NEW Fusor V build under way.

For posts specifically relating to fusor design, construction, and operation.
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: NEW Fusor V build under way.

Post by Richard Hull »

True, it does but that is what I get from the data sheet for the 3He tube I am using. I did an update on calculating this in the FAQ on Calibrating neutron counters just a few days ago. You should have seen it. It is near the end of the pdf. It begins at the addendum.


Richard Hull
Attachments
Calibration of neutron counters.pdf
(189.25 KiB) Downloaded 231 times
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: NEW Fusor V build under way.

Post by Richard Hull »

I made some really bad assumptions related to the counting efficiency 59 cps/nv from 63cps/nv. I was also off on the average distance from the 3He tube to the net source of neutrons, from 18cm to corrected to 24cm. These adjustments considerably corrected the TIER and my constant of multiplication. The TIER is not 137,000 n/s, but is now 248,717 n/s. Likewise the multiplication factor is no longer 1.135 but is now 2.06 times the cpm rate.

Thanks Jim for pushing me to really question my numbers. I can do a detailed presentation at HEAS on the large white board as to the adjustments.

All the PDF files are now fully corrected. You might reload them if you want the math corrections. They are the same, so just reload the original post's PDF.

Always refining by closer examination of the parameters.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Bob Reite
Posts: 576
Joined: Sun Aug 25, 2013 9:03 pm
Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Re: NEW Fusor V build under way.

Post by Bob Reite »

I really didn't think that you could successfully activate silver with only 137, 000 n/s. 248,717 is more realistic, but I still thought that you had to be near the mega mark to do activation.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
User avatar
Aidan_Roy
Posts: 80
Joined: Wed Jan 01, 2020 10:08 am
Real name: Aidan Roy
Location: Massachusetts

Re: NEW Fusor V build under way.

Post by Aidan_Roy »

Richard,

I think a detailed view of your TIER calculation adjustment at HEAS would be great, definitely something I would enjoy to see.

Aidan
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: NEW Fusor V build under way.

Post by Richard Hull »

You will see the complete derivation update on my white board. I put it up today and ran through a verbal explanation for practice to an empty lab. Talking to myself again....tsk...tsk.

Unfortunately, on rechecking the cps/nv on the spec sheet, the figure of 63 is given with the stated accuracy of +/-20%?! So, it could be either 198640 or 297360 or anywhere in between the computed 248,717n/s.
It is to be remembered that a 3He tube is a proportional counter and once out of the manufacturers hands, it can be biased anywhere from 1500-2000 volts and be in spec, this can affect pulse height and the proportional slope. In addition, the windowing can benefit or limit the neutron count. I think they took this into consideration.

I am going to pull out the digital o'scope and tune this thing up a bit from the preamp on to the main amp. Again, and this has been said by me many times.... There is no absolute neutron counting system. There is absolute precision to 1% or better in a fixed neutron counting system to relative quantitative improvement or degradation between runs.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Jim Kovalchick
Posts: 717
Joined: Wed Apr 13, 2011 8:00 pm
Real name:

Re: NEW Fusor V build under way.

Post by Jim Kovalchick »

Richard,
I hope to discuss this with you in greater detail at HEAS next week, but I think your detector geometry makes trying to calculate the TIER rather complicated. Your detector does not intersect a uniform neutron field. Point source calculation does not work.
I am also curious about your hdpe thickness. There is an optimum thickness, but that is affected by geometry too. As I recall, Carl Willis showed that for activation, about 1.5" was optimum. Any thicker lowered counts. I dont know what the predominant factor was but I think its a combination of thicker moving the sample point further from the source and experiencing moderator absorption of the neutrons once they made it to thermal. Have you tried different hdpe widths?
Jim K
Jon Rosenstiel
Posts: 1494
Joined: Thu Jun 28, 2001 1:30 am
Real name: Jon Rosenstiel
Location: Southern California

Re: NEW Fusor V build under way.

Post by Jon Rosenstiel »

I've found that 1 to 1.75-inches of HPDE moderator works well for silver activation. (Reflector thickness of 4")

I think on paper 1" would not be enough, but I suspect the increased neutron flux more than makes up for it. (Inverse square law)

Edit: And we also need to take into account silver's large cross section for resonance neutrons.

JonR
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: NEW Fusor V build under way.

Post by Richard Hull »

I have taken most all of the non-uniform moderator into account. Again, you will see it all. I detailed with precision my moderator in the neutron radiation forum.

viewtopic.php?f=13&t=13553

If one follows, assiduously, Mark Rowley's postings he is using a similar dimensioned moderator and is doing great! An image is in the above thread of his setup.
The old water moderator with this same tube and circuitry never recorded much over 60,000 cpm with Fusor IV. I just counted 133,757 CPM yesterday. (298,000 TIER by the new calcs) Better moderation in this setup with similar moderator geometry (offset vertically in fusor IV, offset horizontally in fusor V).

I am fully aware of all the possible non-linearities that can creep into this related to geometry, neutron loss in an overly thick moderator. I have tried to make adjustments, though still less than precise and less than ideal with the attendant +/-20% related to the tube itself.

Current graph below

Richard Hull
Attachments
Neutron Activation AG 9-25-20A.jpg
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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Cai Arcos
Posts: 163
Joined: Fri Oct 12, 2018 9:30 am
Real name: Cai Arcos
Location: Barcelona, Spain.

Re: NEW Fusor V build under way.

Post by Cai Arcos »

Richard:

Would you consider posting the derivation of the calibration factor here after HEAS? I'm really interested in it, but unable to attend (I have, in fact, never travelled outside Europe, and only once with in).
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: NEW Fusor V build under way.

Post by Richard Hull »

I will pull it together after the HEAS as I wish to have other's inputs to refine and refresh my first pass at deep thoughts related to the 3He system. It all seemed so simple with the tube specs to mathematically figure the flux. Geometry is a complicating factor that fouls a simple calculating approach. Based on my new approach I managed to chase the cps/nv from 63 to 54 and expand the distance to the sensitive neutron counting region or zone. (enlarge the TIER sphere a bit). This has resulted in a 3X TIER result from just a bit over 100k counts to nearly 300k counts. See the updated PDF in the first posting...updated to 9/25/20 results.

Cai, you are much like me. I hate to travel. Unfortunately the Air Force flew me all over hell's half acre during my 4 year tour in the Vietnam war era. I was in England, the Netherlands, Vietnam, Japan and Thailand outside the US. In the States, I have been in Alaska, Colorado, Utah, New Mexico, Kentucky, West Virginia, North Carolina, Florida, Mississippi, New York, Maryland, Louisiana, Georgia, Pennsylvania and Delaware. I still have never been in 35 of our 50 states. My favorites, outside of my home state of Virginia, would be Colorado and Utah due to their grandeur in variegated scenery and other attractions that drew me there.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Cai Arcos
Posts: 163
Joined: Fri Oct 12, 2018 9:30 am
Real name: Cai Arcos
Location: Barcelona, Spain.

Re: NEW Fusor V build under way.

Post by Cai Arcos »

I do tend to dislike travel. Home is called home for a reason! Your comment about never visiting 35 states made an European like me realize how huge and vast the USA really is. You could in fact visit almost all climates without changing country.

The calculation of flux in a non uniform scenario seems to me, unless you assumed all neutron flow was thermalized and just diffused into the detector aftet, would require some notable mathematical/geometrical skills. I found the FAQs about simulation to be a lot more instantaneous. If I recall correctly, Experimental Nuclear Physics by Mukhin, had some detailed explanations. Will check when I got time and if so, post them here.

EDIT: Here are 9 pages, the more "practical" ones I could find of a notable section that talks about moderation. I'm sorry these are photos and not scans, but I'm fearful of damaging the spine of the book (bough it "new" at a scientific library which only has original and reprints of MIR editions, and I've made every effort to keep them intact). It is a really great book that I would recommed to anyone here. Also note his remark about light moderators (only a very rough estimation can be given, and the exact value should be determined experimentally) after spending several pages discussing possible models! Finally, it is also important to me that (at least for what I've gathered), the only "easy" way to estimate the flux of neutrons in a semi quantitave manner is through diffusion.
Attachments
Moderator1.jpeg
Moderator2.jpeg
Moderator3.jpeg
Moderator4.jpeg
Moderator5.jpeg
Moderator6.jpeg
Moderator7.jpeg
Moderator8.jpeg
Moderator9.jpeg
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: NEW Fusor V build under way.

Post by Richard Hull »

We come back to the old saw. Exact neutron numbers based on all the mathematical gyrations is, in effect only a close approximation, assuming the moderators covered in the 9 pages. HDPE is another medium altogether! Geometry in this case is also critical. Theoretical machinations are great under precise, controlled and unchanging input parameters There are no neutron beams from a fusor. Detectors are macroscopic with considerable extent.

Most of the more recent postings here are a crude attempt to get a feel for the TIER for fusor V and avoid the necessity of spending $300 plus for a 6 month life span bubble detector that is carefully binned to a precise number of bubbles per mrem of fast neutrons.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Bob Reite
Posts: 576
Joined: Sun Aug 25, 2013 9:03 pm
Real name: Bob Reite
Location: Wilkes Barre/Scranton area

Re: NEW Fusor V build under way.

Post by Bob Reite »

Hopefully my REM ball will let you know to within 20% of what Fusor V is actually putting out. If someone else is bringing a calibrated neutron detector, the more the merrier!
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
User avatar
Richard Hull
Moderator
Posts: 14992
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: NEW Fusor V build under way.

Post by Richard Hull »

Sad news... I am once again going to make up a new fusor V as fusor V "C". the saga of fusor V "A" was short and not sweet.
Fusor V "B", the current model, was going great as witnessed during HEAS during October. The real work appeared in the neutron forum with the silver activation reports and calibrations. Unfortunately, over the last three runs the old insulator arced externally. I think I know why. I have started to run the fan over the fusor to increase the output via external cooling and it has done marvelously as my recent reports on activation show. Note: All of the relevant information between the last post by Bob Reite and this one is to be found in the large number of posts in the URL below.

viewtopic.php?f=13&t=13568

The URL above really speaks to the best work done by Fusor V "B"! I consider this my best work with fusor V thus far.

The reason for yet another or third iteration of fusor V

I had an external arc condition 6 days ago. It carbonized, (blackened the silicone HV putty). I picked out the little area of putty and replaced it with fresh putty. The next day another run reached 41 kv and the external arc re-occurred. This shook me considerably. What changed? The fusor has worked flawlessly from July onward! I suddenly realized it was the fan! It seemed the fan blowing over the tilted fusor, carried the stream of hot air over the insulator. Hot air in a moving stream will reduce the breakdown in air. My old days in Tesla coiling taught me that lesson well.

I repaired the fusor putty once again and again it broke down at 42kv. That was yet another straw to break the camel's back and my patience!! Over the last three days I have pondered deeply and have decided a fusor V "C' is in order. All here will remember the A,B, episodes and now will suffer a C episode. I will, once again upon completion of fusor V "C", in future, refer to it as simply fusor V. Hopefully, a long term fusor V will some improvements!

I have just secured and purchased a 6 way 6" conflat cross. I want more interior room than the old "A" cross. I am sure the 4" open area In "C" will be more kind than the 1.5" area in "A"

So, I am signing off and will be closing out this post's thread to start yet another new fusor posting around the new fusor embodiment in the near future. The one saving grace is that in spite of the three external arcs, unlike Fusor V "A" 7 internal arcings, the Turbo and controller survived the EMP and RFI bursts. Whew.... 2020 has just been a year for the history books in many ways.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Post Reply

Return to “Fusor Construction & Operation (& FAQs)”