Retriving branch index of sucsessful intersection

Hello

I have a list of lines that are normal to a surface and i need to extract the lines that run through a certain radius on the surface.

What i have done is that i have done an intersection between the lines and the surface of the radius. and this gives me the points where the lines that intersect the surface intersect.

Now i would need to retrive the index of the branches that do actually intersect with the surface. how would i go about this?

In the picture I have circeld the index that i am trying to retrive since i am not 100% sure i have used the correct terms for everything.

In total theres about 500 000 and roughly 1500 of them intersect with the radius.

Greateful for any pointers or suggestions

Axel