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Marx generator power supply

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Proud Mary

Thu Feb 26 2009, 02:27AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Download wrote ...

Did you say you where going to use this to power a laser? because Marx generators create pulses. For any gaseous lasers you need continuous power.

In fact, Marx generators have been used to excite high power nitrogen lasers:

See: A high-power TEA N2 laser using a modified Marx generator

T Jitsuno et al 1979 J. Phys. D: Appl. Phys. 12 1503-1507 14 September 1979

Abstract. A new design of TEA N2 laser for producing high-density excitation by combined use of a modified Marx generator and a pair of high-speed capacitors is described. Laser output of 1.5 MW (1.2 mJ, 0.8 ns) is obtained from a 12 cm long uniform discharge at a charging voltage of 25 kV.

Download

Thu Feb 26 2009, 03:34AM

Registered Member #561 Joined: Sat Mar 03 2007, 02:46AM
Location: Adelaide Australia
Posts: 230

Harry wrote ...

Download wrote ...

Did you say you where going to use this to power a laser? because Marx generators create pulses. For any gaseous lasers you need continuous power.

Ok then, With an exception to a TEA Nitrogen laser

Proud Mary

Thu Feb 26 2009, 04:26AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Download wrote ...

Ok then, With an exception to a TEA Nitrogen laser

Umm...

Here is the entire circuit diagram for an MOT-powered Marx generator exciter for a copper vapour laser:

And let's not forget the excimer krypton-fluorine laser while we're at it!

Marx generator: KrF laser
Rijntjes, J. P. H.
Ph.D. Thesis Technische Hogeschool Twente, Enschede (Netherlands). Vakgroep Quantum Electronica.

The impact of dimensioning and material choice upon a vacuum diode, consisting of a cathode with a hollow coaxial anode inside, was investigated using an optically triggered Marx generator with a 120 J maximum power capacity and a 50 nsec pulse length. The effects of different division pressure of Ar, Kr, and Fl upon the output power of the laser were examined in this set-up, in which accelerated electrons were provided in the anode for excitation or ionization of the Ar-gas. Measurements to determine the effects of different diode impedances upon the output power were carried out.

mnr

Thu Feb 26 2009, 05:02AM

Registered Member #996 Joined: Sun Sept 09 2007, 06:17PM
Location: Canada
Posts: 16

Hrothgar wrote ...

Hello denizens of 4HV, I have a proposition to make to you all. I' am designing my first Marx generator, what I am thinking of is a probably a bipolar setup with 12 stages in either tower, I'm tentative about my capacitors (18nF, 12 kV) my question is though, is the diode setup in the power supply (which is an NST) a good plan? what should the specs be for the resistors (simply enormous, or are the equations I should follow along to?) but more to the point, will this lay out even work (sorry about the wretched quality, I only have MS paint and ten minutes to work with) Any and all help is much appreciated, this is my first leap into what I hope is going to lead me to my electrolaser

A good example of how to build a bipolar marx generator can be seen on http://www.electricstuff.co.uk/marxthree.html. For your resistor values, the higher you go, the slower your bank will charge (hence lower repetition rate), but the less effect they will have on the output wave shape (i.e. it will appear closer to an open circuit). Also, make sure your capacitors are rated for at least the peak voltage of your NST's output (1.414 * Vout).

Download wrote ...

Ok then, With an exception to a TEA Nitrogen laser

In addition, high powered CO2 and excimer lasers can use marx generators as power supplies to allow them to be operated at higher pressures, giving them very high power densities with relatively good output efficiencies.

Hrothgar

Fri Feb 27 2009, 12:06AM

Registered Member #1180 Joined: Mon Dec 17 2007, 12:26AM
Location: Nope
Posts: 28

,not a laser as in pew pew laser, the IR pulse laser is separately powered, the Marx generator uses the laser induced plasma channel to connect it to ground,

lasers aside, I still need to find out about those resistors, is there a minimum value I can get away with, or am I just going to strap on a few 1Mega Ohm resistors and hope for the best?

Conundrum

Fri Feb 27 2009, 07:45AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

old flat panels have a nice HV supply but they are a little fragile. I tend to rip out the drive transformer(s) and build a basic ZVS :)

The really annoying thing is that the native drive (resonant) frequency is around 100 kHz which can cause excessive switching losses in the diodes. #include "$$$diode$$$fryage.h"

Best bet is to design and build your own custom transformer. a good form is reels of solder once properly cleaned up and insulated, then to wind the coils use a model aircraft servo or other geared motor with a foot switch.

I did find that the multipliers DO NOT like output shorts, you absolutely have to use a proper series resistor. For this purpose obtain a broken laser printer or 10 for the diodes, as well as the special expensive thin film HV resistors.
RS do these if you don't mind spending Â£8 apiece.

Another useful tip, get some "Moon Sand" from your local toy shop :) this does not look like it will take HV but my tests indicate that it does when compacted and is fairly easy to remove in the event of a problem.

-A

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