<div dir="ltr">Hello,<div><br></div><div>Jonathan Davies, Po-Yu Chang, and I have measured laser burn through of plastic windows using both FLASH and our own in-house rad-hydro code DRACO. Specifically, I want to address the idea that the disk undergoes uniform expansion. This is correct in the model, however empirically has been shown not to be the case. As a good check, it might be worth your while to read the paper, simulate a plastic window that's a bit thicker, and compare to our experimental results. It should give you a good idea as to the limitation of the predictive capabilities of FLASH.</div><div><br></div><div><a href="https://aip.scitation.org/doi/full/10.1063/1.5030107">https://aip.scitation.org/doi/full/10.1063/1.5030107</a> <br></div><div><br></div><div>Cheers,</div><div><br></div><div>Dan<br clear="all"><div><div dir="ltr" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><br></div><div dir="ltr">Daniel Barnak</div><div dir="ltr">Assistant Scientist</div><div dir="ltr">Laboratory for Laser Energetics</div><div dir="ltr">University of Rochester</div><div dir="ltr">250 E River Rd</div><div dir="ltr">Rochester, NY 14623-1299</div><div dir="ltr">W: 585-276-4332</div></div></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Feb 17, 2020 at 5:26 PM Scott Feister <<a href="mailto:sfeister@gmail.com" target="_blank">sfeister@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>I will <i>also </i>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".<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Feb 17, 2020 at 2:19 PM Scott Feister <<a href="mailto:sfeister@gmail.com" target="_blank">sfeister@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Zhang,</div><div><br></div><div>
Temporal dynamics can matter!
I will just add a comment that two lasers with the <i>same </i>amount of energy but <i>different </i>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.<br></div><div><br></div><div>
I haven't looked at the specific parfile, and maybe something else is going on here as well! <br></div><div><br></div><div>-Scott<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Feb 17, 2020 at 2:40 AM Zhang Shizheng <<a href="mailto:zsz526654434@stu.xjtu.edu.cn" target="_blank">zsz526654434@stu.xjtu.edu.cn</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span style="font-family:SimSun"></span><br>
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<span style="font-family:SimSun">Hi all,</span>
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<span style="font-family:SimSun"> 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.</span>
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<span style="font-family:SimSun"> (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</span>
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<span style="font-family:SimSun"> (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.</span>
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<span style="font-family:SimSun"> 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, <span style="font-size:13px"><strong>what might cause the difference between these two results?</strong></span> 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. <br>
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<span style="font-family:SimSun">Best Wishes</span><br>
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<span style="font-family:SimSun">Zhang Shizheng</span>
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<span style="font-family:SimSun">PHD</span>
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<span style="font-family:SimSun">Xi'an Jiaotong University</span>
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<span style="font-family:SimSun">Institute for Science and Technology of Laser and Particle Beams</span>
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