arXiv subjects

A. Laptev

Publications and source records attributed to A. Laptev.

7 recordsLinked to original sources

arXiv2017

The aCORN Backscatter-Suppressed Beta Spectrometer

Backscatter of electrons from a beta spectrometer, with incomplete energy deposition, can lead to undesirable effects in many types of experiments. We present and discuss the design and operation of a backscatter-suppressed beta spectrometer that was developed as part of a program to measure the electron-antineutrino correlation coefficient in neutron beta decay (aCORN). An array of backscatter veto detectors surrounds a plastic scintillator beta energy detector. The spectrometer contains an axial magnetic field gradient, so electrons are efficiently admitted but have a low probability for escaping back through the entrance after backscattering. The design, construction, calibration, and performance of the spectrometer are discussed.

physics.ins-det↗

arXiv2017

aCORN: an experiment to measure the electron-antineutrino correlation coefficient in free neutron decay

We describe an apparatus used to measure the electron-antineutrino angular correlation coefficient in free neutron decay. The apparatus employs a novel measurement technique in which the angular correlation is converted into a proton time-of-flight asymmetry that is counted directly, avoiding the need for proton spectroscopy. Details of the method, apparatus, detectors, data acquisition, and data reduction scheme are presented, along with a discussion of the important systematic effects.

physics.ins-det↗

arXiv2014

Development of position-sensitive time-of-flight spectrometer for fission fragment research

A position-sensitive, high-resolution time-of-flight detector for fission fragments has been developed. The SPectrometer for Ion DEterminiation in fission Research (SPIDER) is a $2E-2v$ spectrometer designed to measure the mass of light fission fragments to a single mass unit. The time pick-off detector pairs to be used in SPIDER have been tested with $\alpha$-particles from $^{229}$Th and its decay chain and $\alpha$-particles and spontaneous fission fragments from $^{252}$Cf. Each detector module is comprised of a thin electron conversion foil, electrostatic mirror, microchannel plates, and delay-line anodes. Particle trajectories on the order of 700 mm are determined accurately to within 0.7 mm. Flight times on the order of 70 ns were measured with 200 ps resolution FWHM. Computed particle velocities are accurate to within 0.06 mm/ns corresponding to precision of 0.5%. An ionization chamber capable of 400 keV energy resolution coupled with the velocity measurements described here will pave the way for modestly efficient measurements of light fission fragments with unit mass resolution.

physics.ins-det↗

arXiv2012

On spectral estimates for two-dimensional Schrödinger operators

For a two-dimensional Schrödinger operator $H_{αV}=-Δ-αV,\ V\ge 0,$ we study the behavior of the number $N_-(H_{αV})$ of its negative eigenvalues (bound states), as the coupling parameter $α$ tends to infinity. A wide class of potentials is described, for which $N_-(H_{αV})$ has the semi-classical behavior, i.e., $N_-(H_{αV})=O(α)$. For the potentials from this class, the necessary and sufficient condition is found for the validity of the Weyl asymptotic law.

math.SP↗

arXiv2006

Many Particle Hardy-Inequalities

In this paper we prove three differenttypes of the so-called many-particle Hardy inequalities. One of them is a "classical type" which is valid in any dimesnion $d\neq 2$. The second type deals with two-dimensional magnetic Dirichlet forms where every particle is supplied with a soplenoid. Finally we show that Hardy inequalities for Fermions hold true in all dimensions.

math.AP↗

arXiv1999

Sharp Lieb-Thirring Inequalities in High Dimensions

We show how a matrix version of the Buslaev-Faddeev-Zakharov trace formulae for a one-dimensional Schrödinger operator leads to Lieb-Thirring inequalities with sharp constants $L^{cl}_{γ,d}$ with $γ\ge 3/2$ and arbitrary $d\ge 1$. (revised, to appear in Acta Math)

math-ph↗

arXiv1999

New bounds on the Lieb-Thirring constants

Improved estimates on the constants $L_{γ,d}$, for $1/2<γ<3/2$, $d\in N$ in the inequalities for the eigenvalue moments of Schrödinger operators are established.

math-ph↗