[FLASH-USERS] Laser intensity (in W/cm^2) in laserslab problems

[Scott Feister]

Hi Zhao,

My understanding is that both "depo" and "lase" are in units of energy per
volume. So for FLASH default units, I believe that that would be in ergs /
cm^3. I'm not 100% sure about those units, though!

As far as the physical meaning of each of these:

1. Think of "depo" as the total laser energy being *deposited *into a
volume, during that one timestep.
2. Think of "lase" (available in 3D only, see user guide for how to
configure) as the total laser energy *existing *(via the rays) in that same
volume, even if none of it is being deposited. (See user guide Section
17.4.3, Laser Energy Density.)

Both "lase" and "depo" values represent *energy volumetric density *rather
than *power per area*. So, you'll need to do some conversions to get to
intensity.

To get laser intensity from "lase", I believe you would need to multiply by
the velocity that the energy is moving, which is the speed of light (c).
Double check my logic, though!

Scott



On Mon, Jul 4, 2022 at 7:13 AM 赵旭 <xuzhao1994 at sjtu.edu.cn> wrote:

> Dear FLASH user & developers,
>
> I have a question about how to show the 'laser intensity' (in unit like
> W/cm^2) at a certain density contour, i.e., at 1/4 critical denisty
> surface.
>
> The laser intenisty is important for laser-plasma interaction study and
> often provided by hydro codes cause it will be attenuated (like by
> collisional absorption) when the laser penetrate the plasma.
>
>
> 1) So is there any way to show the laser intensity of a laserslab problem ?
>
> 2) I notice that there are 2 VARs named 'depo' and 'lase' related to
> adsorption in FLASH but I dont know the units of them and if they can
> represent the 'laser intensity'.
>
>
> I would appreciate any help.
>
> Thanks !
>
> Zhao Xu
>
> --
> Zhao Xu
> Laboratory for Laser Plasmas (MoE)
> Shanghai Jiao Tong University
> 800 Dongchuan Rd, Shanghai 200240
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