Dear Subramanian,

First, I have to warn you that 1 kV is lethal if adequate mA are available and should avoid using it if you are unfamiliar, better to seek professional guidance.

Second, a Cockroft-Walton circuit does not provide any galvanic isolation and therefore you definitely must use an isolation transformer on the AC side. By using an isolation transformer you could ground either the positive terminal or the negative terminal of the output of the Cockroft-Walton circuit.

Third, I am not familiar with the current requirement of a PMT device but note that the output ripple voltage of a Cockroft-Walton is sensitive to the output current. If the PMT needs several mA of current, the Cockroft-Walton circuit might not be suitable. A better solution will be to use a step-up transformer to step the 110 V AC to 710 V AC and then use a bridge rectifier to get approximately 1000 V DC. This configuration allows for more output current with lower output ripple voltage. If you need a very stable output DC voltage neither of the aforementioned circuits is not a good choice. It would be better to buy a high voltage DC power supply (this offers current limit features to limit the output current to safe levels to avoid electrocution).

Note: If you choose to use the Cockroft-Walton with a transformer or the step-up transformer with the rectifier and the current of the PMT is lower than 30 mA, choose a transformer which has a core which saturates at around 30 mA in order to be more safe for you.

If you need further advice, please provide the power supply specifications of your PMT.

Hi,

Thanks for the note of caution about high voltage related risks. We shall remind ourselves to follow safe practices.

The PMT is Hamamatsu R980-19. The datasheet states average anode current is 0.1mA and supply voltage is 1250V. The model may have been discontinued. We will look for PMTs that meets the characteristics of the power supply we would have built.

I do recognize one could purchase a purpose-built power supply. In our case, it is to provide a learning opportunity for students to build circuits for their senior project.

I understand that the ripple voltage is inversely proportional to the capacitance and signal frequency. It is also proportional ~ to the square of number of stages and current.

Thank you very much for your time.