What is a "Pin-Bar" TEA Laser

[reese houseknecht]

Now from reading wiki i understand there are Pin-bar and non pin-bar, non pin-bar is what people have moved to today with the spark gap. but i read that "These first 'Pin-Bar' TEA lasers, operating at around one pulse per second, were easy and cheap to construct. By operating at atmospheric pressure, complex vacuum and gas-handling systems could be avoided. They could produce MW peak powers of a few 100 ns duration". I also read that Pin-bar was more of an early model, and that in the pin bar laser one electrode took the form of a plain bar, and another a series of pins. I don't know if that will help you answering this but i want to construct one of these pin-bar lasers but can't seem to find anything anywhere. I see CO2 TEA lasers with spark gaps but i think that's non pin bar?

 

[Gordianus]

If I´m not mistaken, the pin-bar TEA CO2 laser was the first successful "high pressure" CO2 laser. The idea is quite simple; a cylindrical bar serves es the anode and a set of pins (simple resistors pierced through the envelope) make a "distributed" cathode. The pins were 1 cm apart and with a reliable spark-gap it worked quite well.
However, it had a shortcoming; the gain zone resembled a wedge with its apex on the pins and its "base" on the bar. Therefore, the output mode had a rather poor beam quality.