High energy bremsstrahlung production in non vacuum environments

[Rev. Cheeseman]

Vacuum is used when generating bremsstrahlung rays because it:

Prevents scattering
Preserves phase coherence
Allows long acceleration distances
Maintains beam quality

Without these four, is it still possible to generate 100 MeV bremsstrahlung rays although the 100 MeV bremsstrahlung rays may be not as good as when using vacuum?

 

[Astronuc]

Vacuum is used when generating bremsstrahlung rays because it:

Prevents scattering
Preserves phase coherence
Allows long acceleration distances
Maintains beam quality

Acceleration of charged particles takes place in a vacuum so that the bulk of the particles are accelerated to more or less the same energy, prevent scattering, and so on.

Bremsstrahlung radiation (rays) occur when charged particles interact, e.g., when an electron is accelerated (or declerated) near a proton or nucleus, and the acceleration/deceleration of a charged particle in an electric field generates a photon.

Bremsstrahlung is a German word that means "braking radiation." It is a type of radiation released when a fast-moving charged particle (such as an electron) slows down suddenly. This happens when the particle interacts with the atoms in a material. The most encountered cases of bremsstrahlung are produced by beta-emitting nuclides and x‑ray machines.

Ref: https://ph.health.mil/topics/workplacehealth/hp/Pages/bremsstrahlung-safety.aspx

In accelerators, there is a 'source' of charged particles, most often electrons and protons, but also nuclei and other subatomic particles. Usually, the beam of particles impinges upon a 'target'. In the case of electrons, for example, bremsstrahlung radiation occurs when an electron slows (brakes) or accelerates in the nuclear Coulomb field.
https://www.sciencedirect.com/topics/physics-and-astronomy/bremsstrahlung


https://ocw.mit.edu/courses/22-105-...05/d6e432ae955f2a598e67c983e42704ab_chap7.pdf

Without these four, is it still possible to generate 100 MeV bremsstrahlung rays although the 100 MeV bremsstrahlung rays may be not as good as when using vacuum?

100 MeV bremsstrahlung photons would be extraordinary. I'm not familiar with an example, at least not in a terrestrial accelerator program.

One concern with high energy photons is the potential for photonuclear reactions, which start in the low MeV range, about 5-10 MeV depending on the nucleus involved. It is a consideration for electron accelerators used to generate X-rays/gamma rays.

 

[Rev. Cheeseman]

Acceleration of charged particles takes place in a vacuum so that the bulk of the particles are accelerated to more or less the same energy, prevent scattering, and so on.

Bremsstrahlung radiation (rays) occur when charged particles interact, e.g., when an electron is accelerated (or declerated) near a proton or nucleus, and the acceleration/deceleration of a charged particle in an electric field generates a photon.


Ref: https://ph.health.mil/topics/workplacehealth/hp/Pages/bremsstrahlung-safety.aspx

In accelerators, there is a 'source' of charged particles, most often electrons and protons, but also nuclei and other subatomic particles. Usually, the beam of particles impinges upon a 'target'. In the case of electrons, for example, bremsstrahlung radiation occurs when an electron slows (brakes) or accelerates in the nuclear Coulomb field.
https://www.sciencedirect.com/topics/physics-and-astronomy/bremsstrahlung


https://ocw.mit.edu/courses/22-105-...05/d6e432ae955f2a598e67c983e42704ab_chap7.pdf


100 MeV bremsstrahlung photons would be extraordinary. I'm not familiar with an example, at least not in a terrestrial accelerator program.

One concern with high energy photons is the potential for photonuclear reactions, which start in the low MeV range, about 5-10 MeV depending on the nucleus involved. It is a consideration for electron accelerators used to generate X-rays/gamma rays.

I think IIRC there were several accelerators that can generate 22-30 MeV bremsstrahlung photons. IMO even without vacuum, 22-30 MeV bremsstrahlung photons productions are possible but with disadvantages like too messy, not safe, etc. Isn't it?

 

[Astronuc]

I think IIRC there were several accelerators that can generate 22-30 MeV bremsstrahlung photons. IMO even without vacuum, 22-30 MeV bremsstrahlung photons productions are possible but with disadvantages like too messy, not safe, etc. Isn't it?

There are electron accelerators used to generate photons in the MeV range. Within the accelerators, the electrons travel in a vacuum between source and target. The photons generated by the bremsstrahlung process can then propagate in air.

Electron linacs, like other charged particle accelerators, incorporate vacuum chambers to avoid energy loss due to scattering.

See 5.5.3 Vacuum Considerations in
https://cds.cern.ch/record/277966/files/p17.pdf?version=1


See Slide 12 and note the vacuum pump attached to the electron tube in
https://ccah.vetmed.ucdavis.edu/sit...rces/pdfs/rad-onc-matney-x-ray-generators.pdf

Without a vacuum, accelerated electrons (from the electron gun) would collide with other electrons in the air, or whatever gas would occupy the accelerator chamber, and the faster electrons would scatter on the atomic electrons and lose energy.

 

[Rev. Cheeseman]

There are electron accelerators used to generate photons in the MeV range. Within the accelerators, the electrons travel in a vacuum between source and target. The photons generated by the bremsstrahlung process can then propagate in air.

Electron linacs, like other charged particle accelerators, incorporate vacuum chambers to avoid energy loss due to scattering.

See 5.5.3 Vacuum Considerations in
https://cds.cern.ch/record/277966/files/p17.pdf?version=1

Therefore, the non-vacuum method although possible is not recommended primarily because it is unsafe: it creates uncontrolled, distributed radiation fields that cannot be reliably shielded or regulated, even though the underlying physics allows it.

 

[Rev. Cheeseman]

Without a vacuum, accelerated electrons (from the electron gun) would collide with other electrons in the air, or whatever gas would occupy the accelerator chamber, and the faster electrons would scatter on the atomic electrons and lose energy.

Sorry just saw your edited comment. Therefore, generating bremstrahlung photons in the MeV range is only possible in vacuum and absolutely not possible in non vacuum environments?

 

[Astronuc]

Therefore, the non-vacuum method although possible is not recommended primarily because it is unsafe: it creates uncontrolled, distributed radiation fields that cannot be reliably shielded or regulated, even though the underlying physics allows it.

Not quite; it is not unsafe, unless proper shielding is excluded.

There are two factors: 1) accelerating charged particle in a gas makes it inefficient; the charged particles would lose energy, and the energy losses would be manifest in heat and radiation, and 2) shielding can be added, but that would increase the mass of the system, which would add to the expense.

In a gas with electrons or ions passing through, the neutral atoms would be ionized, which is what happens in the earth's atmosphere and other planetary atmospheres subject to the solar/stellar/galactic cosmic radiation. In stellar atmosphere, ions recombine with electrons and neutral atoms are continually ionized by interactions with photons, free electrons, ions and atomic collisions.

For reasons of efficiency and economics, electrons and ions are accelerated in a vacuum.

 

[Astronuc]

Therefore, generating bremstrahlung photons in the MeV range is only possible in vacuum and absolutely not possible in non vacuum environments?

Not quite. Electrons used to generate bremsstrahlung photons are accelerated in a vacuum from a source to a target. The electrons interacting with the Coulomb field of the nuclei (in the target) are accelerated (change direction) or decelerated thus producing a photon. The photon energy depends on the electron energy and how close to the nucleus the high energy electron approaches. There is a spectrum of bremsstrahlung photon energies.

 

[Rev. Cheeseman]

Not quite; it is not unsafe, unless proper shielding is excluded.

There are two factors: 1) accelerating charged particle in a gas makes it inefficient; the charged particles would lose energy, and the energy losses would be manifest in heat and radiation, and 2) shielding can be added, but that would increase the mass of the system, which would add to the expense.

In a gas with electrons or ions passing through, the neutral atoms would be ionized, which is what happens in the earth's atmosphere and other planetary atmospheres subject to the solar/stellar/galactic cosmic radiation. In stellar atmosphere, ions recombine with electrons and neutral atoms are continually ionized by interactions with photons, free electrons, ions and atomic collisions.

For reasons of efficiency and economics, electrons and ions are accelerated in a vacuum.

Maybe a little off-topic here because I don't think we are dealing with bremsstrahlung with this link. This link is interesting https://arxiv.org/abs/2310.10100 because it is about PeV protons accelerating through a medium, not vacuum, to generate the highest energy gamma radiations. While the medium for the PeV protons which is Cygnus wind plasma has a density of 10^-3 to 10^-1 cm^-3 and ultra high vacuum lab is 10^-11 cm^-3, the Torr value for the PeV protons environment is much lower which is 10^-20 - 10^-18 Torr compare to lab ultra high vacuum which is around ~3 x 10^-28 Torr. Why is that?

 

[Astronuc]

the Torr value for the PeV protons environment is much lower which is 10^-20 - 10^-18 Torr compare to lab ultra high vacuum which is around ~3 x 10^-28 Torr. Why is that?

Where is one finding the pressure (torr) values? ~3 x 10^-28 Torr is too low for a lab vacuum.

Ultrahgh vacuum (UHV) is considered 10^-9 cm³ and below.

I don't believe lab UHV levels are less than 10^-11 torr.

Extreme Ultrahigh Vacuum (EUHV) is down as low as 10^-13 torr, which is extraordinarily low.

See - https://vacaero.com/information-resources/vac-aero-training/1167-high-and-ultra-high-vacuum.html

Interstellar space has a much lower pressure, ~ 10^-19 to 10^-20 torr, because it's cold and has very low particle density.

Ultra-high vacuum is needed for the pipes in which particle beams travel. This includes 48 km of arc sections, kept at 1.9 K, and 6 km of straight sections, kept at room temperature, where beam-control systems and the insertion regions for the experiments are located.

In the arcs, the ultra-high vacuum is maintained by cryogenic pumping of 9000 cubic metres of gas. As the beam pipes are cooled to extremely low temperatures, the gases condense and adhere to the walls of the beam pipe by adsorption. Just under two weeks of pumping are required to bring the pressures down below 1.013 × 10^-10 mbar (or 10^-13 atmospheres).

Ref: https://home.cern/science/engineering/vacuum-empty-interstellar-space
The 10^-13 atmospheres = 7.6 x 10^-11 torr. Such low pressures require cryogenic conditions, as in liquid He, where gases condense on solid surfaces.

In preparation for evacuating a cyrogenic vacuum chamber, it is customary to 'bakeout' the chamber boundary material in order to remove gaseous atoms, e.g., H, after which the chamber can be cooled to cryogenic temperatures.

See also - THE LHC VACUUM SYSTEM, https://cds.cern.ch/record/455985/files/p291.pdf

 

[Rev. Cheeseman]

Where is one finding the pressure (torr) values? ~3 x 10^-28 Torr is too low for a lab vacuum.

Sorry, I think it must be an error. Thank you for pointing it out.