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    <p>Hi David,<br>
      <br>
      It will be the same pseudovacuum (i.e. low density Helium) if you
      define it as chamber material. And you should, the LaserSlab is
      not made for pure vacuum as it is not handled by the EOS of your
      case.<br>
      <br>
      Best,<br>
      Arthur<br>
    </p>
    <pre class="moz-signature" cols="72">-- 
Dr. Arthur Hirsch-Passicos
Post-doctoral Researcher

Laser Particle Acceleration Division
Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf e.V.</pre>
    <div class="moz-cite-prefix">On 18/06/2025 00:03, David Montgomery
      wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:99302950-6C28-4EBC-907C-851C03A5961B@gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      Hi Xu,
      <div><br>
      </div>
      <div>Thank you for the quick response. </div>
      <div><br>
      </div>
      <div>Will that extra space be truly vacuum, or will it be the same
        as the low density Helium “chamber” species?</div>
      <div><br>
      </div>
      <div>David <br id="lineBreakAtBeginningOfSignature">
        <div dir="ltr">Sent from my iPhone</div>
        <div dir="ltr"><br>
          <blockquote type="cite">On Jun 17, 2025, at 3:57 PM, Xu Zhao
            <a class="moz-txt-link-rfc2396E" href="mailto:xu.zhao@york.ac.uk"><xu.zhao@york.ac.uk></a> wrote:<br>
            <br>
          </blockquote>
        </div>
        <blockquote type="cite">
          <div dir="ltr">
            <div dir="ltr">
              <div dir="ltr">Hi David,
                <div><br>
                </div>
                <div>If you want to add some space behind the target
                  (see attached) compared to the Laserslab default,</div>
                <div><br>
                </div>
                <div>I think just increasing ymax (the box length if you
                  run in 2d) in the .par will work.</div>
                <div><br>
                </div>
                <div>
                  <div>Usually the <u>Simulation_initBlock.F90</u> defines
                    the "blocks (cells)" in the simulations.</div>
                  <div><br>
                  </div>
                  <div>For example line 100 - line 129 in the <u>Simulation_initBlock.F90
                    </u>define which part is the "<font face="monospace">target</font>"
                    species and the other is "<font face="monospace">Cham</font>".</div>
                </div>
                <div><br>
                </div>
                <div>You do not need to modify other files as they
                  define the variables (like "<font face="monospace">sim_targetHeight</font>")
                  and material files ("like eos file").</div>
                <div><br>
                </div>
                <div>Hope this helps,</div>
                <div>Xu</div>
                <div>
                  <div><br>
                  </div>
                </div>
                <div><br>
                </div>
              </div>
              <div class="gmail_quote gmail_quote_container">
                <div dir="ltr" class="gmail_attr">On Tue, 17 Jun 2025 at
                  22:17, David Montgomery <<a
                    href="mailto:dsmont80@gmail.com"
                    moz-do-not-send="true" class="moz-txt-link-freetext">dsmont80@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">Hi
                  All,<br>
                  <br>
                  Another FLASH-newbie question. I’ve successfully run
                  the LaserSlab example, and made some small
                  modifications in my own *.par file.<br>
                  <br>
                  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?<br>
                  <br>
                  Do I have to modify one or more of the local *.F90
                  files?<br>
                  <br>
                  Or can I use the same “species” (Cham) on both the
                  rear and front side of the “target” species?<br>
                  <br>
                  Any advice would be very helpful.<br>
                  <br>
                  Thanks,<br>
                  David Montgomery <br>
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                </blockquote>
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              <div><br clear="all">
              </div>
              <div><br>
              </div>
              <span class="gmail_signature_prefix">-- </span><br>
              <div dir="ltr" class="gmail_signature">
                <div dir="ltr">
                  <div><span style="color:rgb(136,136,136)">Xu Zhao</span></div>
                  <div><span style="color:rgb(136,136,136)">PDRA</span></div>
                  <span style="color:rgb(136,136,136)">York Plasma
                    Institute</span><br style="color:rgb(136,136,136)">
                  <span style="color:rgb(136,136,136)">School of
                    Physics, Engineering and Technology</span><br
                    style="color:rgb(136,136,136)">
                  <span style="color:rgb(136,136,136)">University of
                    York</span><br style="color:rgb(136,136,136)">
                  <span style="color:rgb(136,136,136)">York YO10 5DQ, UK</span><br>
                </div>
              </div>
            </div>
            <div><a class="moz-txt-link-rfc2396E" href="mailto:WX20250617-224328@2x.png"><WX20250617-224328@2x.png></a></div>
          </div>
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      <br>
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