IEC Fusion - Neutron Club Entry

[JakeJHecla]

While I can't speak to the NeutronRAE's efficiency, I have seen 2cm-scale LiI(Eu) crystals used successfully to detect fusor neutrons at a TIER of ~100,000n/s. They can be quite sensitive if set up well.

Bern- Where are you located? If you need a He-3 tube for verification, I can lend you mine for a short while (I'm in Cambridge, Ma but will be in Monona, Wi this summer).

[Bern Bareis]

Hi Richard,

When I started the project, I had not anticipated that results from an off-the-shelf commercial neutron detector would not be accepted as a viable confirmation of neutron generation.

I am wondering though (particularly, since I would not like to incur additional expense for another detector). You have personally tested the NeutronRAE II yourself and described that its neutron detection is working, but weak. Therefore, a NeutronRAE II measuring 35 CPM would actually be in the presence of a greater neutron field. You have also explained that 35 CPM is an acceptable figure for confirmation of neutron generation. If I measure a count of 35 CPM on the NeutronRAE II, will that be acceptable to confirm that neutron generation is occurring since according to your measurements, the actual neutron count would be greater than what is measured?

Kind regards,

Bern

[Jim Kovalchick]

There is an easy solution that lets you apply rigor to your current set up. Insert moderator between your neutronrae and the fusor. Take a reading. Remove the moderator. Take a reading. Compare the results and present here. You are close. Don't be afraid of challenges here. The challenges make your eventual accomplishment real. Trust me on this. Congrats on the good work so far.

[Nick Peskosky]

Jim I'm not so sure that the oft used moderator insertion/removal method will have much of an effect on the Neutron RAE II. The LiI(Eu) scint crystal in the detector has a response range from thermal all the way up to 14MeV neutrons. In my opinion I think it would be beneficial for Bern to provide counting statistics for the following prior to our certification that he is in fact achieving D-D fusion. I won't speak for the group but I would be more inclined to approve his entry if the following were provided with his set-up:

1. Take a statistically significant background count of neutrons and gamma radiation in the room where the Fusor is located (I took overnight counts with my He-3 tube to get a decent sample size)
2. Take the background count again over a multi-minute time scale for the reactor running in glow mode (no D2 admitted) [include chamber pressure, applied -kV]
3. Take the neutron count for a Fusor run where deuterium gas has been leaked into the chamber and provide an average CPS/CPM [include chamber pressure, applied -kV]
4. Take the background count again after the HV has been de-energized

These devices are used by a lot our first responders here on base but as Richard stated they are not designed to be used as sensitive 'portal' detectors, rather as high-field alarming units during emergency/CBRNE incident response.

[Rich Feldman]

Before shutting up, I want to gently present a case that acceptable proof of fusion is not and should not be sufficient.

Refer to Administration / FAQs / Rules for neutron club membership.
viewtopic.php?f=26&t=1125
If we routinely grant waivers, then please

1) update the FAQ. What good is a rule book that stays in the locker room?

2) ask applicants to say a little about themselves, their background, and their motivations.
Not a bio, just what's implicit (IMHO) in one's original Introduction.

Does the Neutron Club roll include honorees known by a name and nothing more?

Our registration rules ucp.php?mode=register are hard to check while logged in. We know that newbs often overlook "2) New members are required to introduce themselves in the "Please Introduce Yourself" forum prior to posting elsewhere on the site.". That's not very specific, but the case at hand is testing a lower bound. Before next time, please add some specifics to the Registration or N.C.Membership rules. Thanks!

Respectfully, and with no intent to disparage Bern,
Rich Feldman

[Jim Kovalchick]

Nick,
I know you are correct that the advertised response range of the Neutronrae includes fast neutrons. I'm not sure I can believe that it is a linear response. The cross section for Li-6 is much better in thermal ranges. I think you will see a change with the moderator change test. If the device is seeing neutrons there will be a change that will look different than x-ray attentuation and reasonably the change could be used to confirm the assertion.

[Nick Peskosky]

Jim,

You are absolutely correct, I failed to account for the higher capture cross section experienced by Li-6 when it is bombarded with thermal neutrons. Aside from the capture resonance in the 100's KeV, Li-6 is almost 2 orders of magnitude more likely to capture a thermal vs. fast N. A moderator test should prove most fruitful in this case!

[Richard Hull]

Again, 15kv is an almost not fusing fusor. Hyper sensitivity is needed at 15kv. Even a moderate sized 3He detector is struggling to produce any sort of obvious signal and a good long run would be needed after careful setup of the detection windowing.

Richard Hull

[Jim Kovalchick]

As always, Richard's advice is sage. You really can do fusion at 15 kV on a well conditioned chamber, but even if your instrument can see it, you won't be able to validate the data without trend data from voltages higher than that. Back when my son first operated his fusor, he saw neutrons with a simple old PNC-1 down as far as 15 or 16 kV. If it weren't for the continuity of his numbers with a trend line drawn by data take at points upward from there to 30 kV, you really could not have said his numbers were real. Even then, it was more qualitative than quantitivative in that low voltage region.

[George Schmermund]

It's not unusual for information that is not directly on the well beaten path here to be ignored. High sensitivity neutron detection has previously been reported sometime back (viewtopic.php?f=13&t=6245), but was ostensibly dissed by a resident oracle and the detector fell by the wayside. Some folks actually understood the experiment and its extreme efficiency (100%) and unambiguous detection of silver activation while others just couldn't wrap their minds around it. To this date no one has reported a single attempt to reproduce the results. Apparently it fell under the rubric of unauthorized use of silver activation.

[Bern Bareis]

Richard and all:

I appreciate the many responses and suggestions. Based on all of the input so far, I would like to then move forward with the following approach: since there are questions regarding the NeutronRAE II, I will instead obtain a neutron dosimeter and qualify neutron detection in that way. Please confirm that this will be an acceptable means to indicate that neutrons have indeed been generated.

Additional Comments:

Nick:

My intention is not to continue the thread on the subject of detection using the NeutronRAE II at this juncture, but I thought I would provide some additional information, in case it is helpful.

Regarding the moderator suggestions offered by John Futter and Jim Kovachick, I believe your April 2nd post is correct, given the detection range and sensitivity of the Lithium Iodide neutron detector in the NeutronRAE II, unless you put a moderator in front of it that essentially blocks all neutrons, the detectable difference will likely be minimal, if at all and even if an ability to generate some thermal neutrons is accomplished, the results will likely fall within the variability of other parameters during the test (e.g. the thickness of the moderator, power supply adjustment, etc.).

John:

As mentioned above, my plan now is to move on to a neutron dosimeter which would alleviate any questions regarding EMI or whether or not neutrons are being detected. However, I thought some additional data points for you might be helpful in case you or others should at some point consider using a NeutronRAE II for neutron detection.

The NeutronRAE II was chosen for detection of D-D 2.5 MeV neutrons for among other things, its published sensitivity and ability to detect thermal to 14 MeV neutrons (it could be useful for testing elements/compounds generating higher energies later). The additional features of the unit, including microprocessor control, data logging, and user programmability for the log interval were additional nice features.

The Lithium Iodide (LiI) detector in the NeutronRAE II has a 1 cm^2 cross sectional area and is 1 cm in depth. Its published sensitivity is 1 to 2 cps per 2.5 neutrons/second/cm^2. Like you, I also had concerns about interference from the EMI generated by the power supply through the HV wire and plasma formed in the vacuum chamber. The LiI detector of the NeutronRAE II is fully enclosed in a metal shield and is hermetically sealed with shielded wire connection to the PCBA. The inner surface of the entire chassis has a secondary metalized shield. In the “air” test I posted earlier, I set the vacuum pressure at 3 mTorr and then proceeded to rapidly increase the voltage to the point where the air plasma was significantly heating the titanium electrode and the electrode was just turning from red to white hot. Increasing the voltage further would be pointless, since there is not a need to go any further or the cathode will be destroyed. I then immediately dropped the voltage level setting back to zero (I can do this, because I am using a D/A for remote control instead of turning the 10-turn potentiometer on the power supply). The purpose of this test was to maximize the dv/dt and di/dt to cause the greatest amount of EMI to be imposed on the NeutronRAE II in the configuration as indicated in the images. In the graph posted with the “air” run, you can see the gamma emissions from when I varied the voltage from minimum to maximum (just prior to where cathode destruction would occur) three times over a reasonably short period. The NeutronRAE II showed no signs of being impacted by the EMI test. If it had been, I would have made additional changes to the configuration. If this was the only question remaining, I would simply put the NeutronRAE II in a fully enclosed, reasonably thick and well-grounded metal or even mu-metal container effectively creating a Faraday cage and show that indeed the measurements are not being affected by EMI. RAE Systems evidently performed a sufficient development effort to take into account the possibility of strong EMI (I suspect that they had some very stringent requirements imposed on them by the military such that the unit will not be impacted by emissions from radio equipment used by first responders).

Jake:

Thank you for your very kind offer, but for now I will seek to apply a neutron dosimeter.

[Rich Feldman]

Hi Bern.

In case you misunderstood the people inviting a moderator experiment:
Surrounding the detector with a generous thickness of neutron moderating material is expected to significantly _increase_ the count rate from neutrons, other variables being unchanged. That familiar effect has often been accepted here as proof of neutrons. How hard is it to try, and see what happens? A positive outcome would add to our collective understanding of LiI scintillators.

[edit]A scintillator maker called Amcrys says:

LiI (Eu) is а scintillator mostly used for thermal neutron detection. Neutrons are detected in 6LiI (Eu) through their interaction with the 6Li atoms of the material through the reaction ...

[/edit]

I bet that data from an electronic neutron dosimeter (e.g. Laurus, Mirion) will meet the same skepticism as data from NeutronRAE II. Even if the datasheet cites compliance with IEC 61526 Ed2, folks will say "Who is in a position to read the standard and summarize it for us?" They are amateur and professional scientists and engineers, not safety office functionaries. They might still ask for a moderator experiment!

No matter what kind of detector (even e.g. bubble dosimeter or plastic track development), scientific review traditionally looks for data from a control experiment. For example, using non-deuterium with voltage, current, and pressure as similar as possible. And/or correlation between different nonzero neutron counts and fusor variables. Unlike in golf, those are not gimmes.

Your NeutronRAE II showed gamma activity in the air example with 15 kV applied. You will find a consensus here that the fusor could not have been producing gamma rays. Lesson: Instrument results must be interpreted with knowledge not given in the datasheet.

Thank you for making and reporting an experiment to dismiss fears of EMI sensitivity. Maybe I misunderstood something there. Were you changing power supply settings as fast as possible, in order to maximize the EMI-inducing dv/dt and di/dt?

Best regards,
Rich

[Richard Hull]

Rich's advice is sage and what we have been discussing all along. Build a pile of moderating material about 3 inched thick all around the instrument. run the fusor and once stable operation is obatined take a 10 minute reading from within the moderator. Record the total counts during that period. Next, just set the naked instrument in the exact same location, prefeably during the same run, and count for ten minutes. If neutrons are really around, the number of counts taken with it buried in the moderator will be higher than when naked. Do this long before you order a neutron dosimeter it is easy and quick.

You are at the very edge of detectability here.

Richard Hull

[Bern Bareis]

Hi Richard and Rich,

I hope everyone's Easter is going well. Based on the prior discussions, I am no longer moving forward with the NeutronRAE II for confirmation of neutron detection. I plan to acquire a BTI PND33 to just show results on a neutron "bubble" dosimeter. I think that will save us all a lot of time and effort. Let me know if that is acceptable and I will move down that path.

For clarification, the following is why Nick and I brought up the issue of variability in detection of neutrons using a moderator with regard to the NeutronRAE II:

The published specification for the LiI(Eu) detector for the NeutronRAE II is

Sensitivity: 1 to 2 cps per 2.5 neutrons/second/cm^2
Cross Sectional Area: 1 cm^2
Depth: 1 cm
Energy Range for Detection: thermal to 14 MeV

Since D-D reactions are at 2.5 MeV and the detector detects thermal to 14 MeV, assuming that the detector meets its published specifications what is it that reducing the energy of the neutrons to say a thermal range is going to help with in respect to detecting neutrons with the neutronRAE II? If you had neutrons at a higher energy level than 14MeV and were then trying to bring them into the detection range of the NeutronRAE II, I could see how a moderator would help. But the NeutronRAE II appears to have a very broad detection range and whether at 2.5 MeV or at a thermal range, the detector is supposed to detect the neutrons quite well.

So that we can move forward without spending more time on the subject of the NeutronRAE II, I think it pertinent to just move forward with a BTI PND33. Let me know if that works and I will be back, once I have acquired one and am ready to post.

Kind Regards,

Bern

[Richard Hull]

The BTI is fine and very expensive with a life span of about 6 months and it is gone forever. At 15kv applied in the fusor you will have to run a long time before a single bubble appears, if at all. Again, You are at the limit of detection. If you have a builder's hands and spirit you might try the large surface area silver activation detection scheme in a scintillation cocktail. You will need a PMT and the associated electronics and all the fixin's. If you have none of this, the BTI might be cheaper, but you will not see a gang of bubbles.

We fusioneers have a vast amount of experience here. We know when detection gets easier. Try and up you voltage to over 20kv applied if you get the bubble detector.

Richard Hull

[Bern Bareis]

Operation on April 22, 2015: 15 minute run time, -25kV to -26kV at 5 mA to 7 mA.
Result: 4 Bubbles on BTI BD-PND67 Dosimeter (closest point located 8.04 cm from center of cathode).

High Voltage Power Supply:

Cathode:

BTI BD-PND67:

[Rich Feldman]

That was fast! Looking good there Bern. If you are planning to stick around after the neutron club discussion, do you want to reconcile your BTI counts with your NeutronRAE counts?

If I were a judge, it would be time to remind you again -- it takes more than a convincing demonstration of neutron production. In most contests and clubs, following the rules is important. It demonstrates respect for the institution and the other members.
So, now sticking my neck out, do any other participants agree? Has anyone ever seen a neutron club application with so many sections not filled in? Details so easy that persistently skipping them could be seen as flaunting a cavalier attitude. The rules are posted for all of us to read, so I will just point out a few lines.

The following will be demanded for neutron club membership.
...
1. You shall have been a poster and member of the forums for at least 60 days.
...
4b. An image of the entire fusor setup with neutron detection assembly in place with yourself in the image with the device. (all must be visible.)
...
4c. A full data set to include ... Operational pressure of the Deuterium fuel in the fusor during fusion. Show metering. [during the same run as the claimed neutron count was collected]
...
Several fusion runs with several sets of data as noted above will be preferred. [ e.g. a 15 minute run with different voltage, current, pressure, or gas, resulting in fewer or no bubbles. Evidence of scientific method. ]

A personal note, after looked through the posting history of the last 10 or 15 neutron club inductees. What leaps out, and I think is unprecedented, is that you have not yet posted a single word about Bern.

Why do you want to be in the neutron club? What other clubs are you in? Are you in a hurry, or can't spare much more time for this particular notch? Do you think the decision should be objective and mechanical (please tell us which rules should matter and which are unimportant) or somewhat colloquial (in which case, who are you?).

Best regards,
Rich

[Richard Hull]

The data is believable at last. I have a good deal of experience with BTI detectors and considering the voltage, current and the images, I am placing you in the Neutron club. Good work in going through the extra effort.

Richard Hull

[Rich Feldman]

You won this one, Bern. Let me be the second fusor.netter to congratulate you.

Are you going to carry on with your fusor? It would be great to see count values from the NeutronRAE II at your new, higher voltage levels. With and without moderator, of course. The guy from RAE did recommend a moderator for maximizing the count values. As discussed in another thread, we think your datasheet interpretation is unrealistically favorable to the instrument. D/s does give sensitivity as 1 to 2 cps (for an unspecified energy spectrum). It does say energy range for detection (with unspecified sensitivity) is thermal to 14 MeV.

How do you feel about telling us about yourself, now that your name is on the honor roll?
Must we continue to use our imaginations?

[Bern Bareis]

Thank you Richard H.

[Bern Bareis]

Additional data April 25, 2015: -28kV 5.5mA to 7mA, 20 minute run time, 67 b/mrem BTI BD-PND67.
Cathode:

Result: 14 Bubbles

14 bubbles.JPG (16.43 KiB) Viewed 6907 times

[Rich Feldman]

Excellent ! What''s that rate in neutrons/cm^2/s, and total fusor neutrons/s?

[Richard Hull]

While this would be great to know and is really icing on the cake, the calcs are easy to do and I posted them a while back. You need to know the distance from the fusor the total run time and that calibration constant for the BTI, and the dose rate number of 2.5mev neutrons/sqcm per mrem/hour.

Work the bubble count to mrem dose
convert to a rate mrem/hr
then figure the flux required to get that rate
figure neutron emission/sec over the entire spherical area at the range used
Double the result to get total fusions/sec in the fusor.

The answer should be within +/- 20%

Not highly accurate as absolute counts go, but it is better than a poke in the eye with a sharp stick and you are smarter and have more data in hand when done. Give it a whirl.

Richard Hull

[Bern Bareis]

[Bern Bareis]

As a scale reference, the cathode grid is 1 inch in diameter and the poissor is approximately 0.1 inch in diameter in this image.