• An Interferometric Characterisation Technique for Extreme Impedance Microwave Devices - 94th Automatic Radio Frequency Techniques Group (ARFTG) Microwave Measurement Symposium
    📅 2020-01-01✍️ H. Votsi , L.T. Stant , C. Matei , M.J. Salter , C. Li , N.M. Ridler , P.H. Aaen📚 IEEE Trans. Instrum. Meas.🎯 inproceedings
    This paper presents a microwave impedance characterization technique for extreme impedance devices. The method is based on active interferometry and uses a 2-source 4-port vector network analyzer, which allows for a compact and straight-forward implementation. A new calibration algorithm is described that incorporates error terms from two separate three-known-load calibrations. Based on simulated and measured data, the proposed technique shows substantial improvement in obtaining the impedance of two offset-short devices when compared with conventional measurements.
  • Overview of Superconducting RF Cavity Reliability at Diamond Light Source - 19th Int. Conf. RF Superconductivity (SRF'19)
    📅 2019-06-01✍️ C. Christou , P. Gu , P.J. Marten , S.A. P, e , A.F. Rankin , D. Spink , L.T. Stant , A. Tropp🎯 inproceedings
    Diamond Light Source has been providing beam for users since January 2007. The electron beam in the storage ring is normally driven by two superconducting CESR-B cavities, with two similar cavities available as spares. Day-to-day reliability of the cavities, measured by storage ring MTBF, has improved enormously over the years. A full analysis of how this improvement has been achieved is given, with particular attention paid to cavity voltage and vacuum pressure management, and the scheduling and procedure of cavity conditioning. The benefits and risks of full and partial warm-ups of the cavities are discussed, and details and impacts of cavity failure and repair are presented.
  • Leveraging Internet of Things Developments for Rapid Prototyping of Synoptic Displays - Proc. 12th International Workshop on Personal Computers and Particle Accelerator Controls (PCaPAC'18)
    📅 2018-11-01✍️ L. T. Stant , T. M. Cobb🎯 inproceedings
    Recently the technology industry has been laying foundations for the eponymous Internet of Things (IoT): efficient publish-subscribe protocols; process control schemas for household items; and improved low-power radio communications. Accelerator controls and IoT have several aspects in common - small payloads, low latency, dashboard/synoptic data presentation format are some examples. The IoT now provides several open-source projects which can provide a partial implementation of one or more accelerator controls software features. Because development is typically a lower priority for accelerator controls groups, there is a valid case to try and utilise the free efforts of others for the benefit of accelerator controls. In this paper, the authors present examples of the use of IoT frameworks for synoptic display/GUI development. The work in this paper enables other developers to access this resource and experiment with their own systems.
  • An Inter-Laboratory Comparison of NVNA Measurements - 2018 Integrated Nonlinear Microwave and Millimetre-wave Circuits Workshop (INMMiC)
    📅 2018-07-01✍️ M.J. Salter , L.T. Stant , K. Buisman , T. Nielsen🎯 inproceedings
    A comparison of nonlinear vector network analyser (NVNA) measurements has been carried out involving four organisations (National Physical Laboratory, UK, University of Surrey, UK, Chalmers University of Technology, Sweden and Keysight Technologies, Denmark). Three nonlinear devices consisting of two amplifiers and a nonlinear verification device (NLVD) were measured by each of the organisations. Results are presented which show generally good agreement between the measurements and give some indication of the typical amount of variability to be expected in measurements of this type.
  • Evaluating residual errors in waveguide network analysers from microwave to submillimetre-wave frequencies - IET Colloquium on Millimetre-Wave and Terahertz Engineering & Technology 2016
    📅 2016-03-01✍️ L.T. Stant , N.M. Ridler , P.H. Aaen🎯 inproceedings
    Vector Network Analysers (VNA) are used extensively for many types of measurement that are made at frequencies ranging from a few kilohertz to at least one terahertz. At radio and microwave frequencies, there are well-established methods for assessing the quality and integrity of these measurements, when they are made in coaxial lines. These methods are usually based on determining the size of residual errors that remain in the VNA after calibration. However, to date, the performance of these methods has not been investigated in rectangular waveguide, and, at higher frequencies (i.e. at millimetre- and submillimetre-wave frequencies). This paper investigates the application of one of these techniques to VNAs configured for waveguide measurements at microwave, millimetre- and submillimetre-wave frequencies. Typical values of residual errors in voltage reflection coefficient (VRC) obtained over microwave and millimetre-wave frequency ranges were between 0.002 to 0.021 linear units. Submillimetre-wave frequency waveguide configurations were found to exhibit significantly larger residual errors and are being investigated further to assess whether the ripple extraction technique is valid at those frequencies. Residual error values obtained in this investigation are considered representative for this technology and so can be used by other users of waveguide VNAs to compare with values obtained on their own systems, therefore helping to verify the performance of their systems.