M. Okamura

Large analyzing power in inclusive π± production at high xF with a 22-GeV/c polarized proton beam

The analyzing power, AN, in inclusive charged-pion production has been measured using a ∼22-GeV/c transversely-polarized proton beam on a carbon target. A large AN was found for xF>0.5 and for 0.6<pT<1.2 GeV/c, with similar magnitudes and opposite sign for π+ and π−. This mirror behavior and the magnitudes are similar to π± production from 200-GeV/c polarized protons on a hydrogen target. The analyzing power for inclusive proton production has also been measured and is consistent with zero.

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 Brookhaven National Laboratory electron beam ion source for RHIC

As part of a new heavy ion preinjector that will supply beams for the Relativistic Heavy Ion Collider and the National Aeronautics and Space Administration Space Radiation Laboratory, construction of a new electron beam ion source (EBIS) is now being completed. This source, based on the successful prototype Brookhaven National Laboratory Test EBIS, is designed to produce milliampere level currents of all ion species, with q/m=(1/6)-(1/2). Among the major components of this source are a 5 T, 2-m-long, 204 mm diameter warm bore superconducting solenoid, an electron gun designed to operate at a nominal current of 10 A, and an electron collector designed to dissipate approximately 300 kW of peak power. Careful attention has been paid to the design of the vacuum system, since a pressure of 10(-10) Torr is required in the trap region. The source includes several differential pumping stages, the trap can be baked to 400 C, and there are non-evaporable getter strips in the trap region. Power supplies include a 15 A, 15 kV electron collector power supply, and fast switchable power supplies for most of the 16 electrodes used for varying the trap potential distribution for ion injection, confinement, and extraction. The EBIS source and all EBIS power supplies sit on an isolated platform, which is pulsed up to a maximum of 100 kV during ion extraction. The EBIS is now fully assembled, and operation will be beginning following final vacuum and power supply tests. Details of the EBIS components are presented.

Nd-YAG laser ion source for direct injection scheme

The feasibility of a “direct injection scheme” using Nd–yttritium–aluminum–garnet laser has been studied experimentally. The relationship between charge distribution and laser power density was measured. The obtained yield rate of C6+ was 46.8% at the peak current pulse with 1.6×1011 W/cm2 laser intensity. The current dependence of the distance from the target at this intensity was measured. The peak current of C6+ will be 60 mA with φ4.8 mm extraction aperture. It was found from the input beam condition simulation by the code PTEQ–HI that high current (from 12 to 28.6 mA) can be accelerated by the TIT–RFQ.

Magnetic plasma confinement for laser ion source

A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.

Simulation of direct injection scheme for RFQ linac

A new efficient injection method from a laser ion source to a RFQ was proposed and is being tested in RIKEN (The Institute of Physical and Chemical Research, Japan). Laser plasma is induced just before the entrance of the RFQ and is injected directly into the RFQ channel. In order to understand this new scheme, a particle tracking simulation study, which focused on the entrance of the RFQ, has been started with three-dimensional (3D) space charge effect in a realistic 3D electric field map. According to the beam tracking calculation, the predicted currents are smaller than experimentally obtained values. To obtain better accuracy of the simulation, motion of electrons should be described adequately.

Scheme for direct plasma injection into an RFQ linac

A new efficient injection method from a laser ion source to a Radio Frequency Quadropole (RFQ) was proposed and is being tested in RIKEN, Japan. A laser plasma is induced just before the entrance of the RFQ and is injected directly into the RFQ channel. Using an existing RFQ, first verification tests have been completed successfully. Finally, the preliminary specifications for the first RFQ dedicated to the new injection scheme are presented.

ACCELERATION OF POLARIZED BEAMS USING MULTIPLE STRONG PARTIAL SIBERIAN SNAKES

Acceleration of polarized protons in the energy range of 5 to 25 GeV is particularly difficult since depolarizing spin resonances are strong enough to cause significant depolarization but full Siberian snakes cause intolerably large orbit excursions. Using a 20 - 30 % partial Siberian snake both imperfection and intrinsic resonances can be overcome. Such a strong partial Siberian snake was designed for the Brookhaven AGS using a dual pitch helical superconducting dipole. Multiple strong partial snakes are also discussed for spin matching at beam injection and extraction.

Measurement of the laser plasma properties of the direct plasma injection method to the RFQ LINAC on the RIKEN laser ion source

The laser plasma properties of the RIKEN laser ion source on the direct plasma injection system (DPIS) were measured for analysis of the DPIS beam dynamics. From the installed electrostatic analyzer and the measured calibration value from Ceratron to Faraday Cup, the current values and pulse time structure for each carbon charge state in the laser plasma were obtained.

Laser ion source with solenoid field

Pulse length extension of highly charged ion beam generated from a laser ion source is experimentally demonstrated. The laser ion source (LIS) has been recognized as one of the most powerful heavy ion source. However, it was difficult to provide long pulse beams. By applying a solenoid field (90 mT, 1 m) at plasma drifting section, a pulse length of carbon ion beam reached 3.2 μs which was 4.4 times longer than the width from a conventional LIS. The particle number of carbon ions accelerated by a radio frequency quadrupole linear accelerator was 1.2 × 1011, which was provided by a single 1 J Nd-YAG laser shot. A laser ion source with solenoid field could be used in a next generation heavy ion accelerator.