Exercise 2:
Broadening Simple Cross Sections




This exercise will make use of the BROADR module of NJOY to Doppler broaden the hydrogen cross sections and to demonstrate how simple cross section shapes change with temperature.

You should still be in your NJOY working directory, and t511 should still be copied to tape20. Edit your input file in1 to look like the following (but you can leave off the comments to the right of the slash symbol): 

           reconr
           20 21
           'exercise 2'/    new tape ID title
           1301 1/          MAT
           .001/            fractional tolerance
           '1-H-1'/         descriptive card for new tape
           0/
           broadr
           20 21 22
           1301 1/          same MAT, one temperature
           .001/            same tolerance
           300./            broaden to 300K
           0/
           stop

Save the file as in2.

This file says to run RECONR on MAT1301 with a reconstruction tolerance of .001 (.1%). The output will be on tape21. The title on the Tape ID card will be "exercise 2," and the single information line in the output file will say "1-H-1." Then run the output of RECONR into BROADR (along with the original ENDF tape). Broaden the cross sections to 300K using .001 (.1%) as the linearization and unionization tolerance. The output is written on tape22.

Run the NJOY job with this input file.

Examine the file called "output" to see the new messages from BROADR. Examine the file called "tape22" to see what the new 300K PENDF tape looks like.

  • Check MF=3, MT=102 (radiative capture). How have the cross sections changed with respect to those on the output file from RECONR (tape21)?

  • Check MF=3, MT=2 (elastic scattering). How have the cross sections changed with respect to those on the output file from RECONR (tape21)?

  • Check MF=3, MT=1 (total cross section). Is the energy grid still unionized? Are the cross section values really equal to the sum of the partial cross sections?

Change the temperature to 10000K and run the NJOY job again.
  • Check MF=3, MT=102 (radiative capture). Have the cross sections changed very much?

  • Check MF=3, MT=2 (elastic scattering). Have the cross sections changed? What do think the analytic shape of the cross section is after Doppler broadening?

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23 January 1998 T-2 Nuclear Information Service ryxm@lanl.gov