The OPAL Discussion Forum

[jjyang <jianjun.yang AT psi.ch>]

Hi Suzie,

You are right, in the file afterEachTurn, 'turn' is defined by per 
STEPSPERTURN steps. If the field map is not perfectly isochronous, it is not 
exactly after 360degree. 
One can see this as a disadvantage when use time as the independent variable, 
but it is vital to calculate space charge fields.  
You can found several papers discussing on this issues.

Their are three output files Angle0.dat, Angle1.dat and Angle2.dat, which 
record the particle parameters at 0 deg, pi/8 deg and pi/4 deg respectively. 
You can use these files to check the closed orbit and minimise phase space 
area. 
You can checked isochronicity by observe the acceleration phase when switch 
on the RF cavity. 

You can use PROBE element to output data at a physical position.

Cheers,
Jianjun

在 2012-2-15，下午4:23， Suzie Sheehy 写道：

> Hi there,
> 
> I have a question about the data outputted from OPAL-CYCL in the 
> .afterEachTurn file. How do you define a 'turn'? Given that the code uses a 
> timestep, is it simply dumped after a certain number of timesteps (perhaps 
> defined by the "STEPSPERTURN" number?), or does it actually ensure that the 
> particle has gone through a full 360 degrees of the map?
> 
> This is obviously also important to find the time-of-flight per turn in the 
> machine to check isochronicity, but it is also crucial in finding a proper 
> closed orbit, so you can see the turn-by-turn position of the particle at a 
> particular point to map out and minimise the phase space area at that 
> point. 
> 
> I also note that the h5 output is done by timestep also. It would seem to 
> make more sense if you could output the data at a physical position (as if 
> you put a 'screen' in the beamline) to reconstruct the phase space... 
> 
> Also, nowhere in the manual does it say what the ".Angle0.dat" and 
> ".Angle1.dat"  files are which I seem to be getting.
> 
> Could someone please clarify?
> 
> Thanks,
> Suzie
> 
> 
> -----------------------------------------
> Suzie Sheehy
> Research Fellow and 2010 Brunel Fellow
> Royal Commission for the Exhibition of 1851
> ASTeC Intense Beams Group
> Rutherford Appleton Laboratory (R2, 403)
> Didcot, Oxon, OX11 0QX
> -----------------------------------------
> +44 (0)1235 446 782
> suzie.sheehy AT stfc.ac.uk
> www.suziesheehy.co.uk
> -----------------------------------------
> 
> 
> 
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