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*DECK PIJS2D
SUBROUTINE PIJS2D(NREG,NSOUT,NSLINE,WEIGHT,RCUTOF,NGSS,SIGANG,
> XGSS,WGSS,SEGLEN,NRSEG,STAYIN,GOSOUT,DPR)
*
*-----------------------------------------------------------------------
*
*Purpose:
* Integration for general 2D specular tracking.
*
*Copyright:
* Copyright (C) 1991 Ecole Polytechnique de Montreal
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version
*
*Author(s): R. Roy, G. Marleau
*
*Parameters: input
* NREG total number of regions.
* NSOUT number of outer surface.
* NSLINE number of segemnts on line.
* WEIGHT line weight.
* RCUTOF MFP cut-off factor (truncate lines).
* NGSS number of Gauss points.
* SIGANG 3D albedo-cross section vector.
* XGSS 2D->3D conversion for integration.
* WGSS 2D->3D conversion for integration.
* SEGLEN length of track.
* NRSEG region crossed by track.
*
*Parameters: output
* DPR collision probabilities.
*
*Parameters: scratch
* STAYIN stay-in zone probability.
* GOSOUT goes-out zone probability.
*
*References:
* R. Roy et al.,
* A Cyclic Tracking Procedure for CP Calculations in 2-D Lattices
* Conf/Advances in Math, Comp & Reactor Physics,
* Pittsburgh, V 1, P 2.2 4-1 (1991).
*
*-----------------------------------------------------------------------
*
IMPLICIT NONE
*----
* VARIABLES
*----
INTEGER NREG,NSOUT,NSLINE,NGSS,NRSEG(NSLINE)
DOUBLE PRECISION WEIGHT,SEGLEN(NSLINE),STAYIN(NGSS,NSLINE),
> GOSOUT(NGSS,NSLINE)
REAL RCUTOF,SIGANG(NGSS,-NSOUT:NREG)
DOUBLE PRECISION DPR(-NSOUT:NREG,-NSOUT:NREG)
*----
* Local variables
*----
INTEGER IL,JL,NOIL,NOJL,ISODD,JSODD,IJDEL,MXGAUS,IGSS
PARAMETER (MXGAUS= 64 )
REAL WGSS(MXGAUS),FINV(MXGAUS),XGSS(MXGAUS),
> ZERO,ONE,HALF,XSIL,CUTOF
DOUBLE PRECISION TTOT(MXGAUS),OPATH
PARAMETER (ZERO=0.0E0, ONE=1.0E0, HALF=0.5E0 )
REAL SIXT,CUTEXP
PARAMETER (SIXT=HALF/3.0,CUTEXP=0.02)
DOUBLE PRECISION EXSIL,XSIL2
DO 20 IGSS= 1,NGSS
TTOT(IGSS)= ONE
20 CONTINUE
*
*1.1) CHANGE PATHS => GOSOUT AND STAYIN PATHS, INCLUDING ALBEDOS
* ADD *PII* LOCAL NON-CYCLIC CONTRIBUTIONS
ISODD=0
DO 30 IL= 1, NSLINE
NOIL = NRSEG(IL)
IF( NOIL .LT. 0 )THEN
IF(ISODD .EQ. 1) THEN
ISODD=0
DO 31 IGSS= 1,NGSS
*----
* FOR SURFACES:
* OLD VERSION BEFORE SURFACE DOUBLING
* GOSOUT= ALBEDO * SURFACE WEIGHT
* WHERE ALL SURFACE WEIGHTS WERE 1.0
* NEW VERSION WITH SURFACE DOUBLING
* GOSOUT= ALBEDO
* STAYIN = 1- ALBEDO * SURFACE WEIGHT
* TTOT = PRODUCT OF GOSOUT
*----
GOSOUT(IGSS,IL)= SIGANG(1,NOIL)
STAYIN(IGSS,IL)= ONE - GOSOUT(IGSS,IL)
TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,IL)
31 CONTINUE
ELSE
ISODD=1
DO 32 IGSS= 1,NGSS
*----
* FOR SURFACES:
* OLD VERSION BEFORE SURFACE DOUBLING
* GOSOUT= ALBEDO * SURFACE WEIGHT
* WHERE ALL SURFACE WEIGHTS WERE 1.0
* NEW VERSION WITH SURFACE DOUBLING
* GOSOUT= ALBEDO
* STAYIN = 1- ALBEDO * SURFACE WEIGHT
* TTOT = PRODUCT OF GOSOUT
*----
GOSOUT(IGSS,IL)= SIGANG(1,NOIL)
STAYIN(IGSS,IL)= ONE
* TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,IL)
32 CONTINUE
ENDIF
ELSE IF(NOIL .GT. 0) THEN
*----
* FOR REGIONS
* STAYIN = 1 - EXP[ -CROSS SECTION * LENGTH OF NSLINE]
* GOSOUT = 1 - STAYIN
* TTOT = PRODUCT OF GOSOUT
*----
XSIL = SIGANG(1,NOIL)
IF( XSIL .EQ. ZERO) THEN
DO 33 IGSS= 1,NGSS
GOSOUT(IGSS,IL)= ONE
STAYIN(IGSS,IL)= SEGLEN(IL)*XGSS(IGSS)
DPR(NOIL,NOIL)= DPR(NOIL,NOIL)+HALF*WEIGHT*
> WGSS(IGSS)*STAYIN(IGSS,IL)*STAYIN(IGSS,IL)
33 CONTINUE
ELSE IF( XSIL .LT. CUTEXP) THEN
DO 333 IGSS= 1,NGSS
OPATH= SIGANG(IGSS,NOIL)*SEGLEN(IL)
XSIL2=OPATH*OPATH
EXSIL=XSIL2*(HALF-SIXT*OPATH+XSIL2/24.0)
STAYIN(IGSS,IL)=OPATH-EXSIL
GOSOUT(IGSS,IL)= ONE - STAYIN(IGSS,IL)
TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,IL)
DPR(NOIL,NOIL)= DPR(NOIL,NOIL) + WEIGHT*WGSS(IGSS)*EXSIL
333 CONTINUE
ELSE
DO 34 IGSS=1,NGSS
OPATH= SIGANG(IGSS,NOIL)*SEGLEN(IL)
EXSIL= EXP(-OPATH)
STAYIN(IGSS,IL)= ONE - EXSIL
GOSOUT(IGSS,IL)= EXSIL
TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,IL)
DPR(NOIL,NOIL)= DPR(NOIL,NOIL)
> + WEIGHT*WGSS(IGSS)*(OPATH-STAYIN(IGSS,IL))
34 CONTINUE
ENDIF
ENDIF
30 CONTINUE
*
*1.2) COMPUTE CYCLIC FACTORS BY ANGLE
* USING GLOBAL TRACK ATTENUATION: BETA(TOT)*EXP(-MFP(TOT))
DO 40 IGSS= 1,NGSS
IF( TTOT(IGSS).GE.ONE )THEN
CALL XABORT( 'PIJS2D: ALBEDOS ARE NOT COMPATIBLE')
ENDIF
FINV(IGSS)= REAL(WEIGHT * WGSS(IGSS) / (ONE-TTOT(IGSS)))
40 CONTINUE
*
*1.3) ADD *PIJ* CONTRIBUTIONS FOR FORWARD SOURCES
ISODD=0
DO 50 IL= 1, NSLINE
NOIL = NRSEG(IL)
DO 60 IGSS= 1, NGSS
TTOT(IGSS)= FINV(IGSS) * STAYIN(IGSS,IL)
60 CONTINUE
CUTOF= REAL(RCUTOF*TTOT(1))
IF( NOIL .LT. 0) THEN
ISODD=MOD(ISODD+1,2)
JSODD=ISODD
DO 70 IJDEL= 1, NSLINE
JL= MOD(IL+IJDEL-1,NSLINE) + 1
NOJL=NRSEG(JL)
IF( NOJL .LT. 0 ) THEN
JSODD=MOD(JSODD+1,2)
IF( ISODD.EQ.1 .AND. JSODD .EQ.0) THEN
DO 71 IGSS= 1, NGSS
DPR(NOJL,NOIL)= DPR(NOJL,NOIL)
> + TTOT(IGSS) * STAYIN(IGSS,JL)
TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,JL)
71 CONTINUE
IF( TTOT(1).LE.CUTOF ) GO TO 55
ENDIF
ELSE IF((ISODD.EQ.1).AND.( NOJL .GT. 0 )) THEN
DO 72 IGSS= 1, NGSS
DPR(NOJL,NOIL)= DPR(NOJL,NOIL)
> + TTOT(IGSS) * STAYIN(IGSS,JL)
TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,JL)
72 CONTINUE
IF( TTOT(1).LE.CUTOF ) GO TO 55
ENDIF
70 CONTINUE
ELSE IF( NOIL .GT. 0) THEN
JSODD=ISODD
DO 80 IJDEL= 1, NSLINE
JL= MOD(IL+IJDEL-1,NSLINE) + 1
NOJL=NRSEG(JL)
IF( NOJL .LT. 0 ) THEN
JSODD=MOD(JSODD+1,2)
IF( JSODD .EQ.0) THEN
DO 81 IGSS= 1, NGSS
DPR(NOJL,NOIL)= DPR(NOJL,NOIL)
> + TTOT(IGSS) * STAYIN(IGSS,JL)
TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,JL)
81 CONTINUE
IF( TTOT(1).LE.CUTOF ) GO TO 55
ENDIF
ELSE IF( NOJL .GT. 0 ) THEN
DO 82 IGSS= 1, NGSS
DPR(NOJL,NOIL)= DPR(NOJL,NOIL)
> + TTOT(IGSS) * STAYIN(IGSS,JL)
TTOT(IGSS)= TTOT(IGSS) * GOSOUT(IGSS,JL)
82 CONTINUE
IF( TTOT(1).LE.CUTOF ) GO TO 55
ENDIF
80 CONTINUE
ENDIF
55 CONTINUE
50 CONTINUE
RETURN
END
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