The Electric Arc.

[ACUV]

This is a view of an electric arc using an apparatus of William Gurstelle.

 

 

Can an electric arc jump a vacuum gap?

[swansont]

This is a view of an electric arc using an apparatus of William Gurstelle.

 

 

Can an electric arc jump a vacuum gap?

Yes. Arcing was a problem with our ion optics in the experiment I worked on at TRIUMF. It limited the voltage you could apply. Fortunately, the arcing tends to destroy the tiny protrusions that enable it in such devices, so you can "condition" a device to withstand higher values over time.

[ACUV]

What colour is an electric arc through a vacuum?

[swansont]

What colour is an electric arc through a vacuum?

I don't recall seeing them. They would, of course, give off x-rays, as tends to happen when you slam a many kV electron into a surface.

[ACUV]

Does lightning hitting a structural lightning conductor generate x-rays?

[John Cuthber]

This is a view of an electric arc using an apparatus of William Gurstelle.

 

Can an electric arc jump a vacuum gap?

No

From

http://en.wikipedia.org/wiki/Electric_arc

"An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current through normally nonconductive media such as air."

No gas: no arc.

 

You can get discharges in low pressure systems, but not in a strict vacuum.

I don't think a fairly good vacuum would carry enough current to heat the electrodes far enough to get significant thermionic emission.

[ACUV]

As I understand it, I see no conflict here. There is merely a difference in defining the circumstances of what the arc is, whether it be a flow through a gas or a flow of electrode material in a vacuum. For the benefit of those to follow, correct me if I'm wrong.

 

I was led to the following on seeking further explanations. http://en.wikipedia.org/wiki/Paschen's_law

[swansont]

http://en.wikipedia.org/wiki/Spark_gap

"It is impossible for a visible spark to form in a vacuum. Without intervening matter capable of electromagnetic transitions, the spark will be invisible (see vacuum arc)"

(emphasis added)

 

http://en.wikipedia.org/wiki/Vacuum_arc

"A vacuum arc can arise when the surfaces of metal electrodes in contact with a good vacuum begin to emit electrons either through heating (thermionic emission) or via an electric field that is sufficient to cause field electron emission."

[Enthalpy]

The article at Wiki was very presomptuous!

 

Vacuum discharge (which you may call arc or not, I don't care) is known to occur at fields that can't possibly create field emission, and at electrode temperature (even locally) that makes thermoionic emission impossible. In fact, it's still a mystery, and the subject of research.

 

And by the way, vacuum discharge is not just a faint glow, it's an authentic zap.