Okamura M, Beebe E, Ikeda S, Kanesue T, Raparia D, Muench L, Karino T, Haba H
Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198, Japan.
Rev Sci Instrum. 2020 Jan 1;91(1):013319. doi: 10.1063/1.5128618.
To investigate the chiral magnetic effect, Zr and Ru beams were accelerated at the relativistic heavy ion collider (RHIC) during Run-18 at Brookhaven National Laboratory. The Zr beam was provided from the electron beam ion source (EBIS) injector, which consists of a laser ion source, an EBIS high charge state ion breeder, a 300 keV/u radio frequency quadrupole, and a 2 MeV/u interdigital H type drift tube linear accelerator (IH-DTL). The natural abundance of Zr is only 2.8% with about 50% of Zr. To obtain a sufficient beam current, Zr material enriched to about 60% of Zr was used. The only available form of the enriched material was zirconium oxide (ZrO) powder, which was not well suited for a laser ion source target. We studied and established a sintering technique of the ZrO powder to make a solid sample which could be installed into the laser ion source. The singly charged Zr was produced in a laser ablation plasma, extracted, and delivered to the EBIS to be ionized further to Zr. We optimized the laser irradiation condition, the EBIS confinement time, and transport through the RF linacs to maximize the performance of the injector. The total number of shots provided from the laser ion source for injection into the EBIS was 489 910. The EBIS facility provided a 192 MeV stable beam of Zr ions to the booster ring of alternating gradient synchrotron (AGS) for further acceleration and stripping in the AGS/RHIC complex, allowing for successful data acquisition at the Solenoidal Tracker at the RHIC.
为了研究手征磁效应，在布鲁克海文国家实验室的18号运行期间，锆（Zr）和钌（Ru）束在相对论重离子对撞机（RHIC）中被加速。Zr束由电子束离子源（EBIS）注入器提供，该注入器由激光离子源、EBIS高电荷态离子增殖器、一台300 keV/u的射频四极杆以及一台2 MeV/u的叉指式H型漂移管直线加速器（IH-DTL）组成。Zr的天然丰度仅为2.8%，其中约50%为Zr。为了获得足够的束流，使用了富集到约60%Zr的Zr材料。富集材料唯一可用的形式是氧化锆（ZrO）粉末，它不太适合作为激光离子源靶材。我们研究并建立了ZrO粉末的烧结技术，以制成可安装到激光离子源中的固体样品。单电荷Zr在激光烧蚀等离子体中产生，被提取出来并输送到EBIS中进一步电离为Zr。我们优化了激光辐照条件、EBIS约束时间以及通过射频直线加速器的传输，以最大限度地提高注入器的性能。从激光离子源提供给EBIS用于注入的总脉冲数为489910。EBIS设施向交变梯度同步加速器（AGS）的增强器环提供了一束192 MeV的稳定Zr离子束，以便在AGS/RHIC复合体中进一步加速和剥离，从而在RHIC的螺线管追踪器上成功采集数据。
