7.53 ramp_elements

• type: setup command.
• function: define parameters for time-dependent ramping of elements
• sequence: must follow run_setup.
• N.B.: if the ramped element is modeled with a matrix, a significant performance hit may be seen. It is best to use symplectic variants of the elements, since these don’t invoke the matrix calculation.
• Command syntax, including use of equations and subcommands, is discussed in 7.2.

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 will also not work well if matrix concatenation is invoked. 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_start and i_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

  (10)

  Note that i = 0 on the first pass.

• refresh_matrix — Frequently there is a matrix associated with an element even if tracking through the element does not use the matrix. In this case, elegant doesn’t normally update the matrix for the element as it modulates the element, since that may involve a significant time penalty. If this parameter is set to a non-zero value, the matrix will be updated. For elements that use a matrix for tracking, the matrix is always updated.
• 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) = v₀ + R(i) (default).
  • differential=0, multiplicative=0: v(t) = R(i).
  • differential=1, multiplicative=1: v(t) = v₀ + v₀R(i).
  • differential=0, multiplicative=1: v(t) = v₀R(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.
• record — Gives a possibly incomplete filename to which will be written a record of the values of the ramp.