Mass proportional damping: which value shall I enter?

[RGX124]

Hi,

In an Explicit model I d like to enter a mass proportional damping with parameter alpha R.
The default value is 0. The units are 1/time
What is the range of alpha R? 1e-5, 1, 10, 10000000?
What is the effect on the CPU time of the simulation.

Thanks for your help
R