631 research outputs found
Evolutionary Status of Long-Period Radio Pulsars
We analyze the evolutionary status of recently discovered long-period radio
sources PSR J0901-4046, GLEAM-X J1627-52, and GPM J1839-10. We discuss the
hypothesis that all three sources are radio pulsars. In the framework of
standard scenarios, it is often accepted that the pulsar mechanism is switched
off when an external matter can penetrate the light cylinder. If the matter is
stopped outside the light cylinder then the neutron star is at the ejector
stage. We demonstrate that for realistic parameters of the interstellar medium,
the 76-second pulsar PSR J0901-4046 might be at this stage. However, sources
GLEAM-X J1627-52 and GPM J1839-10 with periods s can be ejectors
only in the case of unrealistically large dipolar fields G.
Also, we show that neutron stars with spin periods s and dipolar
magnetic fields G cannot be ejectors in a typical
interstellar medium. Thus, we predict that long-period pulsars with standard
fields will not be discovered.Comment: 7 pages, 2 figures, accepted to Astronomy Letters, translation by the
author
Early Accretion Onset in Long-Period Isolated Pulsars
We model long-term magneto-rotational evolution of isolated neutron stars
with long initial spin periods. This analysis is motivated by the recent
discovery of young long-period neutron stars observed as periodic radio
sources: PSR J0901-4046, GLEAM-X J1627-52, and GPM J1839-10. Our calculations
demonstrate that for realistically rapid spin-down during the propeller stage
all isolated neutron stars with velocities km s are able
to reach the stage of accretion from the interstellar medium within a few
billion years. If neutron stars with long initial spin periods form a
relatively large fraction of all Galactic neutron stars then the number of
isolated accretors is sufficiently larger than it has been predicted by
previous studies.Comment: 12 pages, 2 figures, submitted to PAS
Tevatron Beam Halo Collimation System: Design, Operational Experience and New Methods
Collimation of proton and antiproton beams in the Tevatron collider is
required to protect CDF and D0 detectors and minimize their background rates,
to keep irradiation of superconducting magnets under control, to maintain
long-term operational reliability, and to reduce the impact of beam-induced
radiation on the environment. In this article we briefly describe the design,
practical implementation and performance of the collider collimation system,
methods to control transverse and longitudinal beam halo and two novel
collimation techniques tested in the Tevatron.Comment: 25 p
Crystal experiments on efficient beam extraction
Silicon crystal was channeling and extracting 70-GeV protons from the U-70
accelerator with efficiency of 85.3+-2.8% as measured for a beam of 10^12
protons directed towards crystals of 2 mm length in spills of 1-2 s duration.
The experimental data follow very well the prediction of Monte Carlo
simulations. This success is important to devise a more efficient use of the
U-70 accelerator in Protvino and provides a crucial support for implementation
of crystal-assisted collimation of gold ion beam in RHIC and slow extraction
from AGS onto E952, now in preparation at Brookhaven Nat'l Lab. Future
applications, spanning in the energy from sub-GeV (medical) to order of 1 GeV
(scraping in the SNS, extraction from COSY) to order of 1 TeV and beyond
(scraping in the Tevatron, LHC, VLHC), can benefit from these studies.Comment: 12pp. Presented at 19-th Intern. Conference on Atomic Collisions in
Solids (ICACS-19: Paris, July 29 - August 3, 2001
Progress in crystal extraction and collimation
Recent IHEP Protvino experiments show efficiencies of crystal-assisted slow
extraction and collimation of 85.3+-2.8%, at the intensities of the channeled
beam on the order of 10^12 proton per spill of 2 s duration. The obtained
experimental data well follows the theory predictions. We compare the
measurements against theory and outline the theoretical potential for further
improvement in the efficiency of the technique. This success is important for
the efficient use of IHEP accelerator and for implementation of
crystal-assisted collimation at RHIC and slow extraction from AGS onto E952,
now in preparation. Future applications, spanning in the energy from order of 1
GeV (scraping in SNS, slow extraction from COSY and medical accelerators) to
order of 1 TeV and beyond (scraping in Tevatron, LHC, VLHC), can benefit from
these studies.Comment: 7pp. Presented at HEACC 2001 (Tsukuba, March 25-30
Synthesis and spectral properties of colloidal solutions of metal sulfides
Cadmium, lead, and zinc sulfides as well as cadmium and lead (cadmium and zinc) complex sulfides have been synthesized in the colloidal state by reaction of metal trifluoroacetates with thioacetamide in ethyl acetate and methylmethacrylate. Synthesis products have been isolated from the reaction solutions and studied by X-ray diffraction, vibrational and electronic spectroscopy, and electronic microscopy. The effect of the composition on spectral properties of formulations has been discussed. The formation of colloidal particles and the stability of solutions are related to the complexation
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