Injection of high energetic ion beams to superfluid helium as a host matrix of laser spectroscopic study of radioisotope atoms

• Published in: Hyperfine interactions 2024-04, Vol.245 (1), Article 69
• Main Authors: Imamura, K., Takamine, A., Kikuchi, K., Mitsuyasu, R., Akimoto, S., Ito, M., Tsubura, K., Gladkov, A., Tajima, M., Go, S., Mukai, M., Doi, M., Nishimura, M., Yamamoto, T., Endo, H., Fukuzawa, Y., Sasamori, S., Takahashi, S., Hase, M., Kawata, K., Nishibata, H., Ichikawa, Y., Kitagawa, A., Wakui, T., Ueno, H., Matsuo, Y.
• Format: Article
• Language: English
• Subjects: Atomic; Atomic structure; Condensed Matter Physics; Experiments; Fluids; Hadrons; Heavy Ions; Helium isotopes; Ion beams; Laser beams; Laser induced fluorescence; Lasers; Liquid helium; Molecular; Nuclear Physics; Nuclear structure; Optical and Plasma Physics; Physics; Physics and Astronomy; Projectiles; Radioisotopes; Rubidium; Scintillation counters; Spectroscopic analysis; Superfluidity; Surfaces and Interfaces; Thin Films
• ISSN: 3005-0731; 0304-3843; 3005-0731; 1572-9540
• DOI: 10.1007/s10751-024-01889-y

We are developing a laser spectroscopic method to study the nuclear structure of radioactive isotopes utilizing superfluid helium (He II) as an efficient stopper for highly energetic ion beams and as an in-situ laser spectroscopic environment. Recently, we conducted an ion stopping experiment for the 84 Rb 37 + beams with the energy of approximately 350 A  MeV at QST-HIMAC with a cryostat system used for 66 A  MeV at RIKEN-RIPS experiment (Appl. Phys. Express 12 , 016502 (2019)). The radioactive 84 Rb ions were produced via a projectile fragmentation reaction using accelerated 84 Kr 36 + beams and a 12-mm thick Be target. As a first step, we measured the stopping range distribution of the injected ion beams in liquid N 2 to estimate the stopping range distribution in He II and the spot size of the injected ion beams using a plastic scintillator. Then, a laser-induced fluorescence (LIF) detection experiment was performed using He II. We successfully observed the LIF from 84 Rb atoms. We estimated the longitudinal range straggling of 84 Rb ions in superfluid helium from the obtained results. The details of experiment at QST-HIMAC and results are given in this report.