The interaction between laser and plasma above critical density (aluminum target)

[xinyingyixia]

input.txt

I would like to use EPOCH to simulate the interaction of the laser with an AI target, however, from the output it seems that the laser does not pass through the aluminum target and the plasma distribution is almost unchanged, why is this. Is the plasma density too high? But in the lab such a strong laser is able to pass completely through the AI.

[DanRRRR]

xinyingyixia,

"...But in the lab such a strong laser is able to pass completely through the AI" Can you show the reference where this was seen?

[xinyingyixia]

xinyingyixia,

"...But in the lab such a strong laser is able to pass completely through the AI" Can you show the reference where this was seen?

I can show some information (but in Chinese) to show that a strong laser can pass through plasma higher than its own critical density, or at least have an effect on the density distribution of the plasma. For example, n=100nc here. And for aluminum targets, I can't provide references at the moment, but it is possible to do this in our lab.

[DanRRRR]

Interesting. Are you claiming that black or gray area has density 6e22 cm-3 Z where Z is charge which has to be probably at least Z~5 giving total density 3e23 cm-3. That is 3.e23/1.75e21 > 150 times the critical density. While with your a0=22 (Lorentz gamma ~ 15) maximum you can get through would be density N_crit gamma = 1.75e21 15 ~ 3.e22 cm-3

I still do not understand some things here in experimental setup. What strange form densiiy profile is here? Was the target flat solid Aluminum target or some initially prepared plasma?

And how the black area so quickly and homogeneously changes from black to gray ? Is this how density changes (decreases ) with time?

[xinyingyixia]

Interesting. Are you claiming that black or gray area has density 6e22 cm-3 Z .....

Thank you for your response and discussion.

In fact, the simulation I mentioned in my reply and the simulation I want to perform (with the input.txt file I uploaded) are not the same.

I am just trying to simulate the interaction between a laser and an aluminum target, as my colleague is using lasers with a0~20 to penetrate an aluminum target, specifically a solid aluminum foil. In my simulation, I have set up an ionized aluminum model. You mentioned the need to consider the Lorentz factor to determine the upper limit of density.

However, I would like to ask if this means that the electron distribution remains almost unchanged after being acted upon by the laser (at least according to the simulation using the input.txt file).

[DanRRRR]

Well, such dense plasma would be not easy to model correctly. Self-heating and energy disbalances will be waiting you on this tricky road...

[xinyingyixia]

Well, such dense plasma would be not easy to model correctly. Self-heating and energy disbalances will be waiting you on this tricky road...

I have also noticed this. Energy is not conserved (the kinetic energy of particles is much greater than the energy input of the laser). Actually, yesterday I asked someone about this, and he replied that it could be due to self-heating phenomenon. However, I am still clueless.

Therefore, could you kindly tell me how to accurately simulate this (or maybe just where to find the answer)?

[DanRRRR]

Unfortunately i do not have amicable solution here yet. Let me know if you will find one.

[xinyingyixia]

fine

[Status-Mirror]

Hey all,

Unfortunately 3D simulations are a bit too expensive for our normal debugging efforts. From a quick look through your simulation parameters, it seems like you're using 100nm cells and 4 particles per cell. I think the resolution is too low for a $6\times 10^{28} m^{-3}$ plasma, and maybe the resolution issues are interfereing with your results?

Typically I would say to use a minimum of 20 cells per wavelength, and to set particles per cell to a number high enough to minimise self-heating. We have a good demo for estimating the resolution needed to minimise self heating.

Hope this helps, Stuart