60 research outputs found
Studying temporal variability of GRS1739-278 during the 2014 outburst
We report a discovery of low-frequency quasi periodic oscillation at 0.3-0.7
Hz in the power spectra of the accreting black hole GRS1739-278 in the
hard-intermediate state during its 2014 outburst based on the
and Swift/XRT data. The QPO frequency strongly evolved with the source flux
during the NuSTAR observation. The source spectrum became softer with rising
QPO frequency and simultaneous increasing of the power-law index and decreasing
of the cut-off energy. In the power spectrum, a prominent harmonic is clearly
seen together with the main QPO peak. The fluxes in the soft and the hard X-ray
bands are coherent, however, the coherence drops for the energy bands separated
by larger gaps. The phase-lags are generally positive (hard) in the 0.1-3 Hz
frequency range, and negative below 0.1 Hz. The accretion disc inner radius
estimated with the relativistic reflection spectral model appears to be . In the framework of the relativistic precession model, in
order to satisfy the constraints from the observed QPO frequency and the
accretion disc truncation radius, a massive black hole with M is required.Comment: 15 pages, 12 figures; accepted for publication in MNRA
Light-emitting-diode Fourier-transform spectroscopy of HD16O between 11200 and 12400 cm-1
The absorption spectrum of monodeuterated water, HDO has been investigated between 11200 and 12400 cm-1. The spectrum has been recorded using IFS-125M interferometer with spectral resolution of 0.05 cm-1. For measurements White’s-type cell were used. The bright light emitting diode (LED) EDEI-1LS3-R was applied as a source of radiation. Signal to noise ratio was about 104. The spectral line parameters - line positions, intensities and half-widths were obtained by least square fitting. As a result of the spectrum analysis the line list containing more than 1500 lines was created. The spectral line parameters have been compared with the previous measured and calculated data. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
LED-based Fourier transform spectroscopy of H216O in the range 15500-16000 cm-1
The vibrational-rotational absorption spectrum of water vapor within the range 15500–16000 cm−1 is measured and analyzed. The spectrum is recoded with an IFS-125M Fourier transform spectrometer with a resolution of 0.03 cm−1, at pressure of 25 mbar, at a temperature of 24°C, and at an optical path length of 34.8 m. The measurements are performed using a multipass White cell with a base length of 60 cm. A light-emitting diode is used as a radiation source. The signal-to-noise ratio is about 104, which makes it possible to measure the parameters of lines with intensities on the order of 10−27 cm/molecule. The centers, intensities, and half-widths of lines are determined by fitting the Voigt profile parameters to measured data set by the least squares method. A list of more than 430 lines is formed based on the analysis of the spectrum. The obtained results are compared with calculated and experimental data of other authors
Counting statistics for arbitrary cycles in quantum pumps
Statistics of charge transport in an adiabatic pump are determined by the
dynamics of the scattering matrix S(t). We show that, up to an integer offset,
the statistics depend only on the corresponding path N(t)=S^\dagger\sigma_3 S
in the coset space (the sphere for a single channel). For a general loop S(t)
we solve for the noise-minimizing pumping strategy. The average current is
given by the area enclosed by N(t) in the coset space; its minimal noise by the
area of a minimal surface (soap film) spanned by N(t) in the space of all
matrices. We formulate conditions for quantization of the pumped charge.Comment: 4 pages, 2 figure
Studying temporal variability of GRS1739-278 during the 2014 outburst
We report a discovery of low-frequency quasi-periodic oscillation at 0.3–0.7 Hz in the power spectra of the accreting black hole GRS 1739–278 in the hard-intermediate state during its 2014 outburst based on the NuSTAR and Swift/XRT data. The QPO frequency strongly evolved with the source flux during the NuSTAR observation. The source spectrum became softer with rising QPO frequency and simultaneous increasing of the power-law index and decreasing of the cut-off energy. In the power spectrum, a prominent harmonic is clearly seen together with the main QPO peak. The fluxes in the soft and the hard X-ray bands are coherent, however, the coherence drops for the energy bands separated by larger gaps. The phase lags are generally positive (hard) in the 0.1–3 Hz frequency range, and negative below 0.1 Hz. The accretion disc inner radius estimated with the relativistic reflection spectral model appears to be R_(in) < 7.3R_g. In the framework of the relativistic precession model, in order to satisfy the constraints from the observed QPO frequency and the accretion disc truncation radius, a massive black hole with M_(BH) ≈ 100 M⊙ is required
Studying temporal variability of GRS 1739-278 during the 2014 outburst
We report a discovery of low-frequency quasi-periodic oscillation at 0.3-0.7 Hz in the power spectra of the accreting black hole GRS 1739-278 in the hard-intermediate state during its 2014 outburst based on the NuSTAR and Swift/XRT data. The QPO frequency strongly evolved with the source flux during the NuSTAR observation. The source spectrum became softer with rising QPO frequency and simultaneous increasing of the power-law index and decreasing of the cut-off energy. In the power spectrum, a prominent harmonic is clearly seen together with the main QPO peak. The fluxes in the soft and the hard X-ray bands are coherent, however, the coherence drops for the energy bands separated by larger gaps. The phase lags are generally positive (hard) in the 0.1-3 Hz frequency range, and negative below 0.1 Hz. The accretion disc inner radius estimated with the relativistic reflection spectral model appears to be R-in < 7.3R(g). In the framework of the relativistic precession model, in order to satisfy the constraints from the observed QPO frequency and the accretion disc truncation radius, a massive black hole with M-BH a parts per thousand 100 M-aS (TM) is required
Mitigation of plasma-wall interactions with low-Z powders in DIII-D high confinement plasmas
Experiments with low-Z powder injection in DIII-D high confinement discharges
demonstrated increased divertor dissipation and detachment while maintaining
good core energy confinement. Lithium (Li), boron (B), and boron nitride (BN)
powders were injected in high-confinement mode plasmas (1 MA, 2 T,
6 MW, m) into the
upper small-angle slot (SAS) divertor for 2-s intervals at constant rates of
3-204 mg/s. The multi-species BN powders at a rate of 54 mg/s showed the most
substantial increase in divertor neutral compression by more than an order of
magnitude and lasting detachment with minor degradation of the stored magnetic
energy by 5%. Rates of 204 mg/s of boron nitride powder further
reduce ELM-fluxes on the divertor but also cause a drop in confinement
performance by 24% due to the onset of an tearing mode. The application
of powders also showed a substantial improvement of wall conditions manifesting
in reduced wall fueling source and intrinsic carbon and oxygen content in
response to the cumulative injection of non-recycling materials. The results
suggest that low-Z powder injection, including mixed element compounds, is a
promising new core-edge compatible technique that simultaneously enables
divertor detachment and improves wall conditions during high confinement
operation
In-situ coating of silicon-rich films on tokamak plasma-facing components with real-time Si material injection
Experiments have been conducted in the DIII-D tokamak to explore the in-situ
growth of silicon-rich layers as a potential technique for real-time
replenishment of surface coatings on plasma-facing components (PFCs) during
steady-state long-pulse reactor operation. Silicon (Si) pellets of 1 mm
diameter were injected into low- and high-confinement (L-mode and H-mode)
plasma discharges with densities ranging from m
and input powers ranging from 5.5-9 MW. The small Si pellets were delivered
with the impurity granule injector (IGI) at frequencies ranging from 4-16 Hz
corresponding to mass flow rates of 5-19 mg/s ( Si/s) at
cumulative amounts of up to 34 mg of Si per five-second discharge. Graphite
samples were exposed to the scrape-off layer and private flux region plasmas
through the divertor material evaluation system (DiMES) to evaluate the Si
deposition on the divertor targets. The Si II emission at the sample correlates
with silicon injection and suggests net surface Si-deposition in measurable
amounts. Post-mortem analysis showed Si-rich coatings of varying morphology
mainly containing silicon oxides, with SiO being the dominant component. No
evidence of SiC was found, which is attributed to low divertor surface
temperatures. The Si-rich coating growth rates were found to be at least
nm/s, and the erosion rate was nm/s. The technique is
estimated to coat a surface area of at least 0.94 m on the outer divertor.
These results demonstrate the potential of using real-time material injection
to grow silicon-rich layers on divertor PFCs during reactor operation
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