Search

We study the electric and dust environment near a complex surface structure on the moon: a vertical hole. In order to model an electric field structure near the surface, we performed the particle-in-cell simulations. The simulations provide electric field and plasma current density profiles in three-dimensional space above the complex lunar surface topography. Subsequently, we applied the obtained electric field and plasma current density data to the test-particle simulation on the dynamics of submicronsized charged dust grains. We focus on an effect of a stochastic charging process of such small dust grains. Because of their small surface areas, the dusts will get/lose one elementary charge infrequently. The preliminary simulation results show an evidence of dust mobilization across the sunlight-shadow interface formed inside the lunar hole. [ABSTRACT FROM AUTHOR]

A prototype penning ionization gauge ion source has been developed for the installation of a 1-MeV compact ion microbeam system. The ion source must generate an ion beam with high brightness and low energy while consuming a minimum of low electric power consumption and fitting within a small size. A prototype pemiing ionization gage (PIG) ion source with two electromagnets, which generates an ion beam from high-density plasma in a small volume passing through a cathode with a small through-hole, was designed and constructed. The prototype PIG ion source generated low-energy hydrogen ion beams with the almost same distribution of ion species as a typical PIG ion source in the preliminary tests. The brightnesses of the ion beam with all ion species and proton beam were calculated and estimated to be 80 A/(m2SrV) and 8 A/(m2SrV) using the experimentally measured beam current and on the basis of the ion distribution, respectively. These values are sufficient for the installation in a compact ion microbeam system. [ABSTRACT FROM AUTHOR]

A new 300 kV compact focused gaseous ion beam (gas-FIB) system with three-stage acceleration lens was constructed at JAEA. The preliminary experiments of formation of the focused gaseous ion beams were carried out to show the availability of the gas-FIB system as a writing tool for 3D proton lithography. As a result of the experiments, it was proved that the focal point was kept at the same position under changing the kinetic energy but with keeping the kinetic energy ratio constant, which was defined as the ratio of kinetic energy in object side to that in image side for the third acceleration lens. This characteristic of the gas-FIB is a good point to advance the 3D proton lithography changing penetration depth in a sample by varying the beam energy. [ABSTRACT FROM AUTHOR]

The Materials and Life Science Facility (MLF) is currently under construction at J-PARC in Tokai, Japan. The muon section of the facility will house the muon production target and four secondary beam lines used to transport the muons into two experimental halls. Currently, one of the four beam lines (the Decay beam line) has been completed and is operational. The beam line currently under construction is the large acceptance beam line (the so called Super-Omega beam line) which, when completed, will produce the highest intensity pulsed muon beam in the world. The expected rate of surface muons for this beam line is 4×108 μ+/s, and a cloud muon rate of 107 μ-/s. The beam line consists of the normal-conducting capture solenoids, the superconducting curved transport solenoids, and an axial focusing magnet. The capture solenoids have been fabricated and installed on the beam line, while the transport solenoids are under design, with initial prototype coils under fabrication. [ABSTRACT FROM AUTHOR]

We have measured for the first time yields of both neutron-proton and neutron-neutron pairs emitted from the non-mesonic weak decay of the Λ5He and Λ12C hypernuclei, produced via the (π+,K+) reaction. From the yields of both the back-to-back np-pair events and nn-pair events, we have directly determined the ratio of the neutron- and proton-induced decay widths, Γn(Λn→nn)/Γp(Λp→np). Meanwhile, we have also determined the quenching of the observed numbers of single nucleons and coincident nucleon pairs compared with theoretical calculations. Our results suggest that contributions from the two-nucleon-induced three-body process ΛNN→NNN are significant. [ABSTRACT FROM AUTHOR]

We report recent progress of slow muon beam line constructed at the RIKEN-RAL muon facility. The slow muons are muons which are re-accelerated from the one at thermal velocity. This beam is expected to have very small emittance compared with conventional muon beam, where muons are obtained from decays of pions at rest or on move. Especially, its smallness of energy spread will make it possible to apply μSR technique to the studies of thin films, multilayered systems, nanomaterials, and other objects of restricted dimensionality. Intense slow muon beams which can be realized at future neutrino factories will be a valuable tool for material science. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have been pursuing an ultra-sensitive method for detecting and extracting hydrogen isotopes by utilizing a resonant ionization scheme via the 1S-2P-unbound transition. A time-of-flight measurement by the use of pulsed lasers coupled with mass separation enables us to distinguish hydrogen isotopes with a very low background. By preparing a new “Slow Ion Optics” to extract hydrogen isotope ions, the detection limit of the present method is improved to be much better than 3×10[sup 3] atoms/cm[sup 3]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have been generating Lyman-α laser light by the sum-difference frequency mixing method using two 212.5 nm photons for two-photon resonant excitation of the 4P[sup 5]5P[1/2][sub 0] state in Kr, subtracted by a photon with a tunable difference wave-length. To date, the 212.5 nm emission has been obtained by quadrupling single-mode 850 nm light by using two β-Ba[sub 2]BO[sub 4] crystals. However, because of the low thermal conductivity of β-Ba[sub 2]BO[sub 4] crystal, the generated 212.5nm beam became in an annular form. In this report, we will report on a new method for obtaining the Lyman-α light with CsLiB[sub 6]O[sub 10] crystals together with the experimental results of the resonance spectra of tritium and deuterium generated by nuclear reactions. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The muon science facility (MUSE, abbreviation of MUon Science Establishment ), along with the neutron, hadron, and neutrino facilities, is located in the Materials and Life Science Facility (MLF), which is a building integrated to include both neutron and muon science programs. On the November, 2009 beam cycle, we achieved extraction of the world's strongest pulsed muon beam at J-PARC MUSE by beam tuning at the Decay-Surface muon beam line (D-line). Surface muons (μ+) as much as 1.8×106/s were extracted with the use of 120 kW of protons from the Rapid Cycle Synchrotron (RCS), which corresponds to 1.5×107/s surface muons when a future proton beam reached at the intensity of 1MW. These intensities, at the future 1 MW operation, will correspond to more than ten times those at the RIKEN-RAL Muon facility. [ABSTRACT FROM AUTHOR]

The Superomega muon beamline is currently under construction at Experimental hall No. 2 of the Materials and Life Science Facility at J-PARC in Tokai, Japan. The beamline has a large solid angle acceptance, and will produce the highest intensity pulsed muon beam in the world. The beamline is designed to capture both surface positive and cloud negative muons for simultaneous use in a variety of experiments. The expected rate of surface muons for this beamline is 4×108 μ+/s, and that for cloud muons is 107μ-/s. The beamline consists of the normal-conducting capture solenoid, the superconducting curved transport solenoid and axial focusing solenoid. The construction of the capture solenoid has been completed and installed in March 2009, and the transport solenoid is now fabricated, and will be installed in the summer of 2011. The calculation of the beamline optics of the axial focusing solenoid is underway. [ABSTRACT FROM AUTHOR]

We have measured the angular correlation of the pair nucleons np and nn emitted from the nonmesonic weak decay (NMWD) of Λ12C produced via the (π+,K+) reaction in coincidence measurement. The Λp → np and Λn → nn modes were clearly identified by measuring the back-to-back correlation of the emitted nucleon pairs which is the characteristic of two-body kinematics. From the measured nucleon pair numbers Nnn and Nnp, the ratio Γn/Γp of the partial decay widths Γn(Λn → nn) and Γp(Λp → np) of Λ12C was extracted to be 0.51 ± 0.13(stat)±0.04(syst); this result is almost free from the ambiguity due to the nuclear final state interaction and 3-body decay process, which were inherent in the previous results. The obtained Γn/Γp ratio of Λ12C (p-shell) is close to that of Λ5He (s-shell). The results are consistent with those of recent theoretical calculations. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]