If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Grenadier wrote ...
Well, since proud mary's estimate was .5sv at a meter, the distance from the tube to the far wall of the box is about .5m So 4sv/min. But i will only be running the tube at 1/4 max power, 1sv/min. It was really a complete guess. :) And you're right, it will be at 50kv most of the time whose HVL is .06mm. I'll never take it past 70kvp anyway.
With Va = 50kVp, Ia = 0.5mA, the dose rate at 1 metre centre beam will be about 6 Sv/hr.
With 4.6mm Pb shielding (3.6mm box, plus 1mm apron) the dose rate at 1 metre will fall to about 0.001 uSv/hr.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
good to know.
edit:
ugh, my rheostat just came and it has too much resistance. It's 0-25 ohm and it turns out i need a 5 ohm. Oh well, i suppose i can just use it to control the heater anyway, even if everything from white hot to cold is on 1/8 of a turn.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Proud Mary wrote ...
Grenadier wrote ...
Well, since proud mary's estimate was .5sv at a meter, the distance from the tube to the far wall of the box is about .5m So 4sv/min. But i will only be running the tube at 1/4 max power, 1sv/min. It was really a complete guess. :) And you're right, it will be at 50kv most of the time whose HVL is .06mm. I'll never take it past 70kvp anyway.
With Va = 50kVp, Ia = 0.5mA, the dose rate at 1 metre centre beam will be about 6 Sv/hr.
With 4.6mm Pb shielding (3.6mm box, plus 1mm apron) the dose rate at 1 metre will fall to about 0.001 uSv/hr.
I don't think those numbers are entirely correct.
I tried running those same numbers through RadPro, I don't know if that's what you used. It gave me 5.85 Sv/hr when I selected only 1mm of beryllium filtration in the beam, and the same conditions as you used (50kV, 0.5mA, 100cm). Since Grenadiers tube is not a beryllium window tube, these numbers are a lot higher than they should be. I'm not sure how much filtration the glass of his tube offers, but glass filtration for dental tubes is often quoted as equivalent to around 0.8mm of aluminium. Example: . RadPro doesn't let me add an arbitrary aluminium filter thickness, there are only a few choices, but if I add 0.5mm of aluminium filtration, I get just under 0.35 Sv/hr, or about 1/15 of the previous quote. If I select 1mm of aluminium filtration, I get just about half of that again, so I guess it's somewhere in between those two. It's quite stunning how much difference the glass filtration makes.
Edit: and with the 4.6mm lead shielding it will be down to about 0.064 nSv/hr according to RadPro, or over 4000 times less than background radiation. Bear in mind that this is a meter from the tube. Factoring in the 400' Grenadier said he would be from the experiment, we are talking about 120 million times less than background. Upping the tube voltage to 70kV increases the dose dramatically, to only 40 times less than background. For a one minute exposure, the added radiation dose you will receive is equal the background dose you get from living for 1.5 seconds. Or flying in an airplane for about 140 milliseconds. And even this is assumin the tube is pointing at you inside the box, through it's thinnest point, running at 70kV, and probably with less calculated inherent shielding from the glass than in reality (as RadPro only let me select 0.5mm). And even then, RadPro is made to over-estimate. I'm therefore pretty confident in saying that you are pretty safe with all the precautions you're taking, and to be honest, I think all the working with lead will harm you much more in the long run. Assuming all the safety precautions you mentioned are used, of course.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Anders M. wrote ...
Proud Mary wrote ...
Grenadier wrote ...
Well, since proud mary's estimate was .5sv at a meter, the distance from the tube to the far wall of the box is about .5m So 4sv/min. But i will only be running the tube at 1/4 max power, 1sv/min. It was really a complete guess. :) And you're right, it will be at 50kv most of the time whose HVL is .06mm. I'll never take it past 70kvp anyway.
With Va = 50kVp, Ia = 0.5mA, the dose rate at 1 metre centre beam will be about 6 Sv/hr.
With 4.6mm Pb shielding (3.6mm box, plus 1mm apron) the dose rate at 1 metre will fall to about 0.001 uSv/hr.
I don't think those numbers are entirely correct.
I tried running those same numbers through RadPro, I don't know if that's what you used. It gave me 5.85 Sv/hr when I selected only 1mm of beryllium filtration in the beam, and the same conditions as you used (50kV, 0.5mA, 100cm). Since Grenadiers tube is not a beryllium window tube, these numbers are a lot higher than they should be. I'm not sure how much filtration the glass of his tube offers, but glass filtration for dental tubes is often quoted as equivalent to around 0.8mm of aluminium. Example: . RadPro doesn't let me add an arbitrary aluminium filter thickness, there are only a few choices, but if I add 0.5mm of aluminium filtration, I get just under 0.35 Sv/hr, or about 1/15 of the previous quote. If I select 1mm of aluminium filtration, I get just about half of that again, so I guess it's somewhere in between those two. It's quite stunning how much difference the glass filtration makes.
Your knowledge and practical experience are clearly so much greater than mine, Anders, that I have no hesitation in leaving Mr McGoo in your capable hands.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
I'm not sure if that is sarcasm, Proud Mary, I certainly hope not, as I was just pointing out an error in your calculation. I'm not sure what experience or knowledge has to do with this.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
Very good to know. I was starting to have my doubts about this, but now i am reassured.
I ran into a snag on distance though. My long extension cord is gone, and now i only can find my 100' one. So i came up with a solution; I'll put myself in the basement. The rays would have to go through a whole bunch of earth, and then some cinder block and a lead apron to reach me.
Also, i'm thinking of buying some 1mm lead flashing to line the box, i need it anyway to make an apron. Problem is, it's $125. Maybe if i get this thing running alright, i could start a radiograph service. People could send me an item and $15, then i use $5 to mail it back w/ a pic and keep $10. Idk.
Image, the box isnt drawn to scale. It's only 3 feet high, tube 2.5 ft off ground.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I don't know if i want to do this anymore. But i put so much time and money into it. God i wish i could just sell it all and forget about it. I know i'll hate myself for it but it's just not worth it, but i'm afraid of it. I can't afford any lead sheet.
How much could i sell the tube for? It's in great condition. What could i do with the lead box?
I'll keep the transformer and variac, but even then, i have no use.
F*ck i'm just so conflicted right now. I'd hate to sell it, i don't want to spend the $$ to finish it. Please help me decide.
Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
I'm taking it apart again, this time for good. I'll sell the tube, the holder, the intensifying screens, and the "oil tub" for $200 if anyone is interested. What should i do with the lead box?
Also, what's a good project for me to do with that transformer?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Anders M. wrote ...
I'm not sure if that is sarcasm, Proud Mary, I certainly hope not, as I was just pointing out an error in your calculation. I'm not sure what experience or knowledge has to do with this.
Not at all, Anders. All of my tubes have Be windows, and I didn't stop to think that this dental tube does not when making my calculation. I have no experience at all of using dental tubes, (preferring grounded anode types designed for a few watts input,) but I understand that you do, hence my recommendation.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Oh, ok, I misread it then. Sorry for any confusion.
Grenadier, I'm sorry to hear that you've abandoned the project. X-rays can be a very rewarding hobby, and I'm sure you could do it in a safe way, seeing all the safety precautions you've taken.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Grenadier's big thread of Röntgen related shenanigans
