What is the maximum number of primary histories?

what is the biggest source particles fluka can transprots?

There is no limit on the number of primaries you can simulate. The number should be chosen taking into account the results’ precision needed and your hardware constraints.

but when you input 1e100 at the location on upper picture, it will return an error.
the random number shauld has biggest numbers.

Dear Siyuan1987,

the maximum number of primaries FLUKA can handle (in a single cycle) due to its implementation is approximately 2.0e18.

If you want to use equal or more primaries than 1e10, then you need to input the number with a decimal point (1.0e10). Without a decimal point the number is printed as an integer, which doesn’t fit on the input card.