National Physical Laboratory

About: National Physical Laboratory is a facility organization based out in London, United Kingdom. It is known for research contribution in the topics: Dielectric & Thin film. The organization has 7615 authors who have published 13327 publications receiving 319381 citations.

Properties of superconducting planar resonators at millikelvin temperatures

Abstract: Planar superconducting resonators are now being increasingly used at mK temperatures in a number of novel applications. We have experimentally investigated three types of niobium resonators including a lumped-element design fabricated on sapphire and ${\text{SiO}}_{2}/\text{Si}$ substrates. They all exhibit a nonmonotonic temperature dependence of their center frequency which could be accurately described by resonant absorption by two-level fluctuators (TLF). By analyzing the temperature dependence we extracted information about the distribution of TLF. Our results are consistent with there being a spread of TLF at the interface between superconductor and substrate.

Evaluation of the primary frequency standard NPL-CsF1

Abstract: A new caesium fountain frequency standard (NPL-CsF1) at the National Physical Laboratory is described. Procedures for evaluation of the systematic frequency shifts are presented. The NPL-CsF1 has a short-term stability σy(τ) = 1.4 × 10−13τ−1/2, predominantly due to the local oscillator phase noise. The accuracy of 1 part in 1015 is limited by the uncertainty of the frequency shift due to collisions between cold atoms.

Microstructure-dependent humidity sensitivity of porous MgFe2O4–CeO2 ceramic

Abstract: In this paper cerium oxide is added to MgFe 2 O 4 at concentrations of 2 wt%, 4 wt% and 6 wt% in the precursor, while preparing the samples by a ceramic method in our laboratory. All samples are highly resistive of the order of mega ohms at room temperature and humidity. The decrease in resistance has been observed from 52 MΩ to 2 MΩ for the addition of 6 wt% cerium oxide, obviously with increasing the relative humidity using a two pressure technique-based standard humidity generator. The relative humidity generated is in the range from 10% RH to 90% RH at 25 °C. The addition of cerium oxide in the spinel lattice increases the intergranular porosity, distribution of pore size and open pores. The porosity increases from 2.5% to 26%. With the addition of cerium oxide the sensitivity at low RH increases and shows a better linearity than that of pure magnesium ferrite. The d log R / d RH is measured for all cerium oxide added samples in a range of 40–60% RH range. The spinel phase present in the samples is confirmed by X-ray diffraction (XRD). The porosity is calculated by a porosity equation and confirmed by analyzing the scanning electron micrographs of the samples.