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Conceptual design of a proton polarimeter for RHIC

Description: A two-arm pion polarimeter utilizing toroidal magnets is being considered for use with the polarized protons beam at RHIC. The system will enable measurements of beam polarization at all RHIC energies from injection to flattop. This is a necessary diagnostic tool for tuning the RHIC snake magnets and other polarization controlling elements. Toroidal magnets constrain the pion trajectories allowing the device to be compact so that it can fit within the limited space available. A viable magnet design has been completed and suitable target configuration and operating scenario have been identified.
Date: December 1, 1996
Creator: Alekseev, I.; Belikov, N. & Bunce, G.
Partner: UNT Libraries Government Documents Department

p-Carbon polarimetry at RHIC.

Description: The polarization measurement through elastic ({rvec p},C) reaction plays a crucial role in the polarized proton beam operation of Relativistic Heavy Ion collider at Brookhaven National Laboratory. As well as measuring the polarization, the unknown analyzing power A{sub N} of elastic ({rvec p},C) is determined as well in combination with the absolute polarization measurement by a H-jet polarimeter. The systematic uncertainty of the Run05 measurements are discussed as well as introducing the experimental apparatus of the polarimeter system.
Date: September 10, 2007
Creator: Nakagawa,I.; Makdisi,Y.; Alekseev, I.; Bazilesky, A.; Bravar, A.; Bunce, G. et al.
Partner: UNT Libraries Government Documents Department

ACCELERATING POLARIZED PROTONS TO 250 GEV

Description: The Relativistic Heavy Ion Collider (RHIC) as the first high energy polarized proton collider was designed t o provide polarized proton collisions a t a maximum beam energy of 250 GeV. I t has been providing collisions a t a beam energy of 100 Gel' since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during the acceleration from injection to 100 GeV with careful control of the betatron tunes and the vertical orbit distortions. However, the intrinsic spin resonances beyond 100 GeV are about a factor of two stronger than those below 100 GeV? making it important t o examine the impact of these strong intrinsic spin resonances on polarization survival and the tolerance for vertical orbit distortions. Polarized protons were accelerated t o the record energy of 250 GeV in RHIC with a polarization of 46% measured a t top energy in 2006. The polarization measurement as a function of beam energy also shows some polarization loss around 136 GeV, the first strong intrinsic resonance above 100 GeV. This paper presents the results and discusses the sensitivity of the polarization survival t o orbit distortions.
Date: June 25, 2007
Creator: BAI,M.; AHRENS, L.; ALEKSEEV, I.G.; ALESSI, J.; BEEBE-WANG, J. & AL., ET
Partner: UNT Libraries Government Documents Department

Observation of snake resonances at Relativistic Heavy Ion Collider

Description: The Siberian snakes are powerful tools in preserving polarization in high energy accelerators has been demonstrated at the Brookhaven Relativistic Heavy Ion Collider (RHIC). Equipped with two full Siberian snakes in each ring, polarization is preserved during acceleration from injection to 100 GeV. However, the Siberian snakes also introduce a new set of depolarization resonances, i.e. snake resonances as first discovered by Lee and Tepikian. The intrinsic spin resonances above 100 GeV are about a factor of two stronger than those below 100 GeV which raises the challenge to preserve the polarization up to 250 GeV. In 2009, polarized protons collided for the first time at the RHIC design store energy of 250 GeV. This paper presents the experimental measurements of snake resonances at RHIC. The plan for avoiding these resonances is also presented.
Date: September 27, 2010
Creator: Bai, M.; Ahrens, L.; Alekseev, I.G.; Alessi, J. & al, et
Partner: UNT Libraries Government Documents Department

First polarized proton collision at a beam energy of 250 GeV in RHIC

Description: After providing collisions of polarized protons at a beam energy of 100 GeV since 2001, the Relativistic Heavy Ion Collider (RHIC) at BNL had its first opportunity to collide polarized protons at its maximum beam energy of 250 GeV in the 2009 polarized proton operations. Equipped with two full Siberian snakes [1] in each ring, RHIC preserves polarization during acceleration from injection to 100 GeV with precise control of the betatron tunes and vertical orbit distortions. However, the strong intrinsic spin resonances beyond 100 GeV are more than two times stronger than those below 100 GeV, requiring much tighter tolerances on vertical orbit distortions and betatron tunes. With the currently achieved orbit correction and tune control, average polarizations of {approx_equal} 42% at top energy and average polarizations of {approx_equal} 55% at injection energy were achieved. Polarization measurements as a function of beam energy also indicated aU polarization losses occurred around three strong intrinsic resonances at 136 GeV, 199.3 GeV and 220.8 GeV Peak luminosity of 122 x 10{sup 30} cm{sup -2} s{sup -1} was also demonstrated. This paper presents the performance of the first RHIC 250 GeV operation and discusses the depolarization issues encountered during the run.
Date: May 4, 2009
Creator: Bai,M.; Ahrens, L.; Alekseev, I. G.; Alessi, J. & al., et
Partner: UNT Libraries Government Documents Department

Studies and proposed changes to the RHIC p-Carbon polarimeters for the upcoming RUN-11

Description: The RHIC polarized proton complex utilizes polarimeters in each of the Blue and Yellow beams that measure the beam polarization through the p-Carbon elastic scattering process in the Coulomb Nuclear Interference kinematic region. This along with a Polarized Hydrogen Jet Target that utilizes the proton-proton elastic scattering process to first measure the analyzing power of the reaction and using the reverse process to measure the beam polarization. The latter is used to calibrate the p-Carbon polarimeters at the desired beam energy. In Run 9 RHIC ran with beams at center-of-mass energies of 200 and 500 GeV respectively. The higher beam intensities as well as the fact that the 250 GeV beam size is much smaller than that at 100 GeV resulted in significantly higher rates seen by the polarimeters and led to observed instability. In this paper, we will discuss the problems encountered and the tests that were carried out using the AGS as a proxy in an attempt to solve the problems and the path forward we took towards the upcoming polarized proton Run11.
Date: September 27, 2010
Creator: Makdisi, Y.; Alekseev, I.; Aschenauer, E.; Atoian, G.; Bazilevsky, A.; Gill, R. et al.
Partner: UNT Libraries Government Documents Department

A NEW RELATIVE PROTON POLARIMETER FOR RHIC.

Description: An innovative polarimeter based on proton carbon elastic scattering in the Coulomb Nuclear Interference (CNI) region has been installed and commissioned in the Blue ring of RHIC during the first RHIC polarized proton commissioning in September, 2000. The polarimeter consists of ultra-thin carbon targets and four silicon detectors. All elements are in a 1.6 meter vacuum chamber. This paper summarizes the polarimeter design issues and recent commissioning results.
Date: June 18, 2001
Creator: HUANG,H.; ALEKSEEV,I.; BUNCE,G.; BRUNER,N.; DESHPANDE,A.; GOTO,Y. et al.
Partner: UNT Libraries Government Documents Department

A NEW RELATIVE PROTON POLARIMETER FOR RHIC.

Description: An innovative polarimeter based on proton carbon elastic scattering in the Coulomb Nuclear Interference (CNI) region has been installed and commissioned in the Blue ring of RHIC during the first RHIC polarized proton commissioning in September, 2000. The polarimeter consists of ultra-thin carbon targets and four silicon detectors. All elements are in a 1.6 meter vacuum chamber. This paper summarizes the polarimeter design issues and recent commissioning results.
Date: June 18, 2001
Creator: HUANG,H.; ALEKSEEV,I.; BUNCE,G.; BRUNER,N.; DESHPANDE,A.; GOTO,Y. et al.
Partner: UNT Libraries Government Documents Department

p-Carbon CNI polarimetry in the AGS and RHIC.

Description: Proton polarization measurements in the AGS (Alternate Gradient Synchrotron) and RHIC (Relativistic Heavy Ion Collider) are based on proton-carbon(pC) and proton-proton elastic scattering in the Coulomb Nuclear Interference (CNI) region. The CNI polarimeters are the essential tools for polarized proton acceleration setup and operation. High intensity recoil nuclei from the scattering of the circulating proton beam in the thin carbon target is efficiently utilized in the silicon strip detectors and data acquisition system, which is capable to analyze the event rate up to a few millions/second. This makes it possible for the fast, practically non-destructive polarization measurements. The polarization measurement on the beam energy ramp was implemented in AGS and RHIC, providing locations of polarization losses. Polarimeter operation in the scanning mode also gives polarization profile and beam profile (including bunch by bunch values for the later one). This paper summarizes the recent modifications. Results of polarization measurements are also discussed.
Date: June 23, 2008
Creator: Huang,H.; Alekseev, I.; Bazilevsky, A.; Bravar, A.; Bunce, G.; Dhawan, S. et al.
Partner: UNT Libraries Government Documents Department

Proton Polarimetry at the Relativistic Heavy Ion Collider

Description: The RHIC polarized proton collider employs polarimeters in each of the Blue and Yellow rings that utilize the analyzing power in p-Carbon elastic scattering in the Coulomb Nuclear Interference region to measure the absolute beam polarization. These are calibrated by the polarized Hydrogen Jet Target that measures the absolute beam polarization in pp elastic scattering in the CNI region. This paper describes the status and performance of these polarimeters in the FY09 run which included both a 250 GeV/c and 100 GeV/c physics data taking periods. We will describe some of the difficulties encountered and the efforts underway to improve the performance in better energy resolution, rate handling capability, and reduced systematic uncertainties.
Date: September 7, 2009
Creator: Makdisi, Y.; Aschenauer, E.; Atoian, G.; Bazilevsky, A.; Bunce, G.; Gill, R. et al.
Partner: UNT Libraries Government Documents Department

Run-08 pC polarization analysis - October 16, 2008

Description: In this note we will discuss the analysis of RHIC run 08 pC data that were collected during February 14 - March 10, 2008. An analysis method that is similar to Run 05 and Run 06 was adopted for Run 08 analysis (except few minor changes, which are described below). A detailed analysis note and a NIM article that describe the pC analysis procedure (for run 05 and run 06) can be found elsewhere. In brief, the analysis consists of calibrating the detectors, determining energy corrections ('dead layers'), determining good runs and extracting the polarization from data.
Date: March 1, 2009
Creator: Dharmawardane,V.; Bazilevsky,A.; Bunce, G.; Gill, R.; Huang, H.; Makdisi, Y. et al.
Partner: UNT Libraries Government Documents Department

ACCELERATING POLARIZED PROTONS TO HIGH ENERGY.

Description: The Relativistic Heavy Ion Collider (RHIC) is designed to provide collisions of high energy polarized protons for the quest of understanding the proton spin structure. Polarized proton collisions at a beam energy of 100 GeV have been achieved in RHIC since 2001. Recently, polarized proton beam was accelerated to 250 GeV in RHIC for the first time. Unlike accelerating unpolarized protons, the challenge for achieving high energy polarized protons is to fight the various mechanisms in an accelerator that can lead to partial or total polarization loss due to the interaction of the spin vector with the magnetic fields. We report on the progress of the RHIC polarized proton program. We also present the strategies of how to preserve the polarization through the entire acceleration chain, i.e. a 200 MeV linear accelerator, the Booster, the AGS and RHIC.
Date: October 2, 2006
Creator: Bai, M.; Ahrens, L.; Alekseev, I. G.; Alessi, J.; Beebe-Wang, J.; Blaskiewicz, M. et al.
Partner: UNT Libraries Government Documents Department

Run-09 pC polarimeter analysis

Description: Analysis of PC polarimeter data at {radical}s = 200 and 500 GeV from Run9 is presented. Final polarization results, fill-by-fill, for blue and yellow beams, as to be used by RHIC experiments (in collisions) are released and collected in http://www4.rcf.bnl.gov/cnipol/pubdocs/Run09Offline/. Global relative systematic uncertainties {delta}P/P (to be considered as correlated from fill to fill) are 4.7% for 100 GeV beams, and 8.3% (12.1%) for blue (yellow) 250 GeV beams. For a product of two beam polarizations P{sub B} {center_dot} P{sub Y} (used in double spin asymmetry measurements) the relative uncertainty {delta}(P{sub B} {center_dot} P{sub Y})/(P{sub B} {center_dot} P{sub Y}) 8.8% for 100 GeV beams and 18.5% for 250 GeV beams. For the average between two beam polarization (P{sub B} + P{sub Y})/2 (used in single spin asymmetry measurements, when data from two polarized beams are combined) the relative uncertainty is 4.4% for 100 GeV beams and 9.2% for 250 GeV beams. Larger uncertainties for 250 GeV beams relate to significant rate related systematic effects experienced in the first part of Run9 (due to thicker targets used and smaller trans. beam size at higher beam energy).
Date: August 1, 2010
Creator: Alekseev, I.; Aschenauer, E.; Atoyan, G.; Bazilevsky, A.; Gill, R.; Huang, H. et al.
Partner: UNT Libraries Government Documents Department

Run05 Proton Beam Polarization Measurements by pC-Polarimeter (ver. 1.1)

Description: The polarization of the proton beams [1, 2] at the Relativistic Heavy Ion Collider (RHIC)[3] RHIC ring. The H-Jet polarimeter is located at the collision point allowing measurements of absolute normalization is provided by the hydrogen polarimeter, which measures over 1 {approx} 2 another measurement rather than measuring the absolute polarization. both beams. Two identical pC-polarimeters are equipped in the yellow and blue rings, where carbon ribbon target, providing fast feedback to beam operations and experiments. The days to obtain {approx} 5% statistical uncertainty (in Run05). Thus, the operation of the carbon is measured using both an atomic beam source hydrogen gas jet (H-Jet)[4, 5] and proton-carbon polarimeters was focused on better control of relative stability between one measurement to statistical accuracy within 20 to 30 seconds using an ultra-thin (typically 6 {approx} 8 {micro}g/cm{sup 2}) the rings are separated. The pC-polarimeter measures relative polarization to a few percent.
Date: July 1, 2008
Creator: Nakagawa,I.; Alekseev, I.; Bazilevsky, A.; Bravar, A.; Bunce, G.; Dhawan, S. et al.
Partner: UNT Libraries Government Documents Department

POLARIZED PROTON OPERATIONS IN THE AGS AND RHIC.

Description: Polarized proton beam has been accelerated and stored at 100 GeV in Relativistic Heavy Ion Collider (RHIC) to study spin effects in the hadronic reactions. The essential equipment includes four Siberian snakes and eight spin rotators in two RHIC rings, a partial snake in the AGS, fast relative polarimeters, and ac dipoles in the AGS and RHIC. This paper summarizes the performance of RHIC as a polarized proton collider and of AGS as the injector to RHIC.
Date: May 12, 2003
Creator: HUANG,H.; AHRENS,L.; BAI,M.; BEEBE-WANG,J.; ALESSI,J.; ALEKSEEV,I. et al.
Partner: UNT Libraries Government Documents Department

RHIC Polarized proton operation

Description: The Relativistic Heavy Ion Collider (RHIC) operation as the polarized proton collider presents unique challenges since both luminosity(L) and spin polarization(P) are important. With longitudinally polarized beams at the experiments, the figure of merit is LP{sup 4}. A lot of upgrades and modifications have been made since last polarized proton operation. A 9 MHz rf system is installed to improve longitudinal match at injection and to increase luminosity. The beam dump was upgraded to increase bunch intensity. A vertical survey of RHIC was performed before the run to get better magnet alignment. The orbit control is also improved this year. Additional efforts are put in to improve source polarization and AGS polarization transfer efficiency. To preserve polarization on the ramp, a new working point is chosen such that the vertical tune is near a third order resonance. The overview of the changes and the operation results are presented in this paper. Siberian snakes are essential tools to preserve polarization when accelerating polarized beams to higher energy. At the same time, the higher order resonances still can cause polarization loss. As seen in RHIC, the betatron tune has to be carefully set and maintained on the ramp and during the store to avoid polarization loss. In addition, the orbit control is also critical to preserve polarization. The higher polarization during this run comes from several improvements over last run. First we have a much better orbit on the ramp. The orbit feedback brings down the vertical rms orbit error to 0.1mm, much better than the 0.5mm last run. With correct BPM offset and vertical realignment, this rms orbit error is indeed small. Second, the jump quads in the AGS improved input polarization for RHIC. Third, the vertical tune was pushed further away from 7/10 snake resonance. The tune feedback maintained the ...
Date: March 28, 2011
Creator: Huang, H.; Ahrens, L.; Alekseev, I.G.; Aschenauer, E.; Atoian, G.; Bai, M. et al.
Partner: UNT Libraries Government Documents Department