[FLASH-USERS] [HEDP] Fwd: laser plasma problem

Fri Feb 22 13:50:50 EST 2013

Hello

I appreciate if you can help me through my simulation,i just started to learn flash.
I am simulating the laser focused onto air. Regarding to the LASER SLAB simulation:

1. Should i change the ionization level particularly for air? ms_targetZmin?

2. How can i change the domain boundaries,the one that i am simulating does not show the Target part in VISIT(just shows ray tracing on the CHAM part).

3. How can i compute the electron temperature and electron densities. actually, How can i use the output parameters, SUMY and YE , to calculate the density and temperature?

4. What should i use for EOS of air?

5.VISIT output of ray tracing shows the sub-nanosecond results,although i set the laser pulse duration for 6ns.

It would be great if you can answer the questions.
Hope my questions are clear.

Regards

Regards
________________________________
From: icksa1 at gmail.com [icksa1 at gmail.com] on behalf of Milad Fatenejad [milad at flash.uchicago.edu]
Sent: Thursday, February 21, 2013 9:43 AM
To: Ehsan Vadiee
Subject: Re: [HEDP] Fwd: laser plasma problem

Salam Ehsan:

Yes, I think inverse Bremsstrahlung is a reasonable approximation for modeling the energy deposition - how big is the focal spot? What is the air density? Is it just a single laser beam?

If you don't want to make a new simulation, then I would begin by taking the laser slab simulation and change the properties of CHAM and TARG to be consistent with Air. You will need EOS files for air which someone will provide you...

Next (as I said below) you are actually interested in a simulation where there is no TARG region. So a good idea is to just move the target out of the domain. Then, the entire domain is filled with the CHAM region. To do this, set sim_vacuumHeight to be a large number (as I described in my last email). Then the target won't actually be inside the domain.

Thanks
Milad

On Thu, Feb 21, 2013 at 10:26 AM, Ehsan Vadiee <evadiee at unm.edu<mailto:evadiee at unm.edu>> wrote:
Salam Milad

Thank you for your response. I had a honor to talk to you in APS 2012.

I think, inverse bremsstranhlung process is appropriate to some extent. Collisional cascade ionization is also important in the expansion process of volume of the laser-plasma. Inverse bremsstranhlung can be a good model for the first the stages of laser-plasma evolution.

My laser is Q-switched Nd:YAG with wavelength of 1064 nm, 8 ns pulse width, and energy per pulse of 600 mJ.

Do you think it is a good approximation for my problem?can i get full temporal evolution of plasma with just inverse bremsstranhlung?If yes, what major changes should i take into account? By changing the TARGET and CHAM properties to air, can i still get the ionization in focal spot in all direction? what kind of changes do you think is applicable to my problem?

Thank you
Best regards

________________________________
From: icksa1 at gmail.com<mailto:icksa1 at gmail.com> [icksa1 at gmail.com<mailto:icksa1 at gmail.com>] on behalf of Milad Fatenejad [milad at flash.uchicago.edu<mailto:milad at flash.uchicago.edu>]
Sent: Thursday, February 21, 2013 7:03 AM
To: Ehsan Vadiee
Cc: Christopher Daley; Klaus Weide; Petros Tzeferacos
Subject: Re: [HEDP] Fwd: laser plasma problem

Hi Ehsan:

Thank you for the question...in the future please feel free to sign up for the FLASH-USERS mailing list and send questions there:

http://flash.uchicago.edu/site/flashcode/mailinglists/

You can just modify the LaserSlab simulation. If you set the parameter sim_vacuumHeight to be greater than (ymax-ymin), then the domain will ONLY contain the CHAM species. The reason is that the target will be outside of the domain.

The next question is: Is the FLASH laser energy deposition model appropriate for the conditions you are trying to model? FLASH only models laser energy deposition via the inverse Bremsstrahlung process. Is this model appropriate for your particular laser? What is the intensity of the laser light and the wavelength?

Thanks
Milad

On Wed, Feb 20, 2013 at 4:12 PM, Christopher Daley <cdaley at flash.uchicago.edu<mailto:cdaley at flash.uchicago.edu>> wrote:
Anyone able to help?

I think the answer is yes, but don't know where to start.

Chris

-------- Original Message --------
Subject:        laser plasma problem
Date:   Wed, 20 Feb 2013 21:36:49 +0000
From:   Ehsan Vadiee <evadiee at unm.edu><mailto:evadiee at unm.edu>
To:     cdaley at flash.uchicago.edu<mailto:cdaley at flash.uchicago.edu> <cdaley at flash.uchicago.edu><mailto:cdaley at flash.uchicago.edu>

Hello Mr. Daley

My name is Ehsan Vadiee from High power microwave and electron beam acceleration center at University of New Mexico.

I am doing research on the HEDP. I am working on synchronization of high power microwave and laser induced plasma and part of it is about Laser induced plasma in air. I downloaded Flash code and i am currently trying to implement my research in the code.

As you know, my problem is not solid ablation which is given in the laserslab simulation. I am focusing the pulsed laser beam onto the atmospheric pressure of air. Plasma is propagating in all directions not just in perpendicular to solid slab. CHAM and TARGET, both of them, must be air and has the same material properties.

Do you think that it is possible to simulate my problem, just by changing the laserslab parameters?
I appreciate if you can give me further information

Regards

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