I had removed the HV feedthrough stalk’s alumina insulator tube to see what effect it had on my fusors operation.
0900… After pumping all night I fired up my fusor to check neutron output. Was 12mrem at 28kV, 19mA. (With alumina insulating tube in place neutron output was 20mrem with same input power)
0915… Cranked up power to around 25mA, 35kV. Neutron output was 25 to 30mrem.
0920…. While watching TV monitor noticed my tantalum cathode was “drooping”. Shut down fusor immediately.
0930…. Removed feedthrough. Found hole burned into stainless steel stalk tube next to the cathode attachment point. Also noticed that the end of the feedthrough insulator had a real nice sputter coating of stainless steel. (See attached photo)
0950… On a whim I checked the feedthrough’s sputter coating with my pancake detector. Was floored when the count was TRIPLE background!
1000…. Started count on feedthrough with both pancake detector and gamma detector. With the pancake detector took 2-minute counts for 2 hours. With the gamma detector took a 2-hour count. (Max energy, 3keV)
1200…. Pancake detector data indicated a 28-minute half-life for the radioactivity on the feedthrough. The gamma detector found nothing!
I'm stumped on this one! Ideas anyone?
Jon Rosenstiel
[attachment=0]Radioactive Feedthrough 002.jpg[/attachment]
I Activated my Feedthrough!
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Jon Rosenstiel
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I Activated my Feedthrough!
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Frank Sanns
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Re: I Activated my Feedthrough!
Jon,
Neutron activation of materials will give isotopes that will beta decay. Your pancake probe will detect the beta while your gamma probe will not.
Looking up the elements that would be present in the flange, insulator, and grid would be Fe, Co, Ni, Cr, Al, and Ta. Adding one neutron to any of the naturally occuring isotopes will not give a half life of 28 minutes. Most of thier half lifes are many days.
It may though, be tritium that is the casue of your beta counts. Tritium has a half life of 12 years but it may not be the actual half life that you are measuring. It may be the diffusion out of the feedthrough that you may be detecting.
Before somebody (Richard) screams that we do not PRODUCE measurable quantities of tritium in our fusors to detect, there is another source. The deuterium that we are all using contains quite a bit of tritium. The analysis that came with my ultra high purity deuterium says that the tritium content could be as high as 0.1 milli curies per liter. That should be detectable. I do not know if it is the answer but it is a possibility.
Frank S.
Neutron activation of materials will give isotopes that will beta decay. Your pancake probe will detect the beta while your gamma probe will not.
Looking up the elements that would be present in the flange, insulator, and grid would be Fe, Co, Ni, Cr, Al, and Ta. Adding one neutron to any of the naturally occuring isotopes will not give a half life of 28 minutes. Most of thier half lifes are many days.
It may though, be tritium that is the casue of your beta counts. Tritium has a half life of 12 years but it may not be the actual half life that you are measuring. It may be the diffusion out of the feedthrough that you may be detecting.
Before somebody (Richard) screams that we do not PRODUCE measurable quantities of tritium in our fusors to detect, there is another source. The deuterium that we are all using contains quite a bit of tritium. The analysis that came with my ultra high purity deuterium says that the tritium content could be as high as 0.1 milli curies per liter. That should be detectable. I do not know if it is the answer but it is a possibility.
Frank S.
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
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Jon Rosenstiel
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Re: I Activated my Feedthrough!
Frank,
For a simple test I let a small quantity of deuterium flow over my pancake detector... there was no increase in activity above background.
Don't know if you had this in mind or not, but we need to remember that inside our fusors all neutrons are fast neutrons. (Along with a equal number of protons)
By 1215 (3 hours after the "drooping cathode" event) the activity on the feedthrough had decayed completely, so my 28 minute half-life number may be a little low.
Jon Rosenstiel
For a simple test I let a small quantity of deuterium flow over my pancake detector... there was no increase in activity above background.
Don't know if you had this in mind or not, but we need to remember that inside our fusors all neutrons are fast neutrons. (Along with a equal number of protons)
By 1215 (3 hours after the "drooping cathode" event) the activity on the feedthrough had decayed completely, so my 28 minute half-life number may be a little low.
Jon Rosenstiel
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Richard Hull
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Re: I Activated my Feedthrough!
This is a most interesting post and thanks for sharing the info Jon. You are right in being amazed as there is just little way in which anything in the chamber can activate.
The tritium diffusing out of the ceramic might be a thought as Frank mentioned. I had no idea that one had as much as 100uCi of T in a liter of D2! Probably a result of concentration during the fractionating process in boil off capture of the deuterium. That is 3.7 million disentegrations per second per liter at STP. In a 20 liter cylinder that becomes over 70 million super weak betas per second!
The beta from Tritium is so weak that is will barely pass through the mica window on the pancake. 6-8kev average, 18kev max. This could be tested in future with apiece of aluminum foil. with foil between the detector and the insulator you will see zero beta from tritium. If the betas are activation betas they will zip right through. So many clever ways to skin the cat and narrow the field.
Richard Hull
The tritium diffusing out of the ceramic might be a thought as Frank mentioned. I had no idea that one had as much as 100uCi of T in a liter of D2! Probably a result of concentration during the fractionating process in boil off capture of the deuterium. That is 3.7 million disentegrations per second per liter at STP. In a 20 liter cylinder that becomes over 70 million super weak betas per second!
The beta from Tritium is so weak that is will barely pass through the mica window on the pancake. 6-8kev average, 18kev max. This could be tested in future with apiece of aluminum foil. with foil between the detector and the insulator you will see zero beta from tritium. If the betas are activation betas they will zip right through. So many clever ways to skin the cat and narrow the field.
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
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
Re: I Activated my Feedthrough!
Hi Jon:
Congratulations!
We now are getting good indication that the group is on the right track. I particularly like the fact the event occured at 35 kv.
At 40 kv which is just a little higher voltage , a consistant raising of the neutron numbers seem to occur as the amperage is raised.
Jon,I'm chomping at the bit to get accurate neutron measurement of this stuff.
>>>>> Gentlemen ,Elvis is leaving the building! :^) <<<<<
Here's my theory on this stuff:
I had noticed a very similar event in pulsing that I had chalked up to anomolous behaivor but later I had my mind changed.
I too use ceramic feedthrus....If I pulse say 10 times then on the eleventh or twelveth pulse heck breaks loose. It could be we are
plating the chamber and insulator with tritium. At a critical level the gas readmits itself to the chamber giving the "runaway" reaction. By increasing the pre ignition glow field above 50 ma
the regularity of high neutron events can be repeated with fair regularity. I for one turn off the pumps at the desired vacuum level so any gas would stay put and it would now seem that a sputtering process retains some too. It could be that a rampaging electron beam could disrupt the metal hydride Tantulum Tritide and Tantulum Deuteride coating on the walls producing a Puff of tritium +d gas.
Happy Fusoring!
Larry Leins
Fsuor Tech
Congratulations!
We now are getting good indication that the group is on the right track. I particularly like the fact the event occured at 35 kv.
At 40 kv which is just a little higher voltage , a consistant raising of the neutron numbers seem to occur as the amperage is raised.
Jon,I'm chomping at the bit to get accurate neutron measurement of this stuff.
>>>>> Gentlemen ,Elvis is leaving the building! :^) <<<<<
Here's my theory on this stuff:
I had noticed a very similar event in pulsing that I had chalked up to anomolous behaivor but later I had my mind changed.
I too use ceramic feedthrus....If I pulse say 10 times then on the eleventh or twelveth pulse heck breaks loose. It could be we are
plating the chamber and insulator with tritium. At a critical level the gas readmits itself to the chamber giving the "runaway" reaction. By increasing the pre ignition glow field above 50 ma
the regularity of high neutron events can be repeated with fair regularity. I for one turn off the pumps at the desired vacuum level so any gas would stay put and it would now seem that a sputtering process retains some too. It could be that a rampaging electron beam could disrupt the metal hydride Tantulum Tritide and Tantulum Deuteride coating on the walls producing a Puff of tritium +d gas.
Happy Fusoring!
Larry Leins
Fsuor Tech
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Jon Rosenstiel
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Re: I Activated my Feedthrough!
Larry,
Hmmmm, starting to get quite interesting. I may have to attempt an re-enactment. Then try Richard's suggestion of using Al foil to see if the betas can be blocked. (Would that be considered a beta-blocker)?
Man, this fusion stuff sure is fun!
Jon Rosenstiel
Hmmmm, starting to get quite interesting. I may have to attempt an re-enactment. Then try Richard's suggestion of using Al foil to see if the betas can be blocked. (Would that be considered a beta-blocker)?
Man, this fusion stuff sure is fun!
Jon Rosenstiel
Re: I Activated my Feedthrough!
Hi Jon:
You bet!
This is all new and fairly mysterious but doable.
It beats the heck out of fishing!
Golf! LOL!
I'm bidding on a huge transformer pretty much like yours.
How did you contain it?
Was it a do it yourself or did your tranni have a box with it?
Happy Fusoring!
Larry Leins
Fusor Tech
You bet!
This is all new and fairly mysterious but doable.
It beats the heck out of fishing!
Golf! LOL!
I'm bidding on a huge transformer pretty much like yours.
How did you contain it?
Was it a do it yourself or did your tranni have a box with it?
Happy Fusoring!
Larry Leins
Fusor Tech
Re: I Activated my Feedthrough!
If the pressure keeps rising Jon - we may all be on beta-blockers. 
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Carl Willis
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Re: I Activated my Feedthrough!
Hi Jon,
Wow, this is an interesting result! I'm stymied as well.
For a guess, your background was probably in the 50 cpm range, and so you were seeing ~150 cpm, or ~200 cpm, at the beginning of the measurement? Did you see any evidence of brehmsstrahlung on the gamma spec?
Do you use a backfill or continuous flow method? I did some calculations and am almost certain it is not tritium. However, nothing else makes as much sense to me yet! If you did make a lot of tritium, the positively charged tritons would tend to get buried along the feedthrough and in the cathode and would concentrate there. The brehmsstrahlung from T betas IS detectable by a pancake GM. Unless you were producing thousands of times as much tritium as a normal continuous fusor, though, the tritium explanation falls apart. I'd often monitored my vacuum pump outlet for spurious counts above background with a pancake GM during operation, and never noted anything.
Is the feedthrough itself made from alumina? In that case you should expect to see the 1.7 MeV gamma from Al-28 (half life 2 min.) due to neutron absorption, but would undoubtedly have an easier time detecting the betas. The feedthough is certainly large enough to moderate and reflect many neutrons to thermal energy although it is far from ideal in this respect.
Finally, I think it's inconcievable that a (D, non-D) reaction, or a (P,x) reaction, is occuring and giving rise to a radioisotope. The energies involved are just too low.
Don't know what to say!! Keep up the good experimental work and try to repeat this most interesting experiment.
-Carl
Wow, this is an interesting result! I'm stymied as well.
For a guess, your background was probably in the 50 cpm range, and so you were seeing ~150 cpm, or ~200 cpm, at the beginning of the measurement? Did you see any evidence of brehmsstrahlung on the gamma spec?
Do you use a backfill or continuous flow method? I did some calculations and am almost certain it is not tritium. However, nothing else makes as much sense to me yet! If you did make a lot of tritium, the positively charged tritons would tend to get buried along the feedthrough and in the cathode and would concentrate there. The brehmsstrahlung from T betas IS detectable by a pancake GM. Unless you were producing thousands of times as much tritium as a normal continuous fusor, though, the tritium explanation falls apart. I'd often monitored my vacuum pump outlet for spurious counts above background with a pancake GM during operation, and never noted anything.
Is the feedthrough itself made from alumina? In that case you should expect to see the 1.7 MeV gamma from Al-28 (half life 2 min.) due to neutron absorption, but would undoubtedly have an easier time detecting the betas. The feedthough is certainly large enough to moderate and reflect many neutrons to thermal energy although it is far from ideal in this respect.
Finally, I think it's inconcievable that a (D, non-D) reaction, or a (P,x) reaction, is occuring and giving rise to a radioisotope. The energies involved are just too low.
Don't know what to say!! Keep up the good experimental work and try to repeat this most interesting experiment.
-Carl
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Jon Rosenstiel
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Re: I Activated my Feedthrough!
Larry,
About my transformer, you may have me confused with someone else. I have an old 100kVp, Kenotron rectified, x-ray power supply. It came complete with tank, oil, etc.
Carl,
You're real close, my background is normally 47cpm. My initial count rate was in the 150 to 160cpm range. And that was a good half hour after the "drooping cathode" incident. I'd guess that if I had checked the feedthrough immediately I would have seen around 200cpm!
I’m away from home right now, but when I get back later this week I’ll take another look at the gamma spec. I took a 7000 second gamma spec of the insulator and also took a 7000 second background gamma spec. When I overlaid them there were no obvious differences. (Although I did not look very closely at the low end of the spec).
I use the continuous flow method. I’ve also done the same as you (check vacuum pump exhaust with pancake detector) and found nothing.
My feedthrough is an eBay item, so I’m not 100% certain of its pedigree, but dimensionally it matches Ceramaseal’s 70kV model, which they say is alumina.
Yeah, what happened is very unusual. I checked the feedthrough for activity at least three separate times, once using a different counter (but same probe). All with the same result. When the probe was brought up close to the feedthrough ratemeters went up, speakers clicked faster. It looked, sounded, and felt like radiation, so it must be radiation! (Well, I didn’t actually “feel” the radiation)!
Thanks for your input. Thoughtful as usual.
Jon Rosenstiel
About my transformer, you may have me confused with someone else. I have an old 100kVp, Kenotron rectified, x-ray power supply. It came complete with tank, oil, etc.
Carl,
You're real close, my background is normally 47cpm. My initial count rate was in the 150 to 160cpm range. And that was a good half hour after the "drooping cathode" incident. I'd guess that if I had checked the feedthrough immediately I would have seen around 200cpm!
I’m away from home right now, but when I get back later this week I’ll take another look at the gamma spec. I took a 7000 second gamma spec of the insulator and also took a 7000 second background gamma spec. When I overlaid them there were no obvious differences. (Although I did not look very closely at the low end of the spec).
I use the continuous flow method. I’ve also done the same as you (check vacuum pump exhaust with pancake detector) and found nothing.
My feedthrough is an eBay item, so I’m not 100% certain of its pedigree, but dimensionally it matches Ceramaseal’s 70kV model, which they say is alumina.
Yeah, what happened is very unusual. I checked the feedthrough for activity at least three separate times, once using a different counter (but same probe). All with the same result. When the probe was brought up close to the feedthrough ratemeters went up, speakers clicked faster. It looked, sounded, and felt like radiation, so it must be radiation! (Well, I didn’t actually “feel” the radiation)!
Thanks for your input. Thoughtful as usual.
Jon Rosenstiel
Re: I Activated my Feedthrough!
Hi Jon:
You were correct it was a John!
You were correct it was a John!
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Jon Rosenstiel
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Re: Puzzle Solved!
This past weekend I attempted to recreate the conditions that resulted in my feedthrough becoming radioactive. This time I noticed that the outside of the feedthrough insulator (ribbed portion) was radioactive! (93cpm, background subtracted). Decay time for this activity was just over 3 hours. Again, I could detect no gammas.
I inserted various densities of Al absorber foils between the feedthrough and my pancake detector in an effort to determine the maximum beta energy, but that was inconclusive due to the low count rate.
After the activity decayed I was surprised to note that the feedthrough still had some residual radioactivity. (26cpm, background subtracted).
I then ran an XRFanalysis (X-Ray Fluorescence) on the feedthrough.
BINGO! Barium (32.2keV) and rhodium (20.2keV)!
Note: I believe the following is correct, but if I have it wrong please let me know. I’m still learnin’ this stuff!
Ba-138 (72% of elemental barium) has a thermal neutron cross section of only 9 barns, but at resonance energies (10 to 100keV in Ba-138’s case) the cross section is over 100 barns.
Ba-139’s half-life of 83 minutes is a fair fit (considering the low count rate) to my observed 3 hour decay rate.
An internet search indicated that rhodium is used as a catalyst with alumina. Rh-103 has a thermal neutron cross section of 150 barns. Rh-104 has a half-life of 42 seconds, so if I’m quick with my counter I may be able to catch it.
When my fusor is back together with a proper Ta grid and alumina stalk insulators I should be able to nail all of this down with a little more certainty. (I’ll be able to crank up the voltage and have some “real” neutron numbers to work with).
Jon Rosenstiel
I inserted various densities of Al absorber foils between the feedthrough and my pancake detector in an effort to determine the maximum beta energy, but that was inconclusive due to the low count rate.
After the activity decayed I was surprised to note that the feedthrough still had some residual radioactivity. (26cpm, background subtracted).
I then ran an XRFanalysis (X-Ray Fluorescence) on the feedthrough.
BINGO! Barium (32.2keV) and rhodium (20.2keV)!
Note: I believe the following is correct, but if I have it wrong please let me know. I’m still learnin’ this stuff!
Ba-138 (72% of elemental barium) has a thermal neutron cross section of only 9 barns, but at resonance energies (10 to 100keV in Ba-138’s case) the cross section is over 100 barns.
Ba-139’s half-life of 83 minutes is a fair fit (considering the low count rate) to my observed 3 hour decay rate.
An internet search indicated that rhodium is used as a catalyst with alumina. Rh-103 has a thermal neutron cross section of 150 barns. Rh-104 has a half-life of 42 seconds, so if I’m quick with my counter I may be able to catch it.
When my fusor is back together with a proper Ta grid and alumina stalk insulators I should be able to nail all of this down with a little more certainty. (I’ll be able to crank up the voltage and have some “real” neutron numbers to work with).
Jon Rosenstiel
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Richard Hull
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Re: Puzzle Solved!
Another fine piece of investigative work, Jon!!
Idents are always tough. I would want Carl to look at this and hope he does. I wonder what the Ba and Rh descended or ascended from? I assume you weren't using the Am241 as an exciter here to get the XRF data?
Richard Hull
Idents are always tough. I would want Carl to look at this and hope he does. I wonder what the Ba and Rh descended or ascended from? I assume you weren't using the Am241 as an exciter here to get the XRF data?
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
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
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Jon Rosenstiel
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- Joined: Thu Jun 28, 2001 1:30 am
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- Location: Southern California
Re: Puzzle Solved!
I don't think the Ba and Rh are ascended or descended from anything. They're in the alumina or the glaze. (Or both)
My best guess is that barium is added to the alumina to increase its ability to withstand high temperatures. (My feedthrough is a high temp model)
Rhodium I’m less sure about, but I’ve seen references on the web that indicate it is sometimes added to raw alumina as a catalyst.
I used a Cd-109 disc source as the exciter.
Jon Rosenstiel
My best guess is that barium is added to the alumina to increase its ability to withstand high temperatures. (My feedthrough is a high temp model)
Rhodium I’m less sure about, but I’ve seen references on the web that indicate it is sometimes added to raw alumina as a catalyst.
I used a Cd-109 disc source as the exciter.
Jon Rosenstiel
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Carl Willis
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Re: Puzzle Solved!
Hi Jon,
Sorry it's been a while since I've checked the board.
Your spectrum may show a fluorescence peak at 32.2 keV, but the other peak, in my opinion, is not. At 48.3 keV, according to theory, you should see a Compton-backscattered peak resulting from Compton scattering in the insulator, and indeed you do. In thinner detectors such as this one, the escape of a characteristic iodine x-ray of 28 keV from the NaI(Tl) crystal is rather likely, in theory giving a smaller peak at 20.3 keV. That is what I think your "Rhodium" peak is.
The fluorescence peak at 32.2 keV clearly comes from a target with high atomic number, but I have a hard time deciding whether it's barium or either lanthanum or cerium--the detector resolution is technically not good enough to distinguish. Some ceramics have a high content of either of those rare earths.
The activation of the feedthrough still has me puzzled and thinking. It seems to be a beta emitter with few if any gamma radiations.
One thing you might want to try with the XRF setup is to bombard a known light target such as Al and look for the 32.2 keV peak. It's possible that it is not a "true" peak, or that it may originate in the alpha source itself, although right now I cannot think of what else specifically it might be.
I'll throw a suggestion out there: I could do an activation test with your feedthrough here at OSU by exposing it to fast neutrons from a bare PuBe source, followed immediately by a gamma spec on a state-of-the-art HPGe. If any of the activation products emit gammas, we'd find out.
Keep up the great work. I think we can crack this mystery!
-Carl
Sorry it's been a while since I've checked the board.
Your spectrum may show a fluorescence peak at 32.2 keV, but the other peak, in my opinion, is not. At 48.3 keV, according to theory, you should see a Compton-backscattered peak resulting from Compton scattering in the insulator, and indeed you do. In thinner detectors such as this one, the escape of a characteristic iodine x-ray of 28 keV from the NaI(Tl) crystal is rather likely, in theory giving a smaller peak at 20.3 keV. That is what I think your "Rhodium" peak is.
The fluorescence peak at 32.2 keV clearly comes from a target with high atomic number, but I have a hard time deciding whether it's barium or either lanthanum or cerium--the detector resolution is technically not good enough to distinguish. Some ceramics have a high content of either of those rare earths.
The activation of the feedthrough still has me puzzled and thinking. It seems to be a beta emitter with few if any gamma radiations.
One thing you might want to try with the XRF setup is to bombard a known light target such as Al and look for the 32.2 keV peak. It's possible that it is not a "true" peak, or that it may originate in the alpha source itself, although right now I cannot think of what else specifically it might be.
I'll throw a suggestion out there: I could do an activation test with your feedthrough here at OSU by exposing it to fast neutrons from a bare PuBe source, followed immediately by a gamma spec on a state-of-the-art HPGe. If any of the activation products emit gammas, we'd find out.
Keep up the great work. I think we can crack this mystery!
-Carl
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Jon Rosenstiel
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Re: Puzzle Solved!
Hi Carl,
Sorry I’m late on answering, it was my turn to be away for a few days.
You’re absolutely correct about the 20.3keV peak not being rhodium. I aimed my exciter source at a piece of aluminum and got a peak very similar in energy to the one that I originally thought may be rhodium. Also, the Al did NOT give a peak in the area of 32.2keV, so no confusion there.
I ran a couple more tests trying to narrow things down….
I calibrated my MCA using the k-shell x-rays of iodine (28.6keV) and praseodymium (36.0keV). Using that calibration the insulator came in at 31.8keV.
For another poke at it I calibrated my MCA using the 32.2keV barium k-shell x-ray from a Cs-137 disc source. The peak was at channel 157.9 (Centroid). Next I aimed my exciter source at a chunk of barium-strontium glass. That produced a peak at channel 157.5 (Centroid). Finally, I aimed the same exciter source at my feedthrough insulator. That produced a peak at channel 156.6 (Centroid).
In the first test the insulator came in 0.4keV under barium’s 32.2keV x-ray. In the second test the insulator came in 0.3keV under barium’s 32.2keV x-ray. To me that pretty much rules out La or Ce.
Thank you for your offer, but the thought of my prized feedthrough traveling cross country via UPS kinda scares me!
When my fusor is back in operation and producing some good neutron numbers I’ll take a look for prompt gammas…. maybe something will show up. I will also look more closely at the beta decay rate.
Jon Rosenstiel
Sorry I’m late on answering, it was my turn to be away for a few days.
You’re absolutely correct about the 20.3keV peak not being rhodium. I aimed my exciter source at a piece of aluminum and got a peak very similar in energy to the one that I originally thought may be rhodium. Also, the Al did NOT give a peak in the area of 32.2keV, so no confusion there.
I ran a couple more tests trying to narrow things down….
I calibrated my MCA using the k-shell x-rays of iodine (28.6keV) and praseodymium (36.0keV). Using that calibration the insulator came in at 31.8keV.
For another poke at it I calibrated my MCA using the 32.2keV barium k-shell x-ray from a Cs-137 disc source. The peak was at channel 157.9 (Centroid). Next I aimed my exciter source at a chunk of barium-strontium glass. That produced a peak at channel 157.5 (Centroid). Finally, I aimed the same exciter source at my feedthrough insulator. That produced a peak at channel 156.6 (Centroid).
In the first test the insulator came in 0.4keV under barium’s 32.2keV x-ray. In the second test the insulator came in 0.3keV under barium’s 32.2keV x-ray. To me that pretty much rules out La or Ce.
Thank you for your offer, but the thought of my prized feedthrough traveling cross country via UPS kinda scares me!
When my fusor is back in operation and producing some good neutron numbers I’ll take a look for prompt gammas…. maybe something will show up. I will also look more closely at the beta decay rate.
Jon Rosenstiel
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Jon Rosenstiel
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Re: Puzzle Solved! WRONG!
Occam’s razor strikes the Rosenstiel fusor lab!
In my post titled “Puzzle Solved” I wrote that the outside of my hv feedthrough became radioactive after operating my fusor. I attributed the radioactivity to neutron activation of barium in the ceramic.
Wanna’ really know why my feedthrough became radioactive? How about radium daughters? Yes, it’s that simple! The high negative potential around the feedthrough insulator (and hv cable) attract radium daughter products.
After a fusor run of 5 minutes at 24kV a pancake detector placed hard against the feedthrough recorded an activity of 100cpm. (Background here is around 47cpm) Placing the detector hard against the HV cable insulation resulted in an activity of over 800cpm. The 351keV peak of Pb-214 and the 609keV peak of Bi-214 are clearly seen in a gamma spec taken from the hv cable insulation. Washing the cable and insulator remove the activity completely.
Still to be explained is why the inside (vacuum side) of my feedthrough was radioactive. (Please see the original post)
Jon Rosenstiel
In my post titled “Puzzle Solved” I wrote that the outside of my hv feedthrough became radioactive after operating my fusor. I attributed the radioactivity to neutron activation of barium in the ceramic.
Wanna’ really know why my feedthrough became radioactive? How about radium daughters? Yes, it’s that simple! The high negative potential around the feedthrough insulator (and hv cable) attract radium daughter products.
After a fusor run of 5 minutes at 24kV a pancake detector placed hard against the feedthrough recorded an activity of 100cpm. (Background here is around 47cpm) Placing the detector hard against the HV cable insulation resulted in an activity of over 800cpm. The 351keV peak of Pb-214 and the 609keV peak of Bi-214 are clearly seen in a gamma spec taken from the hv cable insulation. Washing the cable and insulator remove the activity completely.
Still to be explained is why the inside (vacuum side) of my feedthrough was radioactive. (Please see the original post)
Jon Rosenstiel
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Carl Willis
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Re: Puzzle Solved! WRONG!
Hi Jon,
Good observation, and totally consistent with the approximate half-life you observed. That interior radioactivity is still a puzzle though!
-Carl
Good observation, and totally consistent with the approximate half-life you observed. That interior radioactivity is still a puzzle though!
-Carl
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Richard Hull
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Re: Puzzle Solved! WRONG!
It is to be remembered that proton bombardment is going on in the fusor as well. Admittedly, the Proton is relatively weak, as Carl noted, but who knows. The number of protons equals the number of neuts so it is a hail storm in there. The fast neuts should not really activate much in the chamber, of course.
Richard Hull
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
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
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Jon Rosenstiel
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Re: Puzzle Solved! WRONG!
I've been exploring the proton angle also. (PIGE, Partilce Induced Gamma Emission) Seems as though protons can only interact with low the Z elements, (Li, F, Na, Mg, Al)
The feedthrough and stalk insulators are alumina, but so far I have not been able to connect the dots.
Jon Rosenstiel
The feedthrough and stalk insulators are alumina, but so far I have not been able to connect the dots.
Jon Rosenstiel