Development and calibration of a multi-delay coherence imaging diagnostic on the MAST-U tokamak.

The MAST-U Super-X divertor provides the opportunity to study fusion plasma exhaust under novel conditions. However, in order to study these conditions, advanced diagnostics are required. Following the development of the MAST-U Multi-Wavelength Imaging (MWI) diagnostic, we present the installation of a multi-delay coherence imaging spectroscopy (CIS) system within the MAST-U MWI, along with modifications made to the MWI for effective operation. This diagnostic will measure either carbon ion flow velocities and temperatures or electron densities through Dγ emission. We have extended previously developed techniques for wavelength calibration to account for errors due to the misalignment of interferometer components. In addition, we have developed a comprehensive calibration procedure to account for the temperature dependence of the instrument's delays by fitting to a linearly modified version of the delay equation presented by Veiras et al. [Appl. Opt. 49(15), 2769 (2010)]. Together, these procedures reduce the cost and hardware complexity of implementing CIS instruments when compared to those that use in situ or tunable laser calibration systems, as calibrations can be generated to good accuracy using previously measured data.

2D measurements of plasma electron density using coherence imaging with a pixelated phase mask.

In this paper, the pixelated phase mask (PPM) method of interferometry is applied to coherence imaging (CI)-a passive, narrowband spectral imaging technique for diagnosing the edge and divertor regions of fusion plasma experiments. Compared to previous CI designs that use a linear phase mask, the PPM method allows for a higher possible spatial resolution. The PPM method is also observed to give a higher instrument contrast (analogous to a more narrow spectrometer instrument function). A single-delay PPM instrument is introduced as well as a multi-delay system that uses a combination of both pixelated and linear phase masks to encode the coherence of the observed radiation at four different interferometer delays simultaneously. The new methods are demonstrated with measurements of electron density ne, via Stark broadening of the Hγ emission line at 434.0 nm, made on the Magnum-PSI linear plasma experiment. A comparison of the Abel-inverted multi-delay CI measurements with Thomson scattering shows agreement across the 3 × 1019 < ne < 1 × 1021 m-3 range. For the single-delay CI results, agreement is found for ne > 1 × 1020 m-3 only. Accurate and independent interpretation of single-delay CI data at lower ne was not possible due to Doppler broadening and continuum emission.

Robust impurity detection and tracking for tokamaks.

A robust impurity detection and tracking code, able to generate large sets of dust tracks from tokamak camera footage, is presented. This machine learning-based code is tested with cameras from the Joint European Torus, Doublet-III-D, and Magnum-PSI and is able to generate dust tracks with a 65-100% classification accuracy. Moreover, the number dust particles detected from a single camera shot can be up to the order of 1000. Several areas of improvement for the code are highlighted, such as generating more significant training data sets and accounting for selection biases. Although the code is tested with dust in single two-dimensional camera views, it could easily be applied to multiple-camera stereoscopic reconstruction or nondust impurities.

Doppler coherence imaging of scrape-off-layer impurity flows in the HL-2A tokamak.

A new Doppler coherence imaging spectroscopy interferometer has been developed on the HL-2A tokamak for the scrape-off-layer impurity flow measurement. Its spatial resolution is estimated to be up to ∼0.8 mm in the horizontal direction and ∼9 mm in the vertical direction, with a field of view of ∼34°. Its typical temporal resolution is about 1 ms. This salient feature allows for time-resolved 2D measurements in short-time phenomena on HL-2A, such as edge localized modes. Group delay and interference fringe pattern were calibrated with a dedicated calibration system. The robustness of group delay calibration and the feasibility of the extrapolation model for fringe pattern calibration are demonstrated. In this paper, we report the details of the optical instruments, calibration, and the initial experimental results of this Doppler coherence imaging spectroscopy interferometer.

Filament identification in wide-angle high speed imaging of the mega amp spherical tokamak.

A new tomographic inversion technique is presented for the identification of plasma filaments in wide-angle visible camera data. The technique works on the assumption that background subtracted images of filaments can be represented as a superposition of uniformly emitting magnetic equilibrium field lines. A large collection of equilibrium magnetic field lines is traced and projected onto the camera field of view and combined to form a geometry matrix describing the coordinate transformation from magnetic field aligned coordinates to image pixel coordinates. Inverting this matrix enables the reprojection of the emission in the camera images onto a field aligned basis, from which filaments are readily identifiable. The inversion is a poorly conditioned problem which is overcome using a least-squares approach with Laplacian regularization. Blobs are identified using the "watershed" algorithm and 2D Gaussians are fitted to get the positions, widths, and amplitudes of the filaments. A synthetic camera diagnostic generating images containing experimentally representative filaments is utilized to rigorously benchmark the accuracy and reliability of the technique. 74% of synthetic filaments above the detection amplitude threshold are successfully detected, with 98.8% of detected filaments being true positives. The accuracy with which filament properties and their probability density functions are recovered is discussed, along with sources of error and methods to minimize them.

Physically principled reflection models applied to filtered camera imaging inversions in metal walled fusion machines.

Ray-tracing techniques are applied to filtered divertor imaging, a diagnostic that has long suffered from artifacts due to the polluting effect of reflected light in metal walled fusion machines. Physically realistic surface reflections were modeled using a Cook-Torrance micro-facet bi-directional reflection distribution function applied to a high resolution mesh of the vessel geometry. In the absence of gonioreflectometer measurements, a technique was developed to fit the free parameters of the Cook-Torrance model against images of the JET in-vessel light sources. By coupling this model with high fidelity plasma fluid simulations, photo-realistic renderings of a number of tokamak plasma emission scenarios were generated. Finally, a sensitivity matrix describing the optical coupling of a JET divertor camera and the emission profile of the plasma was obtained, including full reflection effects. These matrices are used to perform inversions on measured data and shown to reduce the level of artifacts in inverted emission profiles.

Application of the VUV and the soft x-ray systems on JET for the study of intrinsic impurity behavior in neon seeded hybrid discharges.

This paper reports on impurity behavior in a set of hybrid discharges with Ne seeding-one of the techniques considered to reduce the power load on reactor walls. A series of experiments carried out with light gas injection on JET with the ITER-Like-Wall (ILW) suggests increased tungsten release and impurity accumulation [C. Challis et al., Europhysics Conference Abstracts 41F, 2.153 (2017)]. The presented method relies mainly on the measurements collected by vacuum-ultra-violet and soft X-ray (SXR) diagnostics including the "SOXMOS" spectrometer and the SXR camera system. Both diagnostics have some limitations. Consequently, only a combination of measurements from these systems is able to provide comprehensive information about high-Z [e.g., tungsten (W)] and mid-Z [nickel (Ni), iron (Fe), copper (Cu), and molybdenum (Mo)] impurities for their further quantitative diagnosis. Moreover, thanks to the large number of the SXR lines of sight, determination of a 2D radiation profile was also possible. Additionally, the experimental results were compared with numerical modeling based on integrated simulations with COREDIV. Detailed analysis confirmed that during seeding experiments, higher tungsten release is observed, which was also found in the past. Additionally, it was noticed that besides W, the contribution of molybdenum to SXR radiation was greater, which can be explained by the place of its origin.

In-vessel calibration of the imaging diagnostics for the real-time protection of the JET ITER-like wall.

The in situ absolute calibration of the JET real-time protection imaging system has been performed for the first time by means of radiometric light source placed inside the JET vessel and operated by remote handling. High accuracy of the calibration is confirmed by cross-validation of the near infrared (NIR) cameras against each other, with thermal IR cameras, and with the beryllium evaporator, which lead to successful protection of the JET first wall during the last campaign. The operation temperature ranges of NIR protection cameras for the materials used on JET are Be 650-1600 °C, W coating 600-1320 °C, and W 650-1500 °C.

Recent developments of in-vessel calibration of mid-IR cameras at JET.

Recent improvements in software tools and methodology have allowed us to perform a more comprehensive in-vessel calibration for all mid-infrared camera systems at JET. A comparison of experimental methods to calculate the non-uniformity correction is described as well as the linearity for the different camera systems. Measurements of the temperature are assessed for the different diagnostics.

Coherence imaging of scrape-off-layer and divertor impurity flows in the Mega Amp Spherical Tokamak (invited).

A new coherence imaging Doppler spectroscopy diagnostic has been deployed on the UK's Mega Amp Spherical Tokamak for scrape-off-layer and divertor impurity flow measurements. The system has successfully obtained 2D images of C III, C II, and He II line-of-sight flows, in both the lower divertor and main scrape-off-layer. Flow imaging has been obtained at frame rates up to 1 kHz, with flow resolution of around 1 km/s and spatial resolution better than 1 cm, over a 40° field of view. C III data have been tomographically inverted to obtain poloidal profiles of the parallel impurity flow in the divertor under various conditions. In this paper we present the details of the instrument design, operation, calibration, and data analysis as well as a selection of flow imaging results which demonstrate the diagnostic's capabilities.

Impact assessment of energy-efficient lighting in patients with lupus erythematosus: a pilot study.

BACKGROUND: Patients with lupus erythematosus (LE) are often abnormally photosensitive. Ultraviolet (UV) exposure can not only induce cutaneous lesions but may also contribute to systemic flares and disease progression. Various forms of energy-efficient lighting have been shown to emit UV radiation. OBJECTIVES: To determine the effects of these emissions on individuals with LE. METHODS: This assessment investigated cutaneous responses to repeated exposures from three types of lighting: compact fluorescent lamp (CFL), light-emitting diode (LED) and energy-efficient halogen (EEH). The subjects were 15 patients with LE and a control group of five healthy volunteers. RESULTS: No cutaneous LE lesions were induced by any of the light sources. Delayed skin erythema was induced at the site of CFL irradiation in six of the 15 patients with LE and two of the five healthy subjects. Erythema was increased in severity and more persistent in patients with LE. One patient with LE produced a positive delayed erythema to the EEH. A single patient with LE produced immediate abnormal erythemal responses to the CFL, LED and EEH. Further investigation revealed that this patient also had solar urticaria. All other subjects had negative responses to LED exposure. CONCLUSIONS: Compact fluorescent lamps emit UV that can induce skin erythema in both individuals with LE and healthy individuals when situated in close proximity. However, this occurs to a greater extent and is more persistent in patients with LE. EEHs emit UVA that can induce erythema in patients with LE. LEDs provide a safer alternative light source without risk of UV exposure.

Associations between aggressive behaviour scores and cardiovascular risk factors in childhood.

OBJECTIVE: To examine the influence of aggressive behaviour scores on cardiovascular disease (CVD) risk factors throughout childhood. METHODS: This study utilized cross-sectional and longitudinal data from the Western Australian Pregnancy Cohort (Raine) Study (n = 2900). Aggressive behaviour scores were derived from the Child Behavior Checklist/4-18(CBCL), Youth Self-Report/11-18 (YSR) and Teacher Report Form/6-18 (TRF). CVD risk factors included body mass index (BMI), blood pressure, fasting lipids and homeostasis model of insulin resistance (HOMA-IR). RESULTS: Girls with higher aggressive behaviour scores had higher BMI from 10 years of age (P ≤ 0.001), higher BMI trajectories throughout childhood (P = 0.0003) and at 14 years higher HOMA-IR (P = 0.008). At the 14-year survey, this equated to a difference of 1.7 kg/m2 in the predicted BMI between the extreme CBCL scores in girls (top 5% (CBCL ≥ 17) vs. CBCL score = 0). Boys with higher aggressive behaviour scores had higher BMI at 5 years (P = 0.002), lower diastolic pressure at 14 years (P = 0.002) and lower systolic blood pressure trajectories throughout childhood (P = 0.016). CONCLUSION: Aggressive behaviour influences BMI from early childhood in girls but not boys. If this association is causal, childhood offers the opportunity for early behavioural intervention for obesity prevention.

Maternal death and the onward psychosocial circumstances of Australian Aboriginal children and young people.

BACKGROUND: This study sought to determine the social and emotional impact of maternal loss on Aboriginal children and young people using data from the Western Australian Aboriginal Child Health Survey (WAACHS). METHOD: Data were from a population-based random sample of 5289 Aboriginal children aged under 18 years. Interview data about the children were gathered from primary carers and from their school teachers. Probabilistic record linkage to death registrations was used to ascertain deaths. Association between maternal death and subsequent psychosocial outcomes was assessed using univariate analyses and logistic regression. RESULTS: Of the 5289 Aboriginal children, 57 had experienced the death of their birth mother prior to the survey. Multi-variable adjustment accounting for age and gender found that, relative to children who were living with their birth mother, children whose birth mother had died were at higher risk for sniffing glue or other substances [odds ratio (OR) 3.4, 95% confidence interval (CI) 1.3-8.7], using other drugs (OR 2.8, 95% CI 1.2-6.8), talking about suicide (OR 2.6, 95% CI 1.2-5.7) and attempting suicide (OR 7.0, 95% CI 1.6-31.1). CONCLUSIONS: Although the death of a birth mother is relatively rare and the vast majority of Aboriginal children with adverse developmental outcomes live in families and are cared for by their birth mother, the findings here suggest that the loss of a birth mother and the circumstances arising from this impart a level of onward developmental risk for mental health morbidity in Australian Aboriginal children.

Breast feeding and cognitive development in childhood: a prospective birth cohort study.

The aim of this study was to examine prospectively the relation between duration of breast feeding and cognitive outcomes. A cohort study of 2860 children enrolled before birth provided data from 2393 term infants of English-speaking mothers. Of these, complete infant feeding data in the first year of life and verbal cognitive IQ (Peabody Picture Vocabulary Test - PPVT-R) were available for 1450 children at 6 years, and a performance subtest (Perceptual organisation WISC - Block Design) for 1375 children at 8 years. Full breast feeding was categorised as none,> 0 to < 4 months, 4-6 months and> 6 months. Associations between breast-feeding duration and PPVT-R at 6 years and Block Design at 8 years were estimated before and after adjustment for gender, gestational age, maternal age, maternal education, parental smoking and the presence of older siblings. The early cessation of full breast feeding was associated with reduced verbal IQ and the performance subtest. In unadjusted analysis, mean standardised PPVT-R scores were 6.44 points greater (P < 0.0001) in children fully breast fed for> 6 months compared with those never breast fed. After adjustment, mean PPVT-R scores were 3.56 points higher in children fully breast fed for> 6 months compared with those children never breast fed (P = 0.003). Similarly, Block Design scores were higher in those fully breast fed for> 6 months compared with those never breast fed in unadjusted (P = 0.001) but not adjusted analyses (P = 0.223). Interactions between maternal education (four levels) and breast feeding demonstrated a positive association of maternal education on verbal IQ (F = 2.64; P = 0.005) in children breast fed for longer but not on performance (F = 0.74; P = 0.67). The early introduction of milk other than breast milk was associated with reduced verbal IQ after adjustment for social and perinatal confounders. Although these effects were interacting with maternal education, they may act through undefined mechanisms in human milk.

Mental health disorders in children and young people: scope, cause and prevention.

OBJECTIVE: To review the scope and characteristics of mental health disorders in children and young people in Australia; detail some emerging concepts of the causal pathways of mental health disorders in children and young people; and discuss aspects of the prevention of mental health disorders and the promotion of mental health in children and young people. METHOD: An integrated review of selected literature. RESULTS: (i) While as many as one in five Australian children aged from four to 17 have significant mental health problems there remains a need for prevalence estimates in subsections of the population, notably children and young people of Aboriginal and Torres Strait Islander descent; (ii) appropriate studies of gene-environment interaction will require better measurement and developmental exposition of those risk exposures that are known to be on the causal pathway to mental health disorder; and (iii) universal, selective and indicated prevention trials and evaluations directed at anxiety, depression and conduct disorder are needed. CONCLUSION: Preventive intervention and promotion in mental health must entail effective collaboration at national, state and local levels between health, welfare and education sectors. These sectors must be informed by high quality epidemiology and a knowledge of the causal pathways of mental health disorders. Such intervention must also improve the movement of scientific knowledge to political policy on one hand and to praxis on the other. This will require a clear and persistent vision of the urgency, costs and consequences of mental health disorders in children and young people coupled with effective leadership and political resolve.

Fetal growth and subsequent mental health problems in children aged 4 to 13 years.

To test the hypothesis that children with suboptimal fetal growth have significantly poorer mental health outcomes than those with optimal growth, a population random sample survey of children aged 4 to 16 years in Western Australia in 1993 was conducted. The Child Behavior Checklist (Achenbach 1991a) and the Teacher Report Form (Achenbach 1991b) were used to define mental health morbidity. Survey data for 1775 children aged 4 to 13 years were available for linkage with original birth information. The percentage of expected birthweight (PEBW) was used as the measure of fetal growth. Children below the 2nd centile of PEBW who had achieved only 57% to 72% of their expected birthweight given their gestation at delivery were at significant risk of a mental health morbidity (OR 2.9, 95% CI 1.18, 7.12). In addition, they were more likely to be rated as academically impaired (OR 6.0, 95% CI 2.25, 16.06) and to have poor general health (OR 5.1, 95% CI 1.69, 15.52).