Limiting current draw from a power supply
The physics lab manager wanted to build a CO2 laser. In short, he succeeded; we tested it while wearing special protect-the-eyes goggles. The laser was powered by 2,000 volt 0.1 amp CONSTANT CURRENT supply. Cooling water flowed, removing about 95% of the energy.

He asked my advice for how to control the power(current), and I suggested TRIACS, with pulse transformers to turn on the TRIACS at appropriate timing (phases) of the incoming 60Hz power. Thus his control system, to "regulate" the current, had 120 samples per second "bandwidth".

The laser worked; producing about 10 watts in 1cm*2 beam. Would set the standard lab screen-wire-and-asbestos pads ON FIRE in about 5 seconds.

What size output capacitor was used? I do not recall. But using the maths

dV/dT = I/C, and rearranging to get C = I / (dV/dT) or C = I * dT /dV

we learn, for 10 volts ripple, 1/120 seconds, at 0.1 amp

C = 0.1 amp * 0.00833 seconds / 10 volts 

or

C = 80 microFarads, with 5,000 volt rating??