A   B   C   D   E   F   G   H   J   K   L   M   N   O   P   R   S   T   U   V   W   Z    

Marks, N.

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.