Hidetsugu Katsuragawa

Accumulation of ions from a recoil mass separator in a new type of linear ion trap

Abstract A new type of linear ion trap system in combination with a sextupole ion beam guide (SPIG) has been developed for the accumulation of a continuous ion beam. An axial trapping potential is generated by three cylindrical electrodes mounted outside, but concentric to, the SPIG. The ions in a continuous beam are trapped in the potential well via collisions with He gas. This linear ion trap is called the “SPIG-trap”. The properties of the SPIG-trap were tested off-line with a discharge ion source in a gas cell. Up to 106 ions were trapped and extracted as a bunch with an efficiency of 10% for 10 ms of accumulation. The SPIG-trap system was then connected to a gas filled recoil mass separator (GARIS) and tested with an energetic primary beam from a cyclotron (16O, 107 MeV). The overall efficiency of the SPIG-trap including ion losses in an energy degrader, which was placed in front of the He cell, was measured to be of the order of 10−5 for 10 ms accumulation.

Highly sensitive detection of thallium atoms using resonance ionization

Abstract Highly sensitive detection of thallium atoms has been carried out using resonance ionization. Thallium was vaporized by heating in a proportional counter cell. Two step ionization of thallium atoms was carried out with a pulsed dye laser. A sensitivity was reached in the order of one in 1013 atoms.

High-Resolution Diode-Laser Spectroscopy of the Rare-Earth Elements

High-resolution laser spectroscopy has been performed for the rare-earth elements as well as Ba by using a tunable diode laser together with a well collimated atomic beam. Hyperfine structures and isotope shifts have been measured for eight transitions in Ba I, Ce I, Sm I, Eu I, Gd I and Yb I. Hyperfine constants A and B have been determined for the 4 f 7 5 d 6 s 6 p 11 F 5 level of 155,157 Gd, and the 4 f 14 6 s 6 p 3 P 2 , 4 f 14 6 s 7 s 3 S 1 levels of 171,173 Yb. The field shifts and 6 s -electron densities at the nucleus have been derived for the studied elements and compared with the Hartree–Fock calculation.

Specific Mass Shift in Gd I and Dy I

High-resolution diode-laser spectroscopy has been performed on atomic beams of natural Gd and Dy. Isotope shifts of the even-mass isotopes have been measured for two transitions in Gd I and one transition in Dy I. Specific mass shifts, as well as field shifts, have been derived for transitions of 4 f 7 5 d 6 s 2 –4 f 7 6 s 2 6 p in Gd I, and 4 f 10 6 s 2 –4 f 9 5 d 6 s 2 in Dy I; the specific mass shift is much larger than the normal mass shift. It has been found that the specific mass shift of the 4 f 10 6 s 2 –4 f 9 5 d 6 s 2 transition in Dy I is about one order of magnitude larger than that of the 4 f 7 5 d 6 s 2 –4 f 7 6 s 2 6 p transition in Gd I. This shows that the specific mass shift, related to the correlation effect between electrons, strongly depends on the orbital angular momentum of electrons.

A laser ion source with a thin ohmic-heating ionizer for the TIARA-ISOL

Abstract An ohmic-heating laser ion source with a thin ionizer of thickness of 30 μm has been developed for the TIARA-ISOL. It can form an electric field of 4–5 V/cm inside the ionizer. The properties of the laser ion source were tested on- and off-line with aluminum isotopes. The FWHM of the time distribution of the bunched photoions from the ion source was about 4 μs for 27Al. In on-line experiment, a photoionization efficiency of about 0.1% for 25Al was obtained.

Atomic Beam Diode-Laser Spectroscopy

Combined with a collimated atomic beam source, diode laser without external cavity has been used as a spectroscopic light source to study atomic hyperfine structures and isotope shifts of Ba i. Spectroscopic measurements of the 6s21S0 – 6s6p3P1 transition of Ba i have been carried out. All hyperfine peaks of 135,137Ba have been clearly seen and resolution of 50 MHz has been attained. Hyperfine constants A and B of the 3P1 state of 135,137Ba have been determined. Isotope shifts of stable Ba isotopes have also been measured. From the measured isotope shifts, the 6s electron density at the nucleus has been deduced to be 76.4(53) a.u. and discussed in terms of the Hartree-Fock approximation.

Velocity distribution of ion beams from the RIKEN IGISOL

Abstract A direct measurement of the velocity distribution of ion beams from an ion-guide isotope separator on-line (IGISOL) was carried out at RIKEN with a technique of laser spectroscopy. The skimmer-potential and gas-cell pressure dependence of the velocity distribution were also measured. The velocity distribution was found to be about two times narrower than that estimated from the mass resolving power (MRP). It is pointed out that the velocity spread deduced from MRP is considerably overestimated at various conditions. The way of improvement to make the velocity distribution of the ion beam from the IGISOL narrower and the feasibility of fast atomic-beam collinear laser spectroscopy are discussed.

Hyperfine Structure of 27Al by High-Resolution Ultraviolet Laser Spectroscopy

The high-resolution ultraviolet (UV) laser spectroscopy of 27Al has been performed by the frequency doubling of a tunable diode-laser beam together with a collimated atomic beam. Hyperfine structure spectra have been observed for two UV transitions in Al I, namely, 3s23 p2P1/2–3s24s2S1/2 at 394.401 nm and 3s23 p2P3/2–3s24s2S1/2 at 396.152 nm. The hyperfine structure constants A and B of 27Al have been determined for the 3s23 p2P1/2,3/2 and 3s24s2S1/2 levels, and compared with previously reported results.

J Dependence of the Isotope Shift in the Gd I 4f76s26p9P Term

High-resolution laser spectroscopy in Gd I has been performed using a tunable diode laser. Isotope shifts of the even-mass isotopes have been measured for two transitions from the 4f75d6s29D4 and 9D5 levels to the 4f76s26p9P3 and 9P4 levels in Gd I. The J dependence of the isotope shift, related to the crossed-second-order (CSO) effect, has been obtained for the 4f76s26p9P3 and 9P4 levels. The CSO parameter z6p of the 4f76s26p configuration has been estimated for the first time.

Velocity distribution of RIKEN IGISOL ion beams

Abstract The velocity distribution of an ion beam from an IGISOL ion guide isotope separator on-line was measured directly by means of laser spectroscopy and compared with that estimated from the mass spectrum. The latter is found to be more than two times broader than the former. The emittance of the ion beam as well as its velocity spread was also studied with laser beams. It is noted that the emittance affects the mass spectrum considerably, resulting in a poor resolving power for the net velocity spread. Laser spectroscopy of radioactive atoms with the IGISOL, especially of refractory elements, seems promising.