10.51 LSCDRIFT—Longitudinal space charge impedance

Longitudinal space charge impedance
Parallel capable? : yes
GPU capable? : yes
Back-tracking capable? : yes






Parameter Name UnitsType Default

Description






L M double0.0

length






LEFFECTIVE M double0.0

effective length (used if L=0)






BINS long 0

number of bins for current histogram






SMOOTHING short 0

Use Savitzky-Golay filter to smooth current histogram?






SG_HALFWIDTH short 1

Savitzky-Golay filter half-width for smoothing current histogram






SG_ORDER short 1

Savitzky-Golay filter order for smoothing current histogram






INTERPOLATE short 1

Interpolate wake?






LSC short 1

Include longitudinal space-charge impedance? If zero, acts like ordinary drift.






AUTO_LEFFECTIVE short 0

In nonzero and if L=0, the LEFFECTIVE parameter is set to the length of the previous element.






LOW_FREQUENCY_CUTOFF0 double-1

Highest spatial frequency at which low-frequency cutoff filter is zero. If not positive, no low-frequency cutoff filter is applied. Frequency is in units of Nyquist (0.5/binsize).






LOW_FREQUENCY_CUTOFF1 double-1

Lowest spatial frequency at which low-frequency cutoff filter is 1. If not given, defaults to LOW_FREQUENCY_CUTOFF1.






HIGH_FREQUENCY_CUTOFF0 double-1

Spatial frequency at which smoothing filter begins. If not positive, no frequency filter smoothing is done. Frequency is in units of Nyquist (0.5/binsize).






LSCDRIFT continued

Longitudinal space charge impedance






Parameter Name UnitsType Default

Description






HIGH_FREQUENCY_CUTOFF1 double-1

Spatial frequency at which smoothing filter is 0. If not given, defaults to HIGH_FREQUENCY_CUTOFF0.






RADIUS_FACTOR double1.7

LSC radius is (Sx+Sy)/2*RADIUS_FACTOR






GROUP string NULL

Optionally used to assign an element to a group, with a user-defined name. Group names will appear in the parameter output file in the column ElementGroup






This element simulates longitudinal space charge in a drift space using the method described in [22]. This is based on the longitudinal space charge impedance per unit length

          iZ  [    kr    ( kr ) ]
Zlsc(k ) =---02 1 - --bK1   --b
         πkr b      γ       γ
(68)

If L is 0 and LEFFECTIVE is not, then the element provides a LSC kick with impedance given by ZlscLeffective. This can be used to insert an LSC kick that integrates the longitudinal space charge effect of a section of a lattice. This should be used only for cases where there is very little relative longitudinal motion of particles.

Two simple filters are provided.

]

LSRMDLTR