I am trying to find information on pulse capacitors but there are too many options. Some vendor marked with metalized film capacitor,ceramic capacitor. In particular, I even don't know how to figure out what category should be used.As you known,most vendor suggest their own series only. I know about selecting voltage ratings at least 20% higher than the max possible voltage, or even more cautious selecting at least double the expected voltage. But for pulse grade capacitor,the more important points are its peak current performance and lifetime(pulse time).
Having personally tested a variety of capacitors for surge simulator I was surprised to find that only Polypropylene film capacitors would stay cool instead of burning up from intense ultra-sonic power used for surges and in another fixture for electromagnetic tempering of steel bolts. They were often used to block a DC bias voltage or as high-pass filters to stop LF harmonics.
Polyethylene, Mylar and bi-polar electrolytics all failed by overheating and shorting out or by out-gassing material. Other than huge oil-filled capacitors for laboratory use I have found none more durable under stress than Polypropylene film. This is with the understanding that the AC + DC peak applied to the capacitor was no more than 66% of its rated DC voltage.