[FLASH-USERS] How Laser Break through the Target

[Scott Feister]

I will *also *add something relevant to FLASH: given the inverse
Bremsstrahlung physics model for laser energy absorption in FLASH, light
will mostly reflect from a steep density interface until expansion from
that interface has started -- and so, you may either (1) need to verify
that your energy absorption has converged by increasing and decreasing cell
resolution, or (2) don't use a steep density interface. This effect will
cause more and more trouble as the pulse duration shortens, since less time
is given for expansion before the pulse is "gone".

On Mon, Feb 17, 2020 at 2:19 PM Scott Feister <sfeister at gmail.com> wrote:

> Zhang,
>
> Temporal dynamics can matter! I will just add a comment that two lasers
> with the *same *amount of energy but *different *pulse durations aren't
> necessarily expected to do the same thing. The 0.4 ps pulse has 10x less
> time for the same amount of energy to dissipate into the target, for
> example.
>
> I haven't looked at the specific parfile, and maybe something else is
> going on here as well!
>
> -Scott
>
> On Mon, Feb 17, 2020 at 2:40 AM Zhang Shizheng <
> zsz526654434 at stu.xjtu.edu.cn> wrote:
>
>>
>> Hi all,
>>
>>    I am trying to simulate a single laser beam with energy 400 mJ
>> illuminating a solid Al disc, of which the thickness is 0.8 um.
>>
>>
>>    (1) When the pulse is 4ps and the laser power is 10^11 W, the laser
>> will break through the Al disc and a hole will appear
>>
>>    (2) When the pulse is 0.4 ps and the laser power is 10^12 W, the disk
>> will expand evenly and there will be no hole in the disc.
>>
>>
>>    In my opinion， the moment of light is only related to the energy, so
>> the light in both (1) and (2) should break through the Altarget, *what
>> might cause the difference between these two results?*  The .par file is
>> in attachment, and I have changed nothing but pulse and laser power to get
>> these two results, and the total energy is a constant 400 mJ.
>>
>>
>> Best Wishes
>> ------------------------------
>>
>> Zhang Shizheng
>>
>> PHD
>>
>> Xi'an Jiaotong University
>>
>> Institute for Science and Technology of Laser and Particle Beams
>>
>
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