Abstract
We developed a laser frequency stabilization and an optical fiber transmission system for the the francium electric dipole moment search. The absolute accuracy of a laser frequency ...stabilization scheme using a state-of-the-art commercial wavelength meter was 0.48 MHz at ±2 nm and -1.33 MHz at ±200 nm from calibration wavelength, respectively, and the frequency instability is below 10
-9
with a standard deviation of 0.56 MHz over 60 hours. We also demonstrated that a 400 m long fiber laid between laboratories can transmit 30 mW of trapping laser light, which is sufficient for a magneto-optical trapping of francium. The polarization crosstalk in the fiber was stable at -25 dB over 12 hours of measurement.
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.
Abstract Paul traps are devices that confine particles using an alternating electric field and have been used in undergraduate experimental classes at universities. Owing to the requirement of a high ...voltage ( > 10 3 V), Paul traps are not used in middle and high schools. Therefore, we developed an all-in-one-type Paul trap, including a high-voltage transformer. The Paul trap can be equipped with two different types of electrode attachments, ring-type and linear-type, and the trap image can be observed using a built-in web camera. For example, the charge-to-mass ratio of particles was measured with different types of attachments, and reasonable values were obtained. These types of trap devices are currently used at several educational facilities in Japan.
Differential cross sections of isoscalar and isovector spin-M1 (0(+)→1(+)) transitions are measured using high-energy-resolution proton inelastic scattering at E(p)=295 MeV on (24)Mg, (28)Si, (32)S, ...and (36)Ar at 0°-14°. The squared spin-M1 nuclear transition matrix elements are deduced from the measured differential cross sections by applying empirically determined unit cross sections based on the assumption of isospin symmetry. The ratios of the squared nuclear matrix elements accumulated up to E(x)=16 MeV compared to a shell-model prediction are 1.01(9) for isoscalar and 0.61(6) for isovector spin-M1 transitions, respectively. Thus, no quenching is observed for isoscalar spin-M1 transitions, while the matrix elements for isovector spin-M1 transitions are quenched by an amount comparable with the analogous Gamow-Teller transitions on those target nuclei.
We have developed a dual-rubidium-isotope magneto-optical tap (MOT) for a dual species co-magnetometer used in measurements of the electron electric dipole moment (EDM) using laser-cooled francium ...atoms. The EDM measurement using atoms in an optical dipole force trap exhibits the advantage of less Doppler effects and longer interaction time compared to atomic and molecular beam experiments. In EDM experiments, the fluctuation of the magnetic field and the vector light shift induced by an optical dipole force can cause systematic errors. The dual species co-magnetometer is being developed to simultaneously monitor the fluctuations of both the magnetic field and the vector light shift. We demonstrated the dual-rubidium-isotope MOT for the development of the dual species co-magnetometer.
The direct 3 alpha decay branch from the 02+ state at Ex=7.65 MeV in C12, which is known as the Hoyle state, is considered to affect the triple-a reaction rate strongly and to give crucial ...information on its structure. We have performed a high-precision measurement of the 3a decay from this state using the C12(C12,3 alpha )C12 reaction at EC12=110 MeV. The branching ratio of the direct 3a decay was under the detection limit in the present experiment. By comparing with Monte Carlo simulations for three decay mechanisms as the sequential decay through the ground state of Be8, the direct decay with equal energies of three a particles, and the direct decay to the phase space uniformly, we have obtained the upper limit of 0.2% on the direct 3a decay.
In Japan, research activities by junior and senior high school students show an upward trend. However, there are limited examples of research activities in the field of elementary particles and ...atoms. This is due to the difficulty associated with procuring research tools such as accelerators or particle detectors. Therefore, we hosted the 'Accel Kitchen' in 2018 and 2019 at the Cyclotron and Radioisotope Center (CYRIC) in Tohoku University where junior and senior high school students could participate in ongoing research of particle and atomic physics. At each workshop, 12 junior and senior high school students participated in the beam experiment, including the production of francium atoms (Fr) by the fusion reaction of oxygen and gold, optimizing the transport of the ion beam and identifying the alpha decay nuclei, and laser trapping of Fr for two days. Each group that was involved in the experiment was supported by researchers and university students who acted as mentors. This was the first opportunity for junior and senior high school students to know about the particle beam experiment in Japan.
The finite value of an electron electric dipole moment (eEDM) provides the direct evidence for the violation of time reversal symmetry. Fr atoms, whose enhancement factor is 895, trapped by laser ...cooling and trapping techniques are one of the strongest candidates for measuring the eEDM. We are constructing a beamline for measuring the eEDM using laser- cooled Fr atoms at the Cyclotron and Radioisotope Center. We have developed laser light sources including the frequency stabilization system and a magneto-optical trap system for Fr atoms. As the Fr production requires the cyclotron operation, we also use Rb atoms whose chemical properties are similar to those of the Fr atoms. Thus, the Rb beam is utilized for optimizing the operation parameters of the entire apparatus. We have also developed the laser light sources for Rb atoms and observed the beat signal for frequency stabilization of the source using the frequency offset locking method.
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