at.physics.linear

Coupled or non-coupled 4x4 linear motion

Functions

linopt(ring[, dp, refpts, get_chrom])	Linear analysis of a H/V coupled lattice (deprecated)
linopt2(ring, *args, **kwargs)	Linear analysis of an uncoupled lattice
linopt4(ring, *args, **kwargs)	Linear analysis of a H/V coupled lattice
linopt6(ring, *args, **kwargs)	Linear analysis of a fully coupled lattice using normal modes
avlinopt(ring[, dp, refpts])	Linear analysis of a lattice with average values
get_optics(ring[, refpts, dp, method])	Linear analysis of a fully coupled lattice
get_tune(ring, *[, method, dp, dct, df, orbit])	Computes the tunes using several available methods
get_chrom(ring, *[, method, dp, dct, df, cavpts])	Computes the chromaticities using several available methods

avlinopt(ring, dp=0.0, refpts=None, **kwargs)

Linear analysis of a lattice with average values

avlinopt() returns average beta, mu, dispersion over the lattice elements.

avlinopt() returns average beta, mu, dispersion over the lattice elements. avlinopt() acts on a single cell (periodicity is not taken into account).

Parameters:

• ring (Lattice) – Lattice description.

• dp (float) – Momentum deviation.

• refpts (Type[Element] | Element | Callable[[Element], bool] | str | None | int | Sequence[int] | bool | Sequence[bool] | RefptsCode) –

  Elements at which data is returned. It can be:

  1. an integer in the range [-len(ring), len(ring)-1] selecting the element according to python indexing rules. As a special case, len(ring) is allowed and refers to the end of the last element,

  2. an ordered list of such integers without duplicates,

  3. a numpy array of booleans of maximum length len(ring)+1, where selected elements are True.

Keyword Arguments:

• dct (float) – Path lengthening. Defaults to None

• df (float) – Deviation of RF frequency. Defaults to None

• orbit (Orbit) – Avoids looking for the closed orbit if it is already known ((6,) array)

• get_chrom (bool) – Compute chromaticities. Needs computing the tune at 2 different momentum deviations around the central one.

• get_w (bool) – Computes chromatic amplitude functions (W) [4]. Needs to compute the optics at 2 different momentum deviations around the central one.

• keep_lattice (bool) – Assume no lattice change since the previous tracking. Defaults to False

• XYStep (float) – Step size. Default: DConstant.XYStep

• DPStep (float) – Momentum step size. Default: DConstant.DPStep

• twiss_in –

  Initial conditions for transfer line optics. Record array as output by linopt6(), or dictionary. Keys:

  R or alpha, beta

  mandatory (2,) arrays

  closed_orbit

  Optional (6,) array, default 0

  dispersion

  Optional (6,) array, default 0

  If present, the attribute R will be used, otherwise the attributes alpha and beta will be used. All other attributes are ignored.

Returns:

• elemdata – Linear optics at the points referred to by refpts, if refpts is None an empty lindata structure is returned.

• avebeta – Average beta functions [\(\hat{\beta_x},\hat{\beta_y}\)] at refpts

• avemu – Average phase advances [\(\hat{\mu_x},\hat{\mu_y}\)] at refpts

• avedisp – Average dispersion [\(\hat{\eta_x}, \hat{\eta'_x}, \hat{\eta_y}, \hat{\eta'_y}\)] at refpts

• avespos – Average s position at refpts

• tune – [\(\nu_1,\nu_2\)], linear tunes for the two normal modes of linear motion [1]

• chrom – [\(\xi_1,\xi_2\)], chromaticities

See also

linopt4(), get_optics()

get_chrom(ring, *, method='linopt', dp=None, dct=None, df=None, cavpts=None, **kwargs)

Computes the chromaticities using several available methods

get_tune() may use several methods depending on a method keyword.

Parameters:

• ring (Lattice) – Lattice description.

• method (str) –

  'linopt' returns the tunes from the linopt6() function,

  'fft' tracks a single particle and computes the tunes with fft(),

  'interp_fft' tracks a single particle and computes the tunes with interpolated FFT.

• dp (float) – Momentum deviation.

• dct (float) – Path lengthening.

• df (float) – Deviation of RF frequency.

• cavpts (Type[Element] | Element | Callable[[Element], bool] | str | None | int | Sequence[int] | bool | Sequence[bool] | RefptsCode) – If None, look for ring.cavpts, or otherwise take all cavities.

Keyword Arguments:

DPStep (float) – Momentum step for differentiation Default: DConstant.DPStep

for the 'fft' and 'interp_fft' methods only:

Keyword Arguments:

• nturns (int) – Number of turns. Default: 512

• amplitude (float) – Amplitude of oscillation. Default: 1.E-6

• remove_dc (bool) – Remove the mean of oscillation data. Default: True

• num_harmonics (int) – Number of harmonic components to compute (before mask applied, default: 20)

• fmin (float) – Lower tune bound. Default: 0

• fmax (float) – Upper tune bound. Default: 1

• hann (bool) – Turn on Hanning window. Default: False, Work only for 'fft'

Returns:

chromaticities (ndarray) – array([\(\xi_x,\xi_y\)])

get_optics(ring, refpts=None, dp=None, method=<function linopt6>, **kwargs)

Linear analysis of a fully coupled lattice

get_optics() computes the linear optics parameters on a single cell (periodicity is not taken into account).

Parameters:

• ring (Lattice) – Lattice description.

• refpts (Type[Element] | Element | Callable[[Element], bool] | str | None | int | Sequence[int] | bool | Sequence[bool] | RefptsCode) –

  Elements at which data is returned. It can be:

  1. an integer in the range [-len(ring), len(ring)-1] selecting the element according to python indexing rules. As a special case, len(ring) is allowed and refers to the end of the last element,

  2. an ordered list of such integers without duplicates,

  3. a numpy array of booleans of maximum length len(ring)+1, where selected elements are True.

• dp (float) – Momentum deviation.

• method (Callable) –

  Method for linear optics:

  linopt2: no longitudinal motion, no H/V coupling,

  linopt4: no longitudinal motion, Sagan/Rubin 4D-analysis of coupled motion,

  linopt6 (default): with or without longitudinal motion, normal mode analysis

Keyword Arguments:

• dct (float) – Path lengthening. Defaults to None

• df (float) – Deviation of RF frequency. Defaults to None

• orbit (Orbit) – Avoids looking for the closed orbit if it is already known ((6,) array)

• get_chrom (bool) – Compute chromaticities. Needs computing the tune at 2 different momentum deviations around the central one.

• get_w (bool) – Computes chromatic amplitude functions (W) [4]. Needs to compute the optics at 2 different momentum deviations around the central one.

• keep_lattice (bool) – Assume no lattice change since the previous tracking. Defaults to False

• XYStep (float) – Step size. Default: DConstant.XYStep

• DPStep (float) – Momentum step size. Default: DConstant.DPStep

• twiss_in –

  Initial conditions for transfer line optics. Record array as output by linopt6(), or dictionary. Keys:

  R or alpha, beta

  mandatory (2,) arrays

  closed_orbit

  Optional (6,) array, default 0

  dispersion

  Optional (6,) array, default 0

  If present, the attribute R will be used, otherwise the attributes alpha and beta will be used. All other attributes are ignored.

Returns:

• elemdata0 – Linear optics data at the entrance of the ring

• ringdata – Lattice properties

• elemdata – Linear optics at the points refered to by refpts, if refpts is None an empty lindata structure is returned.

elemdata is a record array, Its fields depend on the selected method. See linopt6, linopt4, linopt2

ringdata is a record array with fields:

tune	Fractional tunes
chromaticity	Chromaticities, only computed if get_chrom is True
damping_time	Damping times [s] (only if radiation is ON)

Warning

The format of output record arrays depends on the selected method. See linopt2(), linopt4(), linopt6().

get_tune(ring, *, method='linopt', dp=None, dct=None, df=None, orbit=None, **kwargs)

Computes the tunes using several available methods

get_tune() may use several methods depending on a method keyword.

Parameters:

• ring (Lattice) – Lattice description

• method (str) –

  'linopt' returns the tunes from the linopt6() function,

  'fft' tracks a single particle and computes the tunes with fft,

  'interp_fft' tracks a single particle and computes the tunes with interpolated FFT.

• dp (float) – Momentum deviation.

• dct (float) – Path lengthening.

• df (float) – Deviation of RF frequency.

• orbit (Orbit) – Avoids looking for the closed orbit if it is already known ((6,) array)

for the 'fft' and 'interp_fft' methods only:

Keyword Arguments:

• nturns (int) – Number of turns. Default: 512

• amplitude (float) – Amplitude of oscillation. Default: 1.E-6

• remove_dc (bool) – Remove the mean of oscillation data. Default: True

• num_harmonics (int) – Number of harmonic components to compute (before mask applied, default: 20)

• fmin (float) – Lower tune bound. Default: 0

• fmax (float) – Upper tune bound. Default: 1

• hann (bool) – Turn on Hanning window. Default: False. Work only for 'fft'

• get_integer (bool) – Turn on integer tune (slower)

Returns:

tunes (ndarray) – array([\(\nu_x,\nu_y\)])

linopt2(ring, *args, **kwargs)

Linear analysis of an uncoupled lattice

linopt2() computes the linear optics parameters on a single cell (periodicity is not taken into account).

Parameters:

ring (Lattice) – Lattice description.

Keyword Arguments:

• refpts (Refpts) –

  Elements at which data is returned. It can be:

  1. an integer in the range [-len(ring), len(ring)-1] selecting the element according to python indexing rules. As a special case, len(ring) is allowed and refers to the end of the last element,

  2. an ordered list of such integers without duplicates,

  3. a numpy array of booleans of maximum length len(ring)+1, where selected elements are True.

• dp (float) – Momentum deviation. Defaults to None

• dct (float) – Path lengthening. Defaults to None

• df (float) – Deviation of RF frequency. Defaults to None

• orbit (Orbit) – Avoids looking for the closed orbit if it is already known ((6,) array)

• get_chrom (bool) – Compute chromaticities. Needs computing the tune at 2 different momentum deviations around the central one.

• get_w (bool) – Computes chromatic amplitude functions (W, WP) [4], and derivatives of the dispersion and twiss parameters versus dp. Needs to compute the optics at 2 different momentum deviations around the central one.

• keep_lattice (bool) – Assume no lattice change since the previous tracking. Defaults to False

• XYStep (float) – Step size. Default: DConstant.XYStep

• DPStep (float) – Momentum step size. Default: DConstant.DPStep

• twiss_in –

  Initial conditions for transfer line optics. Record array as output by linopt6(), or dictionary. Keys:

  R or alpha, beta

  mandatory (2,) arrays

  closed_orbit

  Optional (6,) array, default 0

  dispersion

  Optional (6,) array, default 0

  If present, the attribute R will be used, otherwise the attributes alpha and beta will be used. All other attributes are ignored.

Returns:

• elemdata0 – Linear optics data at the entrance of the ring

• ringdata – Lattice properties

• elemdata – Linear optics at the points referred to by refpts, if refpts is None an empty lindata structure is returned.

elemdata is a record array with fields:

s_pos	longitudinal position [m]
M	(4, 4) transfer matrix M from the beginning of ring to the entrance of the element [2]
closed_orbit	(6,) closed orbit vector
dispersion	(4,) dispersion vector
beta	\(\left[ \beta_x,\beta_y \right]\) vector
alpha	\(\left[ \alpha_x,\alpha_y \right]\) vector
mu	\(\left[ \mu_x,\mu_y \right]\), betatron phase Warning: if the sampling (number of refpts) is too sparse, i.e. if the phase advance is more than 2*pi between 2 points the integer part will not increment correclty
W	\(\left[ W_x,W_y \right]\) only if get_w is True: chromatic amplitude function
Wp	\(\left[ Wp_x,Wp_y \right]\) only if get_w is True: chromatic phase function
dalpha	(2,) alpha derivative vector (\(\Delta \alpha/ \delta_p\))
dbeta	(2,) beta derivative vector (\(\Delta \beta/ \delta_p\))
dmu	(2,) mu derivative vector (\(\Delta \mu/ \delta_p\))
ddispersion	(4,) dispersion derivative vector (\(\Delta D/ \delta_p\))

All values given at the entrance of each element specified in refpts. Field values can be obtained with either lindata[‘idx’] or lindata.idx

ringdata is a record array with fields:

tune	Fractional tunes
chromaticity	Chromaticities, only computed if get_chrom is True

References

[1] D.Edwards,L.Teng IEEE Trans.Nucl.Sci. NS-20, No.3, p.885-888 , 1973

[2]

E.Courant, H.Snyder

[3] D.Sagan, D.Rubin Phys.Rev.Spec.Top.-Accelerators and beams, vol.2 (1999)

[4] (1,2,3)

Brian W. Montague Report LEP Note 165, CERN, 1979

linopt4(ring, *args, **kwargs)

Linear analysis of a H/V coupled lattice

4D-analysis of coupled motion following Sagan/Rubin [7]

linopt4() computes the linear optics parameters on a single cell (periodicity is not taken into account).

Parameters:

ring (Lattice) – Lattice description.

Keyword Arguments:

• refpts (Refpts) –

  Elements at which data is returned. It can be:

  1. an integer in the range [-len(ring), len(ring)-1] selecting the element according to python indexing rules. As a special case, len(ring) is allowed and refers to the end of the last element,

  2. an ordered list of such integers without duplicates,

  3. a numpy array of booleans of maximum length len(ring)+1, where selected elements are True.

• dp (float) – Momentum deviation. Defaults to None

• dct (float) – Path lengthening. Defaults to None

• df (float) – Deviation of RF frequency. Defaults to None

• orbit (Orbit) – Avoids looking for the closed orbit if it is already known ((6,) array)

• get_chrom (bool) – Compute chromaticities. Needs computing the tune at 2 different momentum deviations around the central one.

• get_w (bool) – Computes chromatic amplitude functions (W) [8]. Needs to compute the optics at 2 different momentum deviations around the central one.

• keep_lattice (bool) – Assume no lattice change since the previous tracking. Defaults to False

• XYStep (float) – Step size. Default: DConstant.XYStep

• DPStep (float) – Momentum step size. Default: DConstant.DPStep

• twiss_in –

  Initial conditions for transfer line optics. Record array as output by linopt6(), or dictionary. Keys:

  R or alpha, beta

  mandatory (2,) arrays

  closed_orbit

  Optional (6,) array, default 0

  dispersion

  Optional (6,) array, default 0

  If present, the attribute R will be used, otherwise the attributes alpha and beta will be used. All other attributes are ignored.

Returns:

• elemdata0 – Linear optics data at the entrance of the ring

• ringdata – Lattice properties

• elemdata – Linear optics at the points refered to by refpts, if refpts is None an empty lindata structure is returned.

elemdata is a record array with fields:

s_pos	longitudinal position [m]
M	(4, 4) transfer matrix M from the beginning of ring to the entrance of the element [6]
closed_orbit	(6,) closed orbit vector
dispersion	(4,) dispersion vector
beta	\(\left[ \beta_x,\beta_y \right]\) vector
alpha	\(\left[ \alpha_x,\alpha_y \right]\) vector
mu	\(\left[ \mu_x,\mu_y \right]\), betatron phase Warning: if the sampling (number of refpts) is too sparse, i.e. if the phase advance is more than 2*pi between 2 points the integer part will not increment correclty
gamma	gamma parameter of the transformation to eigenmodes [7]
W	\(\left[ W_x,W_y \right]\) only if get_w is True: chromatic amplitude function
Wp	\(\left[ Wp_x,Wp_y \right]\) only if get_w is True: chromatic phase function
dalpha	(2,) alpha derivative vector (\(\Delta \alpha/ \delta_p\))
dbeta	(2,) beta derivative vector (\(\Delta \beta/ \delta_p\))
dmu	(2,) mu derivative vector (\(\Delta \mu/ \delta_p\))
ddispersion	(4,) dispersion derivative vector (\(\Delta D/ \delta_p\))

All values given at the entrance of each element specified in refpts. Field values can be obtained with either lindata[‘idx’] or lindata.idx

ringdata is a record array with fields:

tune	Fractional tunes
chromaticity	Chromaticities, only computed if get_chrom is True

References

[5] D.Edwards,L.Teng IEEE Trans.Nucl.Sci. NS-20, No.3, p.885-888 , 1973

[6]

E.Courant, H.Snyder

[7] (1,2)

D.Sagan, D.Rubin Phys.Rev.Spec.Top.-Accelerators and beams, vol.2 (1999)

[8]

Brian W. Montague Report LEP Note 165, CERN, 1979

linopt6(ring, *args, **kwargs)

Linear analysis of a fully coupled lattice using normal modes

For circular machines, linopt6() analyses

• the 4x4 1-turn transfer matrix if ring is 4D, or

• the 6x6 1-turn transfer matrix if ring is 6D.

For a transfer line, The “twiss_in” intput must contain either:

• a field R, as provided by ATLINOPT6, or

• the fields beta and alpha, as provided by linopt and linopt6

linopt6() computes the linear optics parameters on a single cell (periodicity is not taken into account).

Parameters:

ring (Lattice) – Lattice description.

Keyword Arguments:

• refpts (Refpts) –

  Elements at which data is returned. It can be:

  1. an integer in the range [-len(ring), len(ring)-1] selecting the element according to python indexing rules. As a special case, len(ring) is allowed and refers to the end of the last element,

  2. an ordered list of such integers without duplicates,

  3. a numpy array of booleans of maximum length len(ring)+1, where selected elements are True.

• dp (float) – Momentum deviation. Defaults to None

• dct (float) – Path lengthening. Defaults to None

• df (float) – Deviation of RF frequency. Defaults to None

• orbit (Orbit) – Avoids looking for the closed orbit if it is already known ((6,) array)

• get_chrom (bool) – Compute chromaticities. Needs computing the tune at 2 different momentum deviations around the central one.

• get_w (bool) – Computes chromatic amplitude functions (W) [11]. Needs to compute the optics at 2 different momentum deviations around the central one.

• keep_lattice (bool) – Assume no lattice change since the previous tracking. Defaults to False

• XYStep (float) – Step size. Default: DConstant.XYStep

• DPStep (float) – Momentum step size. Default: DConstant.DPStep

• twiss_in –

  Initial conditions for transfer line optics. Record array as output by linopt6(), or dictionary. Keys:

  R or alpha, beta

  mandatory (2,) arrays

  closed_orbit

  Optional (6,) array, default 0

  dispersion

  Optional (6,) array, default 0

  If present, the attribute R will be used, otherwise the attributes alpha and beta will be used. All other attributes are ignored.

• cavpts (Refpts) – Cavity location for off-momentum tuning

Returns:

• elemdata0 – Linear optics data at the entrance of the ring

• ringdata – Lattice properties

• elemdata – Linear optics at the points refered to by refpts, if refpts is None an empty lindata structure is returned.

elemdata is a record array with fields:

s_pos	longitudinal position [m]
M	(6, 6) transfer matrix M from the beginning of ring to the entrance of the element
closed_orbit	(6,) closed orbit vector
dispersion	(4,) dispersion vector
A	(6,6) A-matrix
R	(3, 6, 6) R-matrices
beta	\(\left[ \beta_x,\beta_y \right]\) vector
alpha	\(\left[ \alpha_x,\alpha_y \right]\) vector
mu	\(\left[ \mu_x,\mu_y \right]\), betatron phase Warning: if the sampling (number of refpts) is too sparse, i.e. if the phase advance is more than 2*pi between 2 points the integer part will not increment correclty
W	\(\left[ W_x,W_y \right]\) only if get_w is True: chromatic amplitude function
Wp	\(\left[ Wp_x,Wp_y \right]\) only if get_w is True: chromatic phase function
dalpha	(2,) alpha derivative vector (\(\Delta \alpha/ \delta_p\))
dbeta	(2,) beta derivative vector (\(\Delta \beta/ \delta_p\))
dmu	(2,) mu derivative vector (\(\Delta \mu/ \delta_p\))
ddispersion	(4,) dispersion derivative vector (\(\Delta D/ \delta_p\))
dR	(3, 6, 6) R derivative vector (\(\Delta R/ \delta_p\))

All values given at the entrance of each element specified in refpts. Field values can be obtained with either lindata[‘idx’] or lindata.idx

ringdata is a record array with fields:

tune	Fractional tunes
chromaticity	Chromaticities, only computed if get_chrom is True
damping_time	Damping times [s] (only if radiation is ON)

References

[9] Etienne Forest, Phys. Rev. E 58, 2481 – Published 1 August 1998

[10] Andrzej Wolski, Phys. Rev. ST Accel. Beams 9, 024001 – Published 3 February 2006

[11]

Brian W. Montague Report LEP Note 165, CERN, 1979