Magnetic storage of UCN for a measurement of the neutron lifetime Ezhov, V.F.; Andreev, A.Z.; Ban, G. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
12/2009, Letnik:
611, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
We present the status of an experimental setup designed and built for the measurement of the neutron lifetime and we describe also details about the measuring sequence. The central element of the ...setup is a magnetic trap made of permanent magnets. Neutrons surviving in the trap after fixed storage times are counted after their extraction and the trap losses are continuously monitored during the storage periods. The technique has achieved a statistical sensitivity of about 2
s on the storage time what constitutes the most sensitive magnetic trapping technique for ultra-cold neutrons developed so far.
The results of an experiment on transmitting UCN through a rotating disc made of silicon single crystal are reported. They demonstrate that the transmission of the sample remains constant if it moves ...parallel to its surface. The range of neutron velocities in the system of reference associated with the sample is 6–38 m/s. It is found that the real and imaginary parts of the effective potential are constant to within 3×10−3.
Ultracold-neutron infrastructure for the PNPI/ILL neutron EDM experiment Serebrov, A.P.; Geltenbort, P.; Shoka, I.V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2009, Letnik:
611, Številka:
2
Journal Article
Recenzirano
A PNPI/ILL experiment to measure the neutron electric dipole moment (EDM) is currently being prepared at the facility PF2 for ultracold neutrons (UCN) at the Institut Laue-Langevin in Grenoble. To ...enable an improvement of sensitivity, one of PF2's beam positions has been equipped with new components for UCN transport, polarization and beam characterization, comprised of a superconducting solenoid-polarizer with magnetic field 4
T, a neutron guide system with diameter 136
mm prepared in replica technology, and a novel beam chopper for time-of-flight analysis. The whole EDM apparatus is set up on a non-magnetic platform. The total flux of polarized UCN with velocities less than 6.8
m/s along the guide axis is 1.5×10
5
n/s, corresponding to a flux density of 10
3
cm
−2
s
−1. The density of polarized UCN at the experimental position is about 5
cm
−3, which shall lead to an EDM measurement with a counting statistical accuracy of 1.5×10
−26
ecm during 200 days of operation at PF2.
We present the result of an experiment to measure the electric dipole moment (EDM) of the neutron at the Paul Scherrer Institute using Ramsey's method of separated oscillating magnetic fields with ...ultracold neutrons. Our measurement stands in the long history of EDM experiments probing physics violating time-reversal invariance. The salient features of this experiment were the use of a ^{199}Hg comagnetometer and an array of optically pumped cesium vapor magnetometers to cancel and correct for magnetic-field changes. The statistical analysis was performed on blinded datasets by two separate groups, while the estimation of systematic effects profited from an unprecedented knowledge of the magnetic field. The measured value of the neutron EDM is d_{n}=(0.0±1.1_{stat}±0.2_{sys})×10^{-26} e.cm.
The report presents the first experience of using a time-of-flight Fourier spectrometer of ultracold neutrons (UCN). The description of the spectrometer design and first results of its testing are ...presented. The results of the first experiments show that the spectrometer may be used for obtaining UCN energy spectra in the energy range of 60÷200 neV with a resolution of about 5 neV. The application of TOF Fourier spectrometry technique allowed us to obtain the energy spectra from the diffraction of monochromatic ultracold neutrons on a moving grating. Lines of 0, +1 and +2 diffraction orders were simultaneously recorded, which had previously been impossible to be done by other methods. These results have made it possible to make a comparison with the recent theoretical calculations based on the dynamical theory of neutron diffraction on a moving phase grating.
We report the first measurement of an angular correlation parameter in neutron beta decay using polarized ultracold neutrons (UCN). We utilize UCN with energies below about 200 neV, which we guide ...and store for approximately 30 s in a Cu decay volume. The interaction of the neutron magnetic dipole moment with a static 7 T field external to the decay volume provides a 420 neV potential energy barrier to the spin state parallel to the field, polarizing the UCN before they pass through an adiabatic fast passage spin flipper and enter a decay volume, situated within a 1 T field in a 2x2pi solenoidal spectrometer. We determine a value for the beta-asymmetry parameter A_{0}=-0.1138+/-0.0046+/-0.0021.
Currently the most accurate measurements of neutron lifetime are being performed at the Petersburg Nuclear Physics Institute with ultracold neutrons (UCNs) stored in a gravitational trap. A modified ...setup with a large gravitational trap and cooling to 10–15 K is presented. The results of measurements of temperature dependence of UCN losses in collisions with walls, which were coated with a perfluorinated grease (Fomblin UT 18), at 300–77 K, are detailed. The probable heat inflow to the trap is estimated, and the feasibility of cooling to indicated temperatures in experiments with the modified setup is demonstrated.
The neutron gyromagnetic ratio has been measured relative to that of the 199Hg atom with an uncertainty of 0.8 ppm. We employed an apparatus where ultracold neutrons and mercury atoms are stored in ...the same volume and report the result γn/γHg=3.8424574(30).
The total scattering cross sections for slow neutrons with energies in the range 100 neV to 3 meV for solid ortho-2H2 at 18 and 5 K, frozen from the liquid, have been measured. The 18 K cross ...sections are found to be in excellent agreement with theoretical expectations and for ultracold neutrons dominated by thermal up scattering. At 5 K the total scattering cross sections are found to be dominated by the crystal defects originating in temperature induced stress but not deteriorated by temperature cycles between 5 and 10 K.
The method for producing neutron guides for ultracold neutrons based on the replica method has been described. A comparative analysis of the quality of replica neutron guides, neutron guides made ...from polished anode–mechanical steel tubes, and neutron guides from electropolished tubes has been given.
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