Oof, 8 bar is terrifying! Interesting to hear about a tantalum getter, I've never heard of that before. I guess since it is DC the magnetic stabilization can take the form of just a permanent magnet, though I doubt that's actually what they did. Nice lamp, I can't tell the size but I'd imagine at 4500W the whole arc tube might be incandescing.

The lamp is even more terrifying during operation! As for the magnetic stabilization of the arc, an electromagnet connected in series between the lamp and the DC power supply is used. This way the force applied to the arc is adjusted automatically to its current.

I didn’t realise XBO lamps were not universal burning. I have a 2kW Osram lamp and the box makes no mention of burning position, although I think it’s missing the instruction pamphlet. The arc being very short and the large outer bulb made me think it wasn’t critical, although I know when I run it with its ignition voltage the arcs does draw out and run along the bulb surface with convection. I also like they idea of no attached flying leads. It’s quite easy for one of the crimp terminals to swing over and hit the lamp which may not be good.

Remind me never to get a job as a cinema projectionist

When I was a teenager I visited quite a few projection rooms, even a 70-mm IMAX one where huge water-cooled 15-20 kW xenon lamps are used (I'll write a post about that since I have one of those lamps). I can guarantee you that the job of projectionist is rather safe - if you follow the rules and protocols, that is. But you don't strike me as someone who would, so you better stay clear of those lamps indeed

Tuopeek - Yes, there are restrictions in the burning position of those lamps. That's because the arc stability requires some very specific operating conditions. It's not because the electrode gap is small that the arc is necessarily stable, there are very strong forces at work in those high-current arcs, such as the Maecker effect (a magnetodynamic effect at the cathode) and, of course, gas convection, which is particularly potent here due to the strong temperature gradients in the lamp (something not found in metal halide short-arc lamps whose temperature distribution is far more homogeneous).

The first xenon short-arc lamps (Osram 1952) where operated exclusively in the vertical position with the cathode at the bottom so as to align the cathodic jet with the convective gas flow. Improvements in the electrode and bulb designs and the introduction of magnetic arc stabilization eventually enabled the first horizontal-burning xenon projection system, which permitted a much greater optical efficiency since the lamp was now placed along the axis of the elliptical mirror. Ushio, the manufacturer of the lamp shown here, actually claims to be the one responsible for this improvement. That's something that I still need to verify.

@Max, you know me so well