sddsemitproc analyzes quadrupole scan emittance measurement data. It accepts a file containing the transport matrix for each data point and measured beam sizes. Because sddsemitproc uses the matrix rather than a thin-lens model, it can analyze data from arbitrarily complex scans, involving, for example, multiple thick-lens quadrupoles.
The matrix data can be prepared using elegant. For example, the vary_element command can be used to vary one or more quadrupoles. In addition, the beam size data may be prepared using elegant, to allow simulation of emittance measurements.
sddsemitproc will perform error analysis using a Monte Carlo technique. A user-specified number of random error sets are generated and added to all measurements. Analysis is performed for each error set. Statistics over all the error sets provide most likely values and error bars.
The beam parameters computed by sddsemitproc pertain to the beginning of whatever system is simulated in elegant.
Rij, where ij is 11, 12, 33, and 34. These give elements of the horizontal and vertical transport matrices from the beginning of a system to the observation point. The sigma matrix inferred will be that for the beginning of the system. Typically, one starts with the final file from the run_setup command in elegant, and collapses it using sddscollapse. Each page of inputfile corresponds to a different emittance measurement.
In addition to this data, inputfile must also contain columns
giving the rms beam sizes in x and y. The user supplies the names of
the columns using the
-sigmaData option; otherwise, they
Sy. These columns may be from elegant (e.g.,
Sy), if one wants to simulate an
emittance measurement. Note that the theory behind the emittance
measurement is strictly correct only for true RMS beamsize
measurements. Use of FWHM or some other measure will give unreliable
-nErrorSets), then there are also parameters giving the error bars (``sigma's'') of the measured values.