164 research outputs found
Role of the middle ear muscle apparatus in mechanisms of speech signal discrimination
A method of impedance reflexometry was used to examine 101 students with hearing impairment in order to clarify the interrelation between speech discrimination and the state of the middle ear muscles. Ability to discriminate speech signals depends to some extent on the functional state of intraaural muscles. Speech discrimination was greatly impaired in the absence of stapedial muscle acoustic reflex, in the presence of low thresholds of stimulation and in very small values of reflex amplitude increase. Discrimination was not impeded in positive AR, high values of relative thresholds and normal increase of reflex amplitude in response to speech signals with augmenting intensity
Nonlinear double Compton scattering in the full quantum regime
A detailed analysis of the process of two photon emission by an electron
scattered from a high-intensity laser pulse is presented. The calculations are
performed in the framework of strong-field QED and include exactly the presence
of the laser field, described as a plane wave. We investigate the full quantum
regime of interaction, where photon recoil plays an essential role in the
emission process, and substantially alters the emitted photon spectra as
compared to those in previously-studied regimes. We provide a semiclassical
explanation for such differences, based on the possibility of assigning a
trajectory to the electron in the laser field before and after each quantum
photon emission. Our numerical results indicate the feasibility of
investigating experimentally the full quantum regime of nonlinear double
Compton scattering with already available plasma-based electron accelerator and
laser technology.Comment: 5 pages, 3 figure
Benchmarking of 3D space charge codes using direct phase space measurements from photoemission high voltage DC gun
We present a comparison between space charge calculations and direct
measurements of the transverse phase space for space charge dominated electron
bunches after a high voltage photoemission DC gun followed by an emittance
compensation solenoid magnet. The measurements were performed using a
double-slit setup for a set of parameters such as charge per bunch and the
solenoid current. The data is compared with detailed simulations using 3D space
charge codes GPT and Parmela3D with initial particle distributions created from
the measured transverse and temporal laser profiles. Beam brightness as a
function of beam fraction is calculated for the measured phase space maps and
found to approach the theoretical maximum set by the thermal energy and
accelerating field at the photocathode.Comment: 11 pages, 23 figures. submitted to Phys Rev ST-A
New phase structure of the Nambu -- Jona - Lasinio model at nonzero chemical potential
It is shown that in the Nambu -- Jona - Lasinio model at nonzero chemical
potential there are two different massive phases with spontaneously broken
chiral symmetry. In one of them particle density is identically zero, in
another phase it is not equal to zero. The transition between phases is a phase
transition of the second order.Comment: 8 pages, LaTeX, no figures
Simulation of the transit-time optical stochastic cooling process in the Cornell Electron Storage Ring
In preparation for a demonstration of optical stochastic cooling in the
Cornell Electron Storage Ring (CESR) we have developed a particle tracking
simulation to study the relevant beam dynamics. Optical radiation emitted in
the pickup undulator gives a momentum kick to that same particle in the kicker
undulator. The optics of the electron bypass from pickup to kicker couples
betatron amplitude and momentum offset to path length so that the momentum kick
reduces emittance and momentum spread. Nearby electrons contribute an
incoherent noise. Layout of the bypass line is presented that accommodates
optics with a range of transverse and longitudinal cooling parameters. The
simulation is used to determine cooling rates and their dependence on bunch and
lattice parameters for bypass optics with distinct emittance and momentum
acceptance
Synthesis, crystal structure, and thermal stability of double borate Na3ErB2O6
Received: 05.10.2021. Revised: 18.10.2021. Accepted: 18.10.2021. Available online: 20.10.2021.Double borate Na3ErB2O6 was synthesized by the solid-state reaction. The crystal structure of Na3ErB2O6 was refined by the Rietveld method: P21/c, a = 6.49775(14) Å, b = 8.50424(17) Å, c = 12.0067(3) Å, β = 118.4797(9)°, Z = 4. The crystal structure of Na3ErB2O6 consists of –[ErO6]∞-chains along the "b" axis, which are linked by BO3 triangles in a three-dimensional framework. Sodium atoms occupy empty positions inside the channels. The thermal behavior of Na3ErB2O6 was studied in detail in the range of 25–1150 °C range by DSC and TG methods. Na3ErB2O6 congruently melts at 1116 °C. Based on the results of DSC measurements, three reversible phase transitions were found for Na3ErB2O6.The work was supported by Basic Project of BINM SB RAS № 0273-2021-0008. X-ray powder diffraction and thermal analysis were obtained using the equipment of the Collective Use Center BINM SB RAS
Coloration of natural beryl by iron ion implantation
Natural colorless crystals of Ural beryl were implanted at room temperature with 40 keV Fe+ ions with fluences in the range of 0.5-1.5×1017 ion/cm2. As-implanted samples show dark-grey tone due to radiation damage of beryl crystal. Subsequent thermal annealing of irradiated crystals in oxygen at 600 °C for 30 min results in the color change, to yellowish or yellow-orange tones with golden luster, depending on value of iron fluence. The nature of beryl coloration was studied by optical absorption, Mössbauer and Rutherford backscattering (RBS) spectroscopes. It was established that the thermal treatment of iron-irradiated beryl lead to inward diffusive redistribution of iron ions. An appearance of optical absorption bands connected with charge-transfers O2-→FeVI 3+ and O2-→FeIV 2+, FeIV 3+ determine the yellow tone in colored beryls. Most of implanted iron ions are founded in both tetrahedral FeIV 2+ and octahedral FeVI 3+ sites where they may substitute beryllium and aluminum host ions by isomorphic way. © 2003 Elsevier Science B.V. All rights reserved
Beam-Breakup Instability Theory for Energy Recovery Linacs
Here we will derive the general theory of the beam-breakup instability in
recirculating linear accelerators, in which the bunches do not have to be at
the same RF phase during each recirculation turn. This is important for the
description of energy recovery linacs (ERLs) where bunches are recirculated at
a decelerating phase of the RF wave and for other recirculator arrangements
where different RF phases are of an advantage. Furthermore it can be used for
the analysis of phase errors of recirculated bunches. It is shown how the
threshold current for a given linac can be computed and a remarkable agreement
with tracking data is demonstrated. The general formulas are then analyzed for
several analytically solvable cases, which show: (a) Why different higher order
modes (HOM) in one cavity do not couple so that the most dangerous modes can be
considered individually. (b) How different HOM frequencies have to be in order
to consider them separately. (c) That no optics can cause the HOMs of two
cavities to cancel. (d) How an optics can avoid the addition of the
instabilities of two cavities. (e) How a HOM in a multiple-turn recirculator
interferes with itself. Furthermore, a simple method to compute the orbit
deviations produced by cavity misalignments has also been introduced. It is
shown that the BBU instability always occurs before the orbit excursion becomes
very large.Comment: 12 pages, 6 figure
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