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eRHIC Longitudinal Polarimeter. Ideally: Detect electrons and photons Have ~2 m drift for laser interaction region Have “good” g-2 projection at laser IR Do not image long (>5 m) vacuum sections with gamma detector Provide for UHV/XHV and ion clearing at laser IR. HERA Long. Pol. Layout.
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eRHIC Longitudinal Polarimeter • Ideally: • Detect electrons and photons • Have ~2 m drift for laser interaction region • Have “good” g-2 projection at laser IR • Do not image long (>5 m) vacuum sections with gamma detector • Provide for UHV/XHV and ion clearing at laser IR
HERA Long. Pol. Layout Courtesy W. Lorenzon - University of Michigan
Use Last Spin Rotator Dipole Outside IR for Tagger 90º of Spin Precession @ 7.5 GeV 5.3 º Bend 35 mr 35 mr Solenoid Solenoid 10 mr 10 mr e’ 35 mr precesses spin 22º @ 5 GeV, 45 º @ 10 GeV Not Really a Longitudinal Polarimeter 60 mr 10 mr Septum Solenoid Solenoid 10 mr 10 mr e’ 35 mr precesses spin 37º @ 5 GeV, 74º @ 10 GeV Septum Required
Solenoid Solenoid Solenoid Solenoid Longitudinal Polarimeter Downstream? γ Detector IP/Detector -90 mr -10 mr 90 mr -10 mr 10 mr 10 mr e’ 5° Dipole doesn’t require Septum?