Toroid, conduction

Musow, W. Bolland, A. Toroidal Conductivity Sensor Technology Applied to Cvanidation of Flotation Tailings Circuits, Instrument Soc. of America 12 Annual Mining and Metallurgy Industries Symposium, Vancouver, 1984. 

Flow-through conductivity sensors suitable for insertion in pipelines (see Fig. 6.47a) are now available for use at temperatures up to 480 K. and pressures up to 1700 kN/m2(64). As conductivity is temperature sensitive, a thermistor is usually included in the detector circuit as part of a temperature compensator. Screw-in cells (Fig. 6.476) will withstand higher pressures. More recently, electrodeless methods of measuring conductivity have become available. In this case the solution is placed between two energised toroids. The output voltage of the instrument (from the output toroid circuit) is proportional to the conductivity of the solution provided that the input voltage remains constant. This type of conductivity meter can be used under much more severe conditions, e.g. with highly corrosive or dirty systems 43 . 

In the Tokamak fusion reactor depicted in Fig. 21.9, electric current to the poloidal coils on the primary magnetic transformer generates the axial current in the secondary plasma composed of deuterium and tritium ions. These ions are heated to ignition temperature and then the reaction becomes self-sustaining. The toroidal field coil suspends the plasma away from the metal conducting walls. Contact with the wall would both cool the plasma below ignition temperature and contaminate the plasma with heavy ions. The relevant reactions are given below. 

Correct settings of gas flows will form a toroidal or an annual plasma aided with a 40 MHz radio frequency coil which allows reproducible introduction of mist or aerosols. The power in the plasma is dissipated in the outer layers whose electrical conductivity is unaltered by the presence of sample atoms and ions in the tunnel and is independent of the nature and concentration of the sample. This parameter makes the toroidal plasma... 

T. Smith, G. E. Schneider, and M. M. Yovanovich, Numerical Study of Conduction Heat Transfer from Toroidal Surfaces Into an Infinite Domain, AIAA-92-2941, AIAA 27th Thermophysics Conference, Nashville, TN, 1992. 

The electrons emitted by the photocathode are subsequently accelerated to 50 kV and focused on to a toroid-shaped anode. The anode is made of oxygen-free, high conductivity copper and is maintained at a high positive potential. The electron pulses interact with the copper anode forcing the emission of Cu-Ka x-ray photon pulses, which exit the vacuum chamber through a thin beryllium-foil window. A bend germanium crystal monochromator disperses and focuses the x-rays onto the sample. The duration of the x-ray pulses is measured by a Kentech x-ray streak camera fitted with a low density Csl photocathode. The pulse width of the x-rays at 50 kV anode-cathode potential difference is about 50 ps. This value is an upper limit for the width of the x-ray pulses because the transit time-spread of the streak camera has to be taken into consideration. A gold photocathode (100 A Au on 1000 A peiylene) is used to record the 266-nm excitation laser pulses. The intensity of the x-rays is 6.2 x 10 photons an r (per pulse), and is measured by means of a silicon diode array x-ray detector which has a known quantum efficiency of 0.79 for 8 kV photons. 

In some present-day reactor concepts, whose toroidal magnets are assembled from very few widely spaced coils (8 to 12) to facilitate blanket maintainance, the field ripple at the plasma surface is no longer smoothed by appropriate (costly) enlargement of the coil bore, but by normal conducting compensating coils near the plasma in the gaps between the toroidal coils. 

The Spheromak reactor22 based on ideal and resistive MHD stability of a CT having an internal toroidal field. Stability considerations indicate that the overall shape must be sufficiently oblate and with a surrounding conducting shell, and that the overall configuration must be nearly force-free. The calculated maximum local 0 limit is 2-4% using the... 

It is instructive to study the behavior of the passive current induced on the conducting vacuum vessel by plasma movement. Figures 11 and 12 show that the tilting modes are stabilized by a conductor parallel to the axis of toroidal symmetry and the sliding modes are stabilized by a horizontal plate. 

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