Low pass filter to remove 50Hz noise

Now I am testing a RC low pass filter to remove the 50Hz line frequency noise.  Using 4K7 and 2.2uF, I saw that the 50Hz noise gets some 60% smaller, but the spikes gets 2 times longer.  I don't know the reason of these annoying spikes, but they are of course a big problem.

I don't know how to solve this spike amplification problem.  Perhaps I should try a digital filter tomorrow.

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