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RE: [Opal] Reference azimuthal momentum


Chronological Thread 
  • From: "Snuverink Jochem (PSI)" <jochem.snuverink AT psi.ch>
  • To: "'sebastien.toussaint AT uclouvain.be'" <sebastien.toussaint AT uclouvain.be>, "opal AT lists.psi.ch" <opal AT lists.psi.ch>
  • Subject: RE: [Opal] Reference azimuthal momentum
  • Date: Fri, 7 Aug 2020 12:52:08 +0000
  • Accept-language: en-US, de-CH

Dear Sébastien

PC parameter of BEAM is the particle momentum in GeV/c. If you do this:

REAL P0 = gamma*beta*PMASS;
Beam1: BEAM, PARTICLE = PROTON, PC = P0, (...)

It should work:

OPAL> * Bunch global starting momenta:
OPAL> * Initial gamma = 1
OPAL> * Initial beta = 0.000145999
OPAL> * Reference total momentum (beta * gamma) = 0.145999 [MCU]
OPAL> * Reference azimuthal momentum (Pt) = 0 [MCU]
OPAL> * Reference radial momentum (Pr) = 0.145999 [MCU]
OPAL> * Reference axial momentum (Pz) = 0 [MCU]

Best wishes,
Jochem

-----Original Message-----
From: opal-request AT lists.psi.ch <opal-request AT lists.psi.ch> On Behalf Of
sebastien.toussaint AT uclouvain.be
Sent: Freitag, 7. August 2020 11:39
To: opal AT lists.psi.ch
Subject: [Opal] Reference azimuthal momentum

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




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