Hi,
48V, 600W means 12.5A average.
Now the SCR is ON for maybe 10..12 degree (every 180 degrees), so it is ON for about 7% of the time.
During this 7% of time you need to achieve 12A average. So it is no wonder that the peak current is at 200 A or more.
What did you expect?
You may relax this a bit by connecting a series inductance (and maybe a diode, Anode to GND) between SCR and LOAD capacitor.
With the inductance the ON time increases and thus the peak current decreases.
Klaus