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arXiv2013

Future Reactor Experiments

The measurement of the neutrino mixing angle $θ_{13}$ opens a gateway for the next generation experiments to measure the neutrino mass hierarchy and the leptonic CP-violating phase. Future reactor experiments will focus on mass hierarchy determination and the precision measurement of mixing parameters. Mass hierarchy can be determined from the disappearance of reactor electron antineutrinos based on the interference effect of two separated oscillation modes. Relative and absolute measurement techniques have been explored. A proposed experiment JUNO, with a 20 kton liquid scintillator detector of $3%/$$\sqrt{E(MeV)}$ energy resolution, $\sim$ 53 km far from reactors of $\sim$ 36 GW total thermal power, can reach to a sensitivity of $Δχ^{2}>16$ considering the spread of reactor cores and uncertainties of the detector response. Three of mixing parameters are expected to be measured to better than 1% precision. There are multiple detector options for JUNO under investigation. The technical challenges are new type of PMTs with high efficiency and highly transparent liquid scintillator. Funding has been approved from Chinese Academy of Sciences. A similar proposal was from Korea known as RENO-50. Both of them are going to start data taking around 2020.

physics.ins-det↗
arXiv2013

Searches for rare and forbidden kaon decays at the NA62 experiment at CERN

The decay $K^+ \to π^+ν\barν$ is highly suppressed in the Standard Model (SM), while its rate can be predicted with minimal theoretical uncertainty. The branching ratio (BR) for this decay is thus a sensitive probe of the flavor sector of the SM; its measurement, however, is a significant experimental challenge. The primary goal of the NA62 experiment is to measure ${\rm BR}(K^+ \to π^+ν\barν)$ with $\sim$10% precision. This will require the observation of $10^{13}$ $K^+$ decays in the experiment's fiducial volume, as well as the use of high-performance systems for precision tracking, particle identification, and photon vetoing. These aspects of the experiment will also allow NA62 to carry out a rich program of searches for lepton flavor and/or number violating $K^+$ decays. Part of the experimental apparatus was commissioned during a technical run in 2012; installation continues and data taking is expected to begin in late 2014. The physics prospects and the status of the NA62 experiment are reviewed.

hep-ex↗
arXiv2013

Passive Magnetic Shielding in Gradient Fields

The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied. It is found that for concentric cylindrical or spherical shells of high permeability material, higher order multipoles in the magnetic field are shielded progressively better, by a factor related to the order of the multipole. In regard to the design of internal coil systems for the generation of uniform internal fields, we show how one can take advantage of the coupling of the coils to the innermost magnetic shield to further optimize the uniformity of the field. These results demonstrate quantitatively a phenomenon that was previously well-known qualitatively: that the resultant magnetic field within a passively magnetically shielded region can be much more uniform than the applied magnetic field itself. Furthermore we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields close to the outermost magnetic shielding layer. Overall this work provides a comprehensive framework needed to analyze and optimize dc magnetic shields, serving as a theoretical and conceptual design guide as well as a starting point and benchmark for finite-element analysis.

physics.ins-det↗
arXiv2013

Snowmass CF1 Summary: WIMP Dark Matter Direct Detection

As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader Particle Physics community to produce this document. The charge to CF1 was (a) to summarize the current status and projected sensitivity of WIMP direct detection experiments worldwide, (b) motivate WIMP dark matter searches over a broad parameter space by examining a spectrum of WIMP models, (c) establish a community consensus on the type of experimental program required to explore that parameter space, and (d) identify the common infrastructure required to practically meet those goals.

hep-ex↗
arXiv2013

On the synthesis of Quantum Hall Array Resistance Standards

Quantum Hall effect (QHE) is the basis of modern resistance metrology. In Quantum Hall Array Resistance Standards (QHARS), several individual QHE elements, each one having the same QHE resistance (typically half of the von Klitzing constant), are arranged in networks that realize resistance values close to decadic values (such as 1 kiloohm or 100 kiloohm), of direct interest for dissemination. The same decadic value can be approximated with different grades of precision, and even for the same approximation several networks of QHE elements can be conceived. The paper investigates the design of QHARS networks by giving methods to find a proper approximation of the resistance of interest, and to design the corresponding network with a small number of elements. Results for several decadic cases are given.

physics.ins-det↗
arXiv2013

Micro-coil detection of Nuclear Magnetic Resonance for nanofluidic samples

We have developed a novel dc SQUID system with a micro-coil input circuit to act as a local probe of quantum matter and nanosystems. The planar niobium micro-coil pickup loop is located remotely from the SQUID, coupled through a superconducting twisted pair, enabling the sample to be at microkelvin temperatures. A high degree of coupling between the coil and the region of interest of similar dimensions (up to ~ 100 microns) can be achieved. We report nuclear magnetic resonance (NMR) measurements to characterise the sensitivity of these coils to 3He in the gas phase at 4.2 K in a 30 mT magnetic field.

cond-mat.supr-con↗
arXiv2013

Analysis of an attempt at detection of neutrons produced in a plasma discharge electrolytic cell

R. Faccini et al. \cite{Faccini:2013} have attempted a replication of an earlier experiment by D. Cirillo et al. \cite{Cirillo:2012} in which neutrons [as well as nuclear transmutations] were observed in a modified Mizuno cell. No neutron production is observed in the recent experiment \cite{Faccini:2013} and no evidence for microwave radiation or nuclear transmutations are reported. A careful analysis shows major technical differences in the two experiments and we explore the underlying reasons for the lack of any nuclear activity in the newer experiment.

physics.ins-det↗
arXiv2013

Low dimensional neutron moderators for enhanced source brightness

In a recent numerical optimization study we have found that liquid para-hydrogen coupled cold neutron moderators deliver 3 - 5 times higher cold neutron brightness at a spallation neutron source if they take the form of a flat, quasi 2-dimensional disc, in contrast to the conventional more voluminous shapes used by now. In the present paper we describe a simple theoretical explanation of this unexpected behavior, which is based on the large difference in para-hydrogen between the values of the scattering mean free path for thermal neutrons (in the range of 1 cm) and its much larger equivalent for cold neutrons. This model leads to the conclusions that the optimal shape for high brightness para-hydrogen neutron moderators is the quasi 1-dimensional tube and these low dimensional moderators can also deliver much enhanced cold neutron brightness in fission reactor neutron sources, compared to much more voluminous liquid D2 or H2 moderators currently used. Neutronic simulation calculations confirm both of these theoretical conclusions.

physics.ins-det↗
arXiv2013

Sensitivity of the DANSS detector to short range neutrino oscillations

DANSS is a highly segmented 1m^3 plastic scintillator detector. It's 2500 scintillator strips have a Gd loaded reflective cover. Light is collected with 3 wave length shifting fibers per strip and read out with 50 PMTs and 2500 SiPMs. The DANSS will be installed under the industrial 3 GW reactor of the Kalinin Nuclear Power Plant at distances varying from 9.7m to 12.2m from the reactor core. Tests of the detector prototype DANSSino demonstrated that in spite of a small size (20x20x100 cm^3) it is quite sensitive to reactor antineutrinos, detecting about 70 Inverse Beta Decay events per day with the signal-to-background ratio of about unity. The prototype tests have demonstrated feasibility to reach the design performance of the DANSS detector. The DANSS experiment will detect about 10 thousand antineutrino events per day with a background below ~1%. Detector will be calibrated every day and its position will be changed frequently to reduce systematic errors. These features will provide a high sensitivity to reactor antineutrino oscillations to sterile neutrinos, suggested recently to explain a so-called "reactor anomaly". Data taking will start already next year.

physics.ins-det↗
arXiv2013

Status of the MAJORANA DEMONSTRATOR experiment

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.

physics.ins-det↗
arXiv2013

Low Background Materials and Assay - A Supplement to the Cosmic Frontier CF1 Summary

This White Paper provides a supplement to the Snowmass Summary from CF1 (Cosmic Frontier WIMP Direct Detection). It was largely prepared during the August 2013 Community Planning Meeting and relies on information gathered from the larger dark matter community. It is a more detailed answer to the CF1 Charge: "Identify the common infrastructure required to meet the scientific and technical goals of dark matter direct detection." The community as a whole recognizes that sensitive searches for WIMPs require identification, quantification, and procurement of radiopure materials. The lack of sufficient resources in this area is a major project risk for future experiments and can limit scientific reach

hep-ex↗
arXiv2013

Performance of Irradiated Thin Edgeless N-on-P Planar Pixel Sensors for ATLAS Upgrades

In view of the LHC upgrade phases towards the High Luminosity LHC (HL-LHC), the ATLAS experiment plans to upgrade the Inner Detector with an all-silicon system. Because of its radiation hardness and cost effectiveness, the n-on-p silicon technology is a promising candidate for a large area pixel detector. The paper reports on the joint development, by LPNHE and FBK of novel n-on-p edgeless planar pixel sensors, making use of the active trench concept for the reduction of the dead area at the periphery of the device. After discussing the sensor technology, a complete overview of the electrical characterization of several irradiated samples will be discussed. Some comments about detector modules being assembled will be made and eventually some plans will be outlined.

physics.ins-det↗
arXiv2013

Fundamental Limits of Detection of Galaxies in the Near and Mid Infrared

The construction of the James Webb Space Telescope has brought attention to infrared astronomy and cosmology. The potential information about our universe to be gained by this mission and future infrared telescopes is staggering, but infrared observation faces many obstacles. These telescopes face large amounts of noise by many phenomena, from emission off of the mirrors to the cosmic infrared background. Infrared telescopes need to be designed in such a way that noise is minimized to achieve sufficient signal to noise ratio on high redshift objects. We will investigate current and planned space and ground based telescopes, model the noise they encounter, and discover their limitations. The ultimate of our investigation is to compare the sensitivity of these missions in the near and mid IR and to propose new missions. Our investigation is broken down into four major sections: current missions, noise, signal, and proposed missions. In the proposed missions section we investigate historical and current infrared telescopes with attention given to their location and properties. The noise section discusses the noise that an infrared telescope will encounter and set the background limit. The signal section will look at the spectral energy distributions (SED) of a few significant objects in our universe. We will calculate the intensity of the objects at various points on Earth and in orbit. In the final section we use our findings in the signal and noise sections to model integration times (observation time) for a variety of missions to achieve a given signal to noise ratio (SNR).

astro-ph.IM↗
arXiv2013

Output stages inside a negative feedback loop: application to a low-voltage three-phase DC-AC converter for educational purposes

The circuit presented in this paper aims at providing three 40 Vpp 50Hz AC voltages sources with 120-degree phase separation between them. This is a fully analogue circuit that uses standard, low-cost electronic components without resorting to a microcontroller as previously proposed by Shirvasar et al [1]. This circuit may serve as a basis for a low-voltage 3P-AC power supply that students may safely use to realize experiments, i.e. about the principles and applications of three-phase AC power lines, without the risk of electric shocks.

physics.ed-ph↗
arXiv2014

Annihilation of low energy antiprotons in silicon

The goal of the AE$\mathrm{\bar{g}}$IS experiment at the Antiproton Decelerator (AD) at CERN, is to measure directly the Earth's gravitational acceleration on antimatter. To achieve this goal, the AE$\mathrm{\bar{g}}$IS collaboration will produce a pulsed, cold (100 mK) antihydrogen beam with a velocity of a few 100 m/s and measure the magnitude of the vertical deflection of the beam from a straight path. The final position of the falling antihydrogen will be detected by a position sensitive detector. This detector will consist of an active silicon part, where the annihilations take place, followed by an emulsion part. Together, they allow to achieve 1$%$ precision on the measurement of $\bar{g}$ with about 600 reconstructed and time tagged annihilations. We present here, to the best of our knowledge, the first direct measurement of antiproton annihilation in a segmented silicon sensor, the first step towards designing a position sensitive silicon detector for the AE$\mathrm{\bar{g}}$IS experiment. We also present a first comparison with Monte Carlo simulations (GEANT4) for antiproton energies below 5 MeV

physics.ins-det↗
arXiv2013

A setup for the study of surface processes under external homogeneous electric fields

A setup for studying the influence of external electric fields on dynamic surface processes is described. Spatially-extended homogeneous electric fields are realized by applying a DC voltage in between a planar electrode and a metallic substrate, which are separated by a narrow vacuum gap. The functional capability of the device is demonstrated by recording the field-emission characteristic as a function of the applied field up to 2.3 V/nm, revealing proper Fowler-Nordheim tunneling behavior.

physics.ins-det↗
arXiv2013

A Balloon-borne Measurement of High Latitude Atmospheric Neutrons Using a LiCAF Neutron Detector

PoGOLino is a scintillator-based neutron detector. Its main purpose is to provide data on the neutron flux in the upper stratosphere at high latitudes at thermal and nonthermal energies for the PoGOLite instrument. PoGOLite is a balloon borne hard X-ray polarimeter for which the main source of background stems from high energy neutrons. No measurements of the neutron environment for the planned flight latitude and altitude exist. Furthermore this neutron environment changes with altitude, latitude and solar activity, three variables that will vary throughout the PoGOLite flight. PoGOLino was developed to study the neutron environment and the influences from these three variables upon it. PoGOLino consists of two Europium doped Lithium Calcium Aluminium Fluoride (Eu:LiCAF) scintillators, each of which is sandwiched between 2 Bismuth Germanium Oxide (BGO) scintillating crystals, which serve to veto signals produced by gamma-rays and charged particles. This allows the neutron flux to be measured even in high radiation environments. Measurements of neutrons in two separate energy bands are achieved by placing one LiCAF detector inside a moderating polyethylene shield while the second detector remains unshielded. The PoGOLino instrument was launched on March 20th 2013 from the Esrange Space Center in Northern Sweden to an altitude of 30.9 km. A description of the detector design and read-out system is presented. A detailed set of simulations of the atmospheric neutron environment performed using both PLANETOCOSMICS and Geant4 will also be described. The comparison of the neutron flux measured during flight to predictions based on these simulations will be presented and the consequences for the PoGOLite background will be discussed.

astro-ph.IM↗