Patent Number: 046577246
Section: claims

1. For use with a pulsed neutron generator in a logging tool lowered in a borehole, a pulsed high voltage source having an output terminal adapted to be connected to pulse neutron generator, the power supply comprising: (a) high voltage supply means;  (b) field effect transistor means comprising at least a pair of field effect transistors serially connected between said high voltage supply means and ground;  (c) an output terminal between the two transistors of said field effect transistor means, said output terminal adapted to be connected by a conductor to provide pulsed high voltage to a neutron generator;  (d) control pulse forming means connected to the gates of the respective two transistors, said pulse forming means forming control pulses selectively switching said transistors off and on in timed sequence to thereby connect the output terminal to said high voltage supply means, and  (e) diode means connected to said gates of said transistors to limit gate voltage for operation of said transistors. 2. The apparatus of claim 1 including a series cascade of FETs comprising said transistor means, said FETs having gate terminals connected to control voltage means. 3. The apparatus of claim 1 further including means controlling operation of said pair of transistors to prevent making said transistors simultaneously conductive. 4. The apparatus of claim 1 including a floating power supply connected on said high voltage supply means and floating thereon, and also connected to said control pulse forming means. 5. The apparatus of claim 1 wherein said control pulse forming means forms interlocked pulses of said two transistors. 6. The apparatus of claim 1 wherein said diode means are connected to the gates of serially connected FETs comprising said transistor means, and wherein said diode means is connected to clamp gate voltage. 7. The apparatus of claim 1 wherein said control pulse forming means forms two control pulses for said pair of transistors, and the pulses are timed in occurrance and overlap. 8. The apparatus of claim 7 wherein the pulses are formed by flip-flop means to sequence switching of said transistor pair. 9. The apparatus of claim 1 wherein said transistor means comprises said pair of FETs serially connected so that each of said FETs has a gate terminal adapted to be connected to said control pulse forming means to receive a control pulse at each of said gates for transistor switching. 10. The apparatus of claim 9 wherein said transistors are inverted compared to each other, and said gates are thereby enabled to be oppositely driven. 11. The apparatus of claim 10 including means within said control pulse forming means for forming a pulse of one polarity to turn one of said transistors on and wherein a pulse of the same polarity turns off the other of said transistors. 12. The apparatus of claim 11 including series connected third and fourth transistors each having gates, and bias circuit means connected to said gates to cause said third and fourth transistors to operate in response to operation of said first two transistors. 13. The apparatus of claim 1 including flip-flops in said control pulse forming means forming timed signals for operation of said two transistors.