Quite scary lamps. I have a 3kW one with quite a few hours on it. They say the become more fragile with ageing . Can you detect radiation form the cathode if it's thoriated?

Yes, the presence of thorium can be detected. The count per second level rises from 0.5 to about 2.5 Bq when I stick the cathode tip right against the Geiger tube. The measured activity does not rise above background level when the electrode is placed one meter away from the detector, so there is no risk. To be honest I expected more activity from that electrode.

Thanks, that's interesting to know and also similar to what I've experienced with thoriated cathodes in other devices. I also found thoriated welding rods to have very low emission, but I guess that's what you'd hope. Alternatively, I have a gas-mantle I use as a check source which is surprisingly active, (around 20 Bq) while in a plastic container, with the GM tube close to it.

Oh dear, that does not look good Hope nobody was in the vicinity..! One reason I will never have one of these lampses

Although those lamps present a certain risk, there is no need to become paranoid. They are quite safe when handled properly, they are even left unprotected at the factory before they are packed in their shipping box. The risk is higher if the lamp has a manufacturing defect, in which case failure will happen quickly (which incidentally sorts them out before you get them), and if the lamp has been run beyond its rated service life. Manufacturers issue stern warnings about those lamps so as to cover all their legal bases, and to account for the few idiots out there who try to service xenon luminaires while hot and without any protection. I've collected those lamps for nearly 40 years, some new and some aged (I have 40 of those at the moment), and the only case where one ruptured was because of my carelessness. The lamp, an Osram 2 kW XBO, was in my backpack and I threw it at the end of the day (after school) having completely forgotten about it. Needless to say I did not make the same mistake twice... I got the lamp shown here from a movie theater. It had low hours when it burst while in operation due to a manufacturing defect (I cleaned up the tungsten oxide that covered the inner bulb surface). The lamphouse contained all the hot lamp fragments, but the dichroic mirror had to be replaced.

That must have shredded your school homework unless it still had its ballistic jacket on.

Luckily, the lamp had its protective cover, so the explosion was properly contained. Interestingly I also found some plastic shavings among the quartz debris...

All I can say is...
I've never gotten my hands on these, but I also must say that I much have respect for them.

Respect. That's indeed the key! The lack of it is what can cause some serious problems and accidents with these lamps.