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CSRDRIFT

A follow-on element for CSRCSBEND that applies the CSR wake over a drift.
Parallel capable? : yes
Parameter Name Units Type Default Description
L $M$ double 0.0 length
ATTENUATION_LENGTH $M$ double 0.0 exponential attenuation length for wake
DZ   double 0.0 interval between kicks
N_KICKS   long 1 number of kicks (if DZ is zero)
SPREAD   long 0 use spreading function?
USE_OVERTAKING_LENGTH   long 0 use overtaking length for ATTENUATION_LENGTH?
OL_MULTIPLIER   double 1 factor by which to multiply the overtaking length to get the attenuation length
USE_SALDIN54   long 0 Use Saldin et al eq. 54 (NIM A 398 (1997) 373-394 for decay vs z?
SALDIN54POINTS   long 1000 Number of values of position inside bunch to average for Saldin eq 54.
CSR   long 1 do CSR calcuations
SALDIN54NORM_MODE   STRING peak peak or first
SPREAD_MODE   STRING full full, simple, or radiation-only
WAVELENGTH_MODE   STRING sigmaz sigmaz or peak-to-peak
BUNCHLENGTH_MODE   STRING 68-percentile rms, 68-percentile, or 90-percentile
SALDIN54_OUTPUT   STRING NULL Filename for output of CSR intensity vs. z as computed using Saldin eq 54.
USE_STUPAKOV   long 0 Use treatment from G. Stupakov's note of 9/12/2001?
STUPAKOV_OUTPUT   STRING NULL Filename for output of CSR wake vs. s as computed using Stupakov's equations.
STUPAKOV_OUTPUT_INTERVAL   long 1 Interval (in kicks) between output of Stupakov wakes.
SLICE_ANALYSIS_INTERVAL   long 0 interval (in kicks) of output to slice analysis file (from slice_analysis command)

A follow-on element for CSRCSBEND that applies the CSR wake over a drift.
Parameter Name Units Type Default Description
LINEARIZE   long 0 use linear optics for drift pieces?
GROUP   string NULL Optionally used to assign an element to a group, with a user-defined name. Group names will appear in the parameter output file in the column ElementGroup





This element has a number of models for simulation of CSR in drift spaces following CSRCSBEND elements. Note that all models allow support splitting the drift into multiple CSRDRIFT elements. One can also have intervening elements like quadrupoles, as often happens in chicanes. The CSR effects inside such intervening elements are applied in the CSRDRIFT downstream of the element.

For a discussion of some of the methods behind this element, see M. Borland, ``Simple method for particle tracking with coherent synchrotron radiation,'' Phys. Rev. ST Accel. Beams 4, 070701 (2001).

N.B.: by default, this element uses 1 CSR kick (N_KICKS=1) at the center of the drift. This is usually not a good choice. I usually use the DZ parameter instead of N_KICKS, and set it to something like 0.01 (meters). The user should vary this parameter to assess how small it needs to be.

The models are as following, in order of decreasing sophistication and accuracy:

The ``Saldin 54'' and ``overtaking-length'' models rely on computation of the bunch length, which is controlled with the BUNCHLENGTH_MODE parameter. Nominally, one should use the true RMS, but when the beam has temporal spikes, it isn't always clear that this is the best choice. The choices are ``rms'', ``68-percentile'', and ``90-percentile''. The last two imply using half the length determined from the given percentile in place of the rms bunch length. I usually use 68-percentile, which is the default.


next up previous
Next: CWIGGLER Up: Element Dictionary Previous: CSRCSBEND
Robert Soliday 2014-06-26