Tesla reported that, driven by his observation of mysterious damage to photographic plates in his laboratory, he began his investigation of x-rays (at that time still unknown and unnamed) in 1894 (2). Apart from experiments using the Crookes tube, he invented his own vacuum tube, which was a special unipolar x-ray bulb. It consisted of a single electrode that emitted electrons. There was no target electrode; therefore, electrons were accelerated by peaks of the electrical field produced by the high-voltage Tesla coil.
pic: shadowgraph of a foot in a shoe obtained by n tesla in 1896
