Search

In this paper we report on the development and demonstration of density feedback control for MAST-U. Sinusoidal perturbations are used to measure the frequency response from a deuterium gas valve (actuator) to line-integrated core electron density measured by the interferometer (sensor). In the frequency range relevant for control design, only two system-identification experiments were needed to regress a first-order dynamic model. This control-oriented model informs the offline design of a proportional integral controller with the established loop-shaping controller design method. After offline verification of the controller implementation, control is demonstrated by experimentally tracking a staircase reference for the line-integrated electron density. This paper demonstrates the efficiency of controller design using system-identification and loop-shaping, providing reliable density control for MAST-U.

Future fusion reactors require a safe, steady-state divertor operation. With deep divertor detachment, which is typically induced by impurity seeding, the radiation concentrates in a small region at the X-point or on closed flux surfaces above the X-point. This so-called X-point radiator (XPR) moves further inside the confined region with increasing seeding and the location can be actively controlled. At AUG, the parameter space for operation with an XPR was significantly extended, using active feedback on the XPR location. The XPR is observed in nearly the whole operational space of AUG in the high-densities or high collisionality regime. ELM suppression is consistently observed in all cases where the XPR was moved to a significant height above the X-point. Direct measurements of density and temperature from the region around the XPR using the new divertor Thomson scattering system at AUG indicate that the temperature at the location of the XPR remains high (>30eV) and only the region towards the X-point cools down further. In this cold XPR core, the temperature reduces to about 1eV. An XPR is also observed in TCV by the injection of nitrogen as extrinsic impurity. This highlights that the wall material (W for AUG, C for TCV) or machine size does not play a significant role for the existence of the regime. However, the scenario appears to be less stable in TCV. First experiments show the necessity of an active control for the XPR: Depending on the wall conditions and the nitrogen wall storage, the required nitrogen seeding level to achieve an XPR changes. Both, the low temperatures measured radially outside of the radiation zone at AUG, and the lower stability of the XPR regime at TCV with the presence of carbon are consistent with the predictions of a one-dimensional model of the XPR. However, the model would predict the development of the cold XPR core, and significant radiation at the X-point might already exist before reaching this cold temperature solution.

OBJECTIVE: To identify antenatal and early childhood exposures of unintentional injury among infants in New Zealand (NZ). METHOD: The theoretical life-course framework of child injury prevention domains was utilised to analyse data from a prospective longitudinal NZ birth cohort (Growing Up in NZ). Risk and protective factors for injury were identified using Robust Poisson regression models. RESULT: Among children included for the analysis(n=6304), 52% were male, 55% were born to European mothers, and 37% lived in a household with high levels of deprivation. Mothers reported that 6% of infants (n=406) had sustained at least one injury by 9 months. Multivariate analysis showed injury risk among single mothers with antenatal depression were more than twice that (IRR=2.20) of children of mothers with partners and without depression. CONCLUSION: Understanding antenatal risk and protective factors for infant injury will assist in implementing injury prevention programmes or modifying the existing policies that affect these vulnerable age groups.

This paper shows first quantitative analysis of the detachment processes in the MAST Upgrade Super-X divertor (SXD). We identify an unprecedented impact of plasma-molecular interactions involving molecular ions (likely D 2 + ), resulting in strong ion sinks (Molecular Activated Recombination—MAR), leading to a reduction of ion target flux. The MAR ion sinks exceed the divertor ion sources before electron-ion recombination (EIR) starts to occur, suggesting that significant ionisation occurs outside of the divertor chamber. In the EIR region, T e ≪ 0.2 eV is observed and MAR remains significant in these deep detached phases. The total ion sink strength demonstrates the capability for particle (ion) exhaust in the Super-X Configuration. Molecular Activated Dissociation is the dominant volumetric neutral atom creation process can lead to an electron cooling of 20% of P S O L . The measured total radiative power losses in the divertor chamber are consistent with inferred hydrogenic radiative power losses. This suggests that intrinsic divertor impurity radiation, despite the carbon walls, is minor in the divertor chamber. This contrasts previous TCV results, which may be associated with enhanced plasma-neutral interactions and reduced chemical erosion in the detached, tightly baffled SXD. The above observations have also been observed in higher heat flux (narrower SOL width) type I ELMy H-mode discharges. This provides evidence that the characterisation in this paper may be general.

Future fusion reactors require a safe, steady-state divertor operation. With deep divertor detachment, which is typically induced by impurity seeding, the radiation concentrates in a small region at the X-point or on closed flux surfaces above the X-point. This so-called X-point radiator (XPR) moves further inside the confined region with increasing seeding and the location can be actively controlled. At AUG, the parameter space for operation with an XPR was significantly extended, using active feedback on the XPR location. The XPR is observed in nearly the whole operational space of AUG in the high-densities or high collisionality regime. ELM suppression is consistently observed in all cases where the XPR was moved to a significant height above the X-point. Direct measurements of density and temperature from the region around the XPR using the new divertor Thomson scattering system at AUG indicate that the temperature at the location of the XPR remains high (>30eV) and only the region towards the X-point cools down further. In this cold XPR core, the temperature reduces to about 1eV. An XPR is also observed in TCV by the injection of nitrogen as extrinsic impurity. This highlights that the wall material (W for AUG, C for TCV) or machine size does not play a significant role for the existence of the regime. However, the scenario appears to be less stable in TCV. First experiments show the necessity of an active control for the XPR: Depending on the wall conditions and the nitrogen wall storage, the required nitrogen seeding level to achieve an XPR changes. Both, the low temperatures measured radially outside of the radiation zone at AUG, and the lower stability of the XPR regime at TCV with the presence of carbon are consistent with the predictions of a one-dimensional model of the XPR. However, the model would predict the development of the cold XPR core, and significant radiation at the X-point might already exist before reaching this cold temperature soluti

In this work, we provide the first 2D spatially resolved description of radiative detachment in MAST-U Super-X L-mode divertor plasmas. The Super-X magnetic configuration was designed to achieve reduced heat- and particle loads at the divertor target compared to conventional exhaust solutions. We use filtered camera imaging to reconstruct 2D emissivity profiles in the poloidal plane for multiple atomic and molecular emission lines and bands. A set of deuterium fuelling scans is discussed that, together, span attached to deeply detached divertor states observed in MAST-U. Emissivity profiles facilitate separate analysis of locked-mode induced split branches of the scrape-off layer. Molecular deuterium Fulcher band emission front tracking reveals that the deuterium electron-impact ionisation front, for which it serves a proxy, detaches at different upstream electron densities in the split branches. Upon detachment of this ionisation front, Balmer emission attributed to molecular activated recombination appears near-target. We report a simultaneous radial broadening of the emission leg, consistent with previous SOLPS-ITER modelling. With increased fuelling this emission region detaches, implying electron temperatures below ∼ 1 eV. In this phase, 2D Balmer line ratio reconstruction indicates an onset of volumetric direct electron-ion recombination near-target. At the highest fuelling rates this emission region moves off-target, suggesting a drop in near-wall electron density accompanying the low temperatures.

This paper presents the first result using nitrogen-seeded exhaust feedback control of the NII impurity emission front in TCV. The NII emission front position is consistently located below its commonly used CIII counterpart, indicating the NII emission front is representative of a colder plasma region. We demonstrate control of the NII impurity emission front position for two cases: (a) using nitrogen seeding as the sole actuator, and (b) using deuterium fueling as an actuator while injecting a small amount of nitrogen that remains a trace impurity. For sole nitrogen actuation, peak target current density is significantly reduced when the NII emission front approaches the x-point (≈50% for the NII front at the halfway point). When actuating with deuterium, peak target current density is less affected, which is explained by changes in fueling engendering a different scrape-off-layer plasma density. Perturbative (system identification) experiments show that nitrogen actuation induces a stronger, but slower, response of the NII emission front than deuterium actuation. Moving the NII emission front back to the target after pushing it towards the x-point has proven difficult, where both the NII front position and total radiated power do not reach pre-seeding conditions within the discharge time following termination of nitrogen injection. This result highlights the need to account for impurity retention for such seeded discharges in exhaust control strategies.

We present the first analysis of the atomic and molecular processes at play during detachment in the MAST-U Super-X divertor using divertor spectroscopy data. Our analysis indicates detachment in the MAST-U Super-X divertor can be separated into four sequential phases: first, the ionisation region detaches from the target at detachment onset leaving a region of increased molecular densities downstream. The plasma interacts with these molecules, resulting in molecular ions ( D 2 + and/or D 2 − → D + D − ) that further react with the plasma leading to molecular activated recombination and dissociation (MAR and MAD), which results in excited atoms and significant Balmer line emission. Second, the MAR region detaches from the target leaving a sub-eV temperature region downstream. Third, an onset of strong emission from electron-ion recombination (EIR) ensues. Finally, the electron density decays near the target, resulting in the bulk of the electron density moving upstream. The analysis in this paper indicates that plasma-molecule interactions have a larger impact than previously reported and play a critical role in the intensity and interpretation of hydrogen atomic line emission characteristics on MAST-U. Furthermore, we find that the Fulcher band emission profile in the divertor can be used as a proxy for the ionisation region and may also be employed as a plasma temperature diagnostic for improving the separation of hydrogenic emission arising from electron-impact excitation and that from plasma-molecular interactions. We provide evidences for the presence of low electron temperatures (≪0.5 eV) during detachment phases III-IV based on quantitative spectroscopy analysis, a Boltzmann relation of the high-n Balmer line transitions together with an analysis of the brightness of high-n Balmer lines.

Objectives To provide a sociodemographic profile of students enrolled in their first year of a health professional pre-registration programme offered within New Zealand (NZ) tertiary institutions. Design Observational, cross-sectional study. Data were sought from NZ tertiary education institutions for all eligible students accepted into the first ar of a health professional programme for the 5-year period 2016-2020 inclusive. Variables of interest: gender, citizenship, ethnicity, rural classification, socioeconomic deprivation, school type and school socioeconomic scores. Analyses were carried out using the R statistics software. Setting Aotearoa NZ. Participants All students (domestic and international) accepted into the first ar of a health professional programme leading to registration under the Health Practitioners Competence Assurance Act 2003. Results NZ's health workforce pre-registration students do not reflect the diverse communities they will serve in several important dimensions. There is a systematic under-representation of students who identify as Māori and Pacific, and students who come from low socioeconomic and rural backgrounds. The enrolment rate for Māori students is about 99 per 100 000 eligible population and for some Pacific ethnic groups is lower still, compared with 152 per 100 000 for NZ European students. The unadjusted rate ratio for enrolment for both Māori students and Pacific students versus Other' students is approximately 0.7. Conclusions We recommend that: (1) there should be a nationally coordinated system for collecting and reporting on the sociodemographic characteristics of the health workforce pre-registration; (2) mechanisms be developed to allow the agencies that fund tertiary education to base their funding decisions directly on the projected health workforce needs of the health system and (3) tertiary education funding decisions be based on Te Tiriti o Waitangi (the foundational constitutional agreement between the Indigenou

Objective To determine the socio-demographic profile of all students enrolled to study medicine in Aotearoa New Zealand (NZ). Design and setting Observational, cross-sectional study. Data were sought from the Universities of Auckland and Otago, the two NZ tertiary education institutions providing medical education, for the period 2016-2020 inclusive. These data are a subset of the larger project 'Mirror on Society' examining all regulated health professional enrolled students in NZ. Variables of interest: gender, citizenship, ethnicity, rural classification, socioeconomic deprivation, school type and school socioeconomic scores. NZ denominator population data (18-29 years) were sourced from the 2018 census. Participants 2858 students were enrolled to study medicine between 2016 and 2020 inclusive. Results There were more women (59.1%) enrolled to study medicine than men (40.9%) and the majority (96.5%) were in the 18-29 years age range. Maori students (rate ratio 0.92; 95% CI 0.84 to 1.0) and Pacific students (rate ratio 0.85; 95% CI 0.73 to 0.98) had lower overall rates of enrolment. For all ethnic groups, irrespective of rural or urban origin, enrolment rates had a nearly log-linear negative relationship with increasing socioeconomic deprivation. Enrolments were lower for students from rural areas compared with those from urban areas (rate ratio 0.53; 95% CI 0.46-0.61). Overall NZ's medical students do not reflect the diverse communities they will serve, with under-representation of Maori and Pacific students and students who come from low socioeconomic and rural backgrounds. Conclusions To meaningfully address these issues, we suggest the following policy changes: universities commit and act to Indigenise institutional ways of knowing and being; selection policies are reviewed to ensure that communities in greatest need of doctors are prioritised for enrolment into medicine (specifically, the impact of low socioeconomic status should be factored into selection de

AIM: Approaches to understanding child injury tend to focus on short-term proximal influences. Previous analyses have found higher rates of injury among Māori and Pacific children in Aotearoa New Zealand (NZ). This study aimed to investigate how combinations of situations and multiple events act across the life-course to either protect preschool children from, or place them at risk of, repeated injuries requiring medical attention. METHODS: Longitudinal data were used to identify parent-reported injuries requiring medical attention among 6114 preschool NZ children. The environments experienced by children with multiple and/or severe injury were explored using multivariable analyses. RESULTS: Eight percent of children (n=505) experienced 1-3 injuries with at least one hospitalisation or ≥4 injuries (high injury group) from birth to 4.5 years of age. After accounting for antenatal, sociodemographic and psychosocial variables, children of Māori mothers (OR=0.7, 95% CI 0.5 to 0.97) and children of Asian mothers (OR=0.5, 95% CI 0.3 to 0.7) were less likely to be in the high injury group than children of European mothers. After adjusting for maternal ethnicity and child variables (gender, temperament, level of activity and behaviour difficulties), cumulative exposure to factors in four domains was associated with injury category: maternal, family, social and service use. CONCLUSION: This study identified social and economic opportunities to lower rates of injury among preschool children, that might reduce associated direct and indirect costs. Our findings in relation to ethnicity go against the standard public rhetoric and provide support for shifting the apportioning of blame for child injury from individuals to wider environmental exposures for which public health and societal solutions are required.

The heat and particle exhaust in tokamaks is guided to a dedicated region called the divertor. Unmitigated, the expected power fluxes impacting the divertor targets during reactor relevant operation exceed present-day engineering limits [1]. Real-time feedback control of plasma detachment, a regime characterized by a large reduction in plasma temperature and pressure at the divertor target, is required to maintain a sufficient reduction of these fluxes [2, 3]. During plasma detachment a temperature gradient along the divertor leg is established. This gradient gives rise to a sharp optical emission fall-off, frequently referred to as a front. These fronts are indicative of a local electron temperature, and their location can be used as a measure of detachment strength. A real-time algorithm for detection of these radiation fronts using multi-spectral imaging was recently developed [4], and experimentally demonstrated [5] on the Tokamak à Configuration Variable (TCV) [6] utilizing the multi-spectral imaging diagnostic MANTIS [7]. In this talk, we will show the state-of-the art and further development of using MANTIS for feedback control of the divertor plasma. Including: 1) feedback-control of the C-III emission front using deuterium fueling and the N-II emission front using nitrogen seeding, and 2) the use of system identification techniques to obtain control-oriented models for offline controller design. We conclude with our view towards multi-input, multi-output (MIMO) control of the divertor plasma using MANTIS, fully exploiting its 10 available cameras. Specifically, combining multiple spectrally filtered images to obtain real-time information on the loss processes driving detachment. References [1] R. Pitts et al., Nucl. Mat. Ener. 20, 100696 (2019) [2] B. Lipschultz et al., Nuclear Fusion 56, 056007 (2016) [3] A. Leonard, Plasma Phys. Control. Fusion 60, 044001 (2018) [4] T. Ravensbergen et al.

OBJECTIVE: To determine the amount and nature of health professional education related to fall prevention for older adults in Australian and New Zealand universities. METHOD(S): Universities offering medicine, nursing and allied health courses were invited to complete an online survey enquiring about fall prevention course-related information: topics; delivery mode; and time dedicated. RESULT(S): One hundred and five respondents, 11 disciplines and 43 universities completed the survey. Courses were primarily undergraduate level (90%) and delivered face-to-face (93%). Time dedicated to fall prevention was usually one to three hours of lectures (>65% of courses) and 1-3+ hours of tutorials/practical sessions (>80% of courses). CONCLUSION(S): Survey results indicate that education of health professionals across a range of disciplines in Australia and New Zealand does include older adult fall prevention. Education of all health and exercise professionals about falls is vital given their critical role in the prevention and management of falls in our rapidly ageing population.Copyright © 2018 AJA Inc.

In the summer of 2016, a solar powered charging station for electric bicycles and scooters was built on the TU Delft campus next to the EEMCS building. Initially the station could only charge very few types of batteries, due to the fact that each battery manufacturer has its own different requirements for the charger. The aim of this BSc final project is to extend the charging capabilities of the station so that it can work with as many battery brands as possible, with more importance given to the more popular brands. Experiments were carried out on two types of batteries to gain an understanding of how they are charged. In order to realize a universal charger, initially a general concept was formulated, and then its subsystems were designed. Voltage and current sensors were designed to send data from a battery which is connected to the charging station to an Arduino microcontroller. This data can then be used to control a CC/CV (constant current/constant voltage) regulator and a current limiter in order to replicate a battery's original charger. In the end, not all subsystems could be implemented, and a working prototype was not realized, however much work was done that can be used in future designs. Three group members worked on this universal charger. Ron dealt with the microcontroller, the data lines and the charging protocols. Enzo was concerned with the CC/CV controller and the current sensor, as well as helped with the protocols. Bram was responsible for the CC/CV regulator, the current limiter and the voltage sensor., Electrical Engineering, Mathematics and Computer Science, Electrical Engineering