Archived - First Fusion for Bob Reite

Current images of fusor efforts, components, etc. Try to continuously update from your name, a current photo using edit function. Title post with your name once only. Change image and text as needed. See first posting for details.
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Bob Reite
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Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Archived - First Fusion for Bob Reite

Post by Bob Reite » Mon Sep 15, 2014 1:28 am

On Friday, 12 September 2014 I operated my device with deuterium for the first time. The numbers were not very impressive, probably because the chamber had not been totally baked out after a grid change. Yes, I trashed my first grid trying to see how far I could "push it" after adding a second amplifier to get more input current. The ion gauge also quit working (stuck on "splash screen") after the grid failure, but I knew that the chamber was able to do 1.0 -e5 Torr and the convection gauge could measure the range of interest, so I decided to go ahead and attempt fusion. Observant people will note that the new grid is smaller (1.25 inches) than the two inch grid shown in my first plasma photo. I did two more runs on Saturday 13 September. Results follow the photos.
fusor.jpg
I am standing near the operating position, out of the direct path of the viewport. Normally I'm standing more in front of the function generator (to the right of me in the photo) looking at the image in the mirror as I adjust the output of the function generator. The function generator drives a pair of 400 watt audio amplifiers (on the floor to the right of the grey rack) of my own design hooked in parallel. I used the amps because I had them "in stock". Atop the amplifiers are power pots set to 2 ohms to encourage load sharing and limit the current in case of an arc over. The ferrite transformer inside the grey rack works best at 20 KHz to 30 KHz, depending on the load. The ferrite transformer drives an eight stage CW multiplier. The internals of the grey cabinet are archived at viewtopic.php?f=18&t=9596. This power supply is capable of 50 KV at 15 mA. After my grid failure, I have decided to limit the grid dissipation to 400 watts in future runs. The digital volt meter and current meter are at the bottom of the grey rack.

Vacuum System: Easiest to start with the chamber, the most obvious item and work from there. To the left is the viewport and a mirror for safely observing the grid. The ion gauge is mounted in front. To the right is the exhaust valve controller. Behind the exhaust valve controller is the exhaust valve itself, not quite visible. The convection gauge is the black object that is visible. The turbo pump and roughing pump are in the "packaged unit" from Pfeiffer Vacuum.

Gas System: Contained in the black chassis. Electrolysis of deuterium oxide is done in a PEM cell. The box contains a 1.5-3 volt regulated supply, with a 0-3 A meter to monitor the electrolyzer current. Over/Under pressure protection is done with the two vials filled about halfway full of pump oil. A long tube filled with silica gel completes the gas generation system. This implementation is based on Tucker Sandbakken's system described at viewtopic.php?f=6&t=9435 Perhaps unique to my system is the use of a mass flow controller to adjust the rate at which deuterium is admitted to the chamber. The controller is adjustable from 0-10 sccm, although in practice, flow rates below 0.5 sccm are hard to obtain. So far I have operated from 1.5 - 2.5 sccm.

Neutron Detection: The simplest part of the whole setup. A 33 b/mRem BTI bubble detector atop a cardboard box between the view port and ion gauge. The center of the bubble detector is 13.8 cm from the center of the grid.
d2glow1.jpg
Image of the grid with a deuterium glow. Notice that is is deep blue, as contrasted with the purple glow of air. This image is obtained by shutting off the HV till the grid cools off, then turning the HV back on and snapping the photo before the grid has time to heat up.
d2glow2.jpg
Image of the grid during nominal operation. The incandescence of the grid dominates the image.
bubbles1.jpg
Close up of the bubble detector after the first run, in place on the fusor.
bubbles2.jpg
Close up of the bubble detector under more favorable lighting.

During each run I attempted to keep the voltage at 35 KV and current at 10 mA by adjusting flow rate and pressure, as well as the HV supply. I did not bring the bubble detector into play until the system was reasonably stable. This often would use half a vial of gas, leaving only the other half for the actual fusion run, but at the lower flow rate, the half vial would last about 20 minutes. I used the handy on line calculator at http://www.gammaspectacular.com/fusion_calculator.html to calculate the isotropic neutron flux.

Data for each run:
First:

Code: Select all

Eg 35 KV
Ig  10 mA
Pressure 6 microns
Flow Rate 1.7 sccm
7 bubbles over 18 minutes.
calculated isotropic neutron flux 13,200 n/s
After this rather unimpressive run, I let the vacuum system run over night.

Second:

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Eg 35-40 KV
Ig  8-12 mA
Pressure 6 microns
Flow Rate 1.5 - 2.0 sccm
4 bubbles over 10 minutes.
calculated isotropic neutron flux 13,500 n/s
The second run on Saturday was about the same, but the third one was much better.

Third:

Code: Select all

Eg 35-45 KV
Ig  5-10 mA
Pressure 5-7 microns
Flow Rate 2.0-2.5 sccm
12 bubbles over 8 minutes.
calculated isotropic neutron flux 50,800 n/s
The mass flow controller started "hunting" during the third run. The exhaust valve controller tried to follow what the mass flow controller was doing. I discovered that I had allowed the deuterium vial to be become exhausted while I was checking outside the building for X-rays, and some of the oil had advanced into the dryer. The unstable flow of gas through the oil in the dryer was probably causing the servo to hunt. I have 8 extra dryer tubes and enough silica gel to change it all out before the next attempt.

Please note that the pressures listed are uncorrected for the use of deuterium. The manual for my convection gauge did not come with the correction factor for deuterium. I found a correction factor of 0.57 on the 'net' somewhere, but the results did not pass the sanity check. When I get the ion gauge electronics back from the factory warranty repair, I will use the ion gauge (which can be set to read deuterium) to calibrate the convection gauge for deuterium. While I'm waiting for the ion gauge to come back, I will install a video camera and shielding around the view port as the X-ray back scatter while operating at higher voltages is a concern.

I will understand if you wish to wait for more runs with correct pressure readings for deuterium before being added to the neutron club.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Richard Hull
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Re: First Fusion for Bob Reite

Post by Richard Hull » Mon Sep 15, 2014 5:17 am

Bob welcome to the neutron club. I have logged you in there. Your runs will get better with experience in operation of the system. You will get a "feel" for it.

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.

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Rich Feldman
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Re: First Fusion for Bob Reite

Post by Rich Feldman » Tue Sep 16, 2014 11:12 pm

Congratulations, Bob,
and thanks for the wealth of detail along the way.
A practical example of ad-hoc system design by someone who has learned the necessary disciplines.

Your 50+ kV power supply without an oil tank is great.
Have you mentioned whether you are driving the ferrite transformer with square waves or sines?
I would personally enjoy seeing the basic design parameters: turns, core area, etc.

-Rich Feldman
Mike echo oscar whisky! I repeat! Mike echo oscar whisky, how do you copy? Over.

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Bob Reite
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Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Re: First Fusion for Bob Reite

Post by Bob Reite » Wed Sep 17, 2014 6:01 am

I'm driving it with a sine wave. I could probably get more efficiency out of the driver section with square waves, but it's nice not having all the harmonics of square waves floating around. If I ever sell the audio amps, I'll build a switch mode supply with a 555 timer, some IGBT driver chips and an IGBT bridge, similar to what others have done. I'll post a more detailed description of the transformer in the high voltage section of the forum.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

User avatar
Bob Reite
Posts: 348
Joined: Mon Aug 26, 2013 1:03 am
Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Re: First Fusion for Bob Reite

Post by Bob Reite » Sat Oct 04, 2014 4:18 am

I got my ion gauge back from the factory. They had no idea why U5 failed on the display board, but covered it under warranty. So I calibrated my convection gauge against the ion gauge while running deuterium. Since the ion gauge seems to be real fragile electrically, after calibrating the convection gauge I removed the electronics module from the sensor and put it away in an anti-static bag.

Here is my latest run.

Code: Select all

Eg 35 KV
Ig  10 mA
Pressure 12 microns
Flow Rate 3.0 sccm
14 bubbles over 9 minutes.
calculated isotropic neutron flux 52,600 n/s
I plan to do a series of runs trying to hold voltage and current constant while varying the flow rate. It seems that from my results so far that the best results are had by flowing as much gas as you can without the pressure going too high. In my setup using electrolysis of deuterium oxide, the silica gel dryer may not be able to keep up with a fast flow rate, we'll see if there is a peak or if "faster is always better".
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Dennis P Brown
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Re: First Fusion for Bob Reite

Post by Dennis P Brown » Sun Oct 05, 2014 12:21 pm

Very impressive work! Congratulations on successful neutron production!

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Bob Reite
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Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Re: First Fusion for Bob Reite

Post by Bob Reite » Mon Oct 06, 2014 1:20 am

Last night I found and fixed a leak between the dryer and mass flow controller. It was bad enough to adversely affect the purity of the deuterium entering the chamber. The best run after the repair gave me 34 bubbles in 5 minutes.
34bbls.jpg
I will have to recalibrate the convection gauge again, as the last cal I did was with impure gas, so in the data below, pressure is listed as "unknown".

Code: Select all

Eg 35 KV
Ig  10 mA
Pressure unknown
Flow Rate 3.0 sccm
34 bubbles over 5 minutes.
calculated isotropic neutron flux 230,000 n/s
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Richard Hull
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Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: First Fusion for Bob Reite

Post by Richard Hull » Mon Oct 06, 2014 4:29 pm

Fabulous work Bob! .....I told you you would get better and better at it as you gained operational experience and cleaned out some minor bugs.

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.

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Bob Reite
Posts: 348
Joined: Mon Aug 26, 2013 1:03 am
Real name: Bob Reite
Location: Wilkes Barre/Scranton area

I broke the 1/2 meg barrier!

Post by Bob Reite » Sun Oct 12, 2014 11:39 pm

The sheet of lead has arrived and it has been installed. I can now go to 50 KV without any detectable X-rays where people will be. That required moving the location of the bubble detector to a position 20 centimeters away from the grid center, but that's OK, since I'm getting enough neutrons to register at that distance. I also made a little stand for the bubble detector with my 3D printer. The exact position is marked on top of the cabinet so that measurements will be repeatable.
leadshield.jpg
I also came up with a procedure for measuring the operating pressure. At the End of a run, after I shut off the HV, I plug in the ion gauge electronics module and measure, after verifying that the reading from the convection gauge did not change after turning off the HV.

So equipped, I upped the voltage to 40 KV and here are the results

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Eg 40 KV
Ig 7 mA
Pressure 12.5 microns
Flow rate 4.0 sccm
40 bubbles over 5 mins at 20 cm distance
calculated isotropic neutron flux 569,000 n/s
halfmegmark.jpg
The next experiment is to run the fusor two more times at the above voltage, current, flow rate and pressure and see how repeatable the results are.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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Bob Reite
Posts: 348
Joined: Mon Aug 26, 2013 1:03 am
Real name: Bob Reite
Location: Wilkes Barre/Scranton area

More runs at 40KV

Post by Bob Reite » Wed Oct 22, 2014 8:05 am

As long as the system is properly purged, after "walking it in" from standby I am now getting fairly consistent results. Here are my 1/2 meg plus results for today. Between each measurement, I kept the fusor "idling" at 35 KV and 3.0 sccm gas flow for 30 minutes while waiting for the bubble detector to reset.

Run #1

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Eg 40 KV
Ig 7 mA
Pressure 13.4 microns
Flow rate 3.7 sccm
36 bubbles over 5 mins at 20 cm distance
calculated isotropic neutron emission 517,000 n/s
Run #2

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Eg 40 KV
Ig 7 mA
Pressure 13.1 microns
Flow rate 3.8 sccm
37 bubbles over 5 mins at 20 cm distance
calculated isotropic neutron emission 526,000 n/s
Run #3

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Eg 40 KV
Ig 7 mA
Pressure 13.1 microns
Flow rate 5.0 sccm
42 bubbles over 5 mins at 20 cm distance
calculated isotropic neutron emission 577,000 n/s
That's about a 10% difference from best to worst of the three.
Last edited by Bob Reite on Thu Oct 23, 2014 12:11 am, edited 1 time in total.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.

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