Development and test of an L-band magnetron

An L-band relativistic magnetron has been designed, built, and tested at approximately 1.1 GHz. The authors have obtained a peak RMS power of 2.4 GW in one waveguide, and a total of 3.6 GW from two waveguides. The overall efficiency reached 9%, compared with the input power. In contrast with previous S- and X-band magnetron results, the L-band magnetron impedance does not collapse at the end of the pulse, and microwave generation tends to last as long as high voltage is applied. This implies that large total energies can be produced by applying long high-voltage pulses     

Nonperturbative visualization of nanoscale plasmonic field distributions via photon localization microscopy

We demonstrate the nonperturbative use of diffraction-limited optics and photon localization microscopy to visualize the controlled nanoscale shifts of zeptoliter mode volumes within plasmonic nanostructures. Unlike tip- or coating-based methods for mapping near fields, these measurements do not affect the electromagnetic properties of the structure being investigated. We quantify the local field manipulation capabilities of asymmetric bowtie antennas, in agreement with theoretical calculations. The photon-limited localization accuracy of nanoscale mode positions is determined for many of the measured devices to be within a 95% confidence interval of +/-2.5 nm. This accuracy also enables us to characterize the effects of nm-scale fabrication irregularities on local plasmonic mode distributions.     

Nanodiscs for INPHARMA NMR Characterization of GPCRs: Ligand Binding to the Human A2A Adenosine Receptor

G-protein-coupled-receptors (GPCRs) are of fundamental importance for signal transduction through cell membranes. This makes them important drug targets, but structure-based drug design (SBDD) is still hampered by the limitations for structure determination of unmodified GPCRs. We show that the interligand NOEs for pharmacophore mapping (INPHARMA) method can provide valuable information on ligand poses inside the binding site of the unmodified human A_2A adenosine receptor reconstituted in nanodiscs. By comparing experimental INPHARMA spectra with back-calculated spectra based on ligand poses obtained from molecular dynamics simulations, a complex structure for A_2AR with the low-affinity ligand 3-pyrrolidin-1-ylquinoxalin-2-amine was determined based on the X-ray structure of ligand ZM-241,358 in complex with a modified A_2AR.     

Sub-38 nm resolution tabletop microscopy with 13 nm wavelength laser light

We have acquired images with a spatial resolution better than 38 nm by using a tabletop microscope that combines 13 nm wavelength light from a high-brightness tabletop laser and Fresnel zone plate optics. These results open a gateway to the development of compact and widely available extreme-ultraviolet imaging tools capable of inspecting samples in a variety of environments with a 15-20 nm spatial resolution and a picosecond time resolution.     

20-nm resolution x-ray microscopy demonstrated by use of multilayer test structures [corrected

A spatial resolution of 20 nm is demonstrated at 2.07-nm wavelength by use of a soft x-ray microscope based on Fresnel zone plate lenses and partially coherent illumination. Nanostructural test patterns, formed by sputtered multilayer coatings and transmission electron microscopy thinning techniques, provide clear experimental results.     

Direct experimental observation of π-mode oscillation in arelativistic magnetron

The authors report the direct measurement of the operating mode of a relativistic magnetron. The S-band 2.65-GHz magnetron used has a washer cathode and is driven by a 1-MV 2.8-Ω 65-ns pulser. Power and pulse shape are measured simultaneously by calibrated couplers, cables, and crystal diodes. The frequency is measured as the heterodyne or difference frequency between a local oscillator and the extracted signal. This difference frequency is several-hundred megahertz. By directly measuring the phase relationship, any questions concerning perturbations of the resonance by the large current of relativistic electrons are avoided