-lucent as a suffix can have broad definitions. I work in the medical industry. I went to school for and worked as a radiologic technologist for years. Radiolucent and radiopaque were the standard terms used in radiology by both technologists and radiologists (ie: “the X-ray shows multiple radiolucent lesions”)

There may be more technically correct terms from a physician standpoint, but at this point it’s an established set of terms use in medicine. I’d be interested to see if it was terms used initially because of its time period and the definition of -lucent adapted to reflect that over time, or if it’s just terms used by tradition, which does happen.

That’s not quite accurate. An electron beam is accelerated to high speeds towards the anode where photoelectric and bremmstrahlung interactions take place, resulting in energy released as an extreme amount of heat and some X-rays which are emitted isotropically. The X-rays that leave the tube do so through a radiolucent “window” forming the useful xray beam. The rest of the X-rays produced are absorbed by the tube housing.

The rotation of the anode is for heat dissipation. The electron beam can literally melt a hole through the tungsten target. Even with the high rotations, a lot of X-ray tubes tend to be replaced because of vaporization of the tungsten and it’s deposition on the tube walls creating an electrical short from the cathode to anode.