Bonner sphere calibration
-
- Posts: 1494
- Joined: Thu Jun 28, 2001 1:30 am
- Real name: Jon Rosenstiel
- Location: Southern California
Bonner sphere calibration
I'll be sending my Ludlum 12-4 to Ludlum for calibration soon. Is there anything special I should be asking them to do? Or is their standard calibration fine?
Jon Rosenstiel
Jon Rosenstiel
- Richard Hull
- Moderator
- Posts: 15027
- Joined: Fri Jun 15, 2001 9:44 am
- Real name: Richard Hull
Re: Bonner sphere calibration
Well........what can I say.
I told those puddin' heads exactly what I wanted in the way of calibration data returned and they just ignored my requests, puttering along in there little blindered way.
You and I have meters that read in mr/hr. This converts to neut/sq.cm/sec flux per mr/hr via a curve which the manufacturer supplied originally with the manual. (gone now.)
What you need to know is the flux impinging on your rem ball at 1 mr/hr directly.
This means you must get them to move the ball until the thing reads 1 mrem/hr and tell you two simple things. The flux at their source, or, the isotropic emission rate (something that seems to elude them for some reason?) and the exact distance from the ball to the source. (another thing they seem to be mystified over) From here you could do the math.
To them, this is a health safety item for dosimetry and not an absolute neutron counter and all they need do is put the ball where they know is a 1mr/hr, 10mr/hr, 100mr/hr neutron field and turn the pretty pots on the inside until the device reads 1 mrem, 10 mrem, 100mrem, etc. BINGO they are done....NEXT....keep it moving....
I detailed my useage in a nice letter to them and made the request for the above two key pieces of data. I might as well have written it on the stall walls in the men's room in a bus station!!. #$@!#$&*%
Other than failing miserably to do what I instructed. The calibration is perfect in every way, I am sure. I got back several pages of cal data...all on stock forms from which, after a lot of interpolation, mathematical machinations, etc. I managed to INFER the information I needed.
You are on your own pal.......
Richard Hull
I told those puddin' heads exactly what I wanted in the way of calibration data returned and they just ignored my requests, puttering along in there little blindered way.
You and I have meters that read in mr/hr. This converts to neut/sq.cm/sec flux per mr/hr via a curve which the manufacturer supplied originally with the manual. (gone now.)
What you need to know is the flux impinging on your rem ball at 1 mr/hr directly.
This means you must get them to move the ball until the thing reads 1 mrem/hr and tell you two simple things. The flux at their source, or, the isotropic emission rate (something that seems to elude them for some reason?) and the exact distance from the ball to the source. (another thing they seem to be mystified over) From here you could do the math.
To them, this is a health safety item for dosimetry and not an absolute neutron counter and all they need do is put the ball where they know is a 1mr/hr, 10mr/hr, 100mr/hr neutron field and turn the pretty pots on the inside until the device reads 1 mrem, 10 mrem, 100mrem, etc. BINGO they are done....NEXT....keep it moving....
I detailed my useage in a nice letter to them and made the request for the above two key pieces of data. I might as well have written it on the stall walls in the men's room in a bus station!!. #$@!#$&*%
Other than failing miserably to do what I instructed. The calibration is perfect in every way, I am sure. I got back several pages of cal data...all on stock forms from which, after a lot of interpolation, mathematical machinations, etc. I managed to INFER the information I needed.
You are on your own pal.......
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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- Joined: Thu Jul 05, 2001 12:07 am
- Real name:
Re: Bonner sphere calibration
I can't wait to see what happens when I send them a detector with no mR/hr meter, just an output to a scaler....
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- Posts: 1494
- Joined: Thu Jun 28, 2001 1:30 am
- Real name: Jon Rosenstiel
- Location: Southern California
Re: Bonner sphere calibration
Thanks for the reply Richard.
I fired off an e-mail to Ludlum inquiring if they could do our "special" calibration. Also, I offered to pay for the tech's extra time!
We'll see what happens!
Jon Rosenstiel
ps: Richard, (geez, I hate to be so nit-picky, ) but will you please fix the spelling of my last name, (stiel, not steil), in the Fusioneer list? I want to show this off! (major gloat)!
I fired off an e-mail to Ludlum inquiring if they could do our "special" calibration. Also, I offered to pay for the tech's extra time!
We'll see what happens!
Jon Rosenstiel
ps: Richard, (geez, I hate to be so nit-picky, ) but will you please fix the spelling of my last name, (stiel, not steil), in the Fusioneer list? I want to show this off! (major gloat)!
- Richard Hull
- Moderator
- Posts: 15027
- Joined: Fri Jun 15, 2001 9:44 am
- Real name: Richard Hull
Re: Bonner sphere calibration
Jon,
I will correct the name and a thousand pardons, please.
Richard,
Hey, your home-made send in might so befuddle them that they read your attached letter and find out what you really want done.
Richard Hull
I will correct the name and a thousand pardons, please.
Richard,
Hey, your home-made send in might so befuddle them that they read your attached letter and find out what you really want done.
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
-
- Posts: 1494
- Joined: Thu Jun 28, 2001 1:30 am
- Real name: Jon Rosenstiel
- Location: Southern California
Re: Bonner sphere calibration
My Ludlum 12-4 neutron Bonner ball counter has been calibrated and is back in my hot little hands!
I had sent an e-mail to Ludlum explaining what I needed in the way of calibration, and of course I offered to pay them for their extra work. I never received an answer. So I just sent them my 12-4 and let them calibrate it their normal way.
Right before they shipped it back I talked with their tech. He explained that they normally like to set the BF3 tube voltage to an even number but on my unit he had to set it at 1712V because the tube had a rather narrow plateau. He went on to say that he set the input sensitivity at 2.4mV and mentioned that my detector was still very linear across the complete range. He also mentioned that as received it read quite low, (indicated 2mrem/hr instead of 8mrem/hr). This was no doubt due to my un-controlled and excessive knob and dial fiddling! (I wonder if there is a cure)?
The news of my instrument under-indicating was good to hear because that meant I was getting a lot more neuts/sec than I had previously measured!
I placed the freshly calibrated rem ball in position near my fusor and carefully measured and then calculated the “detection sphere” area. (This was after I had read, and re-read, and then re-read a few more times, Richard Hulls post of 08-05-02, “Bonner Sphere-getting the neutron numbers correct”)!
Then I fired up my fusor for some real neutron countin’! At first I was elated by the high neutron counts. Then I started to think something’s not right because the neutron counts seemed to high. I thought I must have somehow screwed up the calculations so I re-read Richard’s post a few more times. The only thing I’m unsure of is the 7.5 neutrons/sq. cm/sec value I’m using for my Ludlum 9” Bonner sphere. (From Ludlum I’ve requested but don’t yet have this number). From Richards post I gather that this number is fairly constant for all Bonner spheres. (Richard, please correct me if this is wrong).
I then remembered seeing a couple of posts from Richard Hull describing fusor runs he’d done complete with neutron counts and input voltage and current. (A post dated 04-11-01 indicated that he achieved 204,100 neutrons/sec with 32.4kV at 5-7mA). (Another post dated 01-23-00 indicated that 20.5kV at 10mA gave 1Mrem)
So, I thought, (dangerous, I know!), maybe I could double-check my numbers by setting my fusor inputs the same and seeing if I get similar neutron counts.
First I set my inputs at 20.5kV, 10mA, (1mrem with Richard’s fusor). And I got…1mrem! (35cpm on my Ludlum, just as the manual indicates). Pretty good so far. Next I set my inputs at 32.4kV, 6mA, (3.25 mrem, 130cpm, 204,100 neutrons/sec with Richard’s fusor).
I did 5 runs, the average being 5.68mrem. With my setup this gave a count of 222,670 neutrons/sec. About 9% higher than Richard’s setup, but still in the ballpark I’d say.
Here is what I got with some other runs: (And why I feel I’m getting inflated neutron count numbers).
40kV at 10mA…..23mrem, 901,675 neutrons/sec.
42kV at 10mA…..26mrem, 1,019,265 neutrons/sec.
And the maximum I’ve ever tried, (with corona hissing like a angry snake)!
45kV at 13mA…..36mrem, 1,411,290 neutrons/sec.
Doesn’t 1.4E+06 neutrons/sec sound kinda high for an amateur fusor?
Two things I’m not sure about. One is the 7.5 neutrons/sq. cm/sec number I’m using for my Ludlum 9” Bonner sphere. The other is the mrem/hr-cpm value. The Ludlum manual states that 1mrem/hr=35cpm, and that’s exactly what I get. When the meter indicates 1mrem/hr I get 34 to 36 counts. When the meter indicates 2mrem/hr I get around 70cpm. But the calibration sheet states that on the X100 range 800mrem/hr=19,400cpm, (1mrem/hr=24.25cpm). What’s going on here?
Jon Rosenstiel
I had sent an e-mail to Ludlum explaining what I needed in the way of calibration, and of course I offered to pay them for their extra work. I never received an answer. So I just sent them my 12-4 and let them calibrate it their normal way.
Right before they shipped it back I talked with their tech. He explained that they normally like to set the BF3 tube voltage to an even number but on my unit he had to set it at 1712V because the tube had a rather narrow plateau. He went on to say that he set the input sensitivity at 2.4mV and mentioned that my detector was still very linear across the complete range. He also mentioned that as received it read quite low, (indicated 2mrem/hr instead of 8mrem/hr). This was no doubt due to my un-controlled and excessive knob and dial fiddling! (I wonder if there is a cure)?
The news of my instrument under-indicating was good to hear because that meant I was getting a lot more neuts/sec than I had previously measured!
I placed the freshly calibrated rem ball in position near my fusor and carefully measured and then calculated the “detection sphere” area. (This was after I had read, and re-read, and then re-read a few more times, Richard Hulls post of 08-05-02, “Bonner Sphere-getting the neutron numbers correct”)!
Then I fired up my fusor for some real neutron countin’! At first I was elated by the high neutron counts. Then I started to think something’s not right because the neutron counts seemed to high. I thought I must have somehow screwed up the calculations so I re-read Richard’s post a few more times. The only thing I’m unsure of is the 7.5 neutrons/sq. cm/sec value I’m using for my Ludlum 9” Bonner sphere. (From Ludlum I’ve requested but don’t yet have this number). From Richards post I gather that this number is fairly constant for all Bonner spheres. (Richard, please correct me if this is wrong).
I then remembered seeing a couple of posts from Richard Hull describing fusor runs he’d done complete with neutron counts and input voltage and current. (A post dated 04-11-01 indicated that he achieved 204,100 neutrons/sec with 32.4kV at 5-7mA). (Another post dated 01-23-00 indicated that 20.5kV at 10mA gave 1Mrem)
So, I thought, (dangerous, I know!), maybe I could double-check my numbers by setting my fusor inputs the same and seeing if I get similar neutron counts.
First I set my inputs at 20.5kV, 10mA, (1mrem with Richard’s fusor). And I got…1mrem! (35cpm on my Ludlum, just as the manual indicates). Pretty good so far. Next I set my inputs at 32.4kV, 6mA, (3.25 mrem, 130cpm, 204,100 neutrons/sec with Richard’s fusor).
I did 5 runs, the average being 5.68mrem. With my setup this gave a count of 222,670 neutrons/sec. About 9% higher than Richard’s setup, but still in the ballpark I’d say.
Here is what I got with some other runs: (And why I feel I’m getting inflated neutron count numbers).
40kV at 10mA…..23mrem, 901,675 neutrons/sec.
42kV at 10mA…..26mrem, 1,019,265 neutrons/sec.
And the maximum I’ve ever tried, (with corona hissing like a angry snake)!
45kV at 13mA…..36mrem, 1,411,290 neutrons/sec.
Doesn’t 1.4E+06 neutrons/sec sound kinda high for an amateur fusor?
Two things I’m not sure about. One is the 7.5 neutrons/sq. cm/sec number I’m using for my Ludlum 9” Bonner sphere. The other is the mrem/hr-cpm value. The Ludlum manual states that 1mrem/hr=35cpm, and that’s exactly what I get. When the meter indicates 1mrem/hr I get 34 to 36 counts. When the meter indicates 2mrem/hr I get around 70cpm. But the calibration sheet states that on the X100 range 800mrem/hr=19,400cpm, (1mrem/hr=24.25cpm). What’s going on here?
Jon Rosenstiel
Re: Bonner sphere calibration
Hi Richard,
Which parameter is a ' #$@!#$&*% ' ?
John
Richard Hull wrote:
> Well........what can I say.
>
> I told those puddin' heads exactly what I wanted in the way of calibration data returned and they just ignored my requests, puttering along in there little blindered way.
>
> You and I have meters that read in mr/hr. This converts to neut/sq.cm/sec flux per mr/hr via a curve which the manufacturer supplied originally with the manual. (gone now.)
>
> What you need to know is the flux impinging on your rem ball at 1 mr/hr directly.
>
> This means you must get them to move the ball until the thing reads 1 mrem/hr and tell you two simple things. The flux at their source, or, the isotropic emission rate (something that seems to elude them for some reason?) and the exact distance from the ball to the source. (another thing they seem to be mystified over) From here you could do the math.
>
> To them, this is a health safety item for dosimetry and not an absolute neutron counter and all they need do is put the ball where they know is a 1mr/hr, 10mr/hr, 100mr/hr neutron field and turn the pretty pots on the inside until the device reads 1 mrem, 10 mrem, 100mrem, etc. BINGO they are done....NEXT....keep it moving....
>
> I detailed my useage in a nice letter to them and made the request for the above two key pieces of data. I might as well have written it on the stall walls in the men's room in a bus station!!. #$@!#$&*%
>
> Other than failing miserably to do what I instructed. The calibration is perfect in every way, I am sure. I got back several pages of cal data...all on stock forms from which, after a lot of interpolation, mathematical machinations, etc. I managed to INFER the information I needed.
>
> You are on your own pal.......
>
> Richard Hull
Which parameter is a ' #$@!#$&*% ' ?
John
Richard Hull wrote:
> Well........what can I say.
>
> I told those puddin' heads exactly what I wanted in the way of calibration data returned and they just ignored my requests, puttering along in there little blindered way.
>
> You and I have meters that read in mr/hr. This converts to neut/sq.cm/sec flux per mr/hr via a curve which the manufacturer supplied originally with the manual. (gone now.)
>
> What you need to know is the flux impinging on your rem ball at 1 mr/hr directly.
>
> This means you must get them to move the ball until the thing reads 1 mrem/hr and tell you two simple things. The flux at their source, or, the isotropic emission rate (something that seems to elude them for some reason?) and the exact distance from the ball to the source. (another thing they seem to be mystified over) From here you could do the math.
>
> To them, this is a health safety item for dosimetry and not an absolute neutron counter and all they need do is put the ball where they know is a 1mr/hr, 10mr/hr, 100mr/hr neutron field and turn the pretty pots on the inside until the device reads 1 mrem, 10 mrem, 100mrem, etc. BINGO they are done....NEXT....keep it moving....
>
> I detailed my useage in a nice letter to them and made the request for the above two key pieces of data. I might as well have written it on the stall walls in the men's room in a bus station!!. #$@!#$&*%
>
> Other than failing miserably to do what I instructed. The calibration is perfect in every way, I am sure. I got back several pages of cal data...all on stock forms from which, after a lot of interpolation, mathematical machinations, etc. I managed to INFER the information I needed.
>
> You are on your own pal.......
>
> Richard Hull
Re: Bonner sphere calibration
Dear Mr Hendron:
The ' #$@!#$&*% ' factor is a polite form of profanity.
I believe it's first use was in Mad magazine during the forties when censorship would not permit the real
article. If you follow the posts here it is fairly common
occurance ' #$@!#$&*% ' it!
Larry Leins
Fusion Tech
The ' #$@!#$&*% ' factor is a polite form of profanity.
I believe it's first use was in Mad magazine during the forties when censorship would not permit the real
article. If you follow the posts here it is fairly common
occurance ' #$@!#$&*% ' it!
Larry Leins
Fusion Tech
- Richard Hull
- Moderator
- Posts: 15027
- Joined: Fri Jun 15, 2001 9:44 am
- Real name: Richard Hull
Re: Bonner sphere calibration
Jon,
I think you might have hit the million neut per second mark!
That would be a record now!
This is likely due to your extremely high fusor voltage. (up on the cross sectional curve) No one has really been here before.
The 7.5 n/sq cm/sec is per mr/hr for a 2.45 mev neutron flux in the center of the rem ball where the tube is. the 24.5 cpm/mr/hr is the remball correction for tube area and efficiency.
Here is the method of linkage for the above two seemingly disparate numberings..... the tube might expose about 10 sq cm of itself to the flux for (7.5 x 10) a ~75 neutron intercept per second. That makes ~4500 or more neuts/minute in the tube. BF3 tubes are under 1% efficient as used in these systems (isotopically un-enhanced BF3 and at only atmospheric pressure) So with ~0.5% efficiency that would work out to about 22.5 or so counts/min/mr/hr or close to the 24.5 actual tallied counts/mr/hr referred to above specifically for the Remball.
Hope this helped out. It is a really tangled web measuring neutrons and a nightmare measuring absolute neutron counts which is what we are trying to do.
I strongly recommend the flux of 7.5n/s/mr/hr for all calcs!
This would mean the central ball point is the point of that flux. Now just note the range center of fusor to center of ball and calculate backwards. 20mrem reading at 30cm would be 20 x 7.5 = 150n/sq cm/sec at 30cm. 4 x 3.14 x 900 = 11,304 sq cm.
Thus, 11,304 X 150 = ~1.7 million n/sec isotropic emission.
WATCHOUT !!!
At this voltage you might be seeing a load of x-rays external to the device. (penetrating shell) You need to check carefully at the 42kv run time with a geiger counter!! Report back to us on this!!!
Richard Hull
I think you might have hit the million neut per second mark!
That would be a record now!
This is likely due to your extremely high fusor voltage. (up on the cross sectional curve) No one has really been here before.
The 7.5 n/sq cm/sec is per mr/hr for a 2.45 mev neutron flux in the center of the rem ball where the tube is. the 24.5 cpm/mr/hr is the remball correction for tube area and efficiency.
Here is the method of linkage for the above two seemingly disparate numberings..... the tube might expose about 10 sq cm of itself to the flux for (7.5 x 10) a ~75 neutron intercept per second. That makes ~4500 or more neuts/minute in the tube. BF3 tubes are under 1% efficient as used in these systems (isotopically un-enhanced BF3 and at only atmospheric pressure) So with ~0.5% efficiency that would work out to about 22.5 or so counts/min/mr/hr or close to the 24.5 actual tallied counts/mr/hr referred to above specifically for the Remball.
Hope this helped out. It is a really tangled web measuring neutrons and a nightmare measuring absolute neutron counts which is what we are trying to do.
I strongly recommend the flux of 7.5n/s/mr/hr for all calcs!
This would mean the central ball point is the point of that flux. Now just note the range center of fusor to center of ball and calculate backwards. 20mrem reading at 30cm would be 20 x 7.5 = 150n/sq cm/sec at 30cm. 4 x 3.14 x 900 = 11,304 sq cm.
Thus, 11,304 X 150 = ~1.7 million n/sec isotropic emission.
WATCHOUT !!!
At this voltage you might be seeing a load of x-rays external to the device. (penetrating shell) You need to check carefully at the 42kv run time with a geiger counter!! Report back to us on this!!!
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
-
- Posts: 1494
- Joined: Thu Jun 28, 2001 1:30 am
- Real name: Jon Rosenstiel
- Location: Southern California
Re: Bonner sphere calibration
Thanks for the explanation Richard. This stuff is gradually sinking into my brain, bit by bit.
I believe I’ve done everything correctly, here’s what I have:
Fusor diameter= 16.51cm, (r=8.255cm)
Bonner sphere diameter= 22.86cm, (r=11.43cm)
Distance between Bonner sphere and fusor=0.71cm
Total center to center distance=20.395cm
So, 20.395 X 20.395 X 4pi =5227sq cm.
Results from a few high power runs earlier this evening:
42kV, 13mA, (546W)=34mrem/hr. 5227 X 7.5 X 34=1.33E+06 n/s
40kV, 13mA, (520W)=32mrem/hr. 5227 X 7.5 X 32=1.25E+06 n/s
40kV, 12mA, (480W)=28mrem/hr. 5227 X 7.5 X 28=1.09E+06 n/s
I performed an x-ray check with the fusor operating at 40kV, 13mA and got the following:
An Eberline HP260 pancake probe 6” from the fusor indicated 10,000cpm. The HP260 probe uses the same detector as the PGM probe. (In one of your videos I believe you were using a PGM probe).
A Victoreen 440RF x-ray survey meter 4” from the fusor indicated close to 3mrem/hr. (Not calibrated for better than 12 years).
If either of these instruments is faced directly up to the viewport they immediately peg out! My ccd camera is not a happy camper at these x-ray levels! I can see 6 pixels that have permanently “turned on”.
What you think about the x-ray hazard, should I be thinking of lead shielding?
Jon Rosenstiel
I believe I’ve done everything correctly, here’s what I have:
Fusor diameter= 16.51cm, (r=8.255cm)
Bonner sphere diameter= 22.86cm, (r=11.43cm)
Distance between Bonner sphere and fusor=0.71cm
Total center to center distance=20.395cm
So, 20.395 X 20.395 X 4pi =5227sq cm.
Results from a few high power runs earlier this evening:
42kV, 13mA, (546W)=34mrem/hr. 5227 X 7.5 X 34=1.33E+06 n/s
40kV, 13mA, (520W)=32mrem/hr. 5227 X 7.5 X 32=1.25E+06 n/s
40kV, 12mA, (480W)=28mrem/hr. 5227 X 7.5 X 28=1.09E+06 n/s
I performed an x-ray check with the fusor operating at 40kV, 13mA and got the following:
An Eberline HP260 pancake probe 6” from the fusor indicated 10,000cpm. The HP260 probe uses the same detector as the PGM probe. (In one of your videos I believe you were using a PGM probe).
A Victoreen 440RF x-ray survey meter 4” from the fusor indicated close to 3mrem/hr. (Not calibrated for better than 12 years).
If either of these instruments is faced directly up to the viewport they immediately peg out! My ccd camera is not a happy camper at these x-ray levels! I can see 6 pixels that have permanently “turned on”.
What you think about the x-ray hazard, should I be thinking of lead shielding?
Jon Rosenstiel
Re: Bonner sphere calibration
Hey John
A major problem wll be observation 45kv xrays
will kill a ccd in short order....you have now entered the high power regiem. I would use a mirror backed with a thin sheet of lead for shielding but much higher than 60kv xray I'd be paranoid and use a 1/4 inch sheet of lead. When I start pulsing all view port observations will be by mirror.
Larry Leins
Fusion Tech
A major problem wll be observation 45kv xrays
will kill a ccd in short order....you have now entered the high power regiem. I would use a mirror backed with a thin sheet of lead for shielding but much higher than 60kv xray I'd be paranoid and use a 1/4 inch sheet of lead. When I start pulsing all view port observations will be by mirror.
Larry Leins
Fusion Tech
- Richard Hull
- Moderator
- Posts: 15027
- Joined: Fri Jun 15, 2001 9:44 am
- Real name: Richard Hull
Re: Bonner sphere calibration
Definitely get a wall of lead between the fusor and you.
You can do fine with a 1/4" or 1/2" lead plate and this will do fine probably up to about 60+ kv. By placing it really close to the fusor, (hard up against it), you can create a huge shadow cone at 1 meter. This reduces the lead weight and volume. If in a basement, remember, "sky shine" will irradiate the folks upstairs. Nothing however beats the protection offered by the good old inverse square law.
As the fusor is not run like a washer/dryer. You really only need to make sure that the operator and observers are all within the shadow cone.
The CCD can be protected a good bit by interposing a thick piece of lead glass. Like a small 1" or 2" diameter disk. (Mc Master-Carr). The classic mirror suggestion is OK as well, but most of the time this is poor due to the added distance making the image smaller in the ultrawide angle lens found on the small security cameras with fixed lens.
Richard Hull
You can do fine with a 1/4" or 1/2" lead plate and this will do fine probably up to about 60+ kv. By placing it really close to the fusor, (hard up against it), you can create a huge shadow cone at 1 meter. This reduces the lead weight and volume. If in a basement, remember, "sky shine" will irradiate the folks upstairs. Nothing however beats the protection offered by the good old inverse square law.
As the fusor is not run like a washer/dryer. You really only need to make sure that the operator and observers are all within the shadow cone.
The CCD can be protected a good bit by interposing a thick piece of lead glass. Like a small 1" or 2" diameter disk. (Mc Master-Carr). The classic mirror suggestion is OK as well, but most of the time this is poor due to the added distance making the image smaller in the ultrawide angle lens found on the small security cameras with fixed lens.
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: Bonner sphere calibration
For those wanting the ultimate radiation protection
http://www.drct.com/dss/lead/leadwea.html
(Leaded underwear). They also sell leaded glass for your CCD protection.
Parts for constructing a fusor: $2500.00
Leaded Underwear : $90.00
Building a working Fusor: Priceless!
Enjoy!
http://www.drct.com/dss/lead/leadwea.html
(Leaded underwear). They also sell leaded glass for your CCD protection.
Parts for constructing a fusor: $2500.00
Leaded Underwear : $90.00
Building a working Fusor: Priceless!
Enjoy!
-
- Posts: 1494
- Joined: Thu Jun 28, 2001 1:30 am
- Real name: Jon Rosenstiel
- Location: Southern California
Re: Bonner sphere calibration
Well put, AG, well put!
Jon Rosenstiel
Jon Rosenstiel
-
- Posts: 1494
- Joined: Thu Jun 28, 2001 1:30 am
- Real name: Jon Rosenstiel
- Location: Southern California
Re: Bonner sphere calibration
I used 0.5", (1.27cm), of lead sheeting to shield myself, (and any observers), from my fusor's x-ray radiation.
With the fusor operating at 42kV, 13mA and my Eberline HP-260 pancake probe located 6", (15.2cm), from the fusor I observed a maximum of 10,000 cpm without the lead shielding in place. With the 0.5" lead shield in place the Eberline indicated 2,500cpm.
With the probe placed against my chest, (lead shield in place), the Eberline indicated 160cpm. (The background here is around 45cpm).
Jon Rosenstiel
With the fusor operating at 42kV, 13mA and my Eberline HP-260 pancake probe located 6", (15.2cm), from the fusor I observed a maximum of 10,000 cpm without the lead shielding in place. With the 0.5" lead shield in place the Eberline indicated 2,500cpm.
With the probe placed against my chest, (lead shield in place), the Eberline indicated 160cpm. (The background here is around 45cpm).
Jon Rosenstiel
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- Posts: 1494
- Joined: Thu Jun 28, 2001 1:30 am
- Real name: Jon Rosenstiel
- Location: Southern California
Re: Bonner sphere calibration
EMR protection:
http://www.lessemf.com/personal.html
Should the silver lined underwear be worn inside or outside the leaded underwear?
Jon Rosenstiel
http://www.lessemf.com/personal.html
Should the silver lined underwear be worn inside or outside the leaded underwear?
Jon Rosenstiel