The OPAL Discussion Forum

[<sebastien.toussaint AT uclouvain.be>]

Dear all,

I conducted some simulations using OPAL-cycl and something puzzled me a bit.

I defined the PC parameter of BEAM to be equal to gammabeta and PRINIT =
gammabeta (with PZINIT = 0). In such circumstances, I would have expected for
the reference azimuthal momentum to be equal to zero. Yet it is not the case
as I can see from the following lines (see below) copied from a terminal. How
can I define a purely radial initial momentum ?

Thanks for the help,

Sébastien

OPAL> * ************* B E A M
************************************************************
                      (...)
OPAL> * REST MASS   0.938272 GeV
OPAL> * MOMENTUM    0.000145999
OPAL> * NPART       1
OPAL> *
**********************************************************************************
                      (...)
OPAL> * Bunch global starting momenta:
OPAL> * Initial gamma = 1
OPAL> * Initial beta = 0.000155604
OPAL> * Reference total momentum (beta * gamma) = 0.155604 [MCU]
OPAL> * Reference azimuthal momentum (Pt) = 0.0538233 [MCU]
OPAL> * Reference radial momentum (Pr) = 0.145999 [MCU]
OPAL> * Reference axial momentum (Pz) = 0 [MCU]

I used these definitions in the input file :

REAL Ebeam                   =10e-09;                     // injection energy
of the beam (GeV)
REAL gamma                   =(Ebeam+PMASS)/PMASS;           // relativistic
gamma
REAL beta                    =sqrt(1-(1/gamma^2));           // relativistic
beta
REAL gammabeta               =gamma*beta;                    // self
explanatory
(...)

CYCLO:   CYCLOTRON, TYPE="BANDRF", CYHARMON=4, PRINIT=gammabeta, PZINIT=0,
PHIINIT= 0, (...)

Beam1: BEAM, PARTICLE = PROTON, PC = gammabeta, (...)

RUN, METHOD = "CYCLOTRON-T", BEAM = Beam1, FIELDSOLVER = FS1, DISTRIBUTION =
Dist,
     MBMODE=force, PARAMB=5.0, TURNS=10, MB_BINNING=GAMMA, MB_ETA=0.01;


And this distribution from a file :

1
0.0         0.0           0.0           0.0          0.0           0.00