how do i set the simulation time and measurement time

Hi

I am raping 2 scenarios as given below. I want these 2 scenarios to run for 30 min duration after the complete ramp up.How to I configure the execution time/simulation time in gatling.

scn1.users(10).ramp(10)
scn2.users(10).ramp(20)

Also I want to understand a way to set a measurement time - collect the metrics with in a specific time window during the execution of 
load testing.

Thanks
Kumar

run for a given duration: during loop
time window metrics: not possible with built-in reports. You’ll have to hack from the csv file.

Thanks Stéphane.

My implementation for 10 min duration. Hope other find this useful.