Visible and near-infrared divertor spectroscopy on the MAST and JET-ILW tokamaks

Passive spectroscopy diagnostics play a key role in advancing the physics of plasma exhaust in the edge and divertor regions of tokamaks. Information obtained from spectral line intensities and profile shapes is crucial for estimating plasma parameters, particularly for studies of cold and dense detached plasmas. This work aims to characterise the visible and near-infrared spectral regions with emphasis on the Balmer and Paschen hydrogen series lines, their diagnostic applications and interpretation techniques. Whereas the Balmer series lines are measured routinely, few observations of the Paschen series lines have been carried out in the fusion plasma context. Extending observations to the near-infrared region for more detailed studies of the Paschen series is addressed through diagnostic development with the aim of providing coverage of the visible to near-infrared spectral range (350-1900 nm) along the same optical line-of-sight. An initial spectral survey on MAST using a purpose built diagnostic provides new insight into the spectral features in the near-infrared and confirms the viability of Paschen line observations. Following the proof of concept measurements on MAST, diagnostic development on the JET ITER-like wall mirror-linked divertor spectroscopy system facilitated more refined measurements. The main outputs include first of its kind measurements of the Pa-alpha line and spatially resolved spectral line profile measurements of the Pa-beta line. In the visible range ELM-resolved Balmer and impurity emission profile measurements at high spatial resolution were obtained using a new filtered camera system. A detailed assessment of the diagnostic scope for parameter estimation from both high-n and low-n Balmer and Paschen series lines is presented, underpinned by a parametrised line profile model which captures the relevant broadening and splitting mechanisms, including the Zeeman, Stark and Doppler processes. Interpretation of JET divertor plasma measurements, in combination with synthetic data simulation results, highlights the importance of complementary Balmer and Paschen series measurements for refining parameter estimates in divertor plasmas

Mitigation of Peak Cooling Demand through the Combination of Residential Zoned Cooling and Window Shading: A Building Simulation Case Study

The present study expands on previous building simulation work con-cerning the potential benefits of residential zoned cooling systems during peak summer days. Such zoned systems provide an opportunity for peak reduction on hot and humid days when the electricity peak is largely caused by increased space cooling demand. In the previous study, control strategies for different occupancy profiles were consid-ered and their impact on peak and cooling energy reduction were compared. The present study builds on these results by considering the benefits of shading as a passive means of reducing the peak cooling load. The analysis is based on integrated building energy simulations of a newer-vintage house using the zoned cooling system model in con-junction with the expanded set of shading models. Total cooling ener-gy demand, peak cooling power reductions and their impact on even-ing recovery times are examined. It was found that zoned control strategies alone can yield signifi-cant peak power reductions, but the long recovery periods limit their practical application. Only with between-pane or outdoor shade con-figurations can very large reductions can be realized without compro-mising occupant comfort during the evening recovery period

Modeling Fenestration With Shading Devices In Building Energy Simulation: A Practical Approach

The use of operable shading devices impacts building loads significantly. The need exists for an explicit treatment of window shading devices in the design of energy efficient buildings through simulation. A general framework for modeling complex fenestration systems has recently been implemented in ESP-r. The underlying models have been developed with emphasis on computational efficiency and straightforward input requirements. The capabilities, which currently include modeling of slat-type blinds in any arrangement between glazing layers, are summarized and an overview of the solar optical and thermal models is given. An analysis of slat-type blind models was carried out comparing the complex fenestration facility in ESP-r to slat-type blind models in EnergyPlus. Simulations were conducted for a test cell with a south facing window. The results show good agreement between the two simulation programs. Considering the complicated nature of shading layer modeling, the new complex fenestration facility in ESP-r yielded encouraging results in this preliminary study.Natural Sciences and Engineering Research Council of Canad

Implementation of Window Shading Models into Dynamic Whole-Building Simulation

An important consideration in energy efficient building design is the management of solar gain, as it is the largest and most variable gain in a building. The design of buildings with highly glazed facades, as well as decreased energy transfer rates through better insulated and tighter envelopes are causing interior spaces to become highly sensitive to solar gain. Shading devices such as operable slat-type louver blinds are very effective in controlling solar gain, yet their impact on peak cooing loads and annual energy consumption is poorly understood. With the ever-increasing role of building energy simulation tools in the design of energy efficient buildings, there is a clear need to model windows with shading devices to assess their impact on building performance. Recent efforts at the University of Waterloo’s Advanced Glazing Systems Laboratory (AGSL) in window shading research have produced a set of flexible shading models. These models were developed with emphasis on generality and computational efficiency, ideally suited for integration into building simulation. The objective of the current research is to develop a complex fenestration facility within a general purpose integrated building simulation software tool, ESP-r, using the AGSL shading models. The strategy for implementation of the AGSL shading models is the addition of a new multi-layer construction within ESP-r, the Complex Fenestration Construction (CFC). The CFC is based on the standard ESP-r multi-layer nodal structure and finite control volume numerical model, with additional measures for coping with the complexities that arise in the solar, convective and radiant exchanges between glazing/shading layers, the interior zone and exterior surroundings. The CFC algorithms process the solar, convective and radiant properties of the glazing/shading system at each time-step, making it possible to add control (e.g., changing the slat angle of a slat-type blind) at the time-step level. Thermal resistances of sealed cavities between glazing/shading layers are calculated at each time-step for various fill gases and mixtures. In addition to modeling glazing/shading layer combinations, the CFC type also provides an alternate method of modeling unshaded windows without relying on third party software to supply the solar optics and cavity resistances. To build confidence in the CFC code implementation, two comparison studies were carried out to compare the CFC type against other models. The first study compared the CFC models for unshaded windows with the standard ESP-r transparent multi-layer construction (TMC) models. The second study compared the CFC slat-type blind models with EnergyPlus 2.0. Good agreement was seen in the simulation results in both studies. The successful implementation of the Complex Fenestration Construction within ESP-r has been demonstrated in the current research. In order for ESP-r users to fully exploit the capabilities of the CFC framework, it is recommended that the current models be extended to include a facility for dynamic shading control as well as the treatment of other types of shading layers. The coupling of daylighting models with the CFC type would provide a useful tool for modeling luminance control in combination with shading control strategies. With these enhancements, it is anticipated that the CFC implementation will be of significant value to practitioners

Heat Transfer Analysis Of Windows With Venetian Blinds: A Comparative Study

The potential to reduce building load and annual energy consumption is widely recognized in the use of shading devices to control solar gain. Consequently, the ability to include and model shading layers in complex glazing systems is needed in evaluating the energy performance of a building envelope. In a previous study, solar-optical calculations were presented for a window with a light and dark coloured venetian blind using simplified models for three different glazing/shading configurations. Results were presented for the hourly transmitted, reflected and absorbed quantities of solar radiation for summer and winter conditions. In this study, a heat transfer analysis is presented to complement the previous study and provide all the relevant information required for building energy analysis. The individual contributions to the net heat gain consisting of total solar transmission, longwave radiant gain and convective gain are presented. The ability to quantify the relative importance of each heat gain component offers significant insight into the thermal characteristics of complex glazing/shading systems.Natural Sciences and Engineering Research Council of Canad

Demonstration Of New ESP-R Capability For Quantifying The Energy Savings Potential Of Window Shading Devices

Buildings with highly glazed facades and well insulated, air-tight envelopes result in interior spaces that are highly sensitive to solar gain. Solar gain through glazing is the largest and most variable gain in buildings and has major implications on energy consumption and peak cooling loads. The peak electricity demand in Ontario, for example, is dominated by space cooling of residential and commercial buildings. The appropriate use of window shading devices can reduce cooling energy consumption and substantially lower the peak cooling load. The potential for reducing the electricity demand on peak summer days is especially significant as the cost to construct and maintain the power distribution grid and generating capacity is directly related to the peak demand. Recently, new capabilities for modeling windows with shading devices were incorporated into ESP-r. The work is based on a set of shading models, designated the ASHWAT (ASHRAE Window Attachment) models, which were developed with emphasis on generality and computational efficiency. Measurements performed at the National Solar Test Facility (NSTF) on a full scale window with various shading attachments were compared to calculated values predicted by the ASHWAT models. The predicted results aligned well with measured data, giving confidence to the applicability of the models. To demonstrate the new modeling capability within ESP-r, simulation examples illustrating the impact of different shading configurations on cooling energy, peak load and thermal comfort are presented. In particular, a simulation of an automated external shading system highlights the role of shading on the energy performance of a solar house design entered into the Solar Decathlon 2009 competition. The external shading design is compared with other options including a solar protective coating on the outside glass as well as indoor shades. Simulations were also carried out to illustrate the impact of shading devices on winter nighttime heat loss and thermal comfort. Finally, a general procedure for using the shading models within ESP-r is outlined, highlighting straightforward user input by means of a user-friendly graphical interface.Natural Sciences and Engineering Research Council of Canad

An efficient stable optical polariser module for calibration of the S4UVN earth observation satellite

We describe here an optical polariser module intended to deliver well characterised polarised light to an imaging spectrometer instrument. The instrument in question is the Sentinel-4/UVN Earth observation imaging spectrometer due to be deployed in 2019 in a geostationary orbit. The polariser module described here will be used in the ground based calibration campaign for this instrument. One critical task of the calibration campaign will be the highly accurate characterisation of the polarisation sensitivity of instrument. The polariser module provides a constant, uniform source of linearly polarised light whose direction can be adjusted without changing the output level or uniformity of the illumination. A critical requirement of the polariser module is that the illumination is uniform across the exit pupil. Unfortunately, a conventional Glan-Taylor arrangement cannot provide this uniformity due to the strong variation in transmission at a refractive surface for angles close to the critical angle. Therefore a modified prism arrangement is proposed and this is described in detail. Detailed tolerance modelling and straylight modelling is also reported here

Nitrogen molecular break-up and transport simulations in the JET divertor

| openaire: EC/H2020/633053/EU//EUROfusionThe density of N+ ions is predicted to decrease by 25 % and the density of N2+ ions to increase by 50 % if nitrogen is assumed to recycle from the divertor walls as molecules in partially detached JET L-mode plasma simulations performed with the 3D Monte Carlo trace impurity code ERO2.0 [1]. These findings are attributed to the kinetic energy gained by the molecular dissociation fragments in the Franck-Condon process and the resulting increase in plasma penetration of the atoms.Non peer reviewe

An efficient stable optical polariser module for calibration of the S4UVN earth observation satellite

We describe here an optical polariser module intended to deliver well characterised polarised light to an imaging spectrometer instrument. The instrument in question is the Sentinel-4/UVN Earth observation imaging spectrometer due to be deployed in 2019 in a geostationary orbit. The polariser module described here will be used in the ground based calibration campaign for this instrument. One critical task of the calibration campaign will be the highly accurate characterisation of the polarisation sensitivity of instrument. The polariser module provides a constant, uniform source of linearly polarised light whose direction can be adjusted without changing the output level or uniformity of the illumination. A critical requirement of the polariser module is that the illumination is uniform across the exit pupil. Unfortunately, a conventional Glan-Taylor arrangement cannot provide this uniformity due to the strong variation in transmission at a refractive surface for angles close to the critical angle. Therefore a modified prism arrangement is proposed and this is described in detail. Detailed tolerance modelling and straylight modelling is also reported here