Posting Comment for "Soft X-ray Output from a Vacuum Rectifier"

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26th April 2011 21:55

Alan Yates wrote...


Not sure of the make or model of the device, but the imaging was performed at the local radiology centre. I was reading the voltage and current settings from the LED display on the remote control head. It was a small flat box which hung on the wall and connected the machine via a cable. The unit itself was quite large, being a orthopantomograph it was floor-standing and the source and detector rotated around my head. I had to sink my shoulders a bit to not get hit by the gantry as it rotated, while still biting on the registration/reference thing.

In the dentists office he used a much more trivial source, one of those gun-like heads mounted on a sprung arm system. The film was loaded into a foil cassette and placed in my mouth. The x-ray head had a stand-off to set the appropriate distance to my cheek. Development was chemical, performed in a few minutes by one of his assistants.

I have seen modern digital detectors which I assume are CCDs? No development and USB-connectivity back to a laptop. Neat - I want one. :)



22nd February 2011 22:24

Dr.Detlef Klaehn wrote...

Hi Alan,

Coming by case to your website I must say that is mind warming. I intended to study Math and Physics but ended as a dentist ;-)) And I'm a radio ham too..DC1JC.

So I would give some feedback with Orthopantomographs for dentist. All OPG machines I know are running between 60 and 90 kV and my 30 year old Siemens machine had 17mAs time-current product. We just bought a new digital x-ray DVT which in OPG mode has only 1/3 of the radiation.What kind of machine has your dentist???still from Conrad Roentgen ( who by the way lived ca. 20 km from here) By the way: the dentists go for digital x-ray and the old filmcasettes have wolramat foils to amplify light emission.So maybe if it's interesting to you ask a dental supply company to hand you over the foils before discarding them..

Best regards and 73


22nd December 2009 17:11

Alan Yates wrote...


Thanks for that info.

I haven't done any more work with radiation of late, but I do mean to build an ionisation chamber detector at some point. I acquired some extremely low input bias Op-Amps that should do the trick but the feedback resistance is a bit more challenging, I need to build an instrument to help me measure terra-Ohm or larger resistances.

I sourced some Sodium Tungstate, but have not attempted to synthesise Calcium or Cadmium Tungstate. I did note a small photoelectric effect on normal 1N4007 rectifier diodes exposed to the x-ray beam, but my source is (thankfully) so dim and soft they are not practical as detectors. I have some cassettes who's scintillator screen plus some photo diodes would probably make excellent detectors.

Some day I'll have to try tomography, the mechanics would be simple enough - more so if Lego Technics or Meccano was still easily available.

I did some calculations the other day that suggest the earth's magnetic field is usable for MR imaging with very long integration times, kinda like a proton precession magnetometer but with gradient coils for imaging. Modern PC power would seem to make it fairly practical with just a sound card and some kind of micro-controller interface to drive the gradient coils and a main alignment coil. MR imaging would be legal and safe as there is no ionising radiation involved at all.

Getting something to hold-still long enough suggests fruit or veg as initial test subjects, their water content should be sufficient to return a signal. Noise would be the biggest problem, and that is where long integration might make it possible to get enough SNR to actually image volumes.



18th December 2009 17:15

Tim Fidler wrote...


Herr Rontgen knocked off is Mamma in law doing this sort of stuff.... perhaps that was his idea in using her as model - so they say.

2. Suggest using CaF2 - calcium flurite as a fluorescer. You can get this at lapiadary rock shop places - shouild not pay 2-3 dollars for say 200g piece. various means will cut it into slivers. Not sure of fluro activity at this level of xrays - certainly will work at 50kV as used in US in 50s for real time imaging this way.

3. if you do find a Cds-Te semiconductor cell for this sort of detection I woujld be most interested in where from and howmuchisit (Emmachisit) - I do industrial xray work and this sort of detector should be (in digital mode - good / bad) be much better than the 90V mini glass tubes in common use.

4. you might be able to get a Minature glass detector tube from Australian Radiation services in Blkburn area Victoria but you might have to pay per nose for it. It you tell them it is for repair of an existing Roffey unit. They may report (Victorian health department) you if you bare your b_m as to what you are doing... and you don't need that.

For instance every irradiating device is supposed to b serial numbered and registered and yes Paid for in terms of licence fees $200 per year.

Tim Fidler - registered Industrial Gamma and Xray , Aindt # 2885 Vic

5th June 2009 00:27

Dmitry wrote...

Very interesting experiment, Alan!

I wonder if some ham people even tried to do something like you do with X-Rays.

Take care and have fun!