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Registered Member #2261
Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581
I've noticed talk about very soft X-Rays here for some time and wondered what it is about them that particularly draws interest? More broadly, since Wikipedia doesn't go into much detail, can anyone sum up what are the particular characteristics and applications of the various regions of the X-Ray Spectrum?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
IntraWinding wrote ...
No one knows, or no one's telling?
Sorry not to have replied quicker, Alan.
X-ray lasers, and x-ray microscopy, both use low energy X-rays, and there is growing interest in x-ray astronomy using these longer wavelengths. There is a large and growing body of scientific research on ultra-soft rays, and their application in biological imaging in particular.
From the point of view of the amateur scientist, low energy x-rays are attractive because power supply requirements are relatively modest, and much lighter and less costly shielding can be used to contain the ionising radiation. As I have written in my Life Below 5 keV project thread: Nothing described or discussed here is a "radiation generator" as defined by The Ionising Radiations Regulations 1999 and European Council Directive 92/3/Euratom as "electrical equipment emitting ionising radiation and containing components operating at a potential difference of more than 5kV"
But great care must still be taken if adverse events are to be avoided.
While tubes with beryllium windows remain the standard small-scale means for producing photons down to a few keV, glow discharges can produce abundant emission in the ultra-soft, offering the amateur the chance to make their own sources using only relatively modest vacuums compared with the pressures needed in thermionic X-ray tubes.
The production, manipulation, detection, and dosimetry of ultra soft x-rays are all open to pioneering and experiment, and all offer the challenge of devising and constructing equipment that cannot be bought off the shelf, or found in electronic scrap yards.
Registered Member #2261
Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581
Thanks - That's a lot of good reasons. I guess though that if these rays are easily shielded, then by the same token they won't be much use for taking conventional looking x-ray photographs. Is it useful to to think of this region as short wave UV instead?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
IntraWinding wrote ...
I guess though that if these rays are easily shielded, then by the same token they won't be much use for taking conventional looking x-ray photographs.
It's more a question of choosing the wavelength most suitable to the task in hand. The 70 keV rays used in dental imaging wouldn't be of any use at all in the radiography of a jellyfish. The ultra soft rays used in the x-ray microscopy of biolgical sections would cut no mustard in the imaging of steel castings.
IntraWinding wrote ...
Is it useful to to think of this region as short wave UV instead?
The term 'Grenz rays' was at one time widely applied to very soft x-rays seen as being on the 'border' (German: grenze) between XUV and X-rays proper.
I have bought the term back into use to indicate rays below 4.999 keV produced by sources using less than a potential difference of 5 kV - and therefor not a 'radiation generator' as defined by IRR 99 and EC law.
A number of manufacturers such as Hamamatsu have started produced equipment using 4.9 kV x-ray tubes in order to avoid the encumbrance of the UK and EC regulatory framework.
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X-Ray Spectrum Characteristics
