FAQ - Bubble Fast Neutron Detector

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Richard Hull
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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull » Thu Nov 18, 2004 9:57 pm

It's all a big secret and they aren't tellin'. Feel free to muddle along trying to "guess engineer" or "roll your own". All that remains is consistency and calibration. I figure the latter are fully 50% of the effort.

For a fact, they mass irradiate and "bin" each detector based on bubble numbers so it ain't even slighly precise at the manufacturing end. What you get is a carefully cal'd luck of the draw, pick o' the litter, bubble detector that is repeatable and reliable.

If you have a hot neutron source, (they used a chalk river reactor), the chemical know-how and access to ultra pure chemicals you should be able to make up a hundred of so and then irradiate them and "bin" them based on performance just as they do.
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Fusion is the energy of the future....and it always will be
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Re: FAQ - Bubble Fast Neutron Detector

Post by Jon Rosenstiel » Fri Dec 10, 2004 5:07 pm

Just got off the phone with these guys...placed an order for the BD100R, 33bubbles/mrem model. Should arrive here before xmas. (Maybe it'll be under the tree)?

Jon Rosenstiel

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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull » Fri Dec 10, 2004 10:06 pm

John,

Fantastic! You must report to us all the details once you put it to use. You WILL love it and hate it.

You will love it because it doesn't lie. You will hate it because it doesn't lie.

I found that after spending a mint and jumping through numerous hoops to obtain the finest electronic neutron detection system around for fusor IV , (He3 system), that the bubble device was much more reliable if not quite as sensitive. It is a snap and a no brainer to use.

My plus ultra He3 system is just clicking away like gang busters and with each upward inching of the voltage control the count is noticibly more active. At 29kv I am getting nearly 200-300 CPM with the He3 but the bubble detector is showing about 50-80,000n/sec., isotropic!

Damn it all! The truth will out.

Some tips when St. Nick drop the thing down the chimney.

Operate and store it within the temp range specified. keep it out of the fusor area until your fusor is cruisin' along at the point that you can satbilize it easily for a minimum of five minutes. Don't try for max output on you machine. Shoot for stability, though this is not actually madatory as the thing is a perfect fast neutron integrator. With stability, your actual final figure will be more representative of the entire run.

Once in your comfort zone with the fusor. Get a ring stand as used in chem labs with a test tube clamp and place the base of the BTS detector at least 4" away from the shell (to avoid radiant heating of the detector) and then open the pressure screw until the screw goes sloppy. (it will be retained).

Start a timer immediately and then run for a period that you like. Watch the bubbles pop into existance. Cool!

DO NOT LOAD THE THING UP WITH BUBBLES. End the count when the device appears to have about 30-40 bubbles in it. Note the time and total exposure period. immediately take it out of the fusor area.

Counting - the nightmare begins.

Surely you can count 30-50 bubbles??? Yes and No. You can count 5 times and get 5 different counts.........!! BTS recommends you have a buddy or others count and do a statistical reduction.

I have found that carefully and slowly rotating the device and counting as in a spiral staircase works for me. Log your result with pencil and paper and then screw the screw all the way back it to just good and snug. BOOM, the bubbles are gone. As age sets in, they will not flashout like when new and a few minutes will be needed to ready the device.

Enjoy! And remember us out here. Give a full report, especially personal comments, problems, delights and thoughts on the device.

Unfortunately, the device is so good that your rem ball might fall into disuse or be religated to backup or confirming actions.

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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Re: FAQ - Bubble Fast Neutron Detector

Post by Alex Aitken » Fri Dec 10, 2004 10:23 pm

This is probably making a very simple detector over technical but....

Ive heard of laser counters for the bubbles and they seem like rather technical devices. If a light was shined through the tube while in operation though, with the result being read by a photo cell wouldnt the apearence of each bubble result in a noticable change of level of the light output? If something monitored the apearence of each bubble that sounds easier than trying to count them all afterwards and you do have the physical evidence of neutrons to check after the experiment.

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Re: FAQ - Bubble Fast Neutron Detector

Post by Jon Rosenstiel » Sat Dec 18, 2004 8:03 pm

Received an early Christmas present today, via FedEx. The BD-100R arrived packed in an oversized box containing bubble wrap (appropriate) and Styrofoam peanuts. Eight days from order placement to holding the detector in my hot little hands. Not so bad, I’d say.

The double ouch was the import/shipping cost, $100.00!

Evidently, one must ask for the temperature response curve when ordering, as none came with it. I’ll have to fire off an e-mail next week requesting the curve.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
UPDATED 12/18/04.....
After posting this (late Friday evening) I sent an email to BTI. The temp response curve was in my inbox this morning (Saturday), with apology.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

With any luck I’ll be able to give it a test run this weekend. I’ll post my findings here.

Based on Richard Hull’s experience with his bubble detector, I expect that my neutron numbers will be nowhere near as high as my Ludlum (just recently re-calibrated) rem ball says they are. I’m preparing myself for a 65% drop in total isotropic emission rate. I’m afraid the truth is gonna’ hurt!

Stay tuned….
Jon Rosenstiel

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Re: FAQ - Bubble Fast Neutron Detector

Post by Jon Rosenstiel » Mon Dec 20, 2004 6:31 am

I finally got some time this afternoon to try out my new bubble detector. This thing is SWEET! Watching the bubbles “pop” into existence is pretty cool. (Better than a lava lamp)! I got a few runs under my belt, but I still need time to sort out the best way count the bubbles. So far, the best method for me is to shine an LED flashlight into the end of the detector, then count the bubbles as I rotate the detector back and forth slightly. (To make sure I haven’t missed any hidden bubbles).

BTI recommends using a video camera with macro lens, then marking the location of the bubbles on the monitor face. (Similar to cell counting)

After Santa delivers the new high-zoot digital camera I asked him for I think I’ll try taking a photo of the detector and see if I can count the bubbles on my computer monitor.

For this afternoon's tests I used a temperature correction factor of 1.4, as my lab was a balmy 27C.

I’m not going to post any data until I become a little more familiar with this device and am more confident and consistent in my bubble counting ability.

FWIW: Roughly speaking, my Ludlum rem ball detector is giving a TIER (Total Isotropic Emission Rate) approximately 40% higher than the bubble detector gives. Not nearly as bad as the 65% I was expecting.

Jon Rosenstiel

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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull » Mon Dec 20, 2004 3:08 pm

Jon, you are experiencing about what I did. I was getting about 50,000- 70,000 isotropic with the BTI bubble device and was used to seeing about 125,000 using the normal BF3 route with my Eberline PNC-1. It is nice to know that we are in the same ball park.

According to the folks at BTI, the accuracy can be in the 5% region. Therefore, I think we need to look at wrong assumptions in the input part of our old neutron counting. The only thing I can think of is the efficiency of the BF3 is a bit higher than .5% and I think the 1% figure is also a bit low.

It all comes back to just how efficient the moderator is. A BF3 tube or He3 tube at a decent pressure could easily be 10%-25% efficient if you could warrant that every neutron entering it were truly at thermal energies. With the rem ball, this is sort of warranted to be the case.

Thus, the rem ball is averaging out dose much like the BTI. So if a rem ball is showing 10mr/hr, the center of the ball is saying that the entire ball is being bathed in a flux of 80n/s/sqcm. If the ball is 30 cm from the fusor then 11,309 X 80 or ~900,000 neutrons/sec is the isotropic emission rate. The tube efficiency is not a factor due to the mated meter ball combo, being calibrated. (the 30cm is center of fusor to center of rem ball). Given this set of circumstances, the BTI detector could supply a correction factor, (scientific term) or a "fudge factor", (real life term), if placed at the same range.

With the BTI, we should be able to establish a calibration factor for any BF3 or He3 system. Once we get the counters in agreement with the bubble detector by using this factor, we will not be so pressed to buy another bubble device when this one blinks out in a couple of years as our electronic numbers will then be good and reliable. This factor would be "counter specific" and would make weak tubes, funky electronics, variable moderation efficiency, oddball and varying geometries and other such variables found counter-to-counter a non-issue.

The BTI bubble device is just too cool as it is free of all the above CRAP!

Again, absolute counting is a bear. Certainly, I would carry a bubble detector to a friends house to check his neutron numbers long before I would ever grab an electronic counter.

I look forward to your future report. Please put it in its own separte posting with an easy search title like "bubble detector results" or something like that. Post a pix or two of the setup.

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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Re: FAQ - Bubble Fast Neutron Detector

Post by Jon Rosenstiel » Tue Dec 21, 2004 5:48 am

Richard, got a question on counting the bubbles.

I've noticed that some of the neutron produced bubbles are quite small, but they do seem to be real neutron bubbles because they disappear when the compression screw is cranked down.

Seems to me that ALL bubbles should be counted if they are produced by neutrons, no matter how small. What are your thoughts on this?

About the high readings the rem ball is giving….. I recall reading somewhere, not sure if it was the Songs list, or Intranets.com, or this list, but it was mentioned that the various manufacturers of our rem ball devices tend to shove them out the door with a fairly conservative calibration. (They want to play it plenty safe, don’t want anyone “overdosing” on their watch).

I wouldn’t think that what we’re seeing can be totally attributed to the manufacturers “playing it safe”, but it may be at least a part of it.


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Re: FAQ - Bubble Fast Neutron Detector

Post by Richard Hull » Tue Dec 21, 2004 4:40 pm

Jon,

Count all bubbles just don't count "Fizz" bubbles which are truly very small. The small bubbles might be one third the size of the largest bubbles. Take another good look at the photos in the original post above. You will see some small bubbles there too. Basically, any bubbles not there when you started are neutron induced.

The conservative ratings on the REM balls might just be the answer. We need the fudge factor that the BTI device will supply.

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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Re: FAQ - Bubble Fast Neutron Detector

Post by badflash » Thu Dec 23, 2004 3:33 am

I've been e-mailing Rob Noulty, Ph.D of Bubble Tech (good people) and asked about the shelf life of the detectors. I've attached a paper he sent me that give the conclusion that you can use these detectors for 2 years if they are not temperature compensated and you close them up when you are done. Once the bubbles don't go away, it is time for a new detector.

Another cool note is that the bubble count should be done 2 hours after the detection is done. The bubbles continue to grow.

I was going to put off ordering until after I got my deuterium, but there is no longer any reason to wait. I'm not putting this project off that far, and the deadline may help.

Thanks to those that came before me, as they are willing to support us. Normally they won't sell just one detector, but for us they make an exception.
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