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Heavy Flavor Measurements at RHIC in the Near Future

Description: We discuss the recent results on open charm measurements at RHIC. The heavy flavor upgrade program for both PHENIX and STAR experiments are briefly discussed. The completion of the program will yield important information on light flavor thermalization of the partonic matter created in high-energy nuclear collisions at RHIC. A new era of RHIC is ahead of us with the progress of the upgrade program.
Date: December 1, 2006
Creator: Xu, Nu
Partner: UNT Libraries Government Documents Department

TRANSVERSE IMPEDANCE MEASUREMENT AT THE RHIC.

Description: The RHIC transverse impedance was measured during the last operation run. Measurement of the imaginary part of the broadband impedance was the main goal. No large difference between the two rings was found nor in either plane. The measured tune shift is larger than the expected by a factor of 2.5 to 3. Several other issues such as the real part impedance measurement are also presented.
Date: June 2, 2002
Creator: ZHANG,S.Y.; HUANG,H.; CAMERON,P.; DREES,A.; FLILLER,R. & SATOGATA,T.
Partner: UNT Libraries Government Documents Department

RHIC ABORT KICKER WITH REDUCED COUPLING IMPEDANCE.

Description: Kicker magnets typically represent the most important contributors to the transverse impedance budget of accelerators and storage rings. Methods of reducing the impedance value of the SNS extraction kicker presently under construction and, in view of a future performance upgrade, that of the RHIC abort kicker have been thoroughly studied at this laboratory. In this paper, the investigation of a potential improvement from using ferrite different from the BNL standard CMD5005 is reported. Permeability measurements of several ferrite types have been performed. Measurements on two kicker magnets using CMD5005 and C2050 suggest that the impedance of a magnet without external resistive damping, such as the RHIC abort kicker, would benefit.
Date: June 2, 2002
Creator: HAHN,H. & DAVINO,D.
Partner: UNT Libraries Government Documents Department

RHIC BPM SYSTEM PERFORMANCE, UPGRADES, AND TOOLS.

Description: During the RHIC 2001-2 run, the beam position monitor (BPM) system provided independent average orbit and turn-by-turn (TBT) position measurements at 162 locations in each measurement plane and RHIC ring. TBT acquisition was successfully upgraded from 128 turns to 1024 turns per trigger, including injection. Closed orbits were acquired and automatically archived every two seconds through each acceleration ramp for orbit analysis and feed-forward orbit correction. This paper presents the overall system performance during this run, including precision, reproducibility, radiation damage, and analysis tools. We also summarize future plans, including million-turn TBT acquisition for nonlinear dynamics studies.
Date: June 2, 2002
Creator: SATOGATA,T.; CAMERON,P.; CERNIGLIA,P.; CUPOLO,J.; DAWSON,C.; DEGEN,C. et al.
Partner: UNT Libraries Government Documents Department

ACCELERATING AND COLLIDING POLARIZED PROTONS IN RHIC WITH SIBERIAN SNAKES.

Description: We successfully injected polarized protons in both RHIC rings and maintained polarization during acceleration up to 100 GeV per ring using two Siberian snakes in each ring. Each snake consists of four helical superconducting dipoles which rotate the polarization by 180{sup o} about a horizontal axis. This is the first time that polarized protons have been accelerated to 100 GeV. We report on our experiences during commissioning and operation of collider with polarized protons.
Date: June 2, 2002
Creator: ROSER,T.; AHRENS,L.; ALESSI,J.; BAI,M.; BEEBE - WANG,J.; BRENNAN,J.M. et al.
Partner: UNT Libraries Government Documents Department

A STATE VARIABLE DESCRIPTION OF THE RHIC RF CONTROL LOOPS.

Description: The beam transfer function changes during the RHIC ramp. The response of the RF control loops changes as a result. A state-variable description of the beam and the RF control loops was developed. This description was used to generate a set of feedback matrices that keeps the response of the RF control loops constant during the ramp. This paper describes the state-variable description and its use in determining the K matrices.
Date: June 2, 2002
Creator: SCHULTHEISS,C. & BRENNAN,J.M.
Partner: UNT Libraries Government Documents Department

LINEAR OPTICS DURING THE RHIC 2001 - 2 RUN.

Description: The RHIC 2001-2 Au and polarized proton runs used several different low-beta optics configurations. Low-beta squeezes were routinely performed through the Au acceleration ramp to optimize injection and transition optics; the polarized proton run injected and accelerated with constant low-beta optics to optimize polarization preservation. This paper summarizes tools, methods and results for linear optics measurement and correction during these runs as well as future plans.
Date: June 2, 2002
Creator: SATOGATA,T.; CARDONA,J.; PTITSYN,V.; TEPIKIAN,S. & VAN ZEIJTS,J.
Partner: UNT Libraries Government Documents Department

MEASUREMENTS OF MECHANICAL TRIPLET VIBRATIONS IN RHIC.

Description: Mechanical vibrations of the RHIC interaction region triplets has been identified as the dominant source of orbit jitter for frequencies up to 20 Hz. We report the results of detailed measurements that were performed to characterize these effects. We discuss the impact on beam dynamics and possible cures.
Date: June 2, 2002
Creator: MONTAG,C.; BRENNAN,M.; BUTLER,J.; BONATI,R. & KOELLO,P.
Partner: UNT Libraries Government Documents Department

REAL TIME BETATRON TUNE CONTROL IN RHIC.

Description: Precise control of the betatron tunes is necessary to preserve proton polarization during the RHIC ramp. In addition, control of the tunes during beam deceleration is necessary due to hysteresis in the superconducting magnets. A real-time feedback system to control the betatron tunes during ramping has been developed for use in RHIC. This paper describes this system and presents the results from commissioning the system during the polarized proton run.
Date: June 2, 2002
Creator: SCHULTHEISS,C.; CAMERON,P.; MARUSIC,A. & VAN ZEIJTS,J.
Partner: UNT Libraries Government Documents Department

SNAKE CALIBRATION IN RHIC.

Description: A proper understanding of the response of the spin orientation due to the currents in the four helices which make up each snake is necessary to control spin tune, avoid snake resonances and facilitate the operation of the RHIC spin flipper. The effect of the helical dipole snakes in RHIC is to rotate the spin orientation an angle {mu} about an axis at an angle {phi} in the horizontal plane. With two snakes the combined effect gives rise to a spin precession frequency which is determined by the {mu} and {phi} angles at each snake. Depolarization or spin flipping can occur when this spin tune is near an external driving frequency. We employed the RHIC spin flipper in this way to determine the spin tune and thus verify spin tune predictions based upon previous field measurements of the snake. We also considered the response of snake resonances locations to spin tune as another way of verifying spin tune predictions.
Date: June 2, 2002
Creator: RANJBAR,V.; BAI,M.; LUCCIO,A.; MACKAY,W.W.; ROSER,T. & LEET,S.Y.
Partner: UNT Libraries Government Documents Department

Rf systems for RHIC

Description: The RHIC rf systems must capture the injected beam, accelerate it through transition to top energy, shorten the bunches prior to rebucketing, and store the beam for 10 hours in the presence of strong intra-beam scattering. These different functions are met by three independent systems. An accelerating system at 26.7 Mhz (h = 342), a storage system at 196.1 MHz (h = 2508), and a wideband system for the damping of injection efforts.
Date: May 1, 1995
Creator: Rose, J.; Brodowski, J.; Connolly, R.; Deng, D.P.; Kwiatkowski, S.; Pirkl, W. et al.
Partner: UNT Libraries Government Documents Department

Possible origin of RHIC R{sub out}/R{sub sid} HBT results

Description: The effects of opacity of the nuclei together with a blackbody type of emission along the system history are considered as a means to explain the ratio R{sub out}=R{sub sid} observed by STAR and PHENIX collaborations at RHIC. Within our model, no flow is required to explain the data trend of this ratio for large surface emissivities.
Date: September 30, 2002
Creator: Padula, Sandra S.
Partner: UNT Libraries Government Documents Department

Longitudinal Stability Calculations

Description: Coupled bunch longitudinal stability in the presence of high frequency impedances is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the new 56 MHz RF system.
Date: January 2, 2009
Creator: Blaskiewicz,M.
Partner: UNT Libraries Government Documents Department

HOTTER, SMALLER, DENSER, FASTER...AND NEARLY-PERFECT: WHAT IS THE MATTER AT RHIC?

Description: The experimental and theoretical status of the ''near perfect fluid'' at RHIC is discussed. While the hydrodynamic paradigm for understanding collisions at RHIC is well established, there remain many important open questions to address in order to understand its relevance and scope. It is also a crucial issue to understand how the early equilibration is achieved, requiring insight into the active degrees of freedom at early times.
Date: July 3, 2006
Creator: STEINBERG,P.
Partner: UNT Libraries Government Documents Department

ELECTRON CLOUD OBSERVATIONS AND CURES IN RHIC.

Description: Since 2081 MIC has experienced electron cloud effects, which have limited the beam intensity. These include dynamic pressure rises - including pressure instabilities, tune shifts: electrons, a reduction of the stability threshold for bunches crossing the transition energy, and possibly slow emittance growth. We summarize the main observations in operation and dedicated experiments, as well as countermeasures including baking, NEG coated warm beam pipes, solenoids, bunch patterns, anti-grazing rings, pre-pumped cold beam pipes, and scrubbing.
Date: March 1, 2007
Creator: FISCHER,W.; BLASKIEWICZ, M.; HUAN, H.; HSEUH, H.C.; PTITSYN, V.; ROSER, T. et al.
Partner: UNT Libraries Government Documents Department

Energy Scaling of Spin Tune due to RHIC Snakes

Description: For a ring like RHIC with two full Siberian snakes on opposite sides of the ring, the spin tune for a flat orbit will be 1/2 if the snake rotation axes are perpendicular, {Delta}{phi} = {phi}{sub 9}-{phi}{sub 3} = {pi}/2. Here {phi}{sup 9} and {phi}{sub 3} are respectively the direction of the rotation axes of the 9 o'clock and 3 o'clock snakes relative to the design trajectory as shown in Figure 1. If the two snakes are slightly detuned by the same amount such that the rotation axes are no longer perpendicular, then the deviation of the closed-orbit spin tune {nu}{sub 0} from 1/2 is given by {Delta}{nu}{sub 0} {approx_equal} ({Delta}{mu}){sup 2}/4{pi} cosG{gamma}{pi} - 2{Delta}{phi}/{pi} {approx_equal} 2{Delta}{phi}/180{sup o} with G{gamma} at a half integer, and where {Delta}{mu} is the deviation of snake rotation angle from 180{sup o}. It should be noted that there is a sign ambiguity in {Delta}{mu}{sub 0} since a spin tune of 0.495 is also a spin tune of 0.505, depending on the direction taken along the stable spin axis. In order to understand the effect of energy scaling on the snake axis direction, I have integrated the trajectory and spin rotation through a model of a RHIC snake (bi9-snk7) and found the energy (U) dependence of the snake axis angle {phi}{sub 9} and rotation angle {mu} as shown. A {approx_equal} p{sup -2} scaling of errors is typical in helical snakes. To first order, the orbit excursion drops as p{sup -1} and the spin precessions about transverse fields increase as {gamma} giving an approximate cancellation with energy, so we do not expect much change during the field ramp. The next order term which comes in is primarily proportional to p{sup -2}; although naively one might expect a slight effect inversely proportional to the velocity since {gamma}/p {proportional_to} ...
Date: January 2, 2009
Creator: MacKay,W.W.
Partner: UNT Libraries Government Documents Department

Two photon physics at RHIC

Description: Because the two photon cross section is proportional to Z{sup 4}, heavy ion colliders offer an unmatched luminosity. However, because nuclei have finite sizes, the photon spectrum is gradually cut off by a nuclear form factor. For RHIC, this cutoff occurs at a few GeV; below this energy, RHIC will have the highest {gamma}{gamma} luminosity in the world when it turns on. In addition to the high rates, because Z{alpha} {approximately} 0.6, the nuclear environment provides a window to strong field QED and new phenomena like multiple pair production. To study {gamma}{gamma} physics, regions where the nuclei interact hadronically must be avoided; this leads to roughly a factor of two loss in usable luminosity. The rates expected by the Solenoidal Tracker at RHIC (STAR) collaboration will be given. Backgrounds will be discussed, along with several rejection techniques.
Date: May 1, 1995
Creator: Klein, S.
Partner: UNT Libraries Government Documents Department

Numerical studies of Siberian snakes and spin rotators for RHIC

Description: For the program of polarized protons in RHIC, two Siberian snakes and four spin rotators per ring will be used. The Snakes will produce a complete spin flip. Spin Rotators, in pairs, will rotate the spin from the vertical direction to the horizontal plane at a given insertion, and back to the vertical after the insertion. Snakes, 180{degrees} apart and with their axis of spin precession at 90{degrees} to each other, are an effective means to avoid depolarization of the proton beam in traversing resonances. Classical snakes and rotators are made with magnetic solenoids or with a sequence of magnetic dipoles with fields alternately directed in the radial and vertical direction. Another possibility is to use helical magnets, essentially twisted dipoles, in which the field, transverse the axis of the magnet, continuously rotates as the particles proceed along it. After some comparative studies, the authors decided to adopt for RHIC an elegant solution with four helical magnets both for the snakes and the rotators proposed by Shatunov and Ptitsin. In order to simplify the construction of the magnets and to minimize cost, four identical super conducting helical modules will be used for each device. Snakes will be built with four right-handed helices. Spin rotators with two right-handed and two left-handed helices. The maximum field will be limited to 4 Tesla. While small bore helical undulators have been built for free electron lasers, large super conducting helical magnets have not been built yet. In spite of this difficulty, this choice is dictated by some distinctive advantages of helical over more conventional transverse snakes/rotators: (i) the devices are modular, they can be built with arrangements of identical modules, (ii) the maximum orbit excursion in the magnet is smaller, (iii) orbit excursion is independent from the separation between adjacent magnets, (iv) they allow ...
Date: April 17, 1995
Creator: Luccio, A.
Partner: UNT Libraries Government Documents Department