Compendium for precise ac measurements of the quantum Hall resistance

In view of the progress achieved in the field of the ac quantum Hall effect, the Working Group of the Comite Consultatif d'Electricite et Magnetisme (CCEM) on the AC Quantum Hall Effect asked the authors of this paper to write a compendium which integrates their experiences with ac measurements of the quantum Hall resistance. In addition to the important early work performed at the Bureau International des Poids et Mesures and the National Physical Laboratory, UK, further experience has been gained during a collaboration of the authors' institutes NRC, METAS, and PTB, and excellent agreement between the results of different national metrology institutes has been achieved. This compendium summarizes the present state of the authors' knowledge and reviews the experiences, tests and precautions that the authors have employed to achieve accurate measurements of the ac quantum Hall effect. This work shows how the ac quantum Hall effect can be reliably used as a quantum standard of ac resistance having a relative uncertainty of a few parts in 10^8.Comment: 26 pages, 8 figure

Realization of an Inductance Scale Traceable to the Quantum Hall Effect Using an Automated Synchronous Sampling System

In this paper, the realization of an inductance scale from 1~$\mu$H to 10~H for frequencies ranging between 50~Hz to 20~kHz is presented. The scale is realized directly from a series of resistance standards using a fully automated synchronous sampling system. A careful systematic characterization of the system shows that the lowest uncertainties, around 12~$\mu$H/H, are obtained for inductances in the range from 10~mH to 100~mH at frequencies in the kHz range. This new measurement system which was successfully evaluated during an international comparison, provides a primary realization of the henry, directly traceable to the quantum Hall effect. An additional key feature of this system is its versatility. In addition to resistance-inductance (R-L) comparison, any kind of impedances can be compared: R-R, R-C, L-L or C-C, giving this sampling system a great potential of use in many laboratories around the world

Total VOC reactivity in the planetary boundary layer: 2. A new indicator for determining the sensitivity of the ozone production to VOC and NO

A new indicator is proposed for determining if tropospheric ozone production in a specifiacr eai s limitedb yV OC or NOx.T he indicato1r 9= r•ø•C/•oød•Xes cribeths e ratio of the lifetimes of OH against the losses by reacting with VOC and NOx. Whereas •oøx• c anb e obtainebdy c onventionmale asurementthse, n ewp umpa ndp robeO H approach which is described in part one of this publication makes it now possible to obtain also ß_ov •o c ßI ndicator values above a thresholdv alue of 0.2 __+50 % are representativeo f NOx-saturatedc onditionsw here an increaseo f NOx emissionsc auses lower ozone production.F or valuesb elow 0.01 the ozone productioni s very insensitivet o changeso f VOC emissionsT. he robustnesso f this indicator againsts everalp arameters sucha s temperature,h umidity,p hotolysisa, nd initial ozone concentrationsis tested in a box model and comparedt o the robustnesso f other earlier proposedi ndicators.I n contrast to earlier proposed indicators, this new one is not based on photochemically producedl ong-liveds peciesb ut describest he instantaneousr egime of an air parcel. Three-dimensionasl imulations howst hat this indicator is quite successfuiln estimatingt he impact of increasedo r reducede missionso n the ozone concentrationsfo r each location in the modeling area. This will make it a very helpful tool for developing ozone abatement strategies

Clinical implementation of deep learning-based automated left breast simultaneous integrated boost radiotherapy treatment planning.

Automation in radiotherapy treatment planning aims to improve both the quality and the efficiency of the process. The aim of this study was to report on a clinical implementation of a Deep Learning (DL) auto-planning model for left-sided breast cancer. The DL model was developed for left-sided breast simultaneous integrated boost treatments under deep-inspiration breath-hold. Eighty manual dose distributions were revised and used for training. Ten patients were used for model validation. The model was then used to design 17 clinical auto-plans. Manual and auto-plans were scored on a list of clinical goals for both targets and organs-at-risk (OARs). For validation, predicted and mimicked dose (PD and MD, respectively) percent error (PE) was calculated with respect to manual dose. Clinical and validation cohorts were compared in terms of MD only. Median values of both PD and MD validation plans fulfilled the evaluation criteria. PE was < 1% for targets for both PD and MD. PD was well aligned to manual dose while MD left lung mean dose was significantly less (median:5.1 Gy vs 6.1 Gy). The left-anterior-descending artery maximum dose was found out of requirements (median values:+5.9 Gy and + 2.9 Gy, for PD and MD respectively) in three validation cases, while it was reduced for clinical cases (median:-1.9 Gy). No other clinically significant differences were observed between clinical and validation cohorts. Small OAR differences observed during the model validation were not found clinically relevant. The clinical implementation outcomes confirmed the robustness of the model

Correction of CCI cloud data over the Swiss Alps using ground-based radiation measurements

The validation of long-term cloud data sets retrieved from satellites is challenging due to their worldwide coverage going back as far as the 1980s. A trustworthy reference cannot be found easily at every location and every time. Mountainous regions present a particular problem since ground-based measurements are sparse. Moreover, as retrievals from passive satellite radiometers are difficult in winter due to the presence of snow on the ground, it is particularly important to develop new ways to evaluate and to correct satellite data sets over elevated areas.In winter for ground levels above 1000&thinsp;m (a.s.l.) in Switzerland, the cloud occurrence of the newly released cloud property data sets of the ESA Climate Change Initiative Cloud_cci Project (Advanced Very High Resolution Radiometer afternoon series (AVHRR-PM) and Moderate-Resolution Imaging Spectroradiometer (MODIS) Aqua series) is 132 to 217&thinsp;% that of surface synoptic (SYNOP) observations, corresponding to a rate of false cloud detections between 24 and 54&thinsp;%. Furthermore, the overestimations increase with the altitude of the sites and are associated with particular retrieved cloud properties.In this study, a novel post-processing approach is proposed to reduce the amount of false cloud detections in the satellite data sets. A combination of ground-based downwelling longwave and shortwave radiation and temperature measurements is used to provide independent validation of the cloud cover over 41 locations in Switzerland. An agreement of 85&thinsp;% is obtained when the cloud cover is compared to surface synoptic observations (90&thinsp;% within ±&thinsp;1 okta difference). The validation data are then co-located with the satellite observations, and a decision tree model is trained to automatically detect the overestimations in the satellite cloud masks. Cross-validated results show that 62&thinsp;±&thinsp;13&thinsp;% of these overestimations can be identified by the model, reducing the systematic error in the satellite data sets from 14.4&thinsp;±&thinsp;15.5&thinsp;% to 4.3&thinsp;±&thinsp;2.8&thinsp;%. The amount of errors is lower, and, importantly, their distribution is more homogeneous as well. These corrections happen at the cost of a global increase of 7&thinsp;±&thinsp;2&thinsp;% of missed clouds. Using this model, it is possible to significantly improve the cloud detection reliability in elevated areas in the Cloud_cci AVHRR-PM and MODIS-Aqua products.</p

Dynamical aperture studies for the CERN LHC: comparison between statistical assignment of magnetic field errors and actual measured field errors

It is customary to evaluate the performance of a circular particle accelerator by computing the dynamical aperture, i.e. the domain in phase space where bounded singleparticle motion occurs. In the case of the LHC the dynamical aperture computation is performed by assuming a statistical distribution of the magnetic field errors of various magnets classes: the numerical computations are repeated for a given set of realisations of the LHC ring. With the progress in the magnet production and allocation of the available positions in the ring, the statistical approach has to be replaced by the computation of one single configuration, namely the actual realisation of the machine. Comparisons between the two approaches are presented and discussed in details.Â

Ozone detection by differential absorption spectroscopy at ambient pressure with a 9.6μm pulsed quantum-cascade laser

We report direct absorption spectroscopic detection of ozone at ambient pressure with a pulsed, DFB quantum-cascade laser (QCL) tuned within 1044-1050cm-1 by temperature scanning. Wavelength calibration curves were derived from FTIR and CO2 spectra and interpreted with respect to the heat transfer from the heterostructure to the sink. The laser linewidth (∼0.13cm-1 FWHM) was found to decrease with temperature, probably as a result of operation at constant current. Spurious spectral features due to baseline inaccuracies were successfully filtered out from the QCL O3 spectra using differential absorption. Reference O3 concentrations were obtained by applying the same method to UV spectra, simultaneously measured with a differential optical absorption spectrometer (DOAS). Column densities retrieved from QCL spectra are in fairly good agreement (±20%) with the DOAS values above 28ppm m. The estimated QCL lowest detectable, absolute and differential absorptions, (7×10-3 and 2×10-3, respectively), entail effective detection limits of 14 and 25ppm m, respectively. Ongoing improvements in the acquisition system should allow the achievement of detection limits at the level of commercial open-path DOAS systems (∼2ppm m) in the near future. Our results demonstrate the applicability of the differential absorption method to QCL spectroscopy at ambient pressure, and encourage its use for open path detectio

Direct measurement of the total reaction rate of OH in the atmosphere

A new method to investigate atmospheric chemical kinetics is presented. It is based on the pump and probe principle. Preliminary measurements are described on the decay rate of OH in the planetary boundary layer after its concentration has been raised by laser flash photolysis of background ozone and subsequent reaction of the O(1D) with atmospheric water vapor. The measured OH disappearance kinetics are compared with model calculations yielding information on the fast reaction of OH. The presented point measurements can be extended to a range resolved differential absorption LIDAR technique

THGEM operation in Ne and Ne/CH4

The operation of Thick Gaseous Electron Multipliers (THGEM) in Ne and Ne/CH4 mixtures, features high multiplication factors at relatively low operation potentials, in both single- and double-THGEM configurations. We present some systematic data measured with UV-photons and soft x-rays, in various Ne mixtures. It includes gain dependence on hole diameter and gas purity, photoelectron extraction efficiency from CsI photocathodes into the gas, long-term gain stability and pulse rise-time. Position resolution of a 100x100 mm^2 X-rays imaging detector is presented. Possible applications are discussed.Comment: Submitted to JINST, 25 pages, 33 figure

Stability of the Horizontal Curvature of the LHC Cryodipoles During Cold Tests

The LHC will be composed of 1232 horizontally curved, 15 meter long, superconducting dipole magnets cooled at 1.9 K. They are supported within their vacuum vessel by three Glass Fiber Reinforced Epoxy (GFRE) support posts. Each cryodipole is individually cold tested at CERN before its installation and interconnection in the LHC 27 km circumference tunnel. As the magnet geometry under cryogenic operation is extremely important for the LHC machine aperture, a new method has been developed at CERN in order to monitor the magnet curvature change between warm and cold states. It enabled us to conclude that there is no permanent horizontal curvature change of the LHC dipole magnet between warm and cold states, although a systematic horizontal transient deformation during cool-down was detected. This deformation generates loads in the dipole supporting system; further investigation permitted us to infer this behavior to the asymmetric thermal contraction of the rigid magnet thermal shield during cool-down. Controlling the helium flow rate in the thermal shield of the cryomagnet enabled us to reduce the maximal deformation by a factor of approximately two, thus increasing significantly the mechanical safety margin of the supporting system during the CERN cold tests