Feedback-controlled puffing of neon and deuterium has been applied to control the edge-localized-mode behavior and the target plate power deposition during high-power $H$-mode discharges in ASDEX Upgrade. A regime has been found in which more than 90% of the heating power is lost through radiation and divertor detachment occurs, without deterioration of the energy confinement. The plasma remains in the $H$ mode, exhibiting small-amplitude, high-frequency ELM's, which do not penetrate to the target plates in the strike zone region.

A model for scene simulation is presented which describes quantitatively the recognized phenomenology of passive millimeter wave imaging in land, sea and air scenarios. The model describes objects in a scene as facets giving them electromagnetic properties from their electrical permittivities. This enables polarimetric effects in scenes to be reproduced. Illumination from the sky and ground is calculated using radiation transport, as are the emissive and absorbing effects of the atmosphere between the objects and the imager. The model includes the effects of image sampling, diffraction effects of finite imager apertures sizes and system noise. Phenomena in experimentally acquired images in the 94 GHz atmospheric transmission window are quantified from three scenarios. These are a helicopter landing site as viewed by the pilot, a coastal region showing boats, land and buildings viewed from sea level, and an airfield viewed from directly above. These are compared quantitatively to the simulated scenes from these scenarios, finding agreement between the radiation temperatures to within a few degrees Kelvin. These discrepancies are accounted for by the uncertainties in the permittivities of materials in the scene. The work constitutes the partial validation of a scene simulation capability for passive millimeter wave imaging in outdoor scenarios.

The aperture synthesis technique, historically used for imaging in radio astronomy, is generalized to three dimensions as a means to generating 3-D images in the near-field. The technique uses a multi-channel electronic cross-correlator and an array of radio receivers to generate a 3-D visibility function. This is transformed by a 3-D inverse Fourier transform into a 3-D image of space. The basic equations, experimentation, and simulation indicate the Abbe microscope half-wavelength spatial resolution is achievable in three dimensions when a subject is surrounded by receivers. At longer ranges, further from the array, the resolution perpendicular to the range is proportional to the ratio of the range to aperture size (corresponding to the Fraunhofer diffraction limit) while the resolution in range is proportional to the square of this ratio (a passive ranging capability). Experimental data from a 10-channel 94-GHz and a 32-channel 22-GHz receiver array and a digital cross-correlator demonstrate the imaging capability. The technique enables arbitrarily large volumes to be imaged using multiple inverse 3-D Fourier transforms for adjacent regions of space, when suitable phase corrections are applied to cross-correlations. The technique is mainly directed at the millimeter-wave band for the application of personnel security screening.

The paper discusses the scene simulation of radiometric imagers and its use to illustrate the phenomenology of full-body screening of people for weapons and threats concealed under clothing. The aperture synthesis technique is introduced as this offers benefits of wide field-of-views and large depths-of-fields in a system that is potentially conformally deployable in the confined spaces of building entrances and at airport departure lounges. The technique offers a non-invasive, non-cooperative screening capability to scrutinize all human body surfaces for illegal items. However, for indoor operation, the realization of this capability is challenging due to the low radiation temperature contrasts in imagery. The contrast is quantified using a polarimetric radiometric layer model of the clothed human subject concealing threats. A radiation frequency of 20 GHz was chosen for the simulation as system component costs here are relatively low and the attainable half-wavelength spatial resolution of 7.5 mm is sufficient for screening. The contrasts against the human body of the threat materials of metal, zirconia ceramic, carbon fiber, nitrogen-based energetic materials, yellow beeswax, and water were calculated to be ≤7 K. Furthermore, the model indicates how some threats frequency modulate the radiation temperatures by ~ ±1 K. These results are confirmed by experiments using a radiometer measuring left-hand circularly polarized radiation. It is also shown using scene simulation how circularly polarized radiation has benefits for reducing false alarms and how threat objects appear in canyon regions of the body, such as between the legs and in the armpits.