Search results for "Optics"
showing 10 items of 10033 documents
Stopping cross-section measurements of 4He in TiN1.1O0.27
2000
Abstract The stopping cross-section for 4He projectiles in TiNx compounds has been measured using the backscattering method. A multi-compound marker layer deposited between the test film and the substrate was used to obtain the stopping cross-section at several energies with one energy of the incident beam. Two RBS spectra at definite tilt angles of the sample are taken for each beam energy. The assistance of computer codes to synthesize RBS spectra is very useful to obtain the pertinent information from the displacements of the peaks of the marker layers. Stopping cross-section values are obtained with an estimated uncertainty of about 6%.
Dielectric properties of potassium–sodium niobate ceramics at low frequencies
2016
ABSTRACTA study of the effects of ageing history on the electrical properties of lead-free ferroelectric ceramics of (K0.5Na0.5)(Nb1−xSbx)O3 + 0.5 mol% MnO2 and (K0.5Na0.5)(Nb1−xTax)O3 + 0.5 mol%MnO2 for x = 0.05 is reported. The samples after storage at a constant temperature have been subject to infra-low-frequency electric field and radiation. Differences of the photoelectric response between the two examined compounds were found and the restoration of polarisation in the aged ceramic materials by cycles of applied field is discussed.
Compact setup for spin-, time-, and angle-resolved photoemission spectroscopy.
2020
Review of scientific instruments 91(6), 063001 (2020). doi:10.1063/5.0004861
Efficiency of gyrotrons with a tapered magnetic field in the regime of soft self-excitation
2018
As a rule, gyrotron operation with high efficiency is realized in the regime of hard self-excitation that requires a special start-up scenario: either a tuning of the external magnetic field or providing certain relations between mod-anode and beam voltages. This paper describes a study of gyrotron operation in slightly tapered external magnetic fields. It is shown how the use of tapered magnetic fields affects the maximum efficiency realizable in hard and soft excitation regimes. First, a model of gyrotron with the Gaussian axial profile of the resonator field is studied. Then, a similar treatment is done for a realistic resonator designed for a 140 GHz Karlsruhe Institute for Technology g…
Enhancement of the Multipactor Threshold Inside Nonrectangular Iris
2018
Multipactor breakdown is studied inside the capacitive iris of a rectangular waveguide with a skewed slot along its longitudinal cross section. Both the iris length and height are assumed to be small compared to the electromagnetic wavelength. Therefore, the quasi-static approximation is applied so as to describe the RF field distribution inside the iris gap, whereas a 2-D model is used to analyze the electron motion. The peculiarities of RF field structure are studied using the conformal mapping approach, which shows that the electric field lines can be approximated by circular arcs when the iris length is much larger than its height. The electron motion inside the iris gap is analyzed usi…
Calculation of the electrostatic field in a dielectric-loaded waveguide due to an arbitrary charge distribution on the dielectric layer
2016
The goal of this paper is to study the electrostatic field due to an arbitrary charge distribution on a dielectric layer in a dielectric-loaded rectangular waveguide. In order to obtain this electrostatic field, the potential due to a point charge on the dielectric layer is solved in advance. The high computational complexity of this problem requires the use of different numerical integration techniques (e.g., Filon, Gauss-Kronrod, Lobatto, …) and interpolation methods. Using the principle of superposition, the potential due to an arbitrary charge distribution on a dielectric layer is obtained by adding the individual contribution of each point charge. Finally, a numerical differentiation o…
ABALONETM Photosensors for the IceCube experiment
2020
Abstract The ABALONE TM Photosensor Technology (U.S. Pat. 9,064,678) is a modern technology specifically invented for cost-effective mass production, robustness, and high performance. We present the performance of advanced fused-silica ABALONE Photosensors, developed specifically for the potential extension of the IceCube neutrino experiment, and stress-tested for 120 days. The resulting performance makes a significant difference: intrinsic gain of ≈ 6 × 108, total afterpulsing rate of only 5 × 10−3 ions per photoelectron , sub-nanosecond timing resolution, single-photon sensitivity, and unique radio-purity and UV sensitivity, thanks to the fused silica components—at no additional cost to t…
Interferences in Locally Resonant Sonic Metamaterials Formed from Helmholtz Resonators
2019
[EN] The emergence of materials artificially designed to control the transmission of waves, generally called metamaterials, has been a hot topic in the field of acoustics for several years. The design of these metamaterials is usually carried out by overlapping different wave control mechanisms. An example of this trend is the so-called Locally Resonant Sonic Materials, being one of them the Phononic Crystals with a local resonant structure. These metamaterials are formed by sets of isolated resonators in such a way that the control of the waves is carried out by resonances and by the existence of Bragg bandgaps, which appear due to the ordered distribution of the resonators. Their use is b…
System for control of polarization state of light and generation of light with continuously rotating linear polarization
2019
We present a technique for generating light in an arbitrary polarization state. The technique is based on interference of two orthogonally polarized light beams, whose amplitudes and phases are controlled with a Mach-Zehnder inteferometer with acousto-optic modulators (AOMs) placed in each arm. We demonstrate that via control over amplitudes, phases, and frequencies of acoustic waves driving the AOMs, any polarization state can be synthesized. In particular, we demonstrate generation of linearly polarized light, whose polarization plane continuously rotates at a rate from 1 kHz to 1 MHz. Such light finds applications in science (e.g., investigations of Bloch-Siegert effect) and technology (…
High efficiency resonance ionization of palladium with Ti:sapphire lasers
2016
This work presents the development and testing of highly efficient excitation schemes for resonance ionization of palladium. To achieve the highest ionization efficiencies, a high-power, high repetition rate Ti:sapphire laser system was used and 2-step, 3-step and 4-step schemes were investigated and compared. Starting from different excited steps, the frequencies of the final ionization steps were tuned across the full accessible spectral range of the laser system, revealing several autoionizing Rydberg series, which converge towards the energetically higher lying state of the Pd+ ion ground state configuration. Through proper choice of these excitation steps, we developed a highly efficie…