Yes i do not think its Ice Carnival at all Looks like Joan Senior but any comparison has to consider height and bloom size also. If you had for a long time say 10 years for example that would also rule out any new whites in the last 10 years.
I have 2 very nice short yellow ones that i have given up hope naming with all the yellow out there. But they are keepers because they always perform so well for me and they both bloom for a solid month.
Your white seems to have a unique shape to it. Keep up the research before settling on Joan Senior because the more hybrids you rule out will only strengthen the case that it is indeed Joan Senior.
