A fast feedback controlled magnetic drive for the ASDEX Upgrade fast-ion loss detectors.

A magnetically driven fast-ion loss detector system for the ASDEX Upgrade tokamak has been designed and will be presented here. The device is feedback controlled to adapt the detector head position to the heat load and physics requirements. Dynamic simulations have been performed taking into account effects such as friction, coil self-induction, and eddy currents. A real time positioning control algorithm to maximize the detector operational window has been developed. This algorithm considers dynamical behavior and mechanical resistance as well as measured and predicted thermal loads. The mechanical design and real time predictive algorithm presented here may be used for other reciprocating systems.

Conceptual design of the ITER fast-ion loss detector.

A conceptual design of a reciprocating fast-ion loss detector for ITER has been developed and is presented here. Fast-ion orbit simulations in a 3D magnetic equilibrium and up-to-date first wall have been carried out to revise the measurement requirements for the lost alpha monitor in ITER. In agreement with recent observations, the simulations presented here suggest that a pitch-angle resolution of ∼5° might be necessary to identify the loss mechanisms. Synthetic measurements including realistic lost alpha-particle as well as neutron and gamma fluxes predict scintillator signal-to-noise levels measurable with standard light acquisition systems with the detector aperture at ∼11 cm outside of the diagnostic first wall. At measurement position, heat load on detector head is comparable to that in present devices.

ST elevation in ECG lead aVR signals severe acute left main coronary artery disease.

Patients with suspected acute coronary syndrome are commonly assessed by acute physicians on arrival in hospital. Although most will recognise the typical ECG features of ST elevation myocardial infarction, the significance of ST elevation in lead aVR may not always be appreciated. This case series describes 6 cases in which this ECG abnormality was the predominant feature in patients whose subsequent angiogram revealed severe acute left main coronary artery disease. The importance of early referral of such patients to a centre in which percutaneous coronary intervention can be performed, is discussed.

Tungsten injector for scrape-off layer impurity transport experiments in the Tore Supra tokamak.

This paper describes the design and operation of a new tungsten (W) injection system for impurity transport experiments in the Tore Supra tokamak. The system is mounted on a reciprocating manipulator and injects a controlled amount of gaseous tungsten hexacarbonyl, W(CO)6 at arbitrary depth in the scrape-off layer, using an inertially activated valve. Injected W(CO)6 is dissociated in the plasma, forming a radially localized plume of W atoms. The injector does not require an external gas feed and can perform a large number of injections from an on-board reservoir of W(CO)6. Some examples of W injections in Tore Supra are included, demonstrating successful operation and discussing some technical issues of the injector prototype.

A magnetically driven reciprocating probe for tokamak scrape-off layer measurements.

A new in situ reciprocating probe system has been developed to provide scrape-off layer measurements in the Tore Supra tokamak. The probe motion is provided by the rotation of an energized coil in the tokamak magnetic field. Simple analytic approximations to the exact numerical model were used to identify the important parameters that govern the dynamics of the system, and optimize the coil geometry, the electrical circuit, and the stiffness of the retaining spring. The linear speed of the probe is directly proportional to the current induced by the coil's rotation; its integral gives the coil position, providing a means to implement real-time feedback control of the probe motion. Two probes were recently mounted on a movable outboard antenna protection limiter in Tore Supra and provided automatic measurements during the 2011 experimental campaign.

On the reliability of scrape-off layer ion temperature measurements by retarding field analyzers.

The retarding field analyzer (RFA) is one of the only widely accepted diagnostics for measurements of ion temperature Ti in the tokamak scrape-off layer. In this paper we analyze some instrumental effects of the RFA and their influence on Ti measurements. It is shown that selective ion transmission through the RFA slit is responsible for an overestimation of Ti by less than 14%, even for a relatively thick slit plate. Therefore, thicker slit plates are preferable, since they reduce, e.g., the risk of melting during off-normal events, and the effect of positive space charge inside the cavity. The influence of the electron repelling grid, as well as misalignment of the slit with respect to the magnetic field on Ti measurements are negligible.