[FLASH-USERS] Laser intensity in 2D cartesian LaserSlab

[Kirill Lezhnin]

Hi all,

I am trying to use the FLASH code (in particular, the LaserSlab branch) for a couple of HEDP applications, and I would really appreciate it if you could help me to clarify a couple of things related to laser intensity in 2D LaserSlab simulations in cartesian geometry.

First: when I define laser pulse for the LaserSlab 2D cartesian simulation, I specify its intensity distribution in the simulation plane (by using cross-section function type “gaussian1D"). I wonder how should I interpret the third dimension (i.e., out of the simulation plane) when calculating laser intensity on target from the power value given in the par file? Should I assume that laser intensity has the same distribution as the in-plane one? Or should I treat the third dimension as a uniform slab with the unit thickness (like, 1 cm)? My current comparisons with inverse Bremsstrahlung absorption suggest that it is the latter, but it would be great to double-check it!

Second: to compare my FLASH results to the PIC results with the laser energy deposition module, I’d like to calculate absorbed laser power density (i.e. quantity with the units of erg/s/cm^3). In FLASH, as far as I am aware, there is a ‘depo’ variable, which calculates “amount of laser energy deposited in a cell per unit mass”, i.e. something like erg/g. I am not quite sure how to convert it to the power density I am looking for. My current assumption is that the deposited laser energy in depo variable is stored for the last timestep, and then the absorbed power density = depo*dens / dt. Is my assumption correct?

Thanks!

Sincerely yours,
Kirill Lezhnin