PEM Cells and Drierite

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Mark Rowley
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PEM Cells and Drierite

Post by Mark Rowley » Thu Mar 05, 2020 10:16 pm

Since the pinch tube is waiting on parts, I decided to begin a series of tests to see if using PEM cell deuterium is any better after being run through a drierite tube.

Over the past several years I’ve spoken to two camps of people...those who insist PEM cells provide a relatively dry product and those who say it’s wet. Since I’ve had decent success without drierite, I’m more of the camp that it’s moisture content would be negligible for Fusor use. Mainly due to the fact the drierite tube needs to be fully purged of regular air before any increase of deuterium purity can be seen. Using a 100ml syringe as a deuterium reservoir, thoroughly purging the drierite tube could use as much as 1/3 of its stored gas.

Today’s test went as follows...
I charged up the 100ml syringe, connected the drierite tube, followed by connecting the other end of the drierite tube to the needle valve on the Fusor. I pinched closed the connecting tube between the syringe and the drierite tube. The Fusor was already evacuated to below 1 mTorr so I slowly opened up the needle valve to evacuate regular air from the drierite tube. As expected the tube contained quite a bit of air and the drierite itself seemed to outgass for quite some time. I doubt there was any leak in the tube but I can’t say so with 100% certainty (The drierite tube was brand new from the factory). Once I got the vacuum down to a couple mTorr I began to let deuterium flow into the tube and Fusor chamber by removing the line pinch.

As expected, neutron production was only about 25% of what it normally was at the same operating conditions. The state of the plasma (visually and extinguishment pressures) were resembling what was found with air, but I was still getting a few neuts. Clearly the drierite tube was still packed with regular air so I decided to purge about 1/3 of my syringe into the system (33mL).

Wow! Did this make a difference! Everything stabilized and this is what I noticed:
1) neutron output was about 15-20% higher than it normally was with the same operating conditions.
2) the plasma was a much brighter pink color. Before it was somewhat purple-pink.
3) the plasma was much more stable and did not suffer the odd fluctuations that have been normally present.
4) the precipitator power supply had no difficulty maintaining input power past 50kV.
5) indium activation yielded a noticeably higher first minute count rate than previous activations. This coincides with the higher neutron count registered from the CHM11 neutron detector.

Thoughts....
Firstly, this is only one test which I’ve yet to repeat. The next time around could be totally different.

Flushing 33ml of hard earned D2 into the drierite tube for optimal performance is not a happy practice. But I guess in the long run it’s not all that bad. I suppose I could get a bigger reservoir or develop the Mylar storage idea.

The idea of putting the drierite tube on the PEM cell and then having that feed the reservoir seems problematic as one can’t thoroughly evacuate and flush the air out. The trickle feed of D2 from the cell will just mix with the air in the tube and provide a diminished percentage of deuterium purity.

So to reiterate the most important thing learned so far, heavily flushing the drierite with deuterium looks to be a prerequisite for effective operation.

Mark Rowley
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Re: PEM Cells and Drierite

Post by Richard Hull » Fri Mar 06, 2020 4:48 am

Nice report and good data for all who might choose to use the PEM cell for their Deuterium source. Too bad about the waste but at least it seems to be pure and dry.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Pablo Llaguno
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Re: PEM Cells and Drierite

Post by Pablo Llaguno » Fri Mar 06, 2020 11:29 pm

Maybe a system such as this one viewtopic.php?f=6&t=9435&hilit=generator will allow for better results?

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Mark Rowley
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Re: PEM Cells and Drierite

Post by Mark Rowley » Sat Mar 07, 2020 3:53 am

Not sure what you mean by working better. I think the plastic mounting hardware makes for a very smart and clean unitized design, but the product is the product. Being familiar with that thread I’m not sure where drying the product beyond utilizing drierite is shown.

To be very clear about something....raw PEM cell deuterium is extremely viable for Fusor use. One can easily make neutrons (and a lot of them at that) from the “wet” product. I have a pretty strong aversion to the word “wet” as I’ve never seen even the slightest hint of condensation along any of my routing tubes with either of the two cells I’ve been using. I will concede that some trace moisture is present. As a comparison, standard electrolysis totally wears the badge of providing a sloppy wet product, but not from a PEM system.

With that being said, my report was not meant to indicate there is any problem with PEM cell deuterium. I’m just saying drierite does seem to purify it to a greater degree.

Beyond drierite, I’ve been told a cold trap or similar design may help further the purity (similar to what Rich Feldman spoke about towards the end of the thread).

The goal is to remain in the DIY realm without breaking the bank. So far the PEM cell, drierite, tubing, syringe, and every ounce of heavy water I used since starting this project has cost less than $150. If a simple yet effective cold trap can be made from copper tubing and grocery store dry ice, then all the better. Could be a very fun sideline project!

Mark Rowley

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