From 332970ea2e03d2512e75575c9939b50b8d576f31 Mon Sep 17 00:00:00 2001 From: Paul Romano Date: Tue, 28 Oct 2014 21:53:39 -0400 Subject: [PATCH] Update documentation for evaporation spectrum. --- docs/source/methods/physics.rst | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/docs/source/methods/physics.rst b/docs/source/methods/physics.rst index 54dc91345..db6cfd89e 100644 --- a/docs/source/methods/physics.rst +++ b/docs/source/methods/physics.rst @@ -682,17 +682,20 @@ nuclear temperature, which is a function of the incoming energy of the neutron. The ACE format contains a list of nuclear temperatures versus incoming energies. The nuclear temperature is interpolated between neighboring incoming energies using a specified interpolation law. Once the temperature :math:`T` is -determined, we then calculate a candidate outgoing energy based on rule C45 in -the `Monte Carlo Sampler`_: +determined, we then calculate a candidate outgoing energy based on the algorithm +given in LA-UR-14-27694_: .. math:: :label: evaporation-E - E' = -T \log (\xi_1 \xi_2) + E' = -T \log ((1 - g\xi_1)(1 - g\xi_2)) -where :math:`\xi_1, \xi_2` are random numbers sampled on the unit -interval. The outgoing energy is only accepted according to a specified -restriction energy as in equation :eq:`maxwell-restriction`. +where :math:`g = 1 - e^{-w}`, :math:`w = (E - U)/T`, :math:`U` is the +restriction energy, and :math:`\xi_1, \xi_2` are random numbers sampled on the +unit interval. The outgoing energy is only accepted according to the restriction +energy as in equation :eq:`maxwell-restriction`. This algorithm has a much +higher rejection efficiency than the standard technique, i.e. rule C45 in the +`Monte Carlo Sampler`_. ACE Law 11 - Energy-Dependent Watt Spectrum +++++++++++++++++++++++++++++++++++++++++++ @@ -1591,6 +1594,8 @@ References .. _Monte Carlo Sampler: https://laws.lanl.gov/vhosts/mcnp.lanl.gov/pdf_files/la-9721_3rdmcsampler.pdf +.. _LA-UR-14-27694: http://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-14-27694 + .. _MC21: http://www.osti.gov/bridge/servlets/purl/903083-HT5p1o/903083.pdf .. _Sutton and Brown: http://www.osti.gov/bridge/product.biblio.jsp?osti_id=307911