| Paper |
Title |
Page |
| IT12 |
Use of Superimposed Alternating Currents in Quadrupoles to Measure Beam Position with Respect to their Magnetic Centre
|
38 |
| |
- N. Marks
CLRC, Daresbury Laboratory, Warrington, UK
|
|
| |
The positional stability of the electron beam in a modern
state-of-the-art synchrotron radiation source is critical, as
the many experimental users require consistency in the
position and dimensions of the incoming photon beams
which are incident on their experimental samples. At the
Daresbury Synchrotron Radiation Source (SRS),
inaccuracies in the measurements of the positions of both
beam position monitors and the lattice quadrupoles can be
overcome by measuring the position of the electron beam
with respect to the magnetic centres of the quadrupoles.
This was achieved by superimposing an alternating
('ripple') current on the direct current excitation of a
single lattice quadrupole and examining the resulting
beam oscillations at remote positions in the storage ring.
If the electron beam is then subjected to a local distortion
at the position of this quadrupole, the amplitude of the
beam oscillation induced by the superimposed current is
minimised (nominally zero) when the beam is at the
quadrupole's magnetic centre. This paper presents details
of the electrical circuit developed to inject an alternating
current into the coils of individual quadrupoles and gives
details of the results achieved to date.
|
|