40 research outputs found
High-time Resolution Astrophysics and Pulsars
The discovery of pulsars in 1968 heralded an era where the temporal
characteristics of detectors had to be reassessed. Up to this point detector
integration times would normally be measured in minutes rather seconds and
definitely not on sub-second time scales. At the start of the 21st century
pulsar observations are still pushing the limits of detector telescope
capabilities. Flux variations on times scales less than 1 nsec have been
observed during giant radio pulses. Pulsar studies over the next 10 to 20 years
will require instruments with time resolutions down to microseconds and below,
high-quantum quantum efficiency, reasonable energy resolution and sensitive to
circular and linear polarisation of stochastic signals. This chapter is review
of temporally resolved optical observations of pulsars. It concludes with
estimates of the observability of pulsars with both existing telescopes and
into the ELT era.Comment: Review; 21 pages, 5 figures, 86 references. Book chapter to appear
in: D.Phelan, O.Ryan & A.Shearer, eds.: High Time Resolution Astrophysics
(Astrophysics and Space Science Library, Springer, 2007). The original
publication will be available at http://www.springerlink.co
UV emission from young and middle-aged pulsars: Connecting X-rays with the optical
We present the UV spectroscopy and timing of three nearby pulsars (Vela,
B0656+14 and Geminga) recently observed with the Space Telescope Imaging
Spectrograph. We also review the optical and X-ray properties of these pulsars
and establish their connection with the UV properties. We show that the
multiwavelengths properties of neutron stars (NSs) vary significantly within
the sample of middle-aged pulsars. Even larger differences are found between
the thermal components of Ge-minga and B0656+14 as compared to those of
radio-quiet isolated NSs. These differences could be attributed to different
properties of the NS surface layers.Comment: To appear in Astrophysics and Space Science, Proceedings of "Isolated
Neutron Stars: from the Interior to the Surface", eds. D. Page, R. Turolla
and S. Zane; 10 pages, 4 figures, 3 table
Atlantic Behavioral Response Study: Experimental Design, Analytical Methods, and Preliminary Results
Excerpted from ESOMM - 2018, 6th International Meeting on the Effects of Sound in the Ocean on Marine Mammals The Hague, The Netherlands
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MFTF-B quasi-optical ECRH transmission system
The microwave transmission system for ERCH on MFTF-B will utilize quasi-optical transmission techniques. The system consists of ten gyrotron oscillators: two gyrotrons at 28 GHz, two at 35 GHz, and six at 56 GHz. The 28 and 35 GHz gyrotrons both heat the electrons in the end plug (potential peak) while the 56 GHz sources heat the minimum-B anchor region (potential minimum). Microwaves are launched into a pair of cylindrical mirrors that form a pseudo-cavity which directs the microwaves through the plasma numerous times before they are lost out of the cavity. The cavity allows the microwave beam to reach the resonance zone over a wide range of plasma densities and temperatures. The fundamental electron cyclotron resonance moves to higher axial positions as a result of beta-depression of the magnetic field, doppler shifting of the resonance, and relativistic mass corrections for the electrons. With this system the microwave beam will reach the resonance surface at the correct angle of incidence for any density or temperature without active aiming of the antennas. The cavity also allows the beam to make multiple passes through the plasma to increase the heating efficiency at low temperatures and densities when the single pass absorption is low. In addition, neutral beams and diagnostics have an unobstructed view of the plasma