562 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
Crystal Undulator As A Novel Compact Source Of Radiation
A crystalline undulator (CU) with periodically deformed crystallographic
planes is capable of deflecting charged particles with the same strength as an
equivalent magnetic field of 1000 T and could provide quite a short period L in
the sub-millimeter range. We present an idea for creation of a CU and report
its first realization. One face of a silicon crystal was given periodic
micro-scratches (grooves), with a period of 1 mm, by means of a diamond blade.
The X-ray tests of the crystal deformation have shown that a sinusoidal-like
shape of crystalline planes goes through the bulk of the crystal. This opens up
the possibility for experiments with high-energy particles channeled in CU, a
novel compact source of radiation. The first experiment on photon emission in
CU has been started at LNF with 800 MeV positrons aiming to produce 50 keV
undulator photons.Comment: Presented at PAC 2003 (Portland, May 12-16
Application of bent crystals at IHEP 70-GeV accelerator to enhance the efficiency of its usage
Bent crystal was extracting 70-GeV protons with average intensity 4*10^11 (as
measured in external beamline) per spill of 1.6 s duration, in parallel to the
simultaneous work of two internal targets in the accelerator ring. An
additional crystal, placed in the external beamline, was deflecting a small
part of the extracted beam with intensity 10^7 protons toward another physics
experiment. Crystal-extracted beam had a typical size of 4 mm by 4 mm fwhm at
the end of the external beamline. Measurements for the extraction efficiency
and other characteristics at the simultaneous work of four experimental set-ups
are presented. With crystal working in the above-said regime during one month,
no degradation of channeling was observed. The studies of extraction efficiency
have been continued with new crystals.Comment: 6pp. Presented at EPAC 200
The Investigations Of Beam Extraction And Collimation At U-70 Proton Synchrotron Of IHEP By Using Short Silicon Crystals
The new results of using short (2-4mm) bent crystals for extraction and
collimation of proton beam at IHEP 70 Gev proton synchrotron are reported. A
broad range of energies from 6 to 65 GeV has been studied in the same crystal
collimation set-up. The efficiency of extraction more than 85% and intensity
more than 10E12 were obtained by using crystal with the length 2-mm and the
angle 1 mrad. The new regime of extraction is applied now at the accelerator to
deliver the beam for different experimental setups within the range of
intensity 10E7-10E12ppp.Comment: Presented at EPAC 2002 (Paris, June 3-7), 3p
Two-mirror Schwarzschild aplanats. Basic relations
It is shown that the theory of aplanatic two-mirror telescopes developed by
Karl Schwarzschild in 1905 leads to the unified description both the prefocal
and the postfocal systems. The class of surfaces in the ZEMAX optical program
has been properly extended to ascertain the image quality in exact
Schwarzschild aplanats. A comparison of Schwarzschild aplanats with approximate
Ritchey-Chretien and Gregory-Maksutov aplanatic telescopes reveals a noticeable
advantage of the former at fast focal ratio of the system.Comment: 19 page
New Projects of Crystal Extraction at IHEP 70 GeV Accelerator
Using channeling in a 5-mm crystal with bending angle of 0.65 mrad, a record high efficiency, over 60%, of particle extraction from accelerator was achieved. The extracted beam intensity was up to 5.2 x 10**11 protons per spill of ~ 0.5 s duration. Also, the first proof-of-principle experiment on crystal collimation' was performed where crystal - serving as a scraper - has reduced the radiation level in the accelerator by a factor of two. The measurements agree with Monte Carlo predictions
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