L. Ahrens

Commissioning of RHIC deuteron-gold collisions

Deuteron and gold beams have been accelerated to a collision energy of /spl radic/s = 200 GeV/u in the Relativistic Heavy Ion Collider (RHIC), providing the first asymmetric-species collisions of this complex. Necessary changes for this mode of operation include new ramping software and asymmetric crossing angle geometries. This paper reviews machine performance, problems encountered and their solutions, and accomplishments during the 16 weeks of ramp-up and operations.

High intensity performance of the Brookhaven AGS

The Brookhaven AGS provides 24 GeV protons for a multi-user program of fixed-target high energy physics experiments, such as the study of extremely rare kaon decays. Up to 7/spl times/10/sup 13/ protons are slowly extracted over 2.2 seconds each 5.1 seconds. The muon storage ring of the g-2 experiment is supplied with bunches of 7/spl times/10/sup 12/ protons. Since the completion of the a 1.9 GeV Booster synchrotron and installation of a new high-power RF system and transition jump system in the AGS various modes of operation have been explored to overcome space charge limits and beam instabilities at these extreme beam intensities. Experiments have been done using barrier cavities to enable accumulation of de-bunched beam in the AGS as a potential path to significantly higher intensities. We report on the present understanding of intensity limitations and prospects for overcoming them.

RHIC challenges for low energy operations

There is significant interest in RHIC heavy ion collisions at radics =5-50 GeV/u, motivated by a search for the QCD phase transition critical point. The lowest energies are well below the nominal RHIC gold injection radics = 19.6 GeV/u. There are several challenges that face RHIC operations in this regime, including longitudinal acceptance, magnet field quality, lattice control, and luminosity monitoring. We report on the status of work to address these challenges, including results from beam tests of low energy RHIC operations with protons and gold.

Status and recent performance of the accelerators that serve as gold injector for RHIC

The recent successful commissioning and operation of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) requires the injection of gold ions of specified energy and intensity with longitudinal and transverse emittances small enough to meet the luminosity requirements of the collider. Ion beams with the desired characteristics are provided by a series of three accelerators, the Tandem, Booster and AGS. The current status and recent performance of these accelerators are reviewed in this paper.

Commissioning and future plans for polarized protons in RHIC

Polarized protons were injected and accelerated in the clockwise ring of RHIC to commission the first full helical Siberian snake ever used in an accelerator. With the snake turned on, the stable spin direction is in the horizontal plane. Vertically polarized protons were injected with the snake off. The snake was adiabatically ramped to give a spin rotation of 180/spl deg/ around a horizontal rotation axis about 13/spl deg/ from the longitudinal. When the beam was accelerated from injection G/spl gamma/ = 46.5 to G/spl gamma/ = 48 the spin flipped sign as expected and polarization was preserved. At G/spl gamma/ = 48 without the snake, no polarization was observed since several spin resonances were crossed. Eventually polarized beam was accelerated to G/spl gamma/ = 55.7 (29.1 GeV). In the next proton running period we plan to run with two full helical snakes in each ring and collide both transversely and longitudinally polarized protons at an energy around 100 GeV per beam.

RHIC sextant test: accelerator systems and performance

One sextant of the RHIC Collider was commissioned in early 1997 with beam. We describe here the performance of the accelerator systems during the test, such as the magnet and power supply systems, instrumentation subsystems and application software. We also describe a ramping test without beam that took place after the commissioning with beam. Finally, we analyze the implications of accelerator systems performance and their impact on the planning for RHIC installation and commissioning.

Operations and Performance of RHIC as a Cu-Cu Collider

The 5thyear of RHIC operations, started in November 2004 and expected to last till June 2005, consists of a physics run with Cu-Cu collisions at 100 GeV/u followed by one with polarized protons (pp) at 100 GeV [1]. We will address here the overall performance of the RHIC complex used for the first time as a Cu-Cu collider, and compare it with previous operational experience with Au, PP and asymmetric d-Au collisions. We will also discuss operational improvements, such as a squeeze to 85cm in the high luminosity interaction regions from the design value of 1m, system improvements, machine performance and limitations, and address reliability and uptime issues.

Commissioning spin rotators in RHIC

During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC in order to control the polarization directions independently at the STAR and PHENIX experiments. Without the rotators, the orientation of polarization at the interaction points would only be vertical. With four rotators around each of the two experiments, we can rotate either or both beams from vertical into the horizontal plane through the interaction region and then back to vertical on the other side. This allows independent control for each beam with vertical, longitudinal, or radial polarization at the experiment. In this paper, we present results from the first run using the new spin rotators at PHENIX.

Commissioning results of slow extraction of heavy ions from the AGS Booster

Brookhavens AGS Booster has been modified to deliver slow extracted beam to a new beam line, the NASA Space Radiation Laboratory (NSRL). This facility was constructed in collaboration with NASA for the purpose of performing radiation effect studies for the NASA space program. The design of the resonant extraction system has been described. A more detailed description, which includes predictions of the slow extracted beam time structure has been described. In this report we present results of the system commissioning and performance.

High intensity proton operations at Brookhaven

In 1995 the AGS upgrade met its design goal of 60 TP (1 TP=10/sup 12/ protons) per pulse, made possible by significant improvements in the AGS Booster and AGS. We summarize these improvements and outline strategies for future upgrades.