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SUBROUTINE AXLOOP (BUF,IBUF,XX,YY,ZZ,HC1,HC2,HC3)
C
INTEGER OTPE
DIMENSION BUF(50),IBUF(50)
CHARACTER UFM*23,UWM*25
COMMON /XMSSG / UFM,UWM
COMMON /SYSTEM/ SYSBUF,OTPE
COMMON /BLANK / IDUM(3),EPSE
C
PI = 3.1415926536
PIBY2 = 1.5707963268
FPI = 12.56637062
C = 1.
C
XJ = BUF(1)
IAXI= IBUF(2)
X1 = BUF(3)
Y1 = BUF(4)
Z1 = BUF(5)
X2 = BUF(6)
Y2 = BUF(7)
Z2 = BUF(8)
XC = BUF(9)
YC = BUF(10)
ZC = BUF(11)
C
C FOR NOW, ICID = 0
C
ICID = IBUF(12)
C
C CHECK FOR AXISYMMETRIC PROBLEM
C
IF (IAXI .NE. 1) GO TO 10
XC = 0.
YC = 0.
ZC = Z1
X2 = 0.
Y2 = X1
Z2 = Z1
10 CONTINUE
C
C DETERMINE THE DIRECTION OF THE CURRENT LOOP AXIS
C
CX = X1 - XC
CY = Y1 - YC
CZ = Z1 - ZC
BX = X2 - XC
BY = Y2 - YC
BZ = Z2 - ZC
C
C THE VECTOR AN IS NORMAL TO THE PLANE OF THE LOOP
C
ANX = CY*BZ - CZ*BY
ANY = CZ*BX - CX*BZ
ANZ = CX*BY - CY*BX
AT1 = SQRT(ANX*ANX + ANY*ANY + ANZ*ANZ)
AT2 = BX*BX + BY*BY + BZ*BZ
RAD2 = CX*CX + CY*CY + CZ*CZ
RADIUS = SQRT(RAD2)
XIACPI = (XJ*RAD2*PI)/C
C
ANX = ANX/AT1
ANY = ANY/AT1
ANZ = ANZ/AT1
C
C THE VECTOR R IS FROM THE CENTER OF LOOP TO THE FIELD POINT
C
RX = XX - XC
RY = YY - YC
RZ = ZZ - ZC
C
R2 = RX*RX + RY*RY + RZ*RZ
R = SQRT(R2)
C
C AT (OR NEAR) CENTER OF LOOP TEST
C
IF (R .GE. .001) GO TO 218
COSTHE = 1.
SINTHE = 0.
SQAR2S = SQRT(RAD2+R2)
RX = ANX
RY = ANY
RZ = ANZ
RPX = 0.
RPY = 0.
RPZ = 0.
GO TO 220
218 CONTINUE
C
RX = RX/R
RY = RY/R
RZ = RZ/R
COSTHE = ANX*RX + ANY*RY + ANZ*RZ
SINTHE = SQRT(1. - COSTHE*COSTHE)
C
C ON (OR VERY NEAR) AXIS OF LOOP TEST
C
IF (SINTHE .GE. .000001) GO TO 219
COSTHE = 1.
SINTHE = 0.
SQAR2S = SQRT(RAD2+R2)
RX = ANX
RY = ANY
RZ = ANZ
RPX = 0.
RPY = 0.
RPZ = 0.
GO TO 220
219 CONTINUE
C
SQAR2S = SQRT(RAD2 + R2 + (2.*RADIUS*R*SINTHE))
REALK2 = (4.*RADIUS*R*SINTHE)/(RAD2+R2+(2.*RADIUS*R*SINTHE))
REALK = SQRT(REALK2)
XIACR = (XJ*RADIUS)/(C*R)
C
C A CROSS R, NORMAL TO THE PLANE OF A AND R
C
TX = ANY*RZ - ANZ*RY
TY = ANZ*RX - ANX*RZ
TZ = ANX*RY - ANY*RX
C
C (A CROSS R) CROSS R, NORMAL TO THE PLANE OF R AND (A AND R)
C
TRPX = TY*RZ - TZ*RY
TRPY = TZ*RX - TX*RZ
TRPZ = TX*RY - TY*RX
AT3 = SQRT(TRPX*TRPX + TRPY*TRPY + TRPZ*TRPZ)
C
C RPERP, PERPENDICULAR TO THE VECTOR FROM THE CENTER TO THE FIELD PT
C
RPX = TRPX/AT3
RPY = TRPY/AT3
RPZ = TRPZ/AT3
C
C FOR SMALL POLAR ANGLE OR SMALL RADIUS USE ALTERNATIVE APPROX.
C
IF (REALK2 .LT. .0001) GO TO 220
C
C COMPUTE ELLIPTIC INTEGRAL OF FIRST KIND
C
F = 1.
DELTF1 = 1.
DO 240 N = 1,15000
XN2 = 2.*FLOAT(N)
XN21 = XN2 - 1.
DELTF1 = DELTF1*(XN21/XN2)*REALK
DELTF2 = DELTF1*DELTF1
F = F + DELTF2
IF (ABS(DELTF2/F) .LE. EPSE) GO TO 250
240 CONTINUE
DELF = ABS(DELTF2/F)
WRITE (OTPE,245) UWM,XX,YY,ZZ,XC,YC,ZC,X1,Y1,Z1,X2,Y2,Z2,DELF,EPSE
245 FORMAT (A25,', CONVERGENCE OF ELLIPTIC INTEGRAL IS UNCERTAIN. ',
1 'GRID OR INTEGRATION POINT AT COORDINATES', /5X,
2 1P,3E15.6,' IS TOO CLOSE TO CURRENT LOOP WITH CENTER AT',
3 /5X,1P,3E15.6,' AND 2 POINTS AT ',1P,3E15.6, /5X,4HAND ,1P,
4 3E15.6,' COMPUTATIONS WILL CONTINUE WITH LAST VALUES', /5X,
5 'CONVERGENCE VALUE WAS ',1P,E15.6,
6 ' CONVERGENCE CRITERION IS ',1P,E15.6)
250 F = PIBY2*F
C
C COMPUTE ELLIPTIC INTEGRAL OF SECOND KIND
C
E = 1.
DELTE1 = 1.
DO 260 N = 1,15000
XN2 = 2.*FLOAT(N)
XN21 = XN2-1.
DELTE1 = DELTE1*(XN21/XN2)*REALK
DELTE2 = (DELTE1*DELTE1)/XN21
E = E - DELTE2
IF (ABS(DELTE2/E) .LE. .000001) GO TO 270
260 CONTINUE
DELE = ABS(DELTE2/E)
WRITE (OTPE,245) UWM,XX,YY,ZZ,XC,YC,ZC,X1,Y1,Z1,X2,Y2,Z2,DELE
270 E = PIBY2*E
C
C COMPUTE THE RADIAL COMPONENT OF THE MAGNETIC FIELD
C
BR = XIACR*(COSTHE/SINTHE)*(E/SQAR2S)*(REALK2/(1.-REALK2))
C
C COMPUTE THE POLAR COMPONENT OF THE MAGNETIC FIELD
C
BTHE = XIACR*(1./(SQAR2S*RADIUS*R*SINTHE))*
1 (((((2.*R2)-((R2+(RADIUS*R*SINTHE))*REALK2))/
2 (1.-REALK2))*E)-(2.*R2*F))
C
C GO TO THE RESOLUTION OF FIELD COMPONENTS
C
GO TO 230
C
C ALTERNATIVE APPROXIMATION FOR SMALL K**2
C
C COMPUTE THE RADIAL COMPONENT OF THE MAGNETIC FIELD
C
220 CONTINUE
BR = XIACPI*COSTHE*(((2.*RAD2)+(2.*R2)+(RADIUS*R*SINTHE))/
1 ((SQAR2S)**5))
C
C COMPUTE THE POLAR COMPONENT OF THE MAGNETIC FIELD
C
BTHE = -XIACPI*SINTHE*
1 (((2.*RAD2)-R2+(RADIUS*R*SINTHE))/((SQAR2S)**5))
C
C RESOLVE MAGNETIC FIELD COMPONENTS INTO RECTANGULAR COMPONENTS
C
230 CONTINUE
HCX = RX*BR + RPX*BTHE
HCY = RY*BR + RPY*BTHE
HCZ = RZ*BR + RPZ*BTHE
HC1 = HCX/FPI
HC2 = HCY/FPI
HC3 = HCZ/FPI
RETURN
END
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