The RHIC C-CNI polarimeter upgrade for 2009 Run. RSC Meeting, December 16, 2008 Anatoli Zelenski for polarimeter upgrade group. T.Russo, T.Curcio, D.Lehn, D.Gassner, G.Mahler, S.Bugros, Y.Makdisi, H.Huang, M.Mapes, R.Todd, M.Sivertz, B.Morozov, R.Gill, A.Bazilevskiy …

New Proposed LEBT/MEBT, keV Spin-rotator Einzel lens OPPIS

New Proposed LEBT/MEBT, keV Spin-rotator Einzel lens OPPIS

A new 750 keV MEBT line

D.Raparia, APEX Workshop Dec.5

 So far the polarization and beam intensity profile measurements in both vertical and horizontal planes were limited by the long target switching time and possible target destruction during this complicated motion.  The RHIC polarimeters were operated near the limit of the counting rate for present silicon strip detectors and this could be a serious limitation for the further RHIC intensity and energy increase. The development of new detectors was very limited by the absence of development time during the polarized RHIC runs. The RHIC p-Carbon CNI polarimeter upgrade for the beam polarization and intensity profile measurements.

The ongoing CAD polarimeter upgrade project will address these problems for the 2009 polarized run.  The plan is two build and install the second polarimeter in each RHIC ring. These two polarimeters will be installed in new vacuum chambers with more powerful vacuum system to improve RHIC vacuum conditions. Two identical Carbon target motion mechanisms and detectors assembly will be installed in each chamber (both ring).  One polarimeter can be used for the vertical polarization and intensity profile measurements and the second can be used for the horizontal profile measurements. It will minimize number of target motions, speed up the measurements (increase efficiency of the stored beam use for about 5-10%) and reduce the risk of the target damages.

The RHIC p-Carbon CNI polarimeter upgrade for the beam polarization and intensity profile measurements (G.Mahler, S.Bugros)

 Additional set of detector ports will facilitate new detectors development, while keeping the established technique intact.  Two sets of targets will extend the period between target replacements and reduce the machine downtime.  Additional polarization and emittance measurements can be done with extra set of targets (polarization and emittance measurements during the energy ramp).

Vacuum system upgrade. Polarimeter will be pumped by two pumps (ion pump and NEG cartridge) isolated by vacuum valves. Diam. 8.0” (ID) nipples will provide sufficient conductance to utilize full pump capacity. Isolation valves will allow proper pump conditioning and faster turn around time after the venting. In future we plan to setup some moderate chamber baking after testing of polarimeter components (targets, detectors, Am-sources) tolerances to temperature.

Electronics upgrade. We will operate one polarimeter at the time (in each ring). This allows multiplexing of existing detector signal processing electronics. Also we will commutate the existing set of step-motor drivers between two polarimeters (no need for additional power supplies and cables). This will save money and also minimize software changes.

New target motion mechanism.

Target drives mechanical part Is near completed. Motion control tests and multiplexing are in progress.

New detectors development using BNL tandem facilities Carbon ion beam from BNL tandem facilities revealed (confirmed observation in RHIC) strong effect of carbon beam intensity on silicon strip detector operation presently used at RHIC polarimeter, which appeared as spectrum shift and distortion. New types of silicon detectors were selected, which have better properties and we plan to test these detectors during 2009 Run in RHIC polarimeter.

November 21 December 4, Blue-target drive installation Yellow-pumping, baking.

Target drives installation December 4

Yellow polarimeter baking, Dec.4 Vacuum torr Dec,15

Operation modes. Polarization measurement scan (main mode). Polarization, polarization profiles, beam intensity profile (including bunch-by bunch. Polarization measurement on the ramp (fixed target with some position adjustment, if necessary). Emittance measurements and calibration in fast scan mode, with dedicated targets.

Polarimeter upgrade commissioning. August- Design, procurement, September target drive prototype. October. Vacuum chamber delivery, baking, leak- check, installation. Target drive manufacturing. November. Installation in the tunnel. Vacuum system commissioning. Wiring. Tests. December. Pumping. Tests.

RHIC luminosity. Figure of merit LP 4.  = beam- beam tune shift. Luminosity: L =3f 0 BN 2  / 2  n  * B=120,  - 250GeV,  *=1.0m 250 GeV 2·10 32

Emittance measurement in AGS, single pulse at flattop. Sigma 0.96 mm~15 pi Horiz emittance Ev=6  (0.96) 2 ·25.3/10.0=14.0 .  h =096 mm

AGS Vertical emittance CNI scan (horizontal target). Intensity=1.6·  =25.3  *=21.7m Ev=6  (1.44) 2 ·25.3/21.7=14.5 .

AGS Emittances at Extraction (2006 setup). 15 pi Horiz. CNI 1.5·10 11 Vert. IPM Horiz IPM

20pi 8000

Polarization evolution during the store. March % 50%

Figure of merit optimization, L·P Y 2 P B 2 Integrated luminosity, lifetime

Blue.horiz. at store, Target #5, Febr.15.08

Target lifetime Carbon strip target is only 5-10  m wide and 4-5  g/cm 2 thick. This corresponds about atoms in the beam. The recoil Carbon production rate is about 10^8 atoms/s at present very high RHIC beam intensity), therefore after one hundred (10 s) measurements about 0.1% of carbon atoms are knocked out of the strip. Some targets survive for two weeks which corresponds to about 300 measurements.

 Additional set of detector ports will facilitate new detectors development, while keeping the established technique intact.  Two sets of targets will extend the period between target replacements and reduce the machine downtime.  Additional polarization and emittance measurements can be done with extra set of targets (polarization and emittance measurements during the energy ramp).  A new carbon target production technique (by the laser ablation developed at TRIUMF, Vancouver, Canada) will be also tested.  The polarimeter upgrade project is funded by CAD ($150k) and RIKEN ($75k) and planned to be completed by the end of December 2008 for operation in 2009 polarized proton run.

The RHIC p-Carbon CNI polarimeter. Ultra thin Carbon ribbon Target (5  g/cm 2 ) Si strip detectors (TOF, E C ) 18cm Polarized proton Recoil carbon Carbon target Elastic scattering: interference between electromagnetic and hadronic amplitudes in the Coulumb-Nuclear Interference (CNI) region. A N (pC)~1%