CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C									C
C  SUBROUTINE    F I E L D R						C
C 									C
C  PURPOSE:  	READS MAGNETIC FIELD VALUES FOR PARTICLE TRACKING	C
C		FOR A TOROIDAL MAGNET					C
C									C
C  WRITTEN BY:  B.A.M.							C
C									C
C  DATE:  	14-AUG-85						C
C									C
C  CHANGES: 		WHAT				WHO  WHEN       C
C		Unix Compatible Version                	BAM  05/11/00	C
C									C
C									C
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
C        1         2         3         4         5         6         7         8
C2345678901234567890123456789012345678901234567890123456789012345678901234567890
C
        SUBROUTINE FIELD(X,B,RI,CHAR,P,FAC,IOUT,ICONT)
	DIMENSION B(3),X(3),RI(3)
	DIMENSION XX(0:200),YY(0:200)
	CHARACTER*10 FNAME
	CHARACTER*5 TEXT(15)
C
C  X		COORDINATE
C  B		MAGNETIC FIELD IN TESLA
C  RI		INVERSE RADIUS IN M**(-1)
C  CHAR  	CHARGE IN UNITS OF E
C  P		MOMENTUM IN GEV/C
C  FAC  	COMMON FACTOR FOR THE MAGNETIC FIELD
C  ICONT	CONTROLLING THE FUNCTION OF THE SUBROUTINE
C
        GOTO(100,200,300),ICONT
C
100     CONTINUE
	PI=P
	IF(IREAD.EQ.1) RETURN
C
C	DO 110 II=1,2*IOUT
C	READ(1,1002) FNAME
C	WRITE(5,1013) II,FNAME
C110	CONTINUE
	IF((IREAD.EQ.1).AND.(IOUT.EQ.0)) RETURN
C	READ(1,1002) FNAME
C	WRITE(5,1011) FNAME
	FNAME='btoro.dat'
        print*,'open b-field file:',FNAME
        OPEN(UNIT=1,ACCESS='SEQUENTIAL',STATUS='OLD',FILE=FNAME)
	DO 101 I=1,3
        READ(1,1012) (TEXT(II),II=1,15)
	IF(TEXT(2).EQ.' R[M]') GOTO 102
101	CONTINUE
102	CONTINUE
C
C  K-LOOP: LOOPS THROUGH RADIAL POSITIONS TO READ MAGNETIC FIELD VALUES
	IMAX=200
	DO 11 K=0,IMAX
           READ(1,1001,ERR=12) DUM1,DUM2,XXK,DUM3,YYK
C           WRITE(3,2001) K,XXK,YYK
C           WRITE(6,2001) K,XXK,YYK
           IF((K.GT.1).AND.(XXK.LE.0.)) GOTO 12
           XX(K)=XXK
           YY(K)=ABS(YYK)
11	CONTINUE
C
12	IMAX=K-1
	DR=XX(IMAX)-XX(IMAX-1)		!STEPSIZE
	IF(INIT.NE.1) THEN
	  WRITE(3,1100) IMAX,DR
	  WRITE(6,1100) IMAX,DR
1100	  FORMAT(/,' SR FIELDR read ',I3,
     1           ' x, B(x) pairs with ',f8.3,' m stepsize ',/)
 	  INIT=1
	ENDIF
	CLOSE(UNIT=1)
	IREAD=1
        RETURN
C
200     CONTINUE
	B(1)=0.
	B(2)=0.
	B(3)=0.
	RAD=SQRT(X(2)**2+X(3)**2)	
	IF((RAD.GT.XX(IMAX)).OR.(RAD.LT.XX(1))) GOTO 201
	RN=RAD/DR
	NR=IFIX(RN)
	BB=YY(NR)+(YY(NR+1)-YY(NR))*(RN-FLOAT(NR))
	B(1)=0.
	B(2)=0.
	B(3)=BB
201	CONTINUE
        DO 1 I=1,3
        RI(I)=B(I)*CHAR*.2997925/PI	    ! 1/R IN 1/METER
1       CONTINUE
        RETURN
300     CONTINUE
        RETURN
1001	FORMAT(3F10.4,2F12.6)
1002	FORMAT(A10)
1011	FORMAT(' SR FIELDR: READING INPUT FILE ',A10,/)
1012	FORMAT(15A5)
1013	FORMAT(' SR FIELDR: ',I3,2X,A10)
2001	FORMAT(' ',I5,8F10.4)
2012	FORMAT(' ',15A5)
        END