Decreasing gas breakdown distance in a spark gap with UV

In summary, the conversation discusses the use of a technique involving spark gaps breaking down synchronously in an enclosed cavity filled with N2 at 1atm and ~25°C. The idea is to use "indirect" photoionization with a UV flash discharge inside the cavity. However, it is noted that the ionization of N2 requires a higher photon energy level than what can be achieved with this method. The speaker wonders if indirect effects such as N2 excitation or thermal effects could help lower the dielectric strength. It is mentioned that triggering the spark gaps with a voltage pulse may be more effective. The conversation ends with a note of caution about the potential hazards of changing the dielectric gas.
  • #1
rodv92
2
0
Hello !
I am currently investigating a technique that would allow several spark gaps to breakdown synchronously in an enclosed but not hermetical cavity, flushed with N2 at 1atm and ~25°C

My idea was to use "indirect" photoionization (basically a synthetic fused quartz UV flash discharge inside the cavity)
The cavity would be enclosed with a highly reflective material to UV from 160nm to the near UV.
However, ionization of the outer electron shell of N2 seems to be at ~15eV, and at 160nm we are nowhere close to this photon energy level.

So, i was wondering if any indirect effect (N2 excitation, thermal effects ?) would eventually "help" to lower the dielectric strength with that method. Keep in mind that the flash lamp would send a burst of 100 to 200 J of light...

Or is it a dead end ? I could always ionize the surroundings with a spark gap trigger not enclosed in a flash lamp, but it is a bit too dirty (because of the "brutal" thermal/accoustic shockwave influence on the secondary spark gaps)

Anyone could shed a bit of light on this issue ? ;) - i would rather not change the dielectric gas because i am afraid of unintended consequences (ozone generation for O2, fire hazards, etc)
Thx.
 
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  • #2
rodv92 said:
Hello !
I am currently investigating a technique that would allow several spark gaps to breakdown synchronously in an enclosed but not hermetical cavity, flushed with N2 at 1atm and ~25°C

My idea was to use "indirect" photoionization (basically a synthetic fused quartz UV flash discharge inside the cavity)
The cavity would be enclosed with a highly reflective material to UV from 160nm to the near UV.
However, ionization of the outer electron shell of N2 seems to be at ~15eV, and at 160nm we are nowhere close to this photon energy level.

So, i was wondering if any indirect effect (N2 excitation, thermal effects ?) would eventually "help" to lower the dielectric strength with that method. Keep in mind that the flash lamp would send a burst of 100 to 200 J of light...

Or is it a dead end ? I could always ionize the surroundings with a spark gap trigger not enclosed in a flash lamp, but it is a bit too dirty (because of the "brutal" thermal/accoustic shockwave influence on the secondary spark gaps)

Anyone could shed a bit of light on this issue ? ;) - i would rather not change the dielectric gas because i am afraid of unintended consequences (ozone generation for O2, fire hazards, etc)
Thx.
I think you will find they trigger randomly due to background radiation. If you intend them to be truly synchronous, bear in mind that a spark gap can fire in picoseconds. Can you just trigger them with an addition voltage pulse?
When Hertz was experimenting with spark gaps as his radio transmitter, he found the UV from one spark triggered another.
 

FAQ: Decreasing gas breakdown distance in a spark gap with UV

What is gas breakdown distance?

Gas breakdown distance refers to the minimum distance between two electrodes in a spark gap at which the gas between them will ionize and allow electrical current to pass through.

What is a spark gap?

A spark gap is a physical gap between two electrodes that allows for the creation of a spark or electrical discharge between them.

How does UV light affect gas breakdown distance?

UV light can ionize gas molecules and decrease the gas breakdown distance in a spark gap. This is because UV light has a shorter wavelength and higher energy than visible light, making it more effective at ionizing gas molecules.

What methods can be used to decrease gas breakdown distance in a spark gap with UV?

One method is to use a higher intensity UV light source. Another method is to decrease the distance between the electrodes, as a shorter gap requires less energy to ionize the gas. Additionally, using a gas with a lower breakdown voltage, such as helium, can also decrease gas breakdown distance.

Why is decreasing gas breakdown distance important?

Decreasing gas breakdown distance can improve the efficiency and reliability of spark gap devices, as it allows for a lower voltage to be used and reduces the risk of spark overs. It is also important in applications such as high voltage switches and lightning protection systems.

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