PPPL-3367 is available in <a href="PPPL-3367.pdf">pdf</a> or 
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<b>An Inexpensive Ohmic Transformer Firing Circuit for the CDX-U Spherical Torus</b>

<p>T. Munsat and R. Majeski</p>

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<b>Date of PPPL Report:</b> October 14, 1999</p>

<b>Submitted To: </b> Review of Scientific Instruments</p>

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We have designed and modeled a simple, efficient circuit for delivering power to the
CDX-U ohmic transformer solenoid. Inexpensive electrolytic capacitors are used to provide the
bulk of the stored energy. One small high-voltage oil-filled capacitor bank is used in the
ignitron-based circuit. Several design objectives are met, including the production of a solenoid current waveform well suited to the breakdown and ohmic current-drive of a tokamak plasma, making efficient use of the available loop volt-seconds. The electrolytic capacitors are protected from reverse-bias conditions, and the ohmic solenoid is protected from voltages above 1 kV, well within the voltage rating, under normal operation and any forseeable fault conditions.

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