Feasibility study of thin film tunnel cathodes

Thin film tunnel cathodes evaluated for use in ultrahigh vacuum gauge

Diffraction Analysis of 2-D Pupil Mapping for High-Contrast Imaging

Pupil-mapping is a technique whereby a uniformly-illuminated input pupil, such as from starlight, can be mapped into a non-uniformly illuminated exit pupil, such that the image formed from this pupil will have suppressed sidelobes, many orders of magnitude weaker than classical Airy ring intensities. Pupil mapping is therefore a candidate technique for coronagraphic imaging of extrasolar planets around nearby stars. Unlike most other high-contrast imaging techniques, pupil mapping is lossless and preserves the full angular resolution of the collecting telescope. So, it could possibly give the highest signal-to-noise ratio of any proposed single-telescope system for detecting extrasolar planets. Prior analyses based on pupil-to-pupil ray-tracing indicate that a planet fainter than 10^{-10} times its parent star, and as close as about 2 lambda/D, should be detectable. In this paper, we describe the results of careful diffraction analysis of pupil mapping systems. These results reveal a serious unresolved issue. Namely, high-contrast pupil mappings distribute light from very near the edge of the first pupil to a broad area of the second pupil and this dramatically amplifies diffraction-based edge effects resulting in a limiting attainable contrast of about 10^{-5}. We hope that by identifying this problem others will provide a solution.Comment: 23 pages, 13 figures, also posted to http://www.orfe.princeton.edu/~rvdb/tex/piaaFresnel/ms.pd

Finite Temperature Phase Diagram in Rotating Bosonic Optical Lattice

Finite temperature phase boundary between superfluid phase and normal state is analytically derived by studying the stability of normal state in rotating bosonic optical lattice. We also prove that the oscillation behavior of critical hopping matrix directly follows the upper boundary of Hofstadter butterfly as the function of effective magnetic field.Comment: 10 pages, 2 figure

Flicker Noise in Bilayer Graphene Transistors

We present the results of the experimental investigation of the low - frequency noise in bilayer graphene transistors. The back - gated devices were fabricated using the electron beam lithography and evaporation. The charge neutrality point for the fabricated transistors was around 10 V. The noise spectra at frequencies above 10 - 100 Hz were of the 1/f - type with the spectral density on the order of 10E-23 - 10E-22 A2/Hz at the frequency of 1 kHz. The deviation from the 1/f spectrum at the frequencies below 10 -100 Hz indicates that the noise is of the carrier - number fluctuation origin due to the carrier trapping by defects. The Hooge parameter of 10E-4 was extracted for this type of devices. The gate dependence of the noise spectral density suggests that the noise is dominated by the contributions from the ungated part of the device channel and by the contacts. The obtained results are important for graphene electronic applications

Electroweak and QCD corrections to top-pair hadroproduction in association with heavy bosons

We compute the contribution of order $\alpha_S^2\alpha^2$ to the cross section of a top-antitop pair in association with at least one heavy Standard Model boson -- $Z$, $W^\pm$, and Higgs -- by including all effects of QCD, QED, and weak origin and by working in the automated MadGraph5_aMC@NLO framework. This next-to-leading order contribution is then combined with that of order $\alpha_S^3\alpha$, and with the two dominant lowest-order ones, $\alpha_S^2\alpha$ and $\alpha_S\alpha^2$, to obtain phenomenological results relevant to a 8, 13, and 100~TeV $pp$ collider.Comment: 27 pages, 8 figure