[FLASH-USERS] "Vacuum" on both sides of target for LaserSlab?

[Xu Zhao]

Hi David,

It will be the same as the low density Helium “chamber” species.
As in the simulation box there are two only species, "Targ" and “chamber” ,
defined by the *Simulation_initBlock.F90* .

Actually, there is no truly vacuum in the usual simulations... The vacuum
is alaway replaced by low-density materials, "chamber" in LaserSlab case.
It works for most cases but sometimes may potentially cause some
nonphysical phenomena.



Best,
Xu

On Tue, 17 Jun 2025 at 23:04, David Montgomery <dsmont80 at gmail.com> wrote:

> Hi Xu,
>
> Thank you for the quick response.
>
> Will that extra space be truly vacuum, or will it be the same as the low
> density Helium “chamber” species?
>
> David
> Sent from my iPhone
>
> On Jun 17, 2025, at 3:57 PM, Xu Zhao <xu.zhao at york.ac.uk> wrote:
>
> 
> Hi David,
>
> If you want to add some space behind the target (see attached) compared to
> the Laserslab default,
>
> I think just increasing ymax (the box length if you run in 2d) in the .par
> will work.
>
> Usually the *Simulation_initBlock.F90* defines the "blocks (cells)" in
> the simulations.
>
> For example line 100 - line 129 in the *Simulation_initBlock.F90 *define
> which part is the "target" species and the other is "Cham".
>
> You do not need to modify other files as they define the variables (like "
> sim_targetHeight") and material files ("like eos file").
>
> Hope this helps,
> Xu
>
>
> On Tue, 17 Jun 2025 at 22:17, David Montgomery <dsmont80 at gmail.com> wrote:
>
>> Hi All,
>>
>> Another FLASH-newbie question. I’ve successfully run the LaserSlab
>> example, and made some small modifications in my own *.par file.
>>
>> If I want to add a “chamber gas” region (low density Helium) to the rear
>> side of the target (surface NOT irradiated by the laser), in addition to
>> the front side of the target, which files do I need to modify besides just
>> the *.par file?
>>
>> Do I have to modify one or more of the local *.F90 files?
>>
>> Or can I use the same “species” (Cham) on both the rear and front side of
>> the “target” species?
>>
>> Any advice would be very helpful.
>>
>> Thanks,
>> David Montgomery
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>
>
> --
> Xu Zhao
> PDRA
> York Plasma Institute
> School of Physics, Engineering and Technology
> University of York
> York YO10 5DQ, UK
> <WX20250617-224328 at 2x.png>
>
>
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