Progress Report for the BPM Energy Spectrometer Test Experiment at ESA

The main physics programme of the International Linear Collider (ILC) requires a measurement of the beam energy with a relative precision of 10 -4 or better. To achieve this goal a spectrometer using high resolution beam position monitors (BPM) and accurately monitored bending magnets has been proposed. A prototype spectrometer chicane using 4 dipoles is now commissioned in End Station A (ESA) at SLAC, intending to demonstrate the required stability of this method and investigate possible systematic effects and operational issues. In this contribution we will describe the experimental setup for this ESA test experiment (T-474/491), which has been finalised during two runs in 2007, and present results from the BPM commissioning runs in 2006.