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 #2012
Joined: Sat Mar 07 2009, 10:22AM
Location: Slovakia
Posts: 45
Will keep you updated on it after May or so, maybe sooner. Will have state exams soon..
Got a few more flybacks from the scrapyard, a Soviet DP-5 radiometer to go along with the czechoslovak one, and a green screen instead of the blue intensifier. In the meantime I'm trying to look for another x-ray tube to try out. 89 dollars for the Bkh-4 just seems too much.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
climatex wrote ...
I'd say a few sieverts per hour, 5-10cm away from the tube. Soft x-rays are difficult to measure, that's why I can provide just a rough estimate.
With anode voltage 50 kV and anode current 1 mA, the dose rate at 500 mm centre beam will be of the order of hundreds of Sv/hr, and perhaps even more. It's not possible to give a better estimate than this without knowing the thickness and mass attenuation coefficient of the glass for photons <50 keV - but certainly very dangerous.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
Proud Mary wrote ...
climatex wrote ...
I'd say a few sieverts per hour, 5-10cm away from the tube. Soft x-rays are difficult to measure, that's why I can provide just a rough estimate.
With anode voltage 50 kV and anode current 1 mA, the dose rate at 500 mm centre beam will be of the order of hundreds of Sv/hr, and perhaps even more. It's not possible to give a better estimate than this without knowing the thickness and mass attenuation coefficient of the glass for photons <50 keV - but certainly very dangerous.
This doesn't sound right. I checked these numbers with the Tucker/Barnes/Chakraborty model for tungsten target x-ray spectra, which is known to be quite accurate. I had to make a few assumptions, I assumed that the anode angle was 19 degrees and that the tube glass was 2mm thick borosilicate. This gave me a dose rate of a hair above 1Gy/hr at 50kV, 1mA.
Medical tubes are as far as I know always made of borosilicate glass (unless they were made before the middle of last century), which has well-known mass attenuation coefficients. Dental x-ray tubes consistently have glass around 2mm thick unless the glass has been ground down where the x-ray beam exits. 19 degrees is also by far the most common anode angle for dental tubes, except for modern ones with sub-0.7mm focal spots which tend to have smaller anode angles.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Wolfram wrote ...
Proud Mary wrote ...
climatex wrote ...
I'd say a few sieverts per hour, 5-10cm away from the tube. Soft x-rays are difficult to measure, that's why I can provide just a rough estimate.
With anode voltage 50 kV and anode current 1 mA, the dose rate at 500 mm centre beam will be of the order of hundreds of Sv/hr, and perhaps even more. It's not possible to give a better estimate than this without knowing the thickness and mass attenuation coefficient of the glass for photons <50 keV - but certainly very dangerous.
I dare say you are right, Anders! I have no experience with dental tubes, and underestimated the thickness of the glass wall. This doesn't sound right. I checked these numbers with the Tucker/Barnes/Chakraborty model for tungsten target x-ray spectra, which is known to be quite accurate. I had to make a few assumptions, I assumed that the anode angle was 19 degrees and that the tube glass was 2mm thick borosilicate. This gave me a dose rate of a hair above 1Gy/hr at 50kV, 1mA.
Medical tubes are as far as I know always made of borosilicate glass (unless they were made before the middle of last century), which has well-known mass attenuation coefficients. Dental x-ray tubes consistently have glass around 2mm thick unless the glass has been ground down where the x-ray beam exits. 19 degrees is also by far the most common anode angle for dental tubes, except for modern ones with sub-0.7mm focal spots which tend to have smaller anode angles.
Registered Member #2012
Joined: Sat Mar 07 2009, 10:22AM
Location: Slovakia
Posts: 45
Agreed with Anders here; I'd say hudreds of sieverts for those Soviet microfocus tubes when overdriven properly.
A nice estimate would also be to measure gamma at one meter away from the anode, with no blocking material, except the bulb itself, standing in the way of the x-ray beam. Radpro calculator would then do the rest.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
climatex wrote ...
I'd say hudreds of sieverts for those Soviet microfocus tubes when overdriven properly.
Yes, that is why I didn't notice my mistake.
According to Radpro, and using a conversion factor of 0.6 for the Ag target, my Svetlana 0.3BSV25-Ag (60kV, 5mA, Be windows) will produce a dose rate of (zeroth order approximation) 16,000 Sv/hr at 5 cm - enough to cause very serious burns in a few seconds.
Registered Member #2012
Joined: Sat Mar 07 2009, 10:22AM
Location: Slovakia
Posts: 45
I've seen some of the Svetlana monster x-ray tubes, could you show a photo of yours? Or, have you got some nice realtime fluoroscope with it? With 60 kilovolts and 5mA that should be a cinch.
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.
X-ray photos, First light
I have no experience with dental tubes, and underestimated the thickness of the glass wall. 