Computation of the bunching factor

[headdoggy64]

Hello all,
Just wondering, if there is a standard way in Elegant/SDDS to compute a bunching factor:

Code: Select all

n(\omega) = \sum{\exp{ I \omega t_i}}^2 

I tried to search the forum, but haven't found it.
Thanks.

[michael_borland]

Sorry for the delayed reply. I was on vacation.

You can use the program sddsprocess to compute the bunching factor:

Code: Select all

sddsprocess output.sdds -pipe=out -define=parameter,omega,1e10 \
  "-define=col,CosWt,omega t * cos n_rows /" "-define=col,SinWt,omega t * sin n_rows /" \
  -process=CosWt,sum,ReB -process=SinWt,sum,ImB \
| sddsprintout -pipe -parameter=??B

Presumably a histogram followed by an FFT would give you the bunching factor vs omega, but you'd need to watch out for numerical factors. Use sddshist followed by sddsfft for this.

--Michael

[michael_borland]

N.B.: a future release (before summer 2015) will include a program (sddsbunchingfactor) to compute bunching factors.

--Michael

[headdoggy64]

Hello Michael,

Is it possible to add a possibility of computing the full three dimensional bunching factor of the distribution?
(For example, using Eq. 2.15 from http://www.slac.stanford.edu/cgi-wrap/g ... -r-576.pdf)

The bunching factor will then depend on the angle \theta, which will be the angle between the detector position and the beam axis.

Thank you,
Alex