J. Tanaka

A new cooling and focusing device for ion guide

Abstract A highly efficient focusing device which uses a RF multipole field (sextupole-ion-beam guide (SPIG)) has been developed for the ion guide isotope separator on-line (IGISOL). The SPIG, placed after the nozzle, consists of six circular rods uniformly distributed on a circle in the plane perpendicular to the axis of symmetry. Under the combined action of the sextupole RF electric field produced by the rods and helium gas flow, well focused ion beams with low energy spread can be transmitted efficiently by use of the SPIG. The experimental results, using a discharge ion source, show that almost nearly 90% of the ions which leave the nozzle can be transported through the SPIG, and that the width of the kinetic energy distribution after the SPIG is about 0.8 eV (FWHM). These experimental results agree with the results of Monte Carlo simulations; the simulation studies also indicate that the size of the spatial distribution in the plane perpendicular to the symmetry axis is less than 1 mm in diameter at the end of the SPIG.

Cyclotron ion guide for energetic radioactive nuclear ions

A new ion guide, with an additional function having an infinite gas thickness by using a strong magnetic field, is proposed, which enables us to stop energetic radioactive nuclear ions in He gas. The stopped singly charged ions, guided in a dc field with a focusing force generated by an rf field in the gas, are extracted with a SPIG (sextupole rf ion guide) of a focusing device for a spectroscopic study of radioactive nuclei.

An ion-guide technique for on-line isotope separation coupled with a recoil-type beam separator

Abstract The efficiency of an ion-guide isotope separator on-line has been shown to increase to a great extent when only nuclear reaction products of interest are guided into a gas region of the ion-guide system after separating them from beam particles using a gas-filled recoil beam separator. An effective volume to the present ion-guide system is larger than in usual, indicating that this method is very effective in heavy-ion reactions yielding high recoil velocities for reaction products.

A high-resolution cylindrical drift chamber for the KEK B-factory

The Central Drift Chamber of the BELLE detector at the KEK B-factory is a cylindrical wire chamber device that uses a helium-based gas and aluminum field wires and is situated in a 1.5 T magnetic field. The transverse momentum resolution for charged tracks with 1.0 GeV/c transverse momentum is 0.35%. This paper describes the chambers configuration and performance.

Proper-time resolution function for measurement of time evolution of B mesons at the KEK B-Factory

Abstract The proper-time resolution function for the measurement of the time evolution of B mesons with the Belle detector at KEKB is studied in detail. The obtained resolution function is applied to the measurement of B meson lifetimes, the B 0 B ¯ 0 oscillation frequency and time-dependent CP asymmetries.

Laser-Microwave Double-Resonance Spectroscopy of Laser-Cooled ^9Be^+ Ions in a Weak Magnetic Field for Studying Unstable Be Isotopes

Laser-microwave double-resonance spectroscopy of laser-cooled 9 Be + ions in a linear Paul trap has been performed aiming at the development of both highly sensitive and precise methods to be applied to the unstable isotopes. By the alternative irradiation of laser and microwave radiationxa0(pulsed-wave method), high accuracy of 4×10 -7 was obtained in the measurement of the ground-state magnetic-dipole hyperfine constant ( A ) of 9 Be + ion in a weak magnetic field. By the continuous-wave method, high sensitive detection of the microwave resonance was demonstrated. These methods can be complementarily applied to the measurements of unknown hyperfine constants of the unstable isotopes for studying the hyperfine anomaly.

An on-line ion trap for unstable nuclei at INS

An on-line ion trap system is under construction at INS in order to study properties of the trapped unstable nuclei produced by a cyclotron beam. Among several subjects on the system, development of a direct trapping method for unstable nuclear ions from a recoil separator is taken to be of first priority. We have successfully developed a new ion cooling device for this purpose using an ion-guide followed by an RF multipole ion beam guide.

Study of a thick target surface ionizer at INS

Abstract A surface-ionization ion source for the use of a thick target has been studied by an isotope separator on-line at INS using the 40Ca(p,2pn)38K reaction. The ionization efficiency and release time were measured for CaC2, CaO and CaF2 targets. The measured efficiency turned out to be about 20% both for tantalum and platinum surface ionizers. The release time was also deduced for each target at various values of temperature by measuring time distributions of the extracted radioactivity after bombarding the target for a short time.

Improvement of radiation hardness of double-sided silicon strip detector for Belle SVD upgrade

We have developed a double-sided silicon strip detector for the Belle silicon vertex detector upgrade. Since a radiation-hard front-end VLSI has been successfully developed, the shot noise due to the radiation-induced leakage current of the sensor will be the dominant source or the noise after irradiation in the Belle apparatus. Test structures with various strip pitches and strip widths were fabricated to study optimum strip width. The temperature dependence of the leakage current was measured with a prototype sensor after /sup 60/C gamma-ray irradiation. It was confirmed that the radiation-induced leakage current can be reduced by half by cooling the sensor from 25 to 15/spl deg/C. A radiation test with a prototype module consisting of a prototype sensor and front-end VLSI was also performed to evaluate the radiation hardness of the whole system. The signal-to-noise ratio was found to be better than 20 up to 5 Mrd(Si).

Laser-microwave spectroscopy of the hyperfine structure of 9Be for the investigation of unstable Be isotopes

Abstract For an investigation concerning the nuclear magnetic moments and their distributions in the nuclei of 7,11Be, an experimental project using laser-microwave double resonance spectroscopy for trapped ions is under progress at INS. Laser cooled ion crystals consisting of a few 9Be+ ions were observed and the ground state hyperfine splitting of 9Be+ was measured with a precision of 10−5. Experiments on the unstable isotope 7Be have been started.