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Beam intensity profile measurements with the RHIC (AGS) C-CNI polarimeters. Polarization profile measurements. Polarimeter target mechanisms upgrades. RSC meeting, January 15, 2008. Yellow polarimeter target motion upgrade -2006.
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Beam intensity profile measurements with the RHIC (AGS) C-CNI polarimeters. • Polarization profile measurements. • Polarimeter target mechanisms upgrades. RSC meeting, January 15, 2008
In 2007 the BLUE target motion mechanisms were upgraded again. • New precision rotary motion feedthroughs were installed. No backlash, high reproducibility, smooth motion.
P-Carbon CNI polarimeter target. 10 mm Scattering angle ~0.5 deg ~1.6 mm ~ 100 mm RHIC beam Target speed 200 steps/sec → 25 mm/sec linear speed. 180 mm
Deutron beam horizontal profile • P-CNI polarimeter as a wire scanner: • Very thin target , practically non-destructive. • Very high rate. • Very good signal/noise ratio. Delayed C-ion detection. • Single bunch measurements. • Problems so far : • Target alignment. • Carbon strips are not straight. • Target mechanism positioning accuracy was not satisfactory (positioning to the detector plane, large backlash, target vibrations). • Broken rotational feed through. P-CNI polarimeter can be an ideal wire-scanner.
Horiz. Emittances at injection, consistent with numbers measured in AGS and ATR.
IPM measurements , Febr.15 17 pi 15 pi 16 pi 17 pi
Emittance measurement in AGS, single pulse at flattop. Sigma 0.96 mm~15 pi Horizemittance
Target mechanism upgrades. • A new target holder and jig for accurate target positioning. • New rotational feedthroughs with direct step-motor coupling, larger (3/8” diam) rod and extended bearing support at the end. • A new feedthrough support with provision for precision alignment of the target motion axis and translational motion stages. • A new target mechanism attachment plates. No need for mechanism realignment. • 4-targets (horizontal) for vertical beam profile scans and 6-targets (vertical) for horizontal profile scans. • The target ladder can be moved under the beam. All six vertical targets can be used in the same fill. • We plan to install one 20um target and one 40 um target in addition to regular (5-10 um) targets to study the systematic error to polarization measurements at different target thickness. • Thicker (hopefully straighter) targets will be used for the beam profile measurements.
Summary. • The rotational feedthroughs do not provide accurate positioning (even after all upgrades) and have to be replaced. • The target thickness for the profile measurements (and polarization measurements ) have to be optimized. • Targets mounting on the ladder has to be improved and tested. • The CNI polarimeter is an amazing device. It worked in spite of all the above mentioned problems. • I hope it will also survive all the improvements we have made with the very best intentions.