Years ago I had purchased an old medium power vacuum diode in hopes that I could get some results, but sadly it lost its hard vacuum before I acquired it. It still had a decent vacuum inside, but not enough to allow electron acceleration sufficient for x-ray production via anode bremsstrahlung. I put the project as a whole on the back burner for quite some time having such a sour experience of wasting money on an expensive tube.
Recently it came to my attention that a very easy to source and inexpensive tube, the DY87 / 1S2A HV vacuum diode, could produce x-rays reliably from even lower voltage HV supplies. I quickly sourced such a tube and gave it a test:
Given that <50kV was the HV source and thus <50KeV is the maximum photon energy, the thin 1.2mm steel plate and short distance is all that was needed for shielding of such a short duration test.
An important note is to use an RFI-shielded Geiger Counter for detection of these xrays, as the HV pulses will create copious RFI which causes false triggers in standard geiger counter circuits. Shown on the left is a Kvarts DRSB-01 that I repaired and enclosed in a 1mm thick Aluminium case which functions as a soft-beta shield and RFI blocking Faraday Cage. The DRSB-01 doesn't use a regulated HV supply so it cannot be used for measurements of radiation, but it functions well for detection of radiation.
Here you can see where I stood in relation to the tube, and the HV source I used...