Demonstration of Safe Termination of Megaampere Relativistic Electron Beams in Tokamaks.

For the first time it is experimentally demonstrated on the JET tokamak that a combination of a low impurity concentration bulk plasma and large magnetohydrodynamic instabilities is able to suppress relativistic electron beams without measurable heat loads onto the plasma facing components. Magnetohydrodynamic simulations of the instability and modeling of the postinstability plasma confirm the prompt loss of runaways and the absence of regeneration during the final current collapse. These surprising findings motivate a new approach to dissipate runaway electrons generated during tokamak plasma disruptions.

Pressure regulating ear plug testing in a pressure chamber.

INTRODUCTION: Middle ear barotrauma is a condition frequently associated with flying. It is usually caused by Eustachian tube (ET) dysfunction. Pressure-regulating earplugs (PREP) should improve complaints due to pressure equalization problems. METHODS: There were 21 patients with a history of pressure equalization problems while flying who were examined. ET function was measured with exploratory tests and in a pressure chamber. In a double-blind study, PREP were examined using continuous impedance measurement in the pressure chamber. Eardrum deflection and pressure-equalizing maneuvers were also examined. During pressure exposure the subjective state of patients with and without PREP was compared. RESULTS: Evidence of ET dysfunction was found in twice as many patients with the impedance method in a pressure chamber compared to tympanometry or the Valsalva test. Use of PREP reduced the rate of pressure changes in the external auditory canal. Maximum pressure was reached with a delay of about 7 min. The number of pressure-equalizing maneuvers did not differ significantly. Using PREP the patients reported a significantly better subjective state on the VAS scale of 2.19 +/- 1.50 compared to 3.38 +/- 2.33 without PREP. CONCLUSIONS: Continuous impedance measurements in the pressure chamber identified ET dysfunction more often than the exploratory ET function tests commonly used in routine diagnostics. This novel finding requires further validation. Although use of PREP showed no signs of improving ET function, it did significantly improve individual subjective state during sudden pressure changes.