C. Gardner

Accumulator ring design for the NSNS project

The goal of the proposed National Spallation Neutron Source (NSNS) is to provide a short pulse proton beam of about 0.5 /spl mu/s with average beam power of 1 MW. To achieve such purpose, a proton storage ring operated at 60 Hz with 1/spl times/10/sup 14/ protons per pulse at 1 GeV is required. The Accumulator Ring (AR) receives 1 msec long H/sup -/ beam bunches of 28 mA from a 1 GeV linac. Scope and design performance goals of the AR are presented, other possible technological choices and design options considered, but not adopted, are also briefly reviewed.

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.

Polarized Proton Acceleration in the AGS with Two Helical Partial Snakes

Acceleration of polarized protons in the energy range of 5 to 25 GeV is particularly difficult: the depolarizing resonances are strong enough to cause significant depolarization but full Siberian snakes cause intolerably large orbit excursions and are not feasible in the AGS since straight sections are too short. Recently, two helical partial snakes have been built and installed in the AGS. With careful setup of optics at injection and along the ramp, this combination can eliminate the intrinsic and imperfection depolarizing resonances encountered during acceleration. This paper presents the accelerator setup and preliminary results.

Commissioning the Polarized Beam in the AGS

After the successful operation of a high energy polarized proton beam at the Argonne Laboratory Zero Gradient Synchrotron (ZGS) was terminated, plans were made to commission such a beam at the Brookhaven National Laboratory Alternating Gradient Synchrotron (AGS). On February 23, 1984, 2 ..mu..A of polarized H/sup -/ was accelerated through the Linac to 200 MeV with a polarization of about 65%. 1 ..mu..A was injected into the AGS and acceleration attempts began. Several relatively short runs were then made during the next three months. Dedicated commissioning began in early June, and on June 26 the AGS polarized beam reached 13.8 GeV/c to exceed the previous ZGS peak momentum of 12.75 GeV/c. Commissioning continued to the point where 10/sup 10/ polarized protons were accelerated to 16.5 GeV/c with 40% polarization. Then, two experiments had a short polarized proton run. We plan to continue commissioning efforts in the fall of this year to reach higher energy, higher intensity, and higher polarization levels. We present a brief description of the facility and of the methods used for preserving the polarization of the accelerating beam.

Accumulator Ring lattice for the National Spallation Neutron Source

The Accumulator Ring for the proposed National Spallation Neutron Source (NSNS) is to accept a 1.03 millisecond beam pulse from a 1 GeV proton linac at a repetition rate of 60 Hz. For each beam pulse, 10/sup 14/ protons are to be accumulated via charge-exchange injection. A 295 nanosecond gap in the beam, maintained by an RF system, will allow for extraction to an external target for the production of neutrons by spallation. This paper describes the four-fold symmetric lattice that has been chosen for the ring. The lattice contains four long dispersion-free straight sections to accommodate injection, extraction, RF cavities, and beam scraping respectively. The four-fold symmetry allows for easy adjustment of the tunes and flexibility in the placement of correction elements, and ensures that potentially dangerous betatron structure resonances are avoided.

Generalized emittance measurements in a beam transport line

A generalized emittance-measurement program has been developed. Beam line specifics are entirely resident in data tables, not in program code. For instrumentation, the program requires one or more multiwire profile monitors; one or multiple profiles are acquired from each monitor, corresponding to one or multiple tunes of the transport line. Emittances and Twiss parameters are calculated using generalized algorithms. The required matrix descriptions of the beam optics are constructed by an online general beam modeling program. Design of the program, its algorithms, and initial experience with it is described.<<ETX>>

Helical dipole partial Siberian snake for the AGS

Overcoming depolarization resonances in medium class synchrotrons (3 to 50 GeV) is one of the key issues in accelerating a highly polarized proton beam up to very high energies. Since such synchrotrons, including the Alternating Gradient Synchrotron (AGS) and the J-PARC Main Ring, generally do not have sufficiently long straight sections to accommodate full Siberian snakes with reasonable beam excursions, the practical solution is to use partial Siberian snakes that rotate the particle spin about a horizontal axis by a fraction of 180 degrees. For the AGS, we designed and installed a new partial Siberian snake consisting of a helical dipole magnet with a double pitch structure. The helical structure reduced the amount of transverse coupling as compared to that achieved by the previous solenoidal partial snake. This coupling led to partial depolarization at certain energies from horizontal betatron oscillations. The helical magnetic field in the snake magnet was calculated using a 3D magnetic field code TOSCA, and was optimized by segmenting the helical pitch and varying the lengths of the segments. Fabrication errors were checked and verified to be within required tolerances. Finally, the transverse field was measured by rotating harmonic coils. After installation, we achieved a 37.5% improvement in polarization - from 40% with the old solenoid to 55% with the new helical snake, thereby demonstrating that the helical partial snake is an effective device to suppress depolarization resonances in medium-sized synchrotrons.

Heavy ion acceleration strategies in the AGS accelerator complex-1994 status report

The strategies invoked to satisfy the injected beam specifications for the Brookhaven Relativistic Heavy ion Collider (RHIC) continue to evolve, in the context of the yearly AGS fixed target heavy ion physics runs. The primary challenge is simply producing the required intensity. The acceleration flexibility available particularly in the Booster main magnet power supply and RF accelerating systems, together with variations in the charge state delivered from the Tandem van de Graaff, and accommodation by the AGS main magnet and RF systems allow the possibility for a wide range of options. The yearly physics run provides the opportunity for exploration of these options with the resulting significant evolution in the acceleration plan. This was particularly true in 1994 with strategies involving three different charge states and low and high acceleration rates employed in the Booster. The present status of this work will be presented.

A Method for Determining the Position, Angle and Other Injection Parameters of a Short Pulsed Beam in the Brookhaven Ags

injection parameters, a -2.4~~ pulse of H- is injected into the AGS and the resulting bunch of protons is observed with a PUE for approximately 40 turns around the machine. A schematic diagram of the PUE and associated electronics is shown in Fig. 1. The PUE consists of four plates and is located approximately one superperiod downstream of the injection region. As the proton bunch circles around the machine it produces in each plate a train of some 40 pulses, each pulse corresponding to the passage of the bunch through the PUE on a given turn. The signals from the upper and lower plates yield the vertical displacement of the bunch with respect to the beam pipe center, while the signals from the inner and outer plates yield the horizontal (radial) displacement. Since the period of revolution for a proton in the AGS is -4.8 ps at injection (200 MeV), a 2.4 us wide bunch of protons will produce in each plate pulses which are -2.4 ps wide and are separated from each other by -2.4 us. The pulse trains from the four plates are amplified (unity voltage gain) in the AGS ring, transmitted 1700 feet on coaxial cables, voltage amplified x10 and then digitized using LeCroy (liTR8837F) digitizers which sample the signals every 250 ns. The digitized data are analyzed with appropriate software to determine the amplitude of each pulse. If we let Anand B respectively be the amplitudes of the pulses from ;he upper and lower plates or from the outer and inner plates of the PUE on the nth

Notes on the setup of Ruthenium and Zirconium ions in Booster and AGS for RHIC Run 18

Notice: This technical note has been authored by employees of Brookhaven Science Associates, LLC under Contract No. with the U.S. Department of Energy. The publisher by accepting the technical note for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this technical note, or allow others to do so, for United States Government purposes. USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26) Collider Accelerator Department July 2018 C. Gardner Notes on the setup of Ruthenium and Zirconium ions in Booster and AGS for RHIC Run 18 BNL-207921-2018-TECH