If using laminated iron cores, you'll want to drop your frequency. Do you have an oscillocope? Very useful tool. To lower the frequency, increase the size of the cap on the '555.
The circuit on EDN. R1 is 0.62 ohm, so when the circuit current rises to 1 amp, the transistor connected to it will turn on. This removes gate drive from the scr, and also base drive from the first transistor. This removes the anode supply from the scr, so it resets, and also removes gate drive from the output fet, so the current through the coil switches off. Once this current stops, the voltage across R1 switches off and the whole process starts over. Note for this circuit the output device must be a fet; The value of R1 determines the overall circuit current drain, and it's a resonant circuit. The frequency determined by the inductor, the capacitor on the transformer's secondary, and the tube.
Overall, a pretty neat circuit.
Amanda