Tesla Apparatus - Answers to Questions About Tesla Coils and X-rays

[90743.] — Tesla Apparatus. — As I have used this apparatus many times for X-ray work, I can give “H. B.” (query 90743) the information he asks for. Working off the main with a transformer and Tesla coil, I have obtained perfect radiographs, and without damaging the Crookes tube. The great point to be observed is to have the current on only for short intervals, say on for five seconds, then off for the same period, and so on; by this means the tube is kept cool, and may be used many times. Do not use the double cathode tubes, as the “focus” is indifferent: the resulting picture obtained with such tubes frequently shows the bones double. With an ordinary focus tube, a carefully-adjusted condenser, a small spark gap, and an intermittent current, the Tesla is quite satisfactory for X-ray work. Moreover, old tubes that refuse to work on an induction coil may be readily excited by the higher tension currents of the Tesla; but if you have a continuous current, use it with an induction coil. I have premised that you intend working off the alternating main, for which the outlay (a transformer and small Tesla) is only £6.
F. J. R.

[90743.] — Tesla Apparatus. — With ordinary “focus” tubes of, say, 3in. to 4in. spark capacity, little or no advantage is gained by using a Tesla, as these tubes can be served equally well by an ordinary 3in. or 4in. induction coil. But with some of the larger bianodic tubes, such as I am now putting on the market, taking 6in. and 8in. sparks to work them, Tesla transformers, worked direct from alternating-current mains, present great advantages. They give at once the high E.M.F., the fairly large ampèrage, and the high frequency of discharge which is essential to rapid photographic and clearly visible “screen” effects.
S. Bottone.

[90743.] — Tesla Apparatus. — I should like to exchange experiences with regard to above. My spark coil gives a full 3in. spark using an accumulator, a good steady current, and I get a fully exposed “radiograph” of the hand in from four to six minutes. I made a Tesla according to a specification which, to be brief, “was to make the above 3in. coil do the work of a 6in. or 8in.” It did nothing of the sort. I, therefore, made another with modifications, an immense improvement on the first; but I do not get an increased length of spark, and with X-ray tubes I do not notice any advantage in the use of the Tesla adaptation—rather the reverse, because the tube appears to tire very rapidly. On the other hand, the luminous effects obtained are remarkable. I get, with ease, the effects (to the extent, of course, of my somewhat limited electrical resources) described by Tesla himself, such being, I need hardly say, most interesting. From a strictly X-ray point of view, so far as my experience goes, I find no advantage whatever from the Tesla over the ordinary coil. I do not find that you get “any more out of it than you put in”—e.g., if you are using a weak and spasmodic source of electrical current, you cannot expect powerful results. I say this because from certain writings (not in the “E.M.”) one would infer that, with a 1in. or 2in. spark coil and two or three chromic-acid cells, you can do the work of a £30 outfit. I am not so rash as to deny this altogether; but in the absence of further detail and information, I rather doubt it.
P.S. — If likely to interest any of our readers, I will send sketch of my own home-made Tesla.
J. P. N.