Hi Imran,
Please have a look here:
https://www.amazon.com/clouddrive/share/rfcxKyahy0tXOFhnZYLke6qLPHJWi6wslUiR8hUbrVP
The Helix is based on the shape of your example form. I placed the Display Tag there for demo purposes only, not needed.
The lower entry in the Force Field list moves the Particles forward (Force Field> Spline Setting> Layer> Along), the one of top of it pulls them to the spline if they got too much centrifugal power (Force Field> Spline Setting> Layer> Radius.)
Check the Remapping tab, and that the one set to Radius is set to Inverse.
Have as well as an eye on the Velocity Type of the Force Field.
I placed a Random Field on top of the two to get some more life into it. It is not urgently needed here.
The main idea is discussed here:
https://www.youtube.com/watch?v=DApBgfpHs2M&list=PLD428BE966FF3B1E9&index=41
But notice that I made changes to it. I think it works better that way. But try both, and decide for yourself.
Have a great weekend