relaxation oscillator based on discharge.

[William Gaatjes]

I was doing some reading about something i find interesting but i only know the basics of (as usual ).

I am thinking of building a high voltage relaxation oscillator. Now this should not be to hard, I just need to charge a capacitor through a current source with a spark gap attached to it. The spark gap determines the breakdown voltage. I think Tesla coils are based on the same principle but i am not sure.
And making high voltages is relatively easy. If i can get my hands on a custom made one, i want to put a vacuum tube in series with it (gas still to determine)where i could create plasma for a short time. I have once again a weird idea because i want to create a relaxation oscillator that periodically discharges and creates a burst of bundled EM waves. First in the Mhz range but the goal is rontgen if i can get the proper safety measures (besides lead shielding)figured out first, otherwise i do not pursue that direction. But what i do not know if it is possible to create a bundled directed beam. Intuitively i know it is possible but how ? The desire is not to use a mechanical shielding device but to use electric fields and magnetic fields only .

Can anybody lead me in the right direction ?
I want to perform some experiments to increase my understanding of the matter.

 

[William Gaatjes]

I thought that it might be a good idea to read more about vacuum tubes and perhaps i do not have to build anything. Wiki is now adays good enough to use a start point (not a reference point).
I found something about the Coolidge tube and the Crookes tube.

http://en.wikipedia.org/wiki/X-ray_tube

There are two designs: end-window tubes and side-window tubes.

End window tubes usually have "transmission target" which is thin enough to allow X-rays to pass through the target (X-rays are emitted in the same direction as the electrons are moving.) In one common type of end-window tube, the filament is around the anode ("annular" or ring-shaped), the electrons have a curved path.(half of a toroid)

This reminds of the plane waves of the dual slit experiment.
Interesting start point.

And does anybody know the asnwer to this one question ?
i have a question because i cannot calculate at the moment and for either people this should be an easy question : What is the shortest wavelength of em radiation that an electron can generate ?

 

[Mark R]

This reminds of the plane waves of the dual slit experiment.
Interesting start point.

Nothing to do with plane waves. When an electron hits a target, X-rays are emitted in all directions. However, very few come out an steep angles, because the target material gets in the way.

So, in a side-window tube, electrons hit an angled target. X-rays are generated in all directions. But, because the target material is in the way, very few come out in the direction of the electron beam. By angling the target, you can ensure that X-rays are emitted at a useful angle.

In an end-window tube, the target is a flat disc, with a ring shaped cathode, outside and slightly in front of the target. Electrons are emitted off the cathode, and attracted towards the target, following a curved path 'backwards' in the tube, eventually striking the front surface of the target. X-rays are then emitted forwards from the front surface.

And does anybody know the asnwer to this one question ?
i have a question because i cannot calculate at the moment and for either people this should be an easy question : What is the shortest wavelength of em radiation that an electron can generate ?

The maximum energy of X-ray photon that can be generated from an electron collision, is the energy of the electron. So, use of a 140 kV acceleration voltage, will yield X-rays up to 140 keV. The collision of electrons in the target, produces x-ray photons of different energies - a smooth spectrum decreasing in intensity as energy increases. This is modified by absorption in the target (some electrons penetrate a short distance into the target, and the generated X-rays may be shielded by the target material itself) to reduce the low energy content - producing a somewhat asymmetrical bell curve.

The actual spectrum depends on the the X-ray fluorescence spectrum of the target material (the resulting spectrum contains large amounts of the characteristic fluorescence energies), resulting in multiple spikes on the otherwise smooth spectrum.

 

[William Gaatjes]

Ah thank you. I was reading and it seems that electrons when pushed enough can also produce gamma radiation ( the part in the picometer range). I have come to understand that now the term gamma radiation is reserved for radiation generated in the nucleus and that the electrons can generate extreme short wave xrays formerly known as gamma rays by bremsstrahlung ?
It is just for interest.

Let's say that i have a string of electrons that after acceleration to extreme energies are extremely decelerated by an external pulsating electric field with the right polarity. If all these electrons are slowed down one by one after another, the combined radiation pattern would extend primarily in the direction that the electrons where traveling yes ?

The field would cause the decelerated electrons to generate bremsstrahlung ?

Let's say that i have a string of electrons that after acceleration to extreme energies are extremely decelerated by an external pulsating magnetic field. If all these electrons are slowed down one by one after another, the combined radiation pattern would extend primarily in the direction that the electrons where traveling yes ?

 

[Mark R]

Ah thank you. I was reading and it seems that electrons when pushed enough can also produce gamma radiation ( the part in the picometer range). I have come to understand that now the term gamma radiation is reserved for radiation generated in the nucleus and that the electrons can generate extreme short wave xrays formerly known as gamma rays by bremsstrahlung ?
It is just for interest.

The terminology of X-ray and gamma-rays is historical and is related to the fact that they were thought to be different processes. The modern definition is that X-rays are high-energy photons produced by electron emissions, whereas gamma-rays are high-energy photons produced by nuclear emissions or annihilation (e.g. electron-positron) reactions. These tend to produce radically different energies, but this they do overlap in a substantial number of cases.

Let's say that i have a string of electrons that after acceleration to extreme energies are extremely decelerated by an external pulsating electric field with the right polarity. If all these electrons are slowed down one by one after another, the combined radiation pattern would extend primarily in the direction that the electrons where traveling yes ?

The field would cause the decelerated electrons to generate bremsstrahlung ?

Any field acting on a moving charged particle and causing it to accelerate will cause emission of bremsstrahlung. This is exactly what happens when an electron beam hits a target material - electrons are accelerated by the extremely intense electric field around atomic nuclei. However, this could also happen with an externally applied electric or magnetic field. (The bending magnets in a particle accelerator produce substantial bremmstrahlung, which drains energy from the beam - however, because the magnetic fields are so weak compared to the nuclear electric field, the bremmstrahlung spectrum produced by bending magnets is of very low energy. More sophisticated magnetic devices can be attached to particle accelerators where intense sources of X-ray photons are needed).

Bremmstrahlung is emitted omnidirectionally. But when the particle velocity approaches c, Doppler shifts of the resulting photons cause a marked change in the radiation pattern. Intense blueshift in the direction of travel results in an intense beam of high energy photons in the direction of the particle beam. Reduced doppler shift (or red shift) in other directions severely reduces the energy in 'off axis'.

 

[William Gaatjes]

Aha, interesting. Thank you. That gives me a lot to think about and visualize. It is an reenforcement for some subjects i was in doubt with.

Research seem to suggest that there exists large potential differences between planets and stars. This could be millions and more volts. From research it seems more and more that for example the solar flares from the sun can act as huge accelerators with levels we are still dreaming of.

To give another example, maybe it is not just the explosion from a star going nova or supernova that accelerates particles but also the electric fields that may be present in the universe. Vacuum is a good insulator. Thus it is highly likely that very high voltage differences can be realized in space. This would cause a large electron flow in plasma yes ? I wonder how this all would work. Taking not only gravity into account but also electric fields and magnetic fields makes space a lot more interesting.

From research from NASA it also seems that every 8 minutes there is a magnetic corridor for a brief moment between the earth and the sun. That would seem like a lot of particles from the sun would travel to the earth or the other way around, that is not known yet, i think.