7.71 twiss_output

    STRING filename = NULL;  
    long matched = 1;  
    long output_at_each_step = 0;  
    long output_before_tune_correction = 0;  
    long final_values_only = 0;  
    long statistics = 0;  
    long radiation_integrals = 0;  
    long concat_order = 3;  
    long higher_order_chromaticity = 0;  
    long higher_order_chromaticity_points = 5;  
    double higher_order_chromaticity_range = 4e-4;  
    double chromatic_tune_spread_half_range = 0;  
    long quick_higher_order_chromaticity = 0;  
    double beta_x = 1;  
    double alpha_x = 0;  
    double eta_x = 0;  
    double etap_x = 0;  
    double beta_y = 1;  
    double alpha_y = 0;  
    double eta_y = 0;  
    double etap_y = 0;  
    STRING reference_file = NULL;  
    STRING reference_element = NULL;  
    long reference_element_occurrence = 0;  
    long reflect_reference_values = 0;  
    long cavities_are_drifts_if_matched = 1;  
    long compute_driving_terms = 0;  
    long leading_order_driving_terms_only = 0;  
    STRING s_dependent_driving_terms_file = NULL;  
    long local_dispersion = 1;  

The output file from this command contains the following columns, giving values of quantities at the exit of each element, unless otherwise noted.

The output file contains the following parameters. Note that chromatic quantities depend on the order settings of the individual elements, the default order (in run_setup), and the concatenation order given in the twiss_output command. These quantities pertain to the end of the lattice or to the lattice as a whole.

N.B.: the higher-order dispersion and higher-order chromaticity are computed using the concatenated third-order matrix. However, elegant only has third-order matrices for three elements: alpha magnets, quadrupoles, and sextupoles. This may be acceptable if any dipoles (for example) have large bending radius. Users who are concerned about these effects should perform off-energy tracking using canonical elements (i.e., CSBEND, KQUAD, KSEXT, and MULT), which include energy dependence to all orders.

Also, note that by default all elements are computed to second order only. You must change the default\_order parameter on run\_setup to 3 in order to use the third-order matrices for alpha magnets, quadrupoles, and sextupoles. You may also use the ORDER parameter on individual element definitions.

Table 2: Meaning of the various driving terms[29].

Term Name Explanation

h11001 drives x chromaticity

h00111 drives y chromaticity

h20001 drives synchro-betatron resonances

h00201 drives momentum-dependence of beta functions

h10002 drives second order dispersion

h21000 drives νx

h30000 drives 3νx

h10110 drives νx

h10020 drives νx - 2νy

h10200 drives νx + 2νy

h22000 drives x∕dJx

h11110 drives x∕dJy

h00220 drives y∕dJy

h31000 drives 2νx

h40000 drives 4νx

h20110 drives 2νx

h11200 drives 2νy

h20020 drives 2νx - 2νy

h20200 drives 2νx + 2νy

h00310 drives 2νy

h00400 drives 4νy