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************************************************************* |
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* |
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* Routine to compute the NPOINT track intersection points |
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* with planes of z-coordinate given by ZIN |
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* given the track parameters |
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* |
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* The routine is based on GRKUTA, which computes the |
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* trajectory of a charged particle in a magnetic field |
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* by solving the equatoins of motion with Runge-Kuta method |
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* |
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* Variables that have to be assigned when the subroutine |
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* is called: |
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* |
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* ZIN(1-NPOINT) ----> z coordinates of the planes |
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* AL_P(1-5) ----> track-parameter vector |
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* |
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* NB !!! |
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* The routine works properly only if the |
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* planes are numbered in descending order starting from the |
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* reference plane (ZINI) |
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* |
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************************************************************** |
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|
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SUBROUTINE TRACK(NPOINT,ZIN,XOUT,YOUT,AL_P,IFAIL) |
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|
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IMPLICIT DOUBLE PRECISION (A-H,O-Z) |
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DIMENSION VECT(7),VECTINI(7),VOUT(7) |
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DATA TOLL/1.d-8/ |
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* tolerance in reaching the next plane during the tracking procedure |
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* ----------------------------------------------- |
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* I/O parameters |
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PARAMETER (NPOINT_MAX=100) |
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DIMENSION ZIN(NPOINT_MAX) |
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DIMENSION XOUT(NPOINT_MAX),YOUT(NPOINT_MAX) |
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DIMENSION AL_P(5) |
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* ----------------------------------------------- |
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DATA ZINI/23.5/ !z coordinate of the reference plane |
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|
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* ================================================================== |
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* divide the track in two parts: below and above the reference plane |
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* ================================================================== |
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IUPDOWN=0 |
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DO I=1,NPOINT |
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IF(ZIN(I).LT.ZINI)THEN |
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if(i.ne.1)IUPDOWN=I |
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GOTO 88 |
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ENDIF |
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IUPDOWN=NPOINT+1 |
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ENDDO |
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88 CONTINUE |
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|
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* ================================================================== |
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* track from reference plane DOWN |
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* ================================================================== |
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* parameters for GRKUTA |
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IF(AL_P(5).NE.0) CHARGE=AL_P(5)/DABS(AL_P(5)) |
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IF(AL_P(5).EQ.0) CHARGE=1. |
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VOUT(1)=AL_P(1) |
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VOUT(2)=AL_P(2) |
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VOUT(3)=ZINI |
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VOUT(4)=AL_P(3)*DCOS(AL_P(4)) |
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VOUT(5)=AL_P(3)*DSIN(AL_P(4)) |
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VOUT(6)=-1.*DSQRT(1.-AL_P(3)**2) |
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IF(AL_P(5).NE.0.) VOUT(7)=DABS(1./AL_P(5)) |
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IF(AL_P(5).EQ.0.) VOUT(7)=1.E8 |
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DO I=MAX(IUPDOWN,1),NPOINT |
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step=vout(3)-zin(i) |
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c$$$ print*,'DOWN ',i,' - Track from ', |
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c$$$ $ vout(3),' to ',zin(i),' step ',step |
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10 DO J=1,7 |
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VECT(J)=VOUT(J) |
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VECTINI(J)=VOUT(J) |
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ENDDO |
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11 continue |
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CALL GRKUTA(CHARGE,STEP,VECT,VOUT) |
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IF(VOUT(3).GT.VECT(3)) THEN |
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IFAIL=1 |
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PRINT *,'=== WARNING ===> tracciamento invertito (DOWN)' |
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print*,'charge',charge |
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print*,'vect',vect |
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print*,'vout',vout |
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print*,'step',step |
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RETURN |
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ENDIF |
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Z=VOUT(3) |
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IF(Z.LE.ZIN(I)+TOLL.AND.Z.GE.ZIN(I)-TOLL) GOTO 100 |
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IF(Z.GT.ZIN(I)+TOLL) GOTO 10 |
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IF(Z.LE.ZIN(I)-TOLL) THEN |
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STEP=STEP*(ZIN(I)-VECT(3))/(Z-VECT(3)) |
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DO J=1,7 |
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VECT(J)=VECTINI(J) |
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ENDDO |
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GOTO 11 |
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ENDIF |
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100 XOUT(I)=VOUT(1) |
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YOUT(I)=VOUT(2) |
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ZIN(I)=VOUT(3) |
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ENDDO |
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|
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|
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|
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* ================================================================== |
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* track from refernce plane UP |
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* ================================================================== |
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* parameters for GRKUTA: |
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* -opposite charge |
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* -opposite momentum direction |
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IF(AL_P(5).NE.0) CHARGE=-AL_P(5)/DABS(AL_P(5)) |
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IF(AL_P(5).EQ.0) CHARGE=-1. |
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VOUT(1)=AL_P(1) |
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VOUT(2)=AL_P(2) |
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VOUT(3)=ZINI |
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VOUT(4)=-AL_P(3)*DCOS(AL_P(4)) |
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VOUT(5)=-AL_P(3)*DSIN(AL_P(4)) |
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VOUT(6)=1.*DSQRT(1.-AL_P(3)**2) |
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IF(AL_P(5).NE.0.) VOUT(7)=DABS(1./AL_P(5)) |
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IF(AL_P(5).EQ.0.) VOUT(7)=1.E8 |
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DO I=MIN((IUPDOWN-1),NPOINT),1,-1 |
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step=vout(3)-zin(i) |
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step = -step |
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c$$$ print*,'UP ',i,' - Track from ', |
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c$$$ $ vout(3),' to ',zin(i),' step ',step |
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20 DO J=1,7 |
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VECT(J)=VOUT(J) |
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VECTINI(J)=VOUT(J) |
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ENDDO |
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22 continue |
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CALL GRKUTA(CHARGE,STEP,VECT,VOUT) |
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IF(VOUT(3).LT.VECT(3)) THEN |
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IFAIL=1 |
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PRINT *,'=== WARNING ===> tracciamento invertito (UP)' |
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print*,'charge',charge |
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print*,'vect',vect |
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print*,'vout',vout |
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print*,'step',step |
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RETURN |
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ENDIF |
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Z=VOUT(3) |
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IF(Z.LE.ZIN(I)+TOLL.AND.Z.GE.ZIN(I)-TOLL) GOTO 200 |
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IF(Z.LT.ZIN(I)-TOLL) GOTO 20 |
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IF(Z.GE.ZIN(I)+TOLL) THEN |
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STEP=STEP*(ZIN(I)-VECT(3))/(Z-VECT(3)) |
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DO J=1,7 |
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VECT(J)=VECTINI(J) |
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ENDDO |
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GOTO 22 |
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ENDIF |
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200 XOUT(I)=VOUT(1) |
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YOUT(I)=VOUT(2) |
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ZIN(I)=VOUT(3) |
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|
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ENDDO |
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|
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RETURN |
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END |
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