ramp_elements

• type: setup command.
• function: define parameters for time-dependent ramping of elements
• N.B.: this feature is somewhat experimental. Please use with caution and report any problems on the forum.

&modulate_elements
    STRING name = NULL;
    STRING item = NULL;
    STRING type = NULL;
    long start_pass = 0;
    long end_pass = LONG_MAX;
    double start_value = 0;
    double end_value = 0;
    long differential = 1;
    long multiplicative = 0;
    long start_occurence = 0;
    long end_occurence = 0;
    double exponent = 1;
    double s_start = -1;
    double s_end = -1;
    STRING before = NULL;
    STRING after = NULL;
    long verbose = 0;
&end

N.B.: This command will produce unpredictable results when used with error_element, alter_elements, modulate_elements, and load_parameters (except when change_defined_values=1). It should work properly with link_elements in turn-by-turn mode when the source element is ramped, but not when the target element is ramped.

• name -- A possibly-wildcard-containing string giving the names of the elements to modulate. If not specified, then one must specify type.
• item -- The name of the parameter to modulate.
• type -- A possibly-wildcard-containing string giving the names of element types to modulate. May be specified with name or by itself.
• start_pass, end_pass -- The starting and ending pass, $i_{\rm start}$ and $i_{\rm end}$ for the ramp. For passes less than start_pass, the ramp value is start_value. For passes greater than end_pass, the ramp value is end_value.
• start_value, end_value -- The end-point values $S$ (start) and $E$ (end) of the ramp.
• exponent -- The exponent $p$ for the variation of values between the start and end of the ramp. The ramp function $R(i)$ is
  

  $$R(i) = S + (E-S)*\left(\frac{i-i_{\rm start}}{i_{\rm end}-i_{\rm start}}\right)^p.$$ (2)

  
  
  Note that $i=0$ on the first pass.
• differential, multiplicative -- Determine how the amplitude function $A(t)$ is used to obtain the new value of the parameter. There are four cases
  • differential=1, multiplicative=0: $v(t) = v_0 + R(i)$ (default).
  • differential=0, multiplicative=0: $v(t) = R(i)$.
  • differential=1, multiplicative=1: $v(t) = v_0 + v_0 R(i)$.
  • differential=0, multiplicative=1: $v(t) = v_0 R(i)$.
• start_occurence, end_occurence -- If nonzero, these give the starting and ending occurrence numbers of elements that will be modulated. N.B.: if wildcards are used, occurrence number counting is for each set of identically-named elements separately, rather than for the sequence of matched elements.
• s_start, s_end -- If non-negative, these give the gaving and ending position limits for the end-of-element locations of elements to be modulated.
• after -- The name of an element. If given, the modulation is applied only to elements that follow the named element in the beamline.
• before -- The name of an element. If given, the modulation is applied only to elements that precede the named element in the beamline.
• verbose -- If nonzero, information is printed to the standard output as changes are made. Use for debugging only, since otherwise it may slow the simulation.