Standard transformer paper.
Usually get 40 or so turns of the 1mm wire per layer, then more paper etc.
So 5 or 6 layers will get close enough.
The primary is two in hand 1.8.....stay with heavy wire for this, as this impedance is critical for max voltage and power transfer... poor as it is.
This type of transformer has served well over here in marine conditions for a decade or so across dozens of units... simple and works.
I originally potted the whole transformer in epoxy, but now just do the coil, and spill the rest over the laminates... seems to do just as well.
If your designing your own board layout, keep the cap terminals very close to their driven elements... as the current is intense at those points from the cap to the tranny, and the cap to the triacs. Reinforce the board between the cap terminal and the triacs, and the triacs output to the inductor and out put terminal. You want the triacs to see the current evenly as possible, or the one closest to the cap or the load will fail first... beefing up the tracks works for this.
As you will have found from the circuit, it is the same as the 12v unit, but uses a doubler or in this case a trippler to get the dump voltage.
The little 1uf is there for timing and for current sourcing for the triac/scr. if you remove the inductor, the voltage will rise, but the pulse will narrow and the triacs will be under more pressure. experiment with this if you want to get different results re: RFI and transmission.
The addition of a nano or similar micro and a mosfet, can easily make it intelligent. .... ie use the fet to switch off the voltage climb where ever you want so you don't have to give the biggest bang all the time.... monitor the output, and the micro can drive more voltage or less voltage to the storage cap depending on fence load... and the micro can trigger at a reliable setable pulse ... without changing components to get the balance between voltage and time exact.
I will get around to this soon ( he said), as for a few dollars we can get a fancy unit as good as the expensive units and better... including voltage read out or led ladder indicator, .so we can see the fence loading at any time, and can set an alarm if the load is getting too high, and needs amelioration... or there is a fence short..... time is the problem.
.............oztules