steady states of the TRIGA MARK II reactor in Vienna, Austria. The primary focus of this work has been the development of an algorithm which provides time series of integral neutron flux after reactivity changes introduced by perturbations without the usage of thermal-hydraulic / neutronic numerical code systems for the TRIGA reactor in Vienna, Austria. The algorithm presented takes into account both external reactivity changes as well as internal reactivity changes caused by feedback mechanisms like effects caused by temperature changes of the fuel and poisoning effects. The resulting time series have been compared to experimental results.

physics.ins-det↗
arXiv2013

In-situ gamma spectrometry measurements of time-dependent Xenon-135 inventory in the TRIGA Mark II reactor Vienna

In this work, it has been shown that the time dependent Xe-135 inventory in the TRIGA Mark II reactor in Vienna, Austria can be measured via gamma spectrometry even in the presence of strong background radiation. It is focussing on the measurement of (but not limited to) the nuclide Xe-135. The time dependent Xe-135 inventory of the TRIGA Mark II reactor Vienna has been measured using a temporary beam line between one fuel element of the core placed onto the thermal column after shutdown and a detector system located just above the water surface of the reactor tank. For the duration of one week, multiple gamma ray spectra were recorded automatically, starting each afternoon after reactor shutdown until the next morning. One measurement series has been recorded over the weekend. The Xe-135 peaks were extracted from a total of 1227 recorded spectra using an automated peak search algorithm and analyzed for their time-dependent properties. Although the background gamma radiation present in the core after shutdown was large especially in the lower energy range, the Xe-135 peak located at 249.8 keV could be extracted from the most spectra where present and could be compared to theoretical calculations.

physics.ins-det↗
arXiv2013

The MAJORANA DEMONSTRATOR: A Search for Neutrinoless Double-beta Decay of Germanium-76

The {\sc Majorana} collaboration is searching for neutrinoless double beta decay using $^{76}$Ge, which has been shown to have a number of advantages in terms of sensitivities and backgrounds. The observation of neutrinoless double-beta decay would show that lepton number is violated and that neutrinos are Majorana particles and would simultaneously provide information on neutrino mass. Attaining sensitivities for neutrino masses in the inverted hierarchy region, $15 - 50$ meV, will require large, tonne-scale detectors with extremely low backgrounds, at the level of $\sim$1 count/t-y or lower in the region of the signal. The {\sc Majorana} collaboration, with funding support from DOE Office of Nuclear Physics and NSF Particle Astrophysics, is constructing the {\sc Demonstrator}, an array consisting of 40 kg of p-type point-contact high-purity germanium (HPGe) detectors, of which $\sim$30 kg will be enriched to 87% in $^{76}$Ge. The {\sc Demonstrator} is being constructed in a clean room laboratory facility at the 4850' level (4300 m.w.e.) of the Sanford Underground Research Facility (SURF) in Lead, SD. It utilizes a compact graded shield approach with the inner portion consisting of ultra-clean Cu that is being electroformed and machined underground. The primary aim of the {\sc Demonstrator} is to show the feasibility of a future tonne-scale measurement in terms of backgrounds and scalability.

physics.ins-det↗
arXiv2013

IRIDE White Book, An Interdisciplinary Research Infrastructure based on Dual Electron linacs&lasers

This report describes the scientific aims and potentials as well as the preliminary technical design of IRIDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity 'particle factory', based on a combination of a high duty cycle radio-frequency superconducting electron linac and of high energy lasers. Conceived to provide unique research possibilities for particle physics, for condensed matter physics, chemistry and material science, for structural biology and industrial applications, IRIDE will open completely new research possibilities and advance our knowledge in many branches of science and technology. IRIDE will contribute to open new avenues of discoveries and to address most important riddles: What does matter consist of? What is the structure of proteins that have a fundamental role in life processes? What can we learn from protein structure to improve the treatment of diseases and to design more efficient drugs? But also how does an electronic chip behave under the effect of radiations? How can the heat flow in a large heat exchanger be optimized? The scientific potential of IRIDE is far reaching and justifies the construction of such a large facility in Italy in synergy with the national research institutes and companies and in the framework of the European and international research. It will impact also on R&D work for ILC, FEL, and will be complementarity to other large scale accelerator projects. IRIDE is also intended to be realized in subsequent stages of development depending on the assigned priorities.

physics.ins-det↗
arXiv2013

Secondary Emission Calorimetry: Fast and Radiation-Hard

A novel calorimeter sensor for electron, photon and hadron energy measurement based on Secondary Emission(SE) to measure ionization is described, using sheet-dynodes directly as the active detection medium; the shower particles in an SE calorimeter cause direct secondary emission from dynode arrays comprising the sampling or absorbing medium. Data is presented on prototype tests and Monte Carlo simulations. This sensor can be made radiation hard at GigaRad levels, is easily transversely segmentable at the mm scale, and in a calorimeter has energy signal rise-times and integration comparable to or better than plastic scintillation/PMT calorimeters. Applications are mainly in the energy and intensity frontiers.

physics.ins-det↗
arXiv2013

Charged Lepton Flavor Violation Experiments

The experimental status of charged lepton flavor violation searches is briefly reviewed, with particular emphasis on the three classical searches involving muon transisions: $μ\to e γ$, $μ\to e$ conversion and $μ\to 3e$.

hep-ex↗
arXiv2013

Quartz Capillary Cladding Anthracene and Polycyclic Aromatic Hydrocarbon(PAH)-Core Scintillating/WLS Fibers for High Rates and Radiation Damage Resistance

Quartz capillary tube/fibers have been filled with anthracene by a melt and vacuum inbibition process to fabricate a scintillating core fiber. Other polcyclic aromatic hydrocarbons(PAH), such as p-Terphenyl (pTP), stilbene or naphthalene are also well-suited to scintillating/shifting fiber cores. The resulting scintillating core with quartz cladding capillary fibers (250-750 micron cores) had a high specific light output when tested with muons (8 p.e. per MIP). These PAH core quartz capillary cladding scintillating/shifting optical fibers have the potential of high radiation resistance, fast response, and are applicable to many energy and intensity frontier experiments.

physics.ins-det↗
arXiv2013

Dark Matter Direct Detection With Low Temperature Detectors

Low Temperature Detectors (LTDs) offer the best signal-to-noise performance and thus, lowest energy threshold among other particle detection technologies available today. The excellent background rejection provided by these detectors is essential to search for very rare and very low energy recoils expected from dark matter interactions. Furthermore, due to their very good event-by-event background rejection capabilities, LTDs do not heavily rely on self-shielding in order to mitigate radioactive backgrounds (in contrast with the monolithic liquid Noble Gas detectors) thus they can be more easily prototyped and tested for basic detector performance. A review of the status and prospects of the major Dark Matter search experiments using LTD technologies is presented here.

astro-ph.IM↗
arXiv2013

Extending the NOvA Physics Program

Following the precise measurement of $θ_{13}$ by reactor experiments three main questions remain within the now standard picture of neutrino oscillations: (1) Is the value of $θ_{23}$ such that the $ν_3$ state contains more muon flavor, more tau flavor, or equal amounts? (2) What is the neutrino mass hierarchy? (3) Is CP violated in the neutrino sector? The NOvA experiment will address all three of these questions. In each case the measurements are statistics limited motivating exploration of what could be accomplished with additional exposure.

hep-ex↗
arXiv2013

Ultra-Low Index and Rad-Hard Total Internal Reflection Claddings for High Numerical Aperture Scintillating, Waveshifting, Cerenkov, or Clear Optical Fibers, Capillaries, and Plates

Novel low index (n less than 1.3)/high light trapping cladding films consisting of nanoporous alumina (sapphire), as formed by controlled anodization of aluminum, are described. These films are mechanically hard, intrinsically very rad-hard, and have an index of refraction n sufficiently small to triple the light capture of waveshifting or scintillating fibers and transparent plastic, glass or quartz core fibers. The low indices enable light-piping of water Cerenkov light. Applications are in Energy, Intensity, and Cosmic/Astroparticle detectors.

physics.ins-det↗