Could you make a gamma ray tube using the same physics as xray tubes? - Page 1
Forum section: electronics / general

author: Beamin
author_rank: Super Contributor
timestamp: September 13, 2019, 09:54:15 pm
content: Can you produce xrays using an oscillator, the same way you make radio waves? Or can you accellerate electrons fast enough to get gamma rays off an xray tube? Or is that not limited by voltage but the electrons in the tungsten target(not the electrons shot at it)?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 13, 2019, 10:51:45 pm
content: https://en.wikipedia.org/wiki/Wiggler_(synchrotron)

author: Nominal Animal
author_rank: Super Contributor
timestamp: September 14, 2019, 12:16:43 am
content: Quote from: Beamin on September 13, 2019, 09:54:15 pmLike Alex Eisenhut wrote above (the link should include the trailing parenthesis!), you can use aWiggler, a type ofsynchrotron, to generate x-ray photons.The "trick" is that the electrons are in vacuum, instead of a conductor, and are accelerated using magnetic fields. It is their acceleration/deceleration that generates the x-ray photons. So, while one could describe it as a harmonic oscillator (tuned to the increasing kinetic energy of the electrons in a synchrotron), it is a different mechanism to how adipole antennaworks; and definitely not an electronic oscillator circuit.Electrons in any conductor are not fast enough (cannot gain enough kinetic energy) to do that, not even in superconductors, because to have 100 keV of kinetic energy, the electrons have to be moving at least half the speed of light in vacuum.Quote from: Beamin on September 13, 2019, 09:54:15 pmThe radiation spectrum from an x-ray tube (or any electron beam) consists of two distinct features.The easier to detect part is the emission spikes, whose location is determined by the electron configuration of the target. Their wavelengths stay the same, only intensity varies depending on the kinetic energy of the accelerated electrons. These spikes are created by electron-electron interactions, between the accelerated electrons and the electrons bound in the target atoms.The other, lower intensity part with a continuous spectrum, is thebremsstrahlung(deceleration radiation) caused by electrons slowing down as they deflect from the target atom nuclei. This part has a smooth "hump" below the maximum energy, corresponding to the acceleration voltage (Emax=eV, whereeis the electron charge, andVis the acceleration voltage).The maximum energy of the bremsstrahlung spectrum is only limited by the effective acceleration voltage; so yes, you can get over 100 keV photons from an x-ray tube.However, the terms "x-ray" and "gamma ray" do not actually describe their actual energies, but are used by us humans to describe how they were generated. Obviously, looking at the photon itself, you cannot tell exactly how it was created; the reason for the terms is more aboutengineeringthanscience.Traditionally, a photon with 100 keV energy or less is considered an "x-ray photon", and a "gamma-ray photon" if the energy is higher. However, that 100 keV is a VERY fuzzy limit, and means roughly .. nothing. You see, if we use a linear electron accelerator, we can accelerate electrons to megaelectronvolt energies, well and truly into the gamma-ray spectrum; however, the photons are still generated by electron-nuclei interaction, not nuclear decay, so they are called "x-rays"!In particular, in treating deep-tissue cancers,megavoltagex-rays are used, with energies in the 4 - 24 MeV range.Based purely on their energy spectra, the photons involved should be called "gamma-ray photons", but because the term "x-ray"/"gamma ray" is used to describe the method of generation rather than the energy range, they are called x-rays. While they are generated in linear electron accelerators and not x-ray tubes, the difference between the two is basically adding more acceleration stages and adjusting/pulsing the voltages to boost the acceleration.

author: German_EE
author_rank: Super Contributor
timestamp: September 14, 2019, 09:03:36 am
content: I get the feeling that you know what you're talking about here