# Energy distribution in OPENMC fixed source **URL:** \ **Category:** User Support\ **Created:** [August 24, 2022, 2:59pm UTC](https://openmc.discourse.group/t/energy-distribution-in-openmc-fixed-source/2250 "2022-08-24T14:59:28Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![SunAK](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@SunAK](https://openmc.discourse.group/u/SunAK)\ **Post date:** [August 24, 2022, 2:59pm UTC](https://openmc.discourse.group/t/energy-distribution-in-openmc-fixed-source/2250/1 "2022-08-24T14:59:28Z")
Hi all๏ผš I am new to OPENMC and am trying to learn how to write fixed sources for OPENMC. Iโ€™m in about learning energy distribution and a little confused. I am attaching my MCNP source card, how should the energy distribution in MCNP be written in OPENMC? Is it with openmc.stats.Tabular? I would greatly appreciate any help in this regard. Thanks! ๐Ÿ˜ƒ MCNP source card: ```auto sdef pos= 0.00000000 0.00000000 15.00000000 vec= 0.00000000 0.00000000 -1.00000000 axs= 0.00000000 0.00000000 -1.00000000 ara= 78.53982 dir=1.0 rad=d1 erg=d2 si1 0 5 si2 S 5 6 7 sp2 0.1 0.89 0.01 # si5 0.000000001 1.06412E-09 1.13235E-09 1.20495E-09 1.28221E-09 1.36442E-09 1.4519E-09 1.545E-09 1.64406E-09 1.74947E-09 1.86165E-09 1.98101E-09 2.10803E-09 2.24319E-09 2.38702E-09 2.54007E-09 2.70293E-09 2.87624E-09 3.06066E-09 3.2569E-09 3.46572E-09 3.68794E-09 3.9244E-09 4.17603E-09 4.44378E-09 4.72871E-09 5.0319E-09 5.35454E-09 5.69786E-09 6.06319E-09 6.45195E-09 6.86563E-09 7.30584E-09 7.77428E-09 8.27275E-09 8.80318E-09 9.36762E-09 9.96825E-09 1.06074E-08 1.12875E-08 1.20112E-08 1.27814E-08 1.36009E-08 1.4473E-08 1.54009E-08 1.63884E-08 1.74392E-08 1.85573E-08 1.97472E-08 2.10134E-08 2.23607E-08 2.37944E-08 2.532E-08 2.69435E-08 2.86711E-08 3.05094E-08 3.24656E-08 3.45472E-08 3.67623E-08 3.91194E-08 4.16277E-08 4.42967E-08 4.71369E-08 5.01593E-08 5.33754E-08 5.67977E-08 6.04394E-08 6.43146E-08 6.84384E-08 7.28265E-08 7.74959E-08 8.24648E-08 8.77523E-08 9.33788E-08 9.9366E-08 1.05737E-07 1.12517E-07 1.19731E-07 1.27408E-07 1.35577E-07 1.4427E-07 1.5352E-07 1.63364E-07 1.73838E-07 1.84984E-07 1.96845E-07 2.09466E-07 2.22897E-07 2.37188E-07 2.52396E-07 2.6858E-07 2.858E-07 3.04125E-07 3.23625E-07 3.44375E-07 3.66456E-07 3.89952E-07 4.14955E-07 4.41561E-07 4.69873E-07 5E-07 sp5 D 0 1 99r c # si6 5.0000000E-07 5.5205240E-07 6.0952371E-07 6.7297806E-07 7.4303831E-07 8.2039217E-07 9.0579893E-07 1.0000970E-06 1.1042119E-06 1.2191656E-06 1.3460866E-06 1.4862207E-06 1.6409434E-06 1.8117735E-06 2.0003878E-06 2.2086378E-06 2.4385676E-06 2.6924342E-06 2.9727296E-06 3.2822050E-06 3.6238983E-06 4.0011636E-06 4.4177039E-06 4.8776081E-06 5.3853906E-06 5.9460356E-06 6.5650465E-06 7.2484994E-06 8.0031030E-06 8.8362645E-06 9.7561621E-06 1.0771825E-05 1.1893224E-05 1.3131366E-05 1.4498404E-05 1.6007758E-05 1.7674242E-05 1.9514216E-05 2.1545740E-05 2.3788755E-05 2.6265278E-05 2.8999620E-05 3.2018620E-05 3.5351912E-05 3.9032216E-05 4.3095657E-05 4.7582122E-05 5.2535650E-05 5.8004864E-05 6.4043449E-05 7.0710679E-05 7.8072001E-05 8.6199671E-05 9.5173471E-05 1.0508149E-04 1.1602097E-04 1.2809932E-04 1.4143507E-04 1.5615914E-04 1.7241606E-04 1.9036540E-04 2.1018335E-04 2.3206445E-04 2.5622347E-04 2.8289757E-04 3.1234856E-04 3.4486555E-04 3.8076771E-04 4.2040746E-04 4.6417389E-04 5.1249663E-04 5.6584999E-04 6.2475769E-04 6.8979797E-04 7.6160925E-04 8.4089644E-04 9.2843780E-04 1.0250926E-03 1.1318097E-03 1.2496365E-03 1.3797297E-03 1.5233662E-03 1.6819559E-03 1.8570556E-03 2.0503840E-03 2.2638389E-03 2.4995154E-03 2.7597269E-03 3.0470278E-03 3.3642380E-03 3.7144714E-03 4.1011657E-03 4.5281167E-03 4.9995154E-03 5.5199890E-03 6.0946464E-03 6.7291284E-03 7.4296630E-03 8.2031266E-03 9.0571115E-03 1.0000000E-02 sp6 D 0 1 99r # si7 1.00E-02 1.0544119E-02 1.1117845E-02 1.1722788E-02 1.2360647E-02 1.3033213E-02 1.3742375E-02 1.4490124E-02 1.5278559E-02 1.6109895E-02 1.6986465E-02 1.7910730E-02 1.8885287E-02 1.9912872E-02 2.0996369E-02 2.2138822E-02 2.3343437E-02 2.4613598E-02 2.5952870E-02 2.7365016E-02 2.8853998E-02 3.0423999E-02 3.2079427E-02 3.3824929E-02 3.5665408E-02 3.7606031E-02 3.9652247E-02 4.1809801E-02 4.4084752E-02 4.6483487E-02 4.9012742E-02 5.1679618E-02 5.4491605E-02 5.7456597E-02 6.0582919E-02 6.3879351E-02 6.7355148E-02 7.1020070E-02 7.4884407E-02 7.8959010E-02 8.3255320E-02 8.7785401E-02 9.2561972E-02 9.7598445E-02 1.0290896E-01 1.0850843E-01 1.1441258E-01 1.2063799E-01 1.2720213E-01 1.3412344E-01 1.4142136E-01 1.4911636E-01 1.5723007E-01 1.6578525E-01 1.7480594E-01 1.8431747E-01 1.9434653E-01 2.0492130E-01 2.1607145E-01 2.2782831E-01 2.4022489E-01 2.5329598E-01 2.6707830E-01 2.8161053E-01 2.9693350E-01 3.1309022E-01 3.3012605E-01 3.4808884E-01 3.6702901E-01 3.8699976E-01 4.0805715E-01 4.3026032E-01 4.5367160E-01 4.7835674E-01 5.0438504E-01 5.3182959E-01 5.6076745E-01 5.9127987E-01 6.2345253E-01 6.5737577E-01 6.9314484E-01 7.3086017E-01 7.7062766E-01 8.1255898E-01 8.5677186E-01 9.0339045E-01 9.5254564E-01 1.0043755E+00 1.0590254E+00 1.1166490E+00 1.1774080E+00 1.2414730E+00 1.3090240E+00 1.3802504E+00 1.4553525E+00 1.5345410E+00 1.6180383E+00 1.7060788E+00 1.7989098E+00 1.8967919E+00 2.0000000E+00 sp7 D 0 1 99r ``` ---
**Author:** ![paulromano](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/paulromano/32/486_2.png) [@paulromano](https://openmc.discourse.group/u/paulromano)\ **Post date:** [September 23, 2022, 4:06am UTC](https://openmc.discourse.group/t/energy-distribution-in-openmc-fixed-source/2250/2 "2022-09-23T04:06:38Z")
Hi @SunAK. In this SDEF, energy is specified as distribution 2 which is given as: > [@SunAK](#): > > ```auto > si2 S 5 6 7 > sp2 0.1 0.89 0.01 > > ``` The OpenMC equivalent of this would be: ```python dist = openmc.stats.Mixture([0.1, 0.89, 0.01], [dist5, dist6, dist7]) ``` where each of the subdistributions would be given as: ```python dist5 = openmc.stats.Tabular(energies1, probs1) dist6 = openmc.stats.Tabular(energies2, probs2) dist7 = openmc.stats.Tabular(energies3, probs3) ``` The `si` cards in that MCNP snippet donโ€™t appear to be complete to me, so Iโ€™m not sure how to interpret the values on the `sp` cards, but depending on what they represent, you can specify the interpolation on the `Tabular` distribution with an argument `interpolation="histogram"` or `interpolation="linear-linear"`. ---
**Author:** ![SunAK](https://avatars.discourse-cdn.com/v4/letter/s/2acd7d/32.png) [@SunAK](https://openmc.discourse.group/u/SunAK)\ **Post date:** [September 29, 2022, 3:33am UTC](https://openmc.discourse.group/t/energy-distribution-in-openmc-fixed-source/2250/3 "2022-09-29T03:33:41Z")
Thank you very much for your advice ๐Ÿ˜ƒ ๐Ÿ˜ƒ ๐Ÿ˜ƒ