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Latest Fusion Run / BTI Bubble Results

Posted: Thu Nov 07, 2019 4:15 am
by Mark Rowley
Took delivery on the bubble neutron detector today. They are of the 22 bubs per mRem version.

I conducted two 3 ninute runs at approx 2mA/33kV.

Detector distance from center of grid: ~18cm

1) 14 bubbles / 29mTorr deuterium
2) 10 bubbles / 30-37mTorr deuterium (voltage fluctuation)

The second run suffered some unexpected deuterium pressure issues. I still need to add another needle valve before the ss-ss4.

This test also roughly confirmed the accuracy of my CHM11 detector tube. I’ll be focusing on its calibration over the next few days.

Mark Rowley

Re: Latest Fusion Run / BTI Bubble Results

Posted: Thu Nov 07, 2019 5:09 am
by Richard Hull
Nice work! This is a real opportunity, as you recognize. Calibration of working electronic neutron detection gear is a must for any future efforts, long after the BTI is dead. The key is to never move the detection tube and its moderator, if possible, from this point on and make no changes in voltage to the detector or any windowing of the signal to retain calibration at least to the level of the original BTI results. I did about 30 10 minute runs over 3 weeks and reduced the results to obtain a simple constant multiplier factor against a chosen 1 minute future electronic run to multiply the digital rate meter timed result to get my isotropic emission. rate/sec.

Richard Hull

Re: Latest Fusion Run / BTI Bubble Results

Posted: Thu Nov 07, 2019 8:47 pm
by Bob Reite
We are fairly certain that our fusors are isotropic sources. Therefore if it does become necessary to move the detector, one can use the inverse square law to calculate what to expect at the new distance. But it is important not to change the voltage to the detector or any other calibration involving the electronics associated with the BF or He3 tube. The moderator for the detector also needs to remain the same.

Re: Latest Fusion Run / BTI Bubble Results

Posted: Mon Nov 11, 2019 9:02 am
by Mark Rowley
Thursday’s run was better. Increased gas flow a few percent but kept pressure essentially the same (28-29mTorr). 2.2mA/33kV / 18cm distance.

24 bubbles in 3 minutes

Mark Rowley.

Re: Latest Fusion Run / BTI Bubble Results

Posted: Mon Nov 11, 2019 2:55 pm
by Richard Hull
I think we posted way back that allowing a bit more gas flow helped the numbers a good deal. The sad part is for the increased pressure, you are blowing through the D2 at an increased rate, but in a smaller volume than the classic sphere. It might just equal out in the end. The lower current is what amazes me. I am glad you are learning the "operational ropes". I have always said this is the key to getting better numbers.

Richard Hull