Recovery of the faulted tube is expected to occur during the one crowbar cycle described (approximately 100 microseconds). In the event that it does not, the logic circuit will recycle the crowbar over several cycles. If, after several cycles, the fault continues to exist, the fuse in series with the shorted load will open, effectively removing the faulted tube from the supply. The remainder of the tubes will continue to operate. 5.6 POWER DISTRIBUTION SYSTEM In applications of crowbar type devices the major design criteria generally is the arc energy dissipated in the rf tube before the stored energy of the power supply is diverted by the crowbar unit. Typical values of energy allowed per arc varies from 4. 0 to 40 joules. A value of 4. 0 joules per arc will be used. In the proposed distribution layout the maximum length of a feeder from the crowbar unit to the tube is 77. 5 meters. Estimating capacity and inductance based upon Number 19 wire one meter from the ground plane gives a conductor inductance and capacitance of: The total energy stored is then given by: where Solving for n with an operating voltage of 20, 000 volts results in a maximum number of tubes per crowbar of 1126 tubes.
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