Fix an optical fibre, into a working steam engine. As the canvas your products, or steam circulate down the fire tubes they is set up a steam plasma. You will get light emission.
The gases shoot up to 3000° C, as they give off X-rays and visible light – of which there is no chemical source. As or steam plasma does molecular nuclear fusion. Flames give off light, as they do Molecular Nuclear Fusion.
This is the source of the X-rays and light, steam engines give out. They also release helium and free radical oxygen gas. So the industrial revolution happened as man first started doing nuclear fusion on earth.