On a CO2 laser power supply, does a stable KV output make a difference?

[GregR]

How does a variation in KV output voltage affect CO2 laser performance over a range of power settings?


After purchasing a 40KV DC high voltage probe, I setup a to test the Chinese power supply for the full range of 10 to 100% and see the KV output (safety is important on this one). Using the 60 watt power supply and a manual current switch, I adjusted the power levels between 10 and 100% and took measurements. Between 20 and 40% current levels, the KV output varied significantly.

Current Setting KV (1st reading) KV (2nd reading)



I ran the test later, on a second 60 watt high voltage CO2 laser power supply and got similar results (same manufacturer, consistent results).

Then, I ran the same test on the 150 watt CO2 laser power supply. Well, the probe began arcing internally at 28 KV DC (rated 40 KV DC). Luckily, the supplier was kind enough to fix it and confessed that the probes are designed for TV tubes and that the rating may be a bit inflated.

Previously, I had measured the current and it is stable, with a range from 5 mA to 30 mA on all the power supplies.

What about the strike voltage? I read that the power supply is supposed to spike before settling at a lower average KV output voltage. The purpose of the spike is to get the laser to fire. My Fluke multimeter never showed a spike. Is it necessary? How much time is required for the spike to do the job?

Any advice or opinions are greatly appreciated.

[mixedgas]

You will not see the 10s of microsecond start pulse on a DMM. In fact most HV probe/oscilloscope combinations will miss it, they have too much capacitance.

Steve