This is my first solid state (semiconductor) Tesla Coil.
Secondary has a length of 48 cm, diameter 7.3 cm, 0.3 mm wire, 1600turns, resonance without the toroid 360kHz. Resonance with the "toroid" from cans and metal boxes
is 235kHz. The secondary was originally designed for the classic TC. for SSTC
secondaries typically use very thin wire. The secondary also works, but its length is a little out of proportion with the length of discharges :).
Primary 4turns 1mm diameter wound on 16cm diameter. Primary is about 2 cm above the beginning of the secondary.
Excitation is single-ended with MOSFET of SMD type STB25NM50N-1. You can also use the equivalent STP25NM50N in TO220 case. Supply voltage is 60V, consumption
is only about 10 - 15W. I used UC3845 (IC for switching supplies) as an oscillator and gate driver, the 555 works as an interrupter
with repetition rate of 20 Hz, duty cycle is about 6%. Control circuit needs
separate voltage cca 14 - 15V from a wall adapter. Using 10k potentiometer the oscillator is tuned into resonance with secondary.
Length of sparks into air is up to 7cm, discharges into grounded objects up to 9cm.