Flow rate vs Neutron Production

[Bob Reite]

Now that I am getting respectable neutron numbers, I decided to try to plot flow rate vs neutron production while holding voltage, current and pressure constant. Actually I adjusted the pressure along with the power supply output to stay at 35 KV at 8 mA. The pressure was between 10 and 12 microns.

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Flow Rate in sccm  Isotopic Neutrons per second.
3.0 171,000
3.5 327,000
4.0 370,000
4.5 213,000
5.0 299,000

To see if I could do it again, I ran at 4.0 sccm a second time and got 412,000 neutrons per second.

My guess is, by flowing too fast, the dryer can't keep up with the flow, although in theory the PEM cells do not have water vapor in the gas output.

I'll have to repeat this experiment another time to see if the results are consistent. Has anyone else tried this experiment?

As a side note, once the lead shielding arrives so that I can operate above 35 KV safely, I'm going to try for the half mega-mark.

[Richard Hull]

You are in uncharted waters. No one has run a PEM cell or simple hydrolyzer with the measurment capabilities you have and reported such well defined data.

My guess is the cell can't keep up with the demand and or some water contamination is entering the system and the flow rate has the water vapor in it above a certain point.

I just wish you had an accurate pressure gauge your system as flow rates are not normally dealt with here. We have a much better feel for increasing pressures creating more and more fusion at specific voltages and currents.

Richard Hull

[Dennis P Brown]

Ideally, one would want the total system pressure to remain constant as flow rate is increased. Considering how little your pressure did change, it would appear your experiment did succeed in achieving that goal. It is rather telling that the current stayed/maintained constant with so small a pressure increase while the total flow rate increased so much - interesting.

[Bob Reite]

I have an exhaust valve controller which keeps the pressure constant. If I increase the flow rate the exhaust valve opens more to allow the vacuum system to pump out the "excess" gas. I found that with my system the maximum flow rate is limited by how fast the vacuum system can pump out the gas to maintain a given pressure, not how fast the electrolyzer can make deuterium. The "raw" uncorrected reading does not vary more than 20 percent, as long as the pressure and power supply drive are adjusted to give 35 KV at 8 mA. Lower pressures causes the voltage to rise and the current to drop while higher pressures do the opposite.

At the lower flow rates, I can start with just a full vial of gas and not even operate the electrolyzer until the run is complete to prepare for the next run. At the faster flow rates I do have to run the electrolyzer while the gas is flowing so that I don't run out. I set up the system so that I can vary the electrolyzer current so that the output can be adjusted to match the demand.

I am keeping my eyes open for a 0.1 Torr full scale capacitance manometer so I can accurately measure chamber pressure without having to know the exact composition of the gas.