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1.
A new technique of alternate two-wavelength oscillation of a CO2 laser is discussed for application to various differential absorption spectroscopic measurements. Power-balanced, two-adjacent branch oscillation using a single CO2 laser was achieved by modulating the angle of a mirror inside the laser cavity and adjusting automatically the cavity length. The two-wavelength modulation frequency was extended up to about 1.2 kHz. Line tuning and power modulation characteristics were studied. The laser was used in long-path differential absorption measurements of ethylene air pollution molecules to demonstrate the capability of this power-balanced, two-wavelength oscillation method. The minimum detectable absorption was nearly 1×10–3 in a short-path cell experiment and 3×10–3 in a long-path experiment.  相似文献   

2.
It is shown that, if the “new neutrino” implied by the Reactor Antineutrino Anomaly exists and is in fact characterized by the suggested relatively high mass squared difference and reasonably large mixing angle, it should clearly reveal itself in the oscillometry measurements. For a judicious neutrino source the “new oscillation length” L14 is expected shorter than 1.5 m. Thus the needed measurements can be implemented with a gaseous spherical TPC of modest dimensions with a very good energy and position resolution, detecting nuclear recoils following the coherent neutrino-nucleus elastic scattering. The best candidates for oscillometry, yielding both monochromatic neutrinos as well as antineutrinos, are discussed. A sensitivity in the mixing angle θ14, sin2(2θ14)=0.1 (99%), can be reached after a few months of data handling.  相似文献   

3.
We report the real time measurements of 7Be and 8B solar neutrino fluxes performed with the Borexino experiment at the Laboratori Nazionali del Gran Sasso. The achievement of these measurements was possible thanks to the excellent levels of the radiopurity reached. The measurement of the 7Be in real time is the first direct measurements of the survival probability for solar electron neutrinos in the vacuum region. For 8B we reached a threshold energy of 3MeV which is the lowest achieved so far in real time. For the first time, the same apparatus can measure two different oscillation regions (vacuum-driven and matter-enhanced) predicted by the MSW-LMA model. Borexino also quotes the ratio between the survival probabilities, corresponding to 1.93 ± 0.75, and validates the presence of the transition region between the two oscillation regimes, according to the MSW-LMA solution.In addition, a preliminary result on the Day-Night Asymmetry (ADN) for the 7Be neutrino flux is presented and corresponds to 0.007 ± 0.073. This measurement makes Borexino able to give once more an independent confirmation of the MSW-LMA solution.  相似文献   

4.
The T2K (Tokai-to-Kamioka) experiment is a long baseline neutrino oscillation experiment designed to probe the θ 13 neutrino mixing parameter by looking for the appearance of ν e in an almost pure ν μ beam. The concurrent measurement of the ν μ disappearance allows refined measurements of the atmospheric Δm 2 and θ 23 mixing parameters.  相似文献   

5.
Abstract

Interactions between ammonium and nitrate as competitive N sources depend on various biotic and abiotic factors. The preference for one of these N sources and the influence of ammonium on nitrate uptake and nitrate reductase activity was investigated in a 15N labelling experiment using 2-year-old potted plants of ash (Fraxinus excelsior L.) and oak (Quercus robur L.) under greenhouse conditions.

Seedlings of both tree species use ammonium and nitrate in equal amounts when both N forms are supplied in a 1:1 ratio (1.5 mM NH4 + + 1.5 mM NO3 ?), although there is a slight tendency that ammonium is preferred. In both species total N uptake is higher if ammonium and nitrate are supplied simultaneously when compared with uptake of nitrate alone (3 mM nitrate). If nitrate is the sole N source N uptake is only half as high as if ammonium and nitrate are supplied in a ratio of 1:1.

The distribution of nitrate reductase between shoot and roots is not influenced by the N-form: nitrate reductase activity is always highest in the roots of both species under the conditions of this experiment.

Xylem sap analyses showed that both species transport higher concentrations of amino acids than of nitrate from the roots to the shoot. The amino acid composition is independent of the type of N source. Furthermore, ash trees contain more nitrate in the xylem sap than oak trees, reflecting the higher N uptake and the higher nitrate reductase activity in the leaves of this species.  相似文献   

6.
A Lamb-shift polarimeter, which has been built for a fast determination of the polarization of protons and deuterons of an atomic-beam source and which is frequently used in the ANKE experiment at COSY-Jülich, is shown to be an excellent device for atomic-spectroscopy measurements of metastable hydrogen isotopes. It is demonstrated that magnetic and electric dipole transitions in hydrogen can be measured as a function of the external magnetic field, giving access to the full Breit-Rabi diagram for the 22S1/2 and the 22P1/2 states. This will allow the study of hyperfine structure, g factors and the classical Lamb shift. Although the data are not yet competitive with state-of-the-art measurements, the potential of the method is enormous, including a possible application to anti-hydrogen spectroscopy.  相似文献   

7.
Abstract

The ion mobility and drift velocity of carbon tetrachloride have been measured at various ratios of E/Po, ranging from 1.0 to 9 volts/ (cm-Torr). The technique employed for these measurements utilizes a polonium alpha particle source which serves both as the source for ionization as well as the means for producing a reference pulse from a solid state silicon barrier detector. The thermal electrons which are produced are readily captured by carbon tetrachloride and the resulting negative ion, assumed to be CC14 ?, is detected by means of a proportional counter located at the end of the drift path. The zero field reduced mobility obtained for CC14 ?was 0.42 cm2/(volt-sec). The nature of the ionic species is explained in terms of the quantum mechanical theory of ionic mobility as put forth by Dalgarno.  相似文献   

8.
F. A. Egorov 《Technical Physics》2013,58(11):1646-1650
The characteristics of fiber-optic oscillation frequency sensors of deformation and temperature that employ the thermal fluctuation resonant oscillations in the SMS(M) fiber structures (sensitive elements that represent oscillation systems with distributed parameters based on series-connected single- and multimode step-index fibers) are developed and studied. The measurements of the fluctuation oscillations are based on the amplitude-phase modulation of the optical wave in the multimode oscillating section due to variations in the path-length difference and tunneling of interfering beams. Accuracies of temperature and relative deformation measurements of ±2°C and ±10?5, respectively, are demonstrated. The estimation of the ultimate measurement sensitivity of the resonance frequency is based on the approximate calculation of the Allan variance that shows a possibility of the above sensors with temperature and deformation threshold sensitivities of 0.001°C and 10?8, respectively.  相似文献   

9.
The neutrino experiment KARMEN is situated at the beam stop neutrino source ISIS which provides νμ's, νe's and from the π+−μ+-decay at rest. The oscillation channels νμ → νe and are investigated with a 56 t liquid scintillation calorimeter. No evidence for oscillations could be found with KARMEN, resulting in 90% CL exclusion limits of sin2(2Θ) < 8.5 · 10−3 ( ) and sin2(2Θ) < 4.0 · 10−2μ → νe) for Δm2 > 100 eV2. In 1996, the experiment has been upgraded by an additional veto counting system with a total coverage of 300 m2. The new system allows the identification of cosmic muons in the vicinity of the detector. Vetoing these muons suppresses energetic neutrons from deep inelastic scattering of muons as well as from μ-capture by a factor of 40. Up to 1996, these neutrons represented the main background for oscillation search. The experimental sensitivity for will be significantly enhanced towards sin2(2Θ) 1.0 · 10−3 after a further measuring period of 2–3 years.  相似文献   

10.
《Nuclear Physics B》1995,434(3):503-532
We report on high statistics measurements of neutrino energy spectra carried out at 15, 40 and 95 meters from a 2800 Megawatt reactor, using detection modules filled with 6Li-loaded liquid scintillator. No oscillations have been observed. Exclusion zones for oscillation parameters are deduced from the observed consistency of the spectra at the three distances. The minimum excluded values of the δm2 and sin22θ parameters are 1 × 10−2eV2and 2 × 10−2 (at 90% CL), respectively.  相似文献   

11.
The KArlsruher TRItium Neutrino experiment KATRIN aims to determine the mass of the electron antineutrino with a sensitivity of 0.2 eV/c2 on m(νe) at 90% confidence level by measuring the kinematics of the tritium beta decay with a spectrometer of MAC-E filter-type. To investigate the properties of the spectrometer, electron sources with special properties are needed. A pulsed UV LED photoelectron source with angular selectivity has been developed for this purpose. The principle has been successfully tested during measurements at the spectrometer of the Mainz neutrino mass experiment.  相似文献   

12.
Nasu  S.  Kawakami  T.  Kawasaki  S.  Takano  M. 《Hyperfine Interactions》2002,144(1-4):119-127

Using a diamond anvil cell and a low-temperature cryostat with a superconducting solenoid, high-pressure 57Fe Mössbauer spectroscopy with a radioactive source at 4.5 K under external magnetic fields up to 7 T has been developed. Pressure-temperature magnetic phase-diagrams for perovskite iron oxides, SrFeO3, CaFeO3 and Sr2LaFe3O9 are presented up to about 70 GPa. High-pressure Mössbauer measurements under external magnetic fields proved that the electronic ground states of these oxides switch to uniform-charge and ferromagnetic (and most probably metallic) states under extremely high pressure.

  相似文献   

13.
The results of gallium measurements of solar neutrino and measurements with artificial sources of neutrinos are presented. Conclusions are drawn from these results, and the potential of the SAGE experiment for studying transitions of active neutrinos to sterile states for Δm 2 > 0.5 eV2 and a sensitivity of a few percent to the disappearance of electron neutrinos is examined.  相似文献   

14.
Wu  XiaoBing  Ouyang  HuaFu  Chi  YunLong  He  Wei  Huang  Tao  Li  Gang  Liu  YingMan  Lu  YanHua  Xu  TaoGuang  Zhang  JunSong  Zhang  HuaShun  Zhao  FuXiang 《中国科学:物理学 力学 天文学(英文版)》2011,54(2):245-248

The accelerator complex of the China Spallation Neutron Source (CSNS) consists of a H linear accelerator (linac) and a rapid cycling synchrotron (RCS). The linac contains a Penning surface H ion source. The designed energy and the beam current of the source are 50 keV and 20 mA respectively, with a normalized root mean square (norm. rms.) emittance of 0.2π mm mrad. The manufactures and tests of the discharge chamber are in great progress. The construction of H ion source test stand has been completed, and the operation of the source is also in progress. Stable H ion beams with energy of 50 keV and current up to 50 mA are attained. Emittance measurement for the H beam is being prepared.

  相似文献   

15.
Advances in experimental searches for a neutron Electric Dipole Moment (nEDM, d n ) are motivated by the potential discovery of a new source of CP violation beyond the Standard Model of particle physics. The nEDM experiment at the Paul Scherrer Institute (PSI), which with accumulated sensitivity of 1.09 × 10?26 e?cm (September 2016) is currently the most sensitive nEDM experiment worldwide, uses the Ramsey technique of separated oscillatory fields applied to stored ultracold neutrons. The nEDM measurements depend upon precise information about the magnetic field, which is monitored by a 199Hg co-magnetometer and an array of 133Cs magnetometers. The principle of the magnetic field measurement is based on the optical detection of the Larmor precession frequency of atoms polarized by optical pumping. In this article we present the recent progress of the nEDM experiment as well as details of a magnetic field measurements with special focus on the laser-operated array of high-sensitivity 133Cs magnetometers.  相似文献   

16.
A new experiment devoted to the fission of 252Cf is described. It continued a series of our experiments based on correlation measurements of γ rays emitted by fission fragment pairs. The measurements of γ-γ and γ-γ-γ coincidences were done at Gammasphere with closed 252Cf sources. The open source was used for the first time in the last experiment. Fission fragment detectors were arranged in the center hole of Gammasphere. Correlations between fission fragment masses, total kinetic energy, and γ rays were observed. The first, preliminary results of data analysis are discussed. The text was submitted by the authors in English.  相似文献   

17.
Our collaboration has installed a long baseline neutrino oscillation experiment at the Palo Verde Nuclear Generating Station in Arizona. 12 tons of Gd loaded liquid scintillator, in a segmented detector, are used to search for oscillations at 740 m distance to three reactors. The anti-neutrino capture on the proton serves as detection reaction. The experiment is expected to reach a sensitivity of Δm2 > 1.3 · 10−3 eV2 and sin22Θ > 0.1. Our range of sensitivity is tuned to test the νμ ↔ νe solution of the atmospheric neutrino anomaly.  相似文献   

18.
Abstract

The electronic transport properties of Dirac fermions in chemical vapour-deposited single-layer epitaxial graphene on anSiO2/Si substrate have been investigated using the Shubnikov–de Haas (SdH) oscillations technique. The magnetoresistance measurements were performed in the temperature range between 1.8 and 43 K and at magnetic fields up to 11 T. The 2D carrier density and the Fermi energy have been determined from the period of the SdH oscillations. In addition, the in-plane effective mass as well as the quantum lifetime of 2D carriers have been calculated from the temperature and magnetic field dependences of the SdH oscillation amplitude. The sheet carrier density (1.42 × 1013 cm?2 at 1.8 K), obtained from the low-field Hall Effect measurements, is larger than that of 2D carrier density (8.13 × 1012 cm?2). On the other hand, the magnetoresistance includes strong magnetic field dependent positive, non-oscillatory background magnetoresistance. The strong magnetic field dependence of the magnetoresistance and the differences between sheet carrier and 2D carrier density can be attributed to the 3D carriers between the graphene sheet and the SiO2/Si substrate.  相似文献   

19.
The purpose of the present paper is to study the neutrino properties as they may appear in the low-energy neutrinos emitted in the triton decay \(_1^3 H \to _2^3 He + e^ - + \bar \nu _e \) with maximum neutrino energy of 18.6 keV. The technical challenges to this end can be summarized as building a very large TPC capable of detecting low-energy recoils, down to a few 100 eV, within the required low-background constraints. More specifically, we propose the development of a spherical gaseous TPC of about 10 m in radius and a 200-MCi triton source in the center of curvature. One can list a number of exciting studies concerning fundamental physics issues that could be made using a large volume TPC and low-energy antineutrinos: (i) The oscillation length involving the small angle δ = sinθ13, directly measured in our νe disappearance experiment, is fully contained inside the detector. Measuring the counting rate of neutrino-electron elastic scattering as a function of the distance of the source will give a precise and unambiguous measurement of the oscillation parameters free of systematic errors. In fact, first estimates show that, even with a year's data taking, a sensitivity of a few percent for the measurement of the above angle will be achieved. (ii) The low-energy detection threshold offers a unique sensitivity for the neutrino magnetic moment which is about two orders of magnitude beyond the current experimental limit of 10?10μB. (iii) Scattering at such low neutrino energies has never been studied and any departure from the expected behavior may be an indication of new physics beyond the Standard Model. We present a summary of various theoretical studies and possible measurements, including a precise measurement of the Weinberg angle at very low momentum transfer.  相似文献   

20.
The success of many measurements in analytical mass spectrometry as well as in precision mass determinations for atomic and nuclear physics is handicapped when the ion sources deliver “contaminations”, i.e., unwanted ions of masses similar to those of the ions of interest. In particular, in ion-trapping devices, large amounts of contaminant ions result in significant systematic errors—if the measurements are possible at all. We present a solution for such cases: The ions from a quasi-continuous source are bunched in a linear radio-frequency-quadrupole ion trap, separated by a multi-reflection time-of-flight section followed by a Bradbury–Nielsen gate, and then captured in a Penning trap. Buffer-gas cooling is used to damp the ion motion in the latter, which allows a repeated opening of the Penning trap for a stacking of mass-selected ion bunches. Proof-of-principle demonstrations have been performed with the ISOLTRAP setup at ISOLDE/CERN, both with 133Cs+ ions from an off-line ion source and by application to an on-line beam of 179Lu+ ions contaminated with 163Dy16O+ ions. In addition, an optimization of the experimental procedure is given, in particular for the number of ion bunches captured as a function of the ions’ lifetimes and the parameters of the experiment .  相似文献   

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