4 HOM Definition SDDS File Format

The general SDDS format is defined by two parts, the header and zero or more data tables. The header contains namelist commands defining, among other things, the interpretation of the data in the tables. A table consists of a list of parameters values followed by columns of data. In the HOM definition file, clinchor requires the presence of columns Frequency, and any two of ShuntImpedance, Q, RoQ (the ratio R∕Q). For many columns of physical quanitities the correct units must be specified.

The allowed column names for the HOM definition file are:

• Frequency or f — Required column. Frequency in units of “Hz” or “MHz”. The program internally converts to Hz.
• ShuntImpedance or R or Rs or Rt — Required column (see above). Shunt impedance in units of “Ohm” for monopole HOMs, and units of “Ohm/m” for dipole HOMs.
• Q or QualityFactor — Required column (see above). Quality factor of the resonator.
• ROverQ or R/Q or ROQ — Required column (see above). Shunt impedance divided by Q. In units of “Ohm” for monopole HOMs, and units of “Ohm/m” for dipole HOMs.
• DeQFactor or deQFactor — Factor by which to reduce the Q of the HOM after reading in this file.
• StaggeringStep or staggeringStep or DeltaFrequency or deltaFrequency or df — Optional column. Units of Hz only. Default value is 0. If larger than one, then the frequencies of the NumberOfCavities HOM resonators are staggered by this interval.
• ShiftToResonance — Optional column. Default value is 0. If non-zero, then the frequency of the HOMs is shifted to the closest resonance. If staggeringStep is non-zero, then the frequency shifting is done after staggering the frequencies.
• NumberOfCavities or NCavities or Cavities or cavities — Optional parameter. Default value is 1. If 0, then this HOM type is not used in the calculation. If greater than one, then the HOM resonator is duplicated internally numberOfCavities times. All resonators will be subjected to randomized frequencies separately (if requested by the randomizeHOMFrequencies command.)

Here is an example of an SDDS HOM definition file for the APS ring cavities: