Archived - A couple BTI bubble detector runs

[Daniel Firth]

I've made 2 good fusion runs with a BTI detector.

The first run was on 9/22/2012. My preferred way to use the BTI detector is to stop every 5 minutes and count again, this makes it easy to count new bubbles instead of trying to count all of them at once at the end of a run.

My fusor seems to be pretty stable. I hold the power supply in constant-current mode to avoid grid melting. I'm able to hold the voltage very close to -19,500VDC by actuating the throttle valve. Typically, I can keep it between -19.3 and -19.7kV.

The bubble detector is held by a test tube stand. Using trigonometry, I calculated the distance from the center of the bubble detector to the center of the grid: 9.91 cm.

The results from the 9/22/2012 run:
Voltage: -19.5kVDC
Current: 7.5mA
Vacuum: 94mT
D2 pressure: 30psi
Power: 146.25W
BTI calibration: 36 bubbles/mRem
Bubbles: 23 bubbles in 30 minutes
BF3 detector: 825 counts in 30 minutes (27.5 CPM)

Using Steve Sesselmann's calculator:
1.23 e4 neutrons/second
1.43 e-8 Watts
Q: 9.81 e-11

Only after the run did I notice that he considers counts under 25 bubbles to be statistically unreliable. If the fusor community isn't satisfied, then neither am I. So I did it again last night.

Same distance from the grid: 9.91cm

The results from the 10/26/2012 run:
Voltage: -19.5kVDC
Current: 7.5mA
Vacuum: 95 to 97mT
D2 pressure: 30psi
Power: 146.25W
BTI calibration: 36 bubbles/mRem
Bubbles: 34 bubbles in 40 minutes
BF3 detector: 921 counts in 40 minutes (23.025 CPM)

Using Steve Sesselmann's calculator:
1.36 e4 neutrons/second
1.59 e-8 Watts
Q: 1.09 e-10

Photos:
1: The whole setup.
2. Detail of the test tube holder & clamp holding bubble detector.
3. Bubbles being produced.
4. Detail shot of the detector from the 9/22/2012 run.
5. Detail shot of the detector from the 10/26/2012 run.

Previous posts with my fusor:
viewtopic.php?f=18&t=7902#p55861

[Steven Sesselmann]

Daniel,

Compliments on a nicely executed experiment.

Can you confirm that it is a chamber from Wiederlabs, and what the diameter of the chamber is?

Steven

[Daniel Firth]

Yes, it was built by Wieder Labs.

It's a 6" diameter sphere with 8" CF flanges.

Each half has a 2.75" CF port and 2 1.33" CF ports.

[Tyler Christensen]

Looks great, and certainly has fusion going on!

There is no reasonable doubt with 25 counts that fusion is occurring... that comment is discussing the accuracy of the actual count rate measured. When radiation counting, the counts recorded in some given time frame has an uncertainty of 100%/sqrt(counts), so if you got 25 counts in a time frame, you would actually have recorded 25 counts +- 5 counts within 68% confidence. Therefore, 25 counts is confident to 5 sigma to be actual radiation, which is a generally accepted point of scientific certainty when publishing results.

[Steven Sesselmann]

Daniel,

Since the recent upgrade of fusor.net, I have lost editing privileges of my Fusion Reactors by energy quotient.

Will need some help on this one...

Steven

[Doug Coulter]

Congrats on the nice clean setup and good runs! Those of us who have also done it know that it's not as simple as it might look....making it look easy is the mark of mastery.

[Richard Hull]

Looks good to me. Nice job. You are getting better at the work.

Richard Hull