T474/T491 abstract for PAC07
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The main physics programme of the international linear collider
requires a measurement of the beam energy with a relative precision on
the order of $10^{-4}$ or better. To achieve this goal a magnetic
spectrometer using high resolution beam position monitors (BPM) has
been proposed. A prototype spectrometer chicane using 4 dipole magnets
is currently under development at the End Station A in SLAC,
intending to demonstrate the required stability of this method, 
investigate possible systematic effects and operational issues. This
contribution reports on the successful commissioning of the beam 
position monitor system and the resolution and stability
achieved. Also, the initial results from a run with a full spectrometer 
chicane are presented.