The OPAL Discussion Forum

[<finn.oshea AT nusano.com>]

Hi All,

I installed opal following the instructions in the wiki for version 2.2.1

I am testing out opal by building a simple transport line of 3 quadrupoles and
I can't get the quadrupoles to show up where I want them to on the beam line.
When I plot the contents of _ElementPositions.sdds versus the contents of
the .stat file, the beam transport is compressed by about a factor of 2/3
relative to the magnet locations, the latter appear consistent with where I
want them to be.  I am using a beam with beta=1/6, so I don't think this is an
s versus t issue.  It is a shame that I cannot attach a picture, because that
would make it really clear what is going on.

I have defined the drifts implicitly:
DTL_Q.01 : QUADRUPOLE, L = 0.040, K1 =-16.50, Z = 0.000;
MDL_Q.01 : QUADRUPOLE, L = 0.202, K1 = 7.18, Z = 0.350;
MDL_Q.02 : QUADRUPOLE, L = 0.202, K1 =-4.30, Z = 1.802;

MDL0:  Line = (DTL_Q.01,MDL_Q.01,MDL_Q.02);

On another note, while the simulation is being setup, the beam parameters are
consistent with the data I entered:
OPAL> * ************* B E A M
************************************************************
OPAL> * BEAM        ABEAM
OPAL> * PARTICLE    ALPHA
OPAL> * CURRENT     1.9019e-02 A
OPAL> * FREQUENCY   3.5220e+02 MHz
OPAL> * CHARGE      +e * 2.0000e+00
OPAL> * REST MASS   3.7274e+00 GeV
OPAL> * MOMENTUM    6.1650e-01
OPAL> * NPART       1.0000e+04
OPAL> *
**********************************************************************************

But during the run opal produces some output that appears to be only modestly
related to the beam I entered:
OPAL> * ************** B U N C H
*********************************************************
OPAL> * NP              = 10000
OPAL> * Qtot            =      108.000 [pC]         Qi    =       10.800 [fC]
OPAL> * Ekin            =     198.643 [MeV]         dEkin =     289.042 [keV]
OPAL> * rmax            = (      3.53720 ,      2.49403 ,      3.31927 ) [mm]
OPAL> * rmin            = (     -3.52925 ,     -2.50719 ,     -3.31159 ) [mm]
OPAL> * rms beam size   = (      1.16025 ,      0.81497 ,      1.10059 ) [mm]
OPAL> * rms momenta     = (  1.67720e-04 ,  2.18495e-04 ,  2.46914e-04 ) [beta
gamma]
OPAL> * mean position   = (      0.00000 ,      0.00000 ,      0.00000 ) [um]
OPAL> * mean momenta    = (  5.70714e-21 , -7.08797e-21 ,  3.30795e-01 ) [beta
gamma]
OPAL> * rms emittance   = (  5.88266e-07 ,  5.38279e-07 ,  8.21465e-07 ) (not
normalized)
OPAL> * rms correlation = ( -3.38481e-03 , -9.28557e-03 ,  1.00952e-02 )
OPAL> * hr              = (    471.09706 ,    333.41492 ,    442.05728 ) [um]
OPAL> * dh              =   1.00000e-10 [%]
OPAL> * t               =        0.000 [fs]         dT    =       21.000 [ps]
OPAL> * spos            =        0.000 [um]
OPAL> *
**********************************************************************************

In particular, Ekin is wrong by a factor of ~4 and the mean momenta in z is
wrong by about a factor of 2.

I cannot make heads nor tails of all of these inconsistencies.  Is there a
description of what this BUNCH output is?  Is there a minimum functioning
example, a FODO lattice perhaps, with known solutions with which I can compare
my results to?

Thanks for any feedback,
Finn