S. Peggs

Polarized proton collider at RHIC

Abstract In addition to heavy ion collisions (RHIC Design Manual, Brookhaven National Laboratory), RHIC will also collide intense beams of polarized protons (I. Alekseev, et al., Design Manual Polarized Proton Collider at RHIC, Brookhaven National Laboratory, 1998 [2]), reaching transverse energies where the protons scatter as beams of polarized quarks and gluons. The study of high energy polarized protons beams has been a long term part of the program at BNL with the development of polarized beams in the Booster and AGS rings for fixed target experiments. We have extended this capability to the RHIC machine. In this paper we describe the design and methods for achieving collisions of both longitudinal and transverse polarized protons in RHIC at energies up to s =500 GeV .

The RHIC design overview

The salient performance objectives for the Relativistic Heavy Ion Collider (RHIC) are presented and the rationale for the design choices of the major collider systems is conveyed. RHIC provides collisions of heavy ions covering the entire mass range from protons to gold. For the prototypical case of Au-on-Au, one obtains energies up to 100 GeV/n per beam and luminosities of B2 � 10 26 cm � 2 s � 1 , averaged over a 10-h storage time. Operation with polarized protons is also possible. The overall accelerator complex used for gold ions consists of the Tandem Van de Graaff, the Booster, the AGS, and the Collider itself, and the scenario for the beam transfer between machines is described. The two separate collider rings cross at six interaction points, where the lattice design provides low-beta insertions for maximum luminosity. The interaction diamond length of o20 cm rms is achieved by bunched beam operation and holding the 56 bunches in a 197 MHz radio-frequency (RF) system after their acceleration in a 28 MHz RF system. The rings are constructed with superconducting magnets, which have a cold bore aperture of 6.9 cm in the arcs. The RHIC specific design challenges posed by intrabeam scattering of heavy ions, passage through transition energy with slow-ramping superconducting magnets, and control of magnetic errors in the low-beta triplet quadrupoles are addressed. r 2002 Elsevier Science B.V. All rights reserved.

Beyond the LHC: a conceptual approach to a future high energy hadron collider

The concept of a post LHC hadron collider operating in the radiation damping regime was discussed in the DPF workshop on future hadron facilities. To date, hadron colliders have all operated in a state of insignificant damping, where phase space dilution from any source results in a costly degradation of instantaneous and thus integrated luminosity. The concept of using radiation damping to enhance the integrated luminosity results in an effective decoupling of the machine performance from the initial beam parameters. By relying more heavily on the damping mechanism, the requirements for tight emittance control through the injector chain and during the collider fill process can be relaxed allowing for less stringent injection field quality and the possibilities for looser tolerances in many other aspects of the machine. In this paper we present some generic parameters and machine characteristics before examining options for lengthening the standard cell (quadrupole and spool piece reduction) and highly lumped correction schemes (correction element reduction).

Helical dipole magnets for polarized protons in RHIC

Superconducting helical dipole magnets will be used in the Brookhaven Relativistic Heavy Ion Collider (RHIC) to maintain polarization of proton beams and to perform localized spin rotations at the two major experimental detector regions. Requirements for the helical dipole system are discussed, and magnet prototype work is reported.

Field quality evaluation of the superconducting magnets of the Relativistic Heavy Ion Collider

In this paper, we first present the procedure established to evaluate the field quality, quench performance, and alignment of the superconducting magnets manufactured for the Relativistic Heavy Ion Collider (RHIC), and then discuss the strategies used to improve the field quality and to minimize undesirable effects by sorting the magnets. The field quality of the various RHIC magnets is briefly summarized.

R&D towards cooling of the RHIC collider

We introduce the R&D program for electron-cooling of the Relativistic Heavy Ion Collider (RHIC). This electron cooler is designed to cool 100 GeV/nucleon bunched-beam ion collider at storage energy using 54 MeV electrons. The electron source will be an RF photocathode gun. The accelerator will be a superconducting energy recovery linac. The frequency of the accelerator is set at 703.75 MHz. The maximum bunch frequency is 28.15 MHz, with bunch charge of 10 nC. The R&D program has the following components: The photoinjector, the superconducting linac, start-to-end beam dynamics with magnetized electrons, electron cooling calculations and development of a large superconducting solenoid.

Focusing and matching properties of the AtR transfer line

The AGS to RHIC (AtR) beam transfer line has been constructed and will be used to transfer beam bunches from the AGS machine into the RHIC machine which is presently under construction at BNL. The original design of the AtR line has been modified. This article presents the optics of the various sections of the existing AtR beam line, as well as the matching capabilities of the AtR line to the RHIC machine.

Alignment and survey of the elements in RHIC

The Relativistic Heavy Ion Collider (RHIC) consists of two rings with cryogenic magnets at a 4.5 K operating temperature. Control of positions of the dipole and quadrupole cold masses (iron laminations) and the beam position monitors (BPMs) during production and installation is presented. The roll of the dipoles is controlled by a combination of rotating coil measurements with the surveying measurements. The center of the quadrupole magnetic field is obtained by direct measurement of the field shape within a colloidal cell placed inside the quadrupoles. Special attention is given to the triplet quadrupole alignment and determination of the field center position.

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.

Simulation of proton therapy treatment verification via PET imaging of induced positron-emitters

Earlier works, including a recent one at BNL, demonstrated that PET is a promising technique to verify the dose distribution of proton therapy, which is increasingly used in radiation oncology because the dose conforms more tightly to the tumor than common x-ray radiation therapy. Proton therapy produces positron-emitting isotopes along the beam path, allowing the therapy dose distribution to be imaged by PET as a form of quality assurance of the treatment. This is especially important when treating inhomogeneous organs such as the lungs or the head-and-neck, where the calculation of the expected dose distribution for treatment planning is more difficult. In this paper, we present Monte Carlo simulations of the yield of positron emitters produced by proton beams up to 250 MeV, followed by statistically realistic Monte Carlo simulation of the images expected from a clinical PET scanner. The emphasis of this study is to accurately predict the positron emitter distribution and to determine the quality of the PET signal in the region near the Bragg peak which is critical to the success of PET imaging for verification of proton beam location and dosimetry. In this paper, we also demonstrate that the image results depend strongly on the available nuclear reaction cross section data. We determine quantitatively the differences in the calculated positron emitter yields resulting from four different sets of input nuclear reaction cross section data. They are compared to the simulated distributions of positron emitter productions and absorbed proton energies.