[en] This paper provides an overview of the UKs response to the Fukushima Daiichi Accident and highlights the influence that this has had on UK nuclear regulation since March 2011. ONR’s Incident Suite was staffed from the first day of the accident and remained active on a 24 hours basis for over two weeks. The purpose was to provide advice to the UK government specifically prompt assurance of why this accident couldn’t take place in the UK and practical advice in relation to the 17,000 UK nationals in Japan at that time. In the early phase of the accident ONR took part in international cooperation with the US, Canadian and French regulators in order to determine the actual technical status of the Fukushima Daiichi power plant units. The UK Secretary of State requested that the ONR Chief Inspector identify any lessons to be learnt by the UK nuclear industry and in doing so cooperate and coordinate with international colleagues. The Interim report was produced (May 2011) this focused on civil NPP’s, provided background to radiation, technology and regulations. This report compared the Japan situation with the UK and identified 11 conclusions and 26 recommendations.

[en] The development of imaging interferometry and multichannel heterodyne scattering systems for fusion plasma diagnosis has dicated the development of high power, stable twin frequency sources in the 100 μm → 1000 μm spectral region. Output powers of 500mW (185 μm), 150mW (393 μm), 100mW (496 μm), and 25mW (1.22mm) have been measured directly on a calorimeter applying no correction factors. These powers have been achieved via the optimization of the CO₂ and FIR laser cavities together with the use of buffer gases (to relative bottlenecking) and variation of the pumped molecular gas temperature (to optimize the groundstate population). The source IF jitter on twin frequency FIR laser systems has also been investigated in detail. The effect of CO₂ and FIR feedback on the IF frequency has been studied with the view of producing low cost stable laser systems without complicated active stabilization. A comparison between a novel twin frequency laser involving a single optical cavity and a conventional system involving two separate cavities has been performed. The conclusions from these studies are discussed. They have been utilized in the design of laser systems operational on the TEXT tokamak and at UCLA

[en] A multi-mixer far-infrared scattering system has been developed which permits the collection of angularly and spatially resolved collective scattering data during a single tokamak discharge. (author)

[en] A detailed description of the design and calibration of a multimixer far-infrared scattering system for the study of collective plasma density fluctuations is presented. The apparatus permits either the determination of single-shot wave dispersion data or angularly resolved scattering data at multispatial locations during a single plasma discharge. Typical scattering data from spontaneously occurring low-frequency microturbulence as well as from kinetic Alfven waves (generated during ICRF heating) in the UCLA Microtor tokamak are presented

[en] A multi-channel FIR scattering system has been installed on TEXT as part of an overall TEXT program to study anomalous transport in Tokamaks. The multiangle scattering system allows single shot measurement of the wavenumber spectra. At present, homodyne detection is being employed utilizing an optically pumped far-infrared laser operating at 245 GHz as the radiation source. Quasi-optical Schottky diode mixers, possessing noise temperatures of about 5000⁰K, form the basis of the low noise receiver system. The scattering apparatus is capable of both horizontal and vertical spatial scans thus enabling the entire plasma cross-section to be probed. In order to accurately obtain the wavenumber spectra as well as the absolute level of the density fluctuations, considerable effort has been devoted to the system calibration. To achieve this goal, system parameters such as relative collection efficiency detector responsivity and LO power assignment factors have been carefully calibrated using an amplitudemodulated FIR beam. Modulation is achieved by launching acoustic waves of the appropriate frequency transversely into a FIR cavity using a PZT. The gain of the FIR laser medium is modified and the FIR emission amplitude-modulated. Finally, it should be noted that the injection of small levels of scandium via the laser ablation technique was found to significantly modify the microturbulence spectra. Fluctuation levels decreased by greater than 20% and frequency spectra were harrowed by apparent partial quenching of the higher frequency components

[en] The paper provides an overview of the UK’s response to the Fukushima Daiichi Accident and highlights the enduring influence that the internationally led and coordinated response has had on the regulation of UK nuclear installations. (author)

[en] The development of imaging interferometry and multichannel heterodyne scattering systems for fusion plasma diagnosis has dictated the development of high-power, stable twin-frequency sources in the 100→1000 μm spectral region. Output powers of 500 mW (185 μm), 150 mW (393 μm), 100 mW (496 μm), and 25 mW (1.22 mm) have been measured directly on a Scientech Calorimeter applying no correction factors. These powers have been achieved via the optimization of the CO₂ and far infrared (FIR) laser cavities together with the use of buffer gases (to relieve bottlenecking) and variation of the pumped molecular gas temperature (to optimize the ground-state population). The source intermediate frequency (IF) jitter in twin-frequency FIR laser systems has also been investigated in detail. The effect of CO₂ and FIR feedback on the IF frequency has been studied with the view of producing low-cost stable laser systems without complicated active stabilization. Finally a comparison between a novel twin-frequency laser involving a single optical cavity and a conventional system involving two separate cavities has been performed. The conclusions drawn from the above studies have been utilized in the design of laser systems operational on the TEXT tokamak and at UCLA

[en] We present a frequency modulation technique for calibration of the displacement actuators of the LIGO 4 km long interferometric gravitational-wave detectors. With the interferometer locked in a single-arm configuration, we modulate the frequency of the laser light, creating an effective length variation that we calibrate by measuring the amplitude of the frequency modulation. By simultaneously driving the voice coil actuators that control the length of the arm cavity, we calibrate the voice coil actuation coefficient with an estimated 1σ uncertainty of less than 1%. This technique enables a force-free, single-step actuator calibration using a displacement fiducial that is fundamentally different from those employed in other calibration methods.

[en] Recent measurements at the LIGO Hanford Observatory have confirmed the predicted high-frequency dynamic response of km scale Fabry-Perot cavities to length and laser frequency variations. The dynamic response functions have been exploited to determine a number of cavity parameters including the cavity length and the resonance width. A new technique based on a variation of these measurements has been utilized to measure the interferometer arm cavity lengths with a precision of 80 μm. We present an overview of these measurements and discuss how the dynamic field responses could be used to measure the cavity g factors which are related to the mirror radii of curvature

[en] As sensitivities improve and more detectors are added to the global network of gravitational wave observatories, calibration accuracy and precision are becoming increasingly important. Photon calibrators, relying on power-modulated auxiliary laser beams reflecting from suspended interferometer optics, enable continuous calibration by generating displacement fiducials proportional to the modulated laser power. Developments in the propagation of laser power calibration via transfer standards to on-line power sensors monitoring the modulated laser power have enabled generation of length fiducials with improved accuracy. Estimated uncertainties are almost a factor of two smaller than the lowest values previously reported. This is partly due to improvements in methodology that have increased confidence in the results reported. Referencing the laser power calibration standards for each observatory to a single transfer standard enables reducing relative calibration errors between elements of the detector network. Efforts within the national metrology institute community to realize improved laser power sensor calibration accuracy are ongoing. (paper)