1. Shielding review for temporary spectrometer for RUBICON experiment, ATF beamline #2 K. Kusche, M. Fedurin RSC meeting, Jan 20, 2015

2. Description Temporary spectrometer required for RUBICON experiment at ATF. Primary goals are electron beam modulation and x-ray detection. Spectrometer consists of dipole, imaging system (within vacuum cross), Be window. Position on beamline #2 constrained by electron and laser beam optics. Too far upstream to utilize existing spectrometer.

3. ATF Experimental Hall

4. Configuration details The dipole center is 115” inches downstream from the existing dipole at the head of beamline #2, aligned along electron beam axis. The dipole can bend the beam in the horizontal plane only (±30 degrees @40 MeV). 1” Beryllium window on the end of the spectrometer’s vacuum cross allows for on-axis x-ray detection. The upstream Be window surface will be under vacuum, the downstream side at atmospheric pressure.

5. Beam parameters Routine operation for this experiment is 50 MeV, 200 pC, 1.5 Hz with no experiment-induced beam modulation. With modulation, the 200 pC will be spread horizontally over 40-110 MeV range on the spectrometer. Modulation only occurs during CO2 laser pulse (limited to 0.05 Hz, which is once per 30 unmodulated bunches). The routine condition is with the dipole powered and electron beam imaged in the spectrometer.

6. Dipole parameters Power supply for the temporary dipole is bipolar and limited to ±10 A. (±30 degrees @40 MeV) Magnet pole gap: vertical =1.25”, horizontal= 8” diameter (limited by vacuum chamber to 30 degree slice) If the dipole were turned off or failed, the electron beam would proceed straight at the Be window.