524
M. Lamont et al.
9.2.3 Generalization
The parameter space of a particle accelerator can be complex and large and might
include the parameters such as tune, chromaticity and orbit but also others such as:
Landau damping octupoles; bunch length control with wigglers; compensation of
eddy current effects; higher order multipole correction with dedicated magnets etc.
In a machine with an energy ramp these parameters and required corrections will be
a function of time.
It should be easy to define combinations of parameters to give other higher level
parameters (a “knob” in CERN parlance). These knobs can be then manipulated to
control the ensemble. A simple example is a closed orbit bump. A more sophisticated example would be an optics correction which could include quadrupole
strength adjustments and tune compensation.
Reliable settings management is mandatory. Generic tools for tracking all
changes to settings should be deployed providing a full record of all settings
changes. Archive and roll back facilities are essential. It is important that all
parameter control be dealt within the same parameter and settings management
system.
Besides the provision of tools for standard operations, the requirements of
machine studies and commissioning should be borne in mind. Exploiting the
machine in study mode often required non-standard measurements and non-standard
control actions on accelerator hardware. An appropriate scripting environment
(e.g. Python) with interfaces to control system functionality should allow the user
to fully exploit the potential of the hardware and control system in a flexible
and experimental way. Many of the tools thus developed can subsequently be
incorporated into the standard operational environment. At the LHC this has
included, for example, tools for beta beating measurement and correction, detection
and logging of beam instabilities etc.
9.3 Orbit Correction
J. Wenninger
The main role of orbit correction is to centre the trajectory (in a transfer line) or
the closed orbit (in a ring) inside the aperture or the magnetic elements, typically
quadrupoles or wiggler magnets. This is usually achieved using global correction
algorithms acting on all or a large part of the accelerator. In some cases local
excursions may be desired, requiring the use of local ‘bumps’ of the orbit or
trajectory.
M. Lamont et al.
9.2.3 Generalization
The parameter space of a particle accelerator can be complex and large and might
include the parameters such as tune, chromaticity and orbit but also others such as:
Landau damping octupoles; bunch length control with wigglers; compensation of
eddy current effects; higher order multipole correction with dedicated magnets etc.
In a machine with an energy ramp these parameters and required corrections will be
a function of time.
It should be easy to define combinations of parameters to give other higher level
parameters (a “knob” in CERN parlance). These knobs can be then manipulated to
control the ensemble. A simple example is a closed orbit bump. A more sophisticated example would be an optics correction which could include quadrupole
strength adjustments and tune compensation.
Reliable settings management is mandatory. Generic tools for tracking all
changes to settings should be deployed providing a full record of all settings
changes. Archive and roll back facilities are essential. It is important that all
parameter control be dealt within the same parameter and settings management
system.
Besides the provision of tools for standard operations, the requirements of
machine studies and commissioning should be borne in mind. Exploiting the
machine in study mode often required non-standard measurements and non-standard
control actions on accelerator hardware. An appropriate scripting environment
(e.g. Python) with interfaces to control system functionality should allow the user
to fully exploit the potential of the hardware and control system in a flexible
and experimental way. Many of the tools thus developed can subsequently be
incorporated into the standard operational environment. At the LHC this has
included, for example, tools for beta beating measurement and correction, detection
and logging of beam instabilities etc.
9.3 Orbit Correction
J. Wenninger
The main role of orbit correction is to centre the trajectory (in a transfer line) or
the closed orbit (in a ring) inside the aperture or the magnetic elements, typically
quadrupoles or wiggler magnets. This is usually achieved using global correction
algorithms acting on all or a large part of the accelerator. In some cases local
excursions may be desired, requiring the use of local ‘bumps’ of the orbit or
trajectory.