A. Zelenski a, G. Atoian a *, A. Bogdanov b, D.Raparia a, M.Runtso b, D. Steski a, V. Zajic a a Brookhaven National Laboratory, Upton, NY, 11973, USA b Moscow Engineering Physical Institute (MEPHI), Moscow , Russia Precision, Absolute Proton Beam Polarimeter at 200MeV PSTP-2013

Polarization facilities at RHIC. 9/12/2013G. Atoian2 STAR PHENIX AGS, 24GeVLINAC BOOSTER 2.5 GeV OPPIS 200MeV polarimeter RHIC pC “CNI” polarimeters RHIC Absolute H-jet polarimeter AGS pC “CNI” polarimeter

Polarized injector, 200MeV LINAC and injection lines OPPIS 200MeV polarimeter 200MeV LINACRFQ Booster 9/12/2013G. Atoian3

The 200 LINAC Polarimeter The 200 MeV LINAC Polarimeter Target proton 200MeV Scattered proton Recoil Atom 9/12/2013G. Atoian4 A new polarimeter for absolute proton beam polarization measurements at 200 MeV to accuracy better than ±0.5% has been developed as a part of the RHIC polarized source upgrade. The polarimeter is based on the elastic pC scattering at 16.2° angle, where the analyzing power is large 99.35% and was measured with high accuracy. The elastically and in-elastically scattered protons are clearly identified by the difference in the propagation through variable copper absorber and energy deposition of the stopped protons in the detectors. The 16.2° elastic scattering polarimeter was used for calibration of a high rate inclusive 12° polarimer, which was used for the on-line polarization tuning and monitoring.

Measurements of the cross section and analyzing power for proton scattering from 12 C at 200 MeV. The blue curves correspond to protons exiting from the ground state of carbon. The green curve corresponds two protons exiting from the first excited state (-4.44MeV). The black curve represents the sum of the two data sets. Edward J. Stephenson, 10/22/2009 ~16.2 o ~50mb/sr ~5mb/sr ~82% Cross section and analyzing power for pC scattering at 200 MeV ~12 ~ % 9/12/2013 G. Atoian 5

elastic GEANT calculation of pC polarimeter for 200MeV proton beam inelastic E p =198.7MeV E p =194.3MeV 41mm of Cu We have shown the possibility of suppression of an inelastic scattering proton from a carbon by an absorber. C- target P-beam Sc1 Sc2 Sc3 9/12/2013 G. Atoian 6

GEANT calculation of pC polarimeter for 200MeV proton beam Energy deposited in the scintillator E, MeV inelastic elastic Ratio N(Inelastic)/N(elastic) by the Cu absorber thickness ~41mm with energy threshold ~15MeV is less than 0.5% elastic inelastic L, cm N, particles stopped in the slice of absorber 9/12/2013 G. Atoian 7 A sharp edges promises a good separation of the inelastic scattered proton from an elastic

Beam setup of the polarimeter 9/12/2013 G. Atoian 8

Polarimeter setup for 200MeV proton beam Cu ~5 mm Horizontal 12 0 and vertical polarimetersHorizontal polarimeter Absorber: Cu from 0 to 1 mm (step by 0.1mm) Absorber: Cu from 0 to 9 mm (step by 1mm) Absorber: Cu from 0 to 38.1 mm (step by 12.7mm) Cu collimator: D=8mm Counters: Sc3 Sc2 Sc1 Motion system Fast photomultiplier with fast scintillator BC-404 (decay time ~1.8nsec) gave the output pulse less than 15nsec (rise time ~2.4nsec). Coincidence signal is formed in the vicinity of the detector in the beam line by fast discriminators. Time resolution without amplitude correction is less then 0.5nsec. Mostly the elastic protons passed through the absorber (41mm) and absorbed into the second scintillator, depositing ~5-40.0MeV of energy. 9/12/2013 G. Atoian 9

Spectrum of counters and efficiency vs. threshold of discriminator 9/12/2013 G. Atoian 10

Systematic error an analyzing power C target proton 200MeV Scattered proton Recoil Carbon The systematic error of the A y by: detector alignment  5mm energy of the beam 200  1.0 MeV size of the scintillators ~10x10mm multiple scattering in target, vacuum wall and air Is about 0.2 %. 9/12/2013 G. Atoian 11

Horizontal scan of the beam by vertical polarimeter Target#1Target#2Target#3Target#4Target#5 Width x thickness, mm2 x x 0.06D 0.34 x 0.1 Rate of horizontal 12 0 polar. evnt./pulse (L abs =6mm of Cu) ~400 ~220~200~800 Rate of horizontal polar. evnt./pulse (L abs =40.1mm of Cu) ~30 ~18~15~60 Rate of vertical polar. events /pulse (L abs =5mm of Cu) ~1600 ~1100~900~2500 By the different targets we can change the rate of the detector almost 4 times. 9/12/2013 G. Atoian 12

Systematic error an accidental coincidence by: beam halo (depends on the adjustment of the LINAC) and the rate of the detector. (By Linac elements and using different targets we can change the rate of the detector almost 4 times). Average counts in the target ‘out’ are less than 1 and target ‘in’ ~250, gave the systematic error ~0.3% Systematic error in polarization measurement by beam halo Target position ‘OUT’ 9/12/2013 G. Atoian 13

I(T9)=295MKA (4.9*10^11) 83.9+/-0.7% 84.2+/-0.5% 15 min 9/12/2013 G. Atoian 14

~83% Polarization fluctuation of 200Mev beam (March 1-4, /12/2013 G. Atoian 15

Measured Analyzing Power vs thickness of absorber 9/12/2013 G. Atoian 16

Suppression of the inelastic scattering proton to first excited state by absorber 9/12/2013 G. Atoian 17 Inelastic scattering protons well suppression First excited state drops the analyzing power ~ 2% Prototype of the first excited state (Energy was decreases by the LINAC) Ratio of the rate Sc1*Sc2: R(200)/R( ) > 10 for the 41mm thick of Cu absorber

Calibration curve of energy monitoring using polarimeter Difference of the rate in the subsequent detectors of the telescope in both arms was used for the beam energy monitoring and tuning to improve polarization measurement accuracy. The energy calibration polarimeter with accuracy better than 0.5 MeV were done by using the magnetic spectrometer and cross-checked at injection to the Booster. Beam energy vs. ratio S3*S1/S2*S1x100 (thickness of absorber 40.1mm) Sc3Sc2Sc1 9/12/2013 G. Atoian 18

Time chart of energy monitoring using calibration curve Ratio N(Sc1*Sc2) / N(Sc1*Sc3) is simple and stabile monitor of beam energy with accuracy better than 0.5 MeV per tens of pulses. 9/12/2013 G. Atoian 19

Horizontal scan and polarization profile of the beam We have a program that makes automatic measurements of a horizontal scan and polarization profile of the beam. 9/12/2013 G. Atoian 20

Polarization vs current of the spin rotator Polarization at the horizontal polarimeter ~ 80.5% 9/12/2013 G. Atoian 21

THE ANALYZING POWER OF THE ELASTIC SCATTERING PROTON FROM 12 C IS WELL KNOWN WITH GOOD ACCURACY AND FOR 16.2 DEGREE SCATTERING ANGLE IT IS CLOSE TO 100%. (PHYS. REV. C, VOL. 45 NUMBER 2, ) WE SHOWN POSSIBILITY OF SUPPRESSION OF THE INELASTIC SCATTERING PROTON FROM AN ELASTIC FOR 41MM CUPPER ABSORBER IS ABOUT 1% ( ~10 TIMES BY CROSS SECTION AND MORE THAN ~10 TIMES BY ABSORBER ). THE IDENTIFIED ELASTIC PROTONS WERE USED FOR POLARIZATION MEASUREMENT.  polarimeter used for the determine of analyzing power 12 0 polarimeter and reference polarization measurement;  Rate effect for polarization measurement less 0.2% to 400 event/pulse (~1.3MHz) and the estimated systematic error ~0.3 %;  Polarization dependence of gain of PMT and threshold of discriminators are insignificant. Deposited energy on the scintillators more then 10MeV (5-40MeV);  Ratio N(Sc1*Sc2)/N(Sc1*Sc3) is simple and stabile monitor of beam energy with accuracy better than 0.5MeV per tens of pulses;  We are capable accuracy measurement of horizontal beam and polarization profile. Summery 9/12/2013 G. Atoian 22

BACKUP 9/12/2013 G. Atoian 23

Beam setup of 200MeV proton polarimeter (before) pD-polarimeter: The analyzing power for pD known with good accuracy: A = / (IUCF); pD polarimeter was used for calibration of the 12 deg. pC polarimeter The rate - less then 1 event per pulse => In 8 hrs a statistical accuracy about 2%; 9/12/2013 G. Atoian 24

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