Recently, we reported the commissioning of the new cryogenic ion storage ring RICE, which demonstrated potential capabilities for the precise studies of molecular structures and reaction dynamics. In the present article, we describe the status of experimental programs ongoing at RICE with a focus on the laser spectroscopy and merged-beam collision experiments.
Collinear laser spectroscopy is one of the essential tools for nuclear-structure studies. It allows nuclear electromagnetic properties of ground and isomeric states to be extracted with high experimental precision. Radioactive-beam facilities worldwide strive to introduce such capabilities or to improve existing ones. Here we present the implementation of collinear laser spectroscopy at the ALTO research laboratory, along with data from successful off-line commissioning using sodium beam. The instrumental constituents are discussed with emphasis on simple technical solutions and maximized use of standard equipment. Potential future applications are outlined.
We present two complementary designs of pneumatically actuated and kinematically positioned optics mounts: one designed for vertical mounting and translation, the other designed for horizontal mounting and translation. The design and measured stability make these mounts well-suited to experiments with laser-cooled atoms.
Several high-performance lab instruments suitable for manual assembly have been developed using low-pin-count 32-bit microcontrollers that communicate with an Android tablet via a USB interface. A single Android tablet app accommodates multiple interface needs by uploading parameter lists and graphical data from the microcontrollers, which are themselves programmed with easily-modified C code. The hardware design of the instruments emphasizes low chip counts and is highly modular, relying on small daughter boards for special functions such as USB power management, waveform generation, and phase-sensitive signal detection. In one example, a daughter board provides a complete waveform generator and direct digital synthesizer that fits on a 1.5 X 0.8 circuit card.
Ions with similar charge-to-mass ratios cannot be separated from existing beam profile monitors (BPMs) in nuclear facilities in which low-energy radioactive ions are produced due to nuclear fusion reactions. In this study, we developed a BPM using a microchannel plate and a charge-coupled device to differentiate the beam profiles of alpha-decaying radioactive isotopes from other ions (reaction products) produced in a nuclear reaction. This BPM was employed to optimize the low-energy radioactive francium ion (Fr+) beam developed at the Cyclotron and Radioisotope Center (CYRIC), Tohoku University, for electron permanent electric dipole moment (e-EDM) search experiments using Fr atoms. We demonstrated the performance of the BPM by separating the Fr+ beam from other reaction products produced during the nuclear fusion reaction of an oxygen (18O) beam and gold (197Au) target. However, as the mass of Au is close to that of Fr, separating the ions of these elements using a mass filter is a challenge, and a dominant number of Au+ renders the Fr+ beam profile invisible when using a typical BPM. Therefore, by employing the new BPM, we could successfully observe the Fr+ beam and other ion beams distinctly by measuring the alpha decay of Fr isotopes. This novel technique to monitor the alpha-emitting radioactive beam covers a broad range of lifetimes, for example, from approximately 1 s to 10 min, and can be implemented for other alpha-emitter beams utilized for medical applications.
We have developed and characterised a stable, narrow linewidth external-cavity laser (ECL) tunable over 100 nm around 1080 nm, using a single-angled-facet gain chip. We propose the ECL as a low-cost, high-performance alternative to fibre and diode lasers in this wavelength range and demonstrate its capability through the spectroscopy of metastable helium. Within the coarse tuning range, the wavelength can be continuously tuned over 30 pm (7.8 GHz) without mode-hopping and modulated with bandwidths up to 3 kHz (piezo) and 37(3) kHz (current). The spectral linewidth of the free-running ECL was measured to be 22(2) kHz (Gaussian) and 4.2(3) kHz (Lorentzian) over 22.5 ms, while a long-term frequency stability better than 40(20) kHz over 11 hours was observed when locked to an atomic reference.