# A transport-based condensed history algorithm

## Abstract

Condensed history algorithms are approximate electron transport Monte Carlo methods in which the cumulative effects of multiple collisions are modeled in a single step of path length s{sub 0}. This path length is the distance each Monte Carlo electron travels between collisions. Current condensed history techniques utilize a splitting routine over the range 0 {le} s {le} s{sub 0}. For example, the PENELOPE method splits each step into two substeps: one with length {xi}s{sub 0} and one with length (1 {minus} {xi})s{sub 0}, where {xi} is a random number from 0 < {xi} < 1. Because s{sub 0} is fixed (not sampled from an exponential distribution), conventional condensed history schemes are not transport processes. Here the authors describe a new condensed history algorithm that is a transport process. The method simulates a transport equation that approximates the exact Boltzmann equation. The new transport equation has a larger mean free path (mfp) than, and preserves two angular moments of, the Boltzmann equation. Thus, the new process is solved more efficiently by Monte Carlo, and it conserves both particles and scattering power.

- Authors:

- Lawrence Livermore National Lab., CA (United States)
- Univ. of Michigan, Ann Arbor, MI (United States)

- Publication Date:

- OSTI Identifier:
- 678131

- Report Number(s):
- CONF-990605-

Journal ID: TANSAO; ISSN 0003-018X; TRN: 99:009116

- Resource Type:
- Journal Article

- Journal Name:
- Transactions of the American Nuclear Society

- Additional Journal Information:
- Journal Volume: 80; Conference: 1999 annual meeting of the American Nuclear Society (ANS), Boston, MA (United States), 6-10 Jun 1999; Other Information: PBD: 1999

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 66 PHYSICS; 99 MATHEMATICS, COMPUTERS, INFORMATION SCIENCE, MANAGEMENT, LAW, MISCELLANEOUS; ALGORITHMS; ELECTRONS; CHARGED-PARTICLE TRANSPORT; MONTE CARLO METHOD; BOLTZMANN EQUATION

### Citation Formats

```
Tolar, D.R. Jr., and Larsen, E.W.
```*A transport-based condensed history algorithm*. United States: N. p., 1999.
Web.

```
Tolar, D.R. Jr., & Larsen, E.W.
```*A transport-based condensed history algorithm*. United States.

```
Tolar, D.R. Jr., and Larsen, E.W. Wed .
"A transport-based condensed history algorithm". United States.
```

```
@article{osti_678131,
```

title = {A transport-based condensed history algorithm},

author = {Tolar, D.R. Jr. and Larsen, E.W.},

abstractNote = {Condensed history algorithms are approximate electron transport Monte Carlo methods in which the cumulative effects of multiple collisions are modeled in a single step of path length s{sub 0}. This path length is the distance each Monte Carlo electron travels between collisions. Current condensed history techniques utilize a splitting routine over the range 0 {le} s {le} s{sub 0}. For example, the PENELOPE method splits each step into two substeps: one with length {xi}s{sub 0} and one with length (1 {minus} {xi})s{sub 0}, where {xi} is a random number from 0 < {xi} < 1. Because s{sub 0} is fixed (not sampled from an exponential distribution), conventional condensed history schemes are not transport processes. Here the authors describe a new condensed history algorithm that is a transport process. The method simulates a transport equation that approximates the exact Boltzmann equation. The new transport equation has a larger mean free path (mfp) than, and preserves two angular moments of, the Boltzmann equation. Thus, the new process is solved more efficiently by Monte Carlo, and it conserves both particles and scattering power.},

doi = {},

journal = {Transactions of the American Nuclear Society},

number = ,

volume = 80,

place = {United States},

year = {1999},

month = {9}

}