Search

The first priority of RHIC operation in 2021 was the Au+Au collisions at 3.85 GeV/nucleon, which is the lowest energy to complete the 3-year Beam Energy Scan II physics program, with RF-based electron cooling. In addition, RHIC also operated for several other physics programs including fixed target experiments, O+O at 100 GeV/nucleon, Au+Au at 8.65 GeV/nucleon, and d+Au at 100 GeV/nucleon. This report presents the operational experience and the results from RHIC operation in 2021. With Au+Au collisions at 3.85 GeV/nucleon reported in a separate report, this paper focuses on the operation conditions for the other programs mentioned above., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Beam Energy Scan phase II (BES-II) operation in the Relativistic Heavy Ion Collider (RHIC), aiming to explore the phase transition between quark-gluon plasma (QGP) and hadronic gas, exceeded the goal of a four-fold increase in the average luminosity over the range of five gold beam energies (9.8, 7.3, 5.75, 4.59 and 3.85 GeV/nucleon) compared to those achieved during Beam Energy Scan phase I (BES-I). We will present the achievements in BES-II together with a summary of the measures taken to improve RHIC performance in the presence of several beam dynamics effects, and details on improvements made during the operation at 3.85 GeV/nucleon in 2021., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

We are studying feasibility of a compact neutron source with a lithium-ion beam driver. The neutron source com-prises a laser ion source, an RFQ linac, and an IH-DTL. Recently, we demonstrated 35-mA 7Li³⁺ ion beam acceler-ation by an RFQ linac with a laser ion source. Based on the result, we performed beam dynamic design of an IH-DTL to accelerate the lithium-ion beam to the energy required for the neutron production, 14 MeV. To obtain a realistic field distribution, we made a rough model of the IH-DTL cavity with Microwave studio. It was confirmed with GPT 3D beam simulation that 1.7-m and 200-kW IH-DTL with two triplets can accelerate 30-mA 7Li³⁺ beam., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

A laser ion source (LION) at Brookhaven National Labor-atory (BNL) has been operational since 2014 to provide low charge state heavy ions of various species for Rela-tivistic Heavy Ion Collider (RHIC) and NASA Space Radiation Laboratory (NSRL). Pulsed ion beams (100~300 µs) with beam current ranging from 100 µA to 1 mA from any solid-state targets can be supplied without memory effect of previous beams at pulse-by-pulse basis. LION is an essential device for the operation of a galactic cosmic ray simulator at NSRL together with high-performance beams for RHIC. Because the importance of LION has been widely recognized, an upgraded version of LION, which is called LION2, is being developed for improved performance and reliability. The design and status of the LION2 will be shown., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Laser ion sources generate plasma and supply ions by focusing energy by light onto a solid surface. The ionization is achieved during the pulsed laser irradiation period. Then the plasma expands vertically from the target surface as it moves forward. Usually, this drift distance is chosen from tens of centimeters to several meters. Once the required pulse width and plasma density are met, an extraction electric field is applied. In most cases, this electric field is set in the same direction as the direction of the plasma. In this study, we experimentally verify how performance is achieved when the direction of the extraction field is at an angle to the direction of motion of the plasma. If the extraction field can be slanted without degradation of the ion source performance, it is considered to be able to shield neutral vapors and debris generated simultaneously with the plasma, which will be advantageous for the long-term operation of the laser ion source., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

A 100.625 MHz quarter wave resonator type rf buncher cavity was fabricated for polarized He-3 spin rotator beam line at BNL. This cavity will be installed in the existing EBIS-To-Booster beam line to provide effective voltage of more than 40 kV for 2 MeV/u 3He²⁺ beam. This cavity has a large drift tube inner diameter of 80 mm and small gap length of 5 mm. The buncher consists of 3 sections, which are a cavity main body including drift tube, stem, and inner wall, a lid with a power coupler, and a lid with an inductive tuner. The main body was machined from a bulk copper only by CNC machining. The result of low power test agreed well with rf simulation without any alignment. The difference between measured and calculated resonant frequency was 0.1 %, and measured Q value was 92 % of that in simulation. The cavity rf design and test results will be shown., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

As part of the Beam Energy Scan (BES) physics program, RHIC operated in Fixed Target mode at various beam energies in 2020. The fixed target experiment, achieved by scraping the beam halo of the circulating beam on a gold ring inserted in the beam pipe upstream of the experimental detectors, extends the range of the center-of-mass energy for BES. The machine configuration, control of rates, and results of the fixed target experiment operation in 2020 will be presented in this report., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Precedent to electron cooling commissioning and collisions of Gold at various energies at RHIC in 2018, the STAR experiment desired an exploration of the chiral magnetic effect in the quark gluon plasma (QGP) with an isobar run, utilizing Ruthenium and Zirconium. Colliding Zr-96 with Zr-96 and Ru-96 with Ru-96 create the same QGP but in a different magnetic field due to the different charges of the Zr (Z=40) and Ru (Z=44) ions. Since the charge difference is only 10%, the experimental program requires exacting store conditions for both ions. These systematic error concerns presented new challenges for the Collider, including frequent reconfiguration of the Collider for the different ion species, and maintaining level amounts of instantaneous and integrated luminosity between two species. Moreover, making beams of Zr-96 and Ru-96 is challenging since the natural abundances of these isotopes are low. Creating viable enriched source material for Zr-96 required assistance processing from RIKEN, while Ru-96 was provided by a new enrichment facility under commissioning at Oak Ridge National Laboratory., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The design effort for the electron-ion collider eRHIC has concentrated on electron-proton collisions at the highest luminosities over the widest possible energy range. The present design also provides for electron-nucleon peak luminosities of up to 4.7·10³³ cm⁻²s^{−1} with strong hadron cooling, and up to 1.7·10³³ cm⁻²s^{−1} with stochastic cooling. Here we discuss the performance limitations and design choices for electron-ion collisions that are different from the electron-proton collisions. These include the ion bunch preparation in the injector chain, acceleration and intrabeam scattering in the hadron ring, path length adjustment and synchronization with the electron ring, stochastic cooling upgrades, machine protection upgrades, and operation with polarized electron beams colliding with either unpolarized ion beams or polarized He-3., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

The FY18 RHIC physics program calls for Ru-Ru and Zr-Zr collisions at 100GeV using isobaric Ruthenium and Zirconium ions, each having 96 nucleons. In the injector chain, these two ions have to come from tandem and EBIS source, respectively. To reduce systematic errors in the detector, the luminosity between the two species combinations is matched as closely as possible, and the species are switched frequently. Several bunch merges are needed in the Booster and AGS to reach the desired bunch intensity for RHIC. The setup and performance of Booster and AGS with these ions are reviewed., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The RHIC-EBIS pre-injector is a heavy ion pre-injector to deliver multiple heavy ion species at 2 MeV/u to the AGS-Booster at the RHIC accelerator complex. In addition to collider experiments at RHIC, multiple heavy ion species are used for the NASA Space Radiation Laboratory (NSRL) to evaluate the risk of radiation in space in radiobiology, physics, and engineering. A GCR simulator is one of the operation modes of NSRL to simulate a galactic cosmic ray event, which requires switching multiple ion species within a short period of time. The RHIC-EBIS pre-injector delivers various heavy ion species independently for simultaneous operation of RHIC and NSRL. We developed an automated scheme of the rapid species change and it is routinely used by NSRL or Main Control Room for daily operation without assistance of RHIC-EBIS experts. The number of species change exceeds one hundred. This paper describes the automated operation of the RHIC-EBIS pre-injector and the operational performance., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

Accelerator-driven compact neutron sources have been developed to conduct nondestructive inspection more conveniently and/or on the spot with lower cost than other neutron sources, such as spallation sources and nuclear reactors. In typical compact source, proton or deuteron are injected into Li or Be. To develop a higher flax source than conventional ones, we propose a source with 7Li beam generated by laser ion source using direct injection scheme (DPIS) into RFQ linac. Because of the higher velocity of center of mass than that in the case of proton beam injection, generated neutrons are more collimated. In addition, laser ion source with DPIS is expected to accelerate mA class fully ionized 7Li beam stably with simple setup, while it is difficult for conventional ion sources. The high collimation and high current are expected to lead to higher neutron flax. In this presentation, we present a design of RFQ linac optimized to accelerate such a high current beam with shorter distance., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

Generation of highly-charged heavy ions such as fully stripped C⁶⁺ of more than hundreds mA of beam current can be possible only with a laser ablation ion source (LIS). Heavy ions are produced from a solid target irradiated by a pulsed high power laser. Recent study showed that only sub-micron range of surface layer contributes for the generation of highly-charged heavy ions. In this paper, we experimentally investigated the difference of the performance of highly-charged carbon ion production from graphite targets of different thickness (25, 70, 254, and 3000 'm) to seek the possibility of a rolled target to overcome the limitation of a target lifetime., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

We are studying a laser ion source (LIS) for a high average beam power heavy ion beam production. A LIS is the most intense source of pulsed highly-charged ions using a laser ablation scheme. By increasing the repetition rate, a LIS based heavy ion beam would approach the average beam power based on a low beam current and continuous beam regime. In addition, a high-repetition-rate LIS can be used as a heavy ion source for a medical accelerator with spot scanning technique. This paper will describe the requirements to realize the high repetition rate operation., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

DPIS (Direct Plasma Injection Scheme) is one of the effective methods for high-intensity heavy ion beam acceleration. In DPIS, ions are extracted from laser-produced plasma at the entrance of an RFQ linac. The plasma generated by high power density laser irradiation consists of multiple charge state ions, therefore, the ions with different charge states are simultaneously injected into an RFQ. In an RFQ, ions whose charge state is comparable with that of ions desired for acceleration are captured by RF bucket. To prevent the unneeded ions from being accelerated, we investigated the beam dynamics in an RFQ and performed the particle tracking simulation. The simulation result shows that the discontinuous transition of the synchronous phase inhibits the acceleration of the unneeded ions without significant loss of desired ions. To validate the designed cell parameter via oncoming beam test, we fabricated the new 4-rod RFQ vanes for carbon 5+ acceleration., Proceedings of the 13th Heavy Ion Accelerator Technology Conference, HIAT2015, Yokohama, Japan

In March 2014, a Laser Ion Source (LIS) was commissioned which delivers high brightness low charge state heavy ions for the hadron accelerator complex in Brookhaven National Laboratory (BNL). Since then, the LIS has provided many heavy ion species successfully. The induced low charge state (mostly singly charged) beams are injected to the Electron Beam Ion Source (EBIS) where ions are then highly ionized to fit to the following accelerator's Q/M acceptance, like Au³²⁺. Recently we upgraded the LIS to be able to provide two different beams into EBIS on a pulse-to-pulse basis . Now the LIS is simultaneously providing beams for both the Relativistic Heavy Ion Collider (RHIC) and NASA Space Radiation Laboratory (NSRL). In the conference we present details of the LIS including effect of plasma confinement solenoid., Proceedings of the 13th Heavy Ion Accelerator Technology Conference, HIAT2015, Yokohama, Japan

Laser ion source can provide high brightness heavy ion beam. In the source, a plasma produced by a pulsed laser irradiation on a solid material drifts toward the extraction electrode. In the meantime, the plasma expands spatially and its flux density at the extraction point dramatically changes within a beam pulse. To stabilize the variation, we try to control the expanding plasma by applying pulsed magnetic field. So that we may achieve flat or tailored beam current profile. For this purpose, we are designing coils and pulsed circuit and these will be experimentally verified., Proceedings of the 13th Heavy Ion Accelerator Technology Conference, HIAT2015, Yokohama, Japan

We discuss the behavior of laser-ablation plasma spreading through a pulsed solenoidal field to minimize the beam emittance of laser-ablation ion source (LIS). LIS is expected to produce high-flux and low emittance ion beams from various solid materials in vacuum because of the high drift velocity and low temperature of the ablation plasma due to the adiabatic expansion. However, the ion flux level from the ablation plasma into an extraction gap changes within a pulse and then the shape of the sheath boundary changes transiently. Then, the integrated emittance is larger than the stroboscopic emittance at a certain time slice. To prevent the transient effect, we tried to control the plasma flux with a pulsed solenoidal magnetic field. The field is expected to change the direction of the plasma flow like a lens. By changing the magnetic flux density according to the transient flux level of ablation plasma, we can expect to control the plasma flux at the extraction gap. To investigate the controllability of the plasma flow, we measured the plasma flux as a function of parameters of the pulsed magnetic field. We scanned ion probes along the beam., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

A new laser ion source (LIS) for low charge state ion production was installed on RHIC-EBIS. This is the first LIS to be combined with an Electron Beam Ion Source (EBIS) type heavy ion source. The LIS provides intense low charge state ions from any solid state material, with low emittance and narrow pulse length. These features make it suitable as an external source of 1+ ions that can be injected into the EBIS trap for charge breeding. In addition, a LIS is the only type ion source which can allow rapid switching among many ion species, even on pulse-by-pulse basis, by changing either laser path or target position, to strike the material of choice. The EBIS works as a charge breeder, with the extracted high charge state ions used in the following accelerators. The beams from LIS will be used for RHIC and NASA Space Radiation Laboratory (NSRL) at BNL. The rapid beam switching, which was not possible with existing ion sources, will expand the research field at NSRL as a galactic cosmic ray simulator. The results of commissioning will be shown., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

In a laser ion source, a high power pulsed laser shot focused on a solid state target produces laser ablation plasma. This plasma has initial velocity towards the normal direction of the target and simultaneously expands three dimensionally. Since charge state distribution, velocity distribution and plasma temperature strongly depends on laser power density, power density is one of the important parameter to the angular distribution of plasma. Angular distribution of expanding plasma was measured by changing laser power density. Details of the experiment will be shown in the paper., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The Electron Beam Ion Source (EBIS) project at Brookhaven National Laboratory is a new heavy ion pre-injector for Relativistic Heavy Ion Collider (RHIC) and NASA Space Radiation Laboratory science programs. An important requirement for EBIS is an ion source capable of efficiently providing a variety of heavy ion species to many users within short period of time. In that respect, Laser Ion Source (LIS), which can supply many heavy ion species from solid targets, is a good candidate for RHIC-EBIS, however, LIS has an issue to be resolved. This is the requirement of limited current in low energy beam transport. LIS in the condition that laser power density is low, is expected to provide limited current with long pulse length. The discussions of the experimental results are presented., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan