What is the purpose of the 220 ohm resistor and C1 in this circuit?

 

It is part of the snubber network.
See Fairchild AN-3006, I believe it gives an explanation there of the circuit and calculation of the dv/dt.
Max.

 

That data sheet doesn't give much. I understand that it's part of the snubber circuit but isn't that what R1 and C1 are for. Why the additional components?

 

They are for filtering the Gate trigger voltage, i would have put the 180R and C1 on the Gate Terminal.

 

What is the purpose of the 220 ohm resistor and C1 in this circuit?

The 220 ohm resistor is there to allow the capacitor to do a bit of filtering. It is in series with the supply voltage, which has a very low source impedance. Trying to shunt a source impedance of much less than one ohm with a capacitor will not be very effective, but increasing the impedance to 220 ohms allows the filtering action to work. With filter circuits, the source and load impedance does matter.