Looking for SUSY with EDELWEISS-I and-II

The latest results obtained by the EDELWEISS WIMP (weakly interacting massive particles) direct detection experiment using three heat-and-ionization 320-g germanium bolometers are given. Presently the most sensitive WIMP direct detection experiment for WIMP mass >30 GeV, EDELWEISSI is testing a first region of SUSY models compatible with accelerator constraints. The status and main characteristics of EDELWEISS-II, involving in a first stage 28 germanium bolometers and able to accommodate up to 120 detectors, are briefly presented, together with neutron background estimates.     

Thermal neutron flux monitoring using new-type detectors

The applicability of new-type unshielded detectors based on zinc sulfide ZnS(Ag) and lithium fluoride enriched with ⁶Li isotope to 90% to thermal neutron measurements is demonstrated. The results of measurements of the thermal neutron counting rate and flux near the Earth’s surface are presented. The existence of the concentration gradient of thermal neutrons near the Earth’s surface at placing the counter at the various levels (from −4 to 10.5 m) in an experimental building is shown. The effect of meteoparameters on the counting rate of thermal neutrons for a long time is shown.     

Energetic neutrons and gamma rays measured on the Aryabhata satellite

An experiment to measure energetic neutrons and gamma rays in space was launched in the first Indian scientific satellite,Aryobhata, on April 19, 1975. From this experiment, the first measurements in space of the Earth’s albedo fiux of neutrons of energy between 20 and 500 MeV have been made; the values obtained for two mean geomagnetic vertical cut-off rigidities of 5.6 and 17.0 GV are (6.3±0.4)×10⁻² and (1.4±0.3)×10⁻² neutrons cm⁻² sec⁻¹ respectively. These measurements confirm that protons arising from cosmic ray albedo neutron decay, can adequately account for the protons in the inner radiation belt. Observations on gamma rays of energy between 0.2 and 24 MeV have enabled the determination of the total background gamma ray flux in space as a function of latitude. This in turn has permitted useful information on the diffuse cosmic gamma rays. We have also observed four events that showed sudden increases in the gamma ray counting rates between 0.2 and 4.0 MeV. Observational details of these events are given.     

Design of the thermal neutron detection system for CJPL-Ⅱ

A low background thermal neutron flux detection system has been designed to measure the ambient thermal neutron flux of the second phase of the China Jinping Underground Laboratory(CJPL-Ⅱ),right after completion of the rock bolting work.A ~3He proportional counter tube combined with an identical ~4He proportional counter tube was employed as the thermal neutron detector,which has been optimised in energy resolution,wall effect and radioactivity of construction materials for low background performance.The readout electronics were specially designed for long-term stable operation and easy maintenance in an underground laboratory under construction.The system was installed in Lab Hall No.3 of CJPL-Ⅱ and accumulated data for about 80 days.The ambient thermal neutron flux was determined under the assumption that the neutron field is fully thermalized,uniform and isotropic at the measurement position.     

Prompt (n,γ) Mass Measurements for the AVOGADRO Project

The aim of the AVOGADRO project is to replace the kilogram artefact by a high-purity, perfect single crystal of natural or isotope-enriched silicon. The isotopic composition and the impurities of the silicon crystal must, therefore, be known with highest possible accuracy and precision. The only method to obtain all this information without destruction of the massive samples is prompt (n,γ)-spectrometry. The measurements are performed at a thermal neutron guide of the ILL (Institut Max von Laue Paul Langevin) in Grenoble, France. The spectrometry of γ-radiation emitted by a nucleus promptly after thermal neutron capture allows a highly precise determination of atomic mass differences, as well as the determination of isotope abundances leading to the molar mass. The uncertainties assigned to the results for the respective atomic masses determined by the mass differences amount to up to 10⁻¹⁰, while the molar mass of an isotope-enriched Si single crystal has so far been determined with an uncertainty of 1 ⋅ 10⁻⁴. A direct comparison (for example, relative value of isotope abundances determined by (n,γ)-spectrometry omitting the thermal neutron cross section) furnishes a value of 7 ⋅ 10⁻⁵. The final aim of the AVOGADRO project is to provide a well specified crystal, which allows a more accurate value of the Avogadro constant to be determined. This constant is the key input parameter for tabulated values of fundamental constants and for a new definition of the unit of mass - the kilogram itself. This revised version was published online in July 2006 with corrections to the Cover Date.     

The LAPEX experiment for observation of the supernova SN 1987A in hard X-rays

Summary The LAPEX payload is described in the configuration that will be launched to observe the supernova SN 1987A. The balloon flight will be performed from Alice Springs (Australia) in April 1989 as a part of a NASA balloon campaign. The experiment will allow simultaneous observations of source and background in order to minimize systematic errors due to background variations. The limiting flux sensitivity of the instrument in the (20÷200) keV energy band is 4·10⁻⁶ ph/(cm²s keV) or ∼2.5 mCrab for a 10⁴ s observation of SN 1987A. The presence of a⁵⁷Co emission line in the SN 1987A photon spectrum could be detected down to an intensity level of ∼8·10⁻⁵ photons/cm²s as at 99.7% confidence level. The high resolution of the event timing (<0.1 ms) will make it possible to detect millisecond pulsations with amplitudes down to ∼4% of the expected average flux from SN 1987A in the (20÷60) keV band. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

Production of transuranium elements in a binary model under conditions of pulse nucleosynthesis

A model for the production of transuranium isotopes under the conditions of pulse nucleosynthesis in a powerful neutron flux (∼10²⁴−10²⁵ neutron cm⁻²) is considered. The explosive nature of the process allows us to separate it into two parts: the process of multiple neutron captures (t < 10⁻⁶ s) and the process of the subsequent β-decays for neutron-rich nuclei. The model of multiple captures neutron includes a variation of the cross section of the (n, γ) reaction as a result of the adiabatic expansion of the explosive nucleosynthesis area. A binary mixture of ²³⁸U and ²³⁹Pu is used as the initial isotope composition.     

Development of a segmented fast neutron spectrometer

We discuss the development of a spectrometer based on full energy absorption using liquid scintillator doped with enriched ⁶Li. Of specific interest, the spectrometer is expected to have good pulse height resolution, estimated to lie in the range 10–15% for 14-MeV neutrons. It should be sensitive to flux rates from 10⁻⁶ cm⁻² s⁻¹ to 10⁶ cm⁻² s⁻¹ above a threshold of 500 keV in an uncorrelated γ background of up to 10⁴ s⁻¹. We have constructed a pilot version of the detector using undoped liquid scintillator, and we report its present status. The detector’s efficiency is determined by the volume of the scintillator (∼1.21) and is estimated to be 0.2–0.5% for 3-MeV neutrons. The good pulse height resolution is achieved by compensation of the nonlinear light yield of the scintillator due to the use of optically separated segments, which collect scintillations from each recoil proton separately. We demonstrate here the response of the detector to neutrons from a Pu-α-Be source, whose energies range up to 10 MeV. Initial testing indicates a low threshold (≈600 keV) and good spectral response after requiring a multiplicity of three segments. Such a spectrometer has applications for low-background experiments in fundamental physics research, characterizations of neutron flux in space, and the health physics community. The text was submitted by the authors in English.     

Neutron Background from the (α, n) Reaction on 13C in the EDELWEISS-II experiment on direct search for weakly interacting particles of nonbaryonic cold dark matter

The purpose of the work is to evaluate the neutron background from an additional neutron source, the (α, n) reaction on ¹³C, in the polyethylene neutron shielding of the EDELWEISS-II experiment on the search for weakly interacting cold matter particles. The characteristic length of radon diffusion into polyethylene is obtained, the neutron energy spectrum is constructed, and the neutron flux from the (α, n) reaction is evaluated.     

Search for Cosmic-Microwave-Background anisotropies at degree angular scales: The ARGO 1993 experiment

Summary We describe a balloon-borne telescope, optimized for observations of the Cosmic Microwave Background (CMB) anisotropies in the mm wavelength region, at angular scales around 1⁰. We stress the scientific motivations for these measurements and the problematics driving the experiment design. Using large throughput bolometers cooled at 0.3K we have a sensitivity high enough to detect CMB anisotropies at level ΔT/T∼10⁻⁵ in few seconds of integration time. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

Simultaneous measurements of atmospheric HONO and NO<Subscript>2</Subscript> via absorption spectroscopy using tunable mid-infrared continuous-wave quantum cascade lasers

Nitrous acid (HONO) is important as a significant source of hydroxyl radical (OH) in the troposphere and as a potent indoor air pollutant. It is thought to be generated in both environments via heterogeneous reactions involving nitrogen dioxide (NO₂). In order to enable fast-response HONO detection suitable for eddy-covariance flux measurements and to provide a direct method that avoids interferences associated with derivatization, we have developed a 2-channel tunable infrared laser differential absorption spectrometer (TILDAS) capable of simultaneous high-frequency measurements of HONO and NO₂. Beams from two mid-infrared continuous-wave mode quantum cascade lasers (cw-QCLs) traverse separate 210 m paths through a multi-pass astigmatic sampling cell at reduced pressure for the direct detection of HONO (1660 cm⁻¹) and NO₂ (1604 cm⁻¹). The resulting one-second detection limits (S/N=3) are 300 and 30 ppt (pmol/mol) for HONO and NO₂, respectively. Our HONO quantification is based on revised line-strengths and peak positions for cis-HONO in the 6-micron spectral region that were derived from laboratory measurements. An essential component of ambient HONO measurements is the inlet system and we demonstrate that heated surfaces and reduced pressure minimize sampling artifacts.     

First experimental observations of neutron bursts under thunderstorm clouds near sea level

The connection of short-term neutron bursts near sea level with the electric and geomagnetic atmospheric fields during thunderstorms in 2009–2011 has been experimentally studied. The data from the cosmic-ray spectrograph named after Kuzmin, an electrostatic fluxmeter, and a three-component fluxgate magnetometer in Yakutsk have been analyzed. It has been shown that short-term (no longer than 4 min) neutron bursts are due to negative lightning discharges. The bursts are detected at the ground level 1–3 km below thunderstorm clouds. In this case, the neutron flux is about 4 × 10⁻³ cm⁻² s⁻¹. The minimum energy of the neutrons that are efficiently detected by the monitor is about 10 MeV. It has been found that short-term neutron bursts are detected when the electric field strength reaches a threshold value of −16 kV/m.     

Coherent backscattering of electromagnetic waves in a magnetised plasma

Summary A microwave coherent backscattering experiment has been carried out on Mirabelle, a weakly ionised plasma device, with the objective of measuring the electron density fluctuation level. The experiment is a preliminary step in order to prepare the detection system for a microwave stimulated backscattering experiment. The incident electromagnetic wave is focused in front of a plane grid which excites ion acoustic or electron Bernstein waves inducing fluctuations in the plasma. The backscattering signal is collected by the launching circuit and detected by homodyne mixing. The typical ratio of the scattered power to the incident power is about 10⁻¹² and the relative density fluctuations are of the order of δn _e/n _e=10⁻³ against a background electron density ofn _e=1–5·10⁹ cm⁻³. The backscattering measurement is compared with Langmuir probe measurements. The spectral width of the backscattered signal has also been studied, by taking into account effects due to the incident wave focusing and plasma wave damping. The authors of this paper have agreed to not receive the proofs for correction     

Optimization Study of the IBR-2 Reactor

The article considers the neutronics aspect of the IBR-2 reactor optimization: whether it is possible in theory to create an IBR-2-type reactor with a neutron flux in beams above the existing 0.5 × 1013 n/(cm2 s). The calculations have shown that the thermal neutron flux theoretically can be increased to (2.0−2.5) × 1013 n/(cm2 s), but only with a complete change in the reactor design: reducing the core volume, replacing the fuel type with a denser one, and changing the beam extraction system from radial to tangential. The technical implementation of these requirements is currently a challenge.     

Gemma experiment: Three years of the search for the neutrino magnetic moment

The result of the 3-year neutrino magnetic moment measurement at the Kalinin Nuclear Power Plant (KNPP) with the GEMMA spectrometer is presented. Antineutrino-electron scattering is investigated. A high-purity germanium detector of 1.5 kg placed at a distance of 13.9 m from the 3 GW_th reactor core is exposed to the antineutrino flux of 2.7 × 10¹³ cm⁻² s⁻¹. The scattered electron spectra taken in (5184 + 6798) and (1853 + 1021) h for the reactor ON and OFF periods are compared. The upper limit for the neutrino magnetic moment μ_v < 3.2 × 10⁻¹¹μ _B at 90% CL is derived from the data processing.     

Background neutron in the endcap and barrel regions of resistive plate chamber for compact muon solenoid/large hadron collider using GEANT4

In this study the performance of double gap RPC has been tested by GEANT4 Monte Carlo simulation code. The detector response calculations taken as a function of the neutron energy in the range of 0.01 eV-1 GeV have been simulated through RPC set-up. In order to evaluate the response of detector in the LHC background environment, the neutron spectrum expected in the CMS muon endcap and barrel region were taken into account. A hit rate of about 165.5 Hz cm⁻², 34 Hz cm⁻², 33.6 Hz cm⁻², and 27.0 Hz cm⁻² due to an isotropic neutron source is calculated using GEANT4 standard electromagnetic package for a 20 × 20 cm² RPC in the ME1, ME2, ME3 and ME4, respectively. While for the same neutron source and using GEANT4 package a hit rate of about 0.42 Hz cm⁻², 0.7182 Hz cm⁻² was measured for the MB1 and MB4 stations respectively. Similar characteristics of hit rates have been observed for GEANT4 low electromagnetic package.      

On the nature of the 17 μs isomer of the <Superscript>133</Superscript>Sb valence nucleus

The decay of the 17 μs isomer of ¹³³Sb was re-investigated experimentally. It was produced by thermal neutron induced fission of ²⁴¹Pu. Its detection is based on time correlation between fission fragments selected by the LOHENGRIN spectrometer at ILL (Grenoble), and the γ-rays, and conversion electrons from the isomer. The interpretation of the level scheme is based on shell model calculations, where empirical two-body matrix elements were employed. The good agreement between theory and experiment suggests that the isomer is the 21/2⁺ member of the 2p-1h πg _7/2ν(f _7/2 h _11/2 ⁻¹) configuration. Received: 20 January 2000 / Revised version: 28 February 2000     

Mid-infrared upconversion spectroscopy based on a Yb:fiber femtosecond laser

We present a system for molecular spectroscopy using a broadband mid-infrared laser with near-infrared detection. Difference frequency generation of a Yb:fiber femtosecond laser produced a mid-infrared (MIR) source tunable from 2100–3700 cm⁻¹ (2.7–4.7 μm) with average power up to 40 mW. The MIR spectrum was upconverted to near-infrared wavelengths for broadband detection using a two-dimensional dispersion imaging technique. Absorption measurements were performed over bandwidths of 240 cm⁻¹ (7.2 THz) with 0.048 cm⁻¹ (1.4 GHz) resolution, and absolute frequency scale uncertainty was better than 0.005 cm⁻¹ (150 MHz). The minimum detectable absorption coefficient per spectral element was determined to be 4.4×10⁻⁷ cm⁻¹ from measurements in low pressure CH₄, leading to a projected detection limit of 2 parts-per-billion of methane in pure nitrogen. In a natural atmospheric sample, the methane detection limit was found to be 30 parts-per-billion. The spectral range, resolution, and frequency accuracy of this system show promise for determination of trace concentrations in gas mixtures containing both narrow and broad overlapping spectral features, and we demonstrate this in measurements of air and solvent samples.     

TeV activity of Cygnus X-3 high mass binary system

Cygnus X-3 is a high mass X-ray binary and microquasar, with a compact object, which is either a neutron star or may be a black hole, and a companion object, which is a Wolf-Rayet star. The nature of the compact object is still uncertain. Cygnus X-3 galactic binary system has been regularly observed since a 1995 by SHALON Atmospheric Cherenkov telescope with the average gamma-ray flux (6.8 ± 0.7) × 10⁻¹³ cm⁻² s⁻¹. The observations of very high-energy gamma-radiation from the sources of this type would be important for understanding the nature of this astrophysical object.     

Counterion condensation in ionic micelles as studied by a combined use of SANS and SAXS

We report a combined use of small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) to the study of counterion condensation in ionic micelles. Small-angle neutron and X-ray scattering measurements have been carried out on two surfactants cetyltrimethylammonium bromide (CTABr) and cetyltrimethylammonium chloride (CTACl), which are similar but having different counterions. SANS measurements show that CTABr surfactant forms much larger micelles than CTACl. This is explained in terms of higher condensation of Br⁻ counterions than Cl⁻ counterions. SAXS data on these systems suggest that the Br⁻ counterions are condensed around the micelles over smaller thickness than those of Cl⁻ counterions.