Kenya Kubo

Development of elemental analysis by muonic X-ray measurement in J-PARC

Muon irradiation and muonic X-ray detection can be applied to non-destructive elemental analysis. In this study, in order to develop the elemental analysis by muonic X-ray measurement we constructed a new X-ray measuring system in J-PARC muon facility. We performed muon irradiation for Tempo-koban (Japanese old coin) for test experiment of elemental analysis. Muonic X-rays originating from muon transition in muonic silver and gold atoms were identified. The contents of Tempo-koban (Au:56%) was determined by muonic X-ray intensities.

Measurement of Muonium Hyperfine Splitting at J-PARC

J-PARC K. S. Tanaka1,3, M. Aoki4, H. Iinuma2, Y. Ikedo2, K. Ishida3, M. Iwasaki3, K. Ueno2, Y. Ueno1, T. Okubo2, T. Ogitsu2, R. Kadono2, O. Kamigaito3, N. Kawamura2, D. Kawall8, S. Kanda2,6, K. Kubo7, A. Koda2, K. M. Kojima2, N. Saito2, N. Sakamoto3, K. Sasaki2, K. Shimomura2, M. Sugano2, M. Tajima1, D. Tomono9, A. Toyoda2, H. A. Torii1, E. Torikai5, K. Nagamine2, K. Nishiyama2, P. Strasser2, Y. Higashi1, T. Higuchi1, Y. Fukao2, Y. Fujiwara6, Y. Matsuda1, T. Mibe2, Y. Miyake2, T. Mizutani1, M. Yoshida2, and A. Yamamoto2

Precise Measurement of Muonium HFS at J-PARC MUSE

Hiroyuki A. Torii1 on behalf of MuSEUM Collaboration∗. H. A. Torii1, M. Aoki2, Y. Fukao3, Y. Higashi1, T. Higuchi1, H. Iinuma3, Y. Ikedo3, K. Ishida4, M. Iwasaki4, R. Kadono3, O. Kamigaito4, S. Kanda5, D. Kawall6, N. Kawamura3, A. Koda3, K. M. Kojima3, K. Kubo7, Y. Matsuda1, T. Mibe3, Y. Miyake3, T. Mizutani1, K. Nagamine4, K. Nishiyama3, T. Ogitsu3, R. Okubo3, N. Saito3, K. Sasaki3, K. Shimomura3, P. Strasser3, M. Sugano3, M. Tajima1, K. S. Tanaka1,4 D. Tomono4†, E. Torikai8, A. Toyoda3, K. Ueno3, Y. Ueno1, A. Yamamoto3, and M. Yoshida3. 1Graduate School of Arts and Sciences, University of Tokyo; 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan 2Osaka University; Toyonaka, Osaka 560-0043, Japan 3KEK; 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan 4RIKEN; 2-1 Hirosawa, Wako, Saitama 351-0198, Japan 5Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 6University of Massachusetts Amherst; MA 01003-9337, USA 7International Christian University (ICU); Mitaka, Tokyo 181-8585, Japan 8University of Yamanashi; Kofu, Yamanashi 400-8511, Japan †Current affiliation: Kyoto University; Kyoto 606-8501, Japan ∗The collaboration name MuSEUM stands for “Muonium Spectroscopy Experiment Using Microwave.” E-mail: torii@radphys4.c.u-tokyo.ac.jp

Muon capture probability of carbon and oxygen for CO, CO2, and COS under low-pressure gas conditions

When a negatively charged muon is stopped in a substance, it is captured by an atom of the substance, and the muonic atom is formed. The muon capture process is significantly affected by the chemical environment of the atom and factors such as molecular structure (chemical effect). In this study, we performed muon irradiation for low-pressure CO, CO2, and COS molecules and measured the muonic X-rays emitted immediately after muon capture by an atom. In this paper, we quantitatively discuss the muon capture probability of each type of atom using the LMM model.

Precision Measurement of Muonium Hyperfine Splitting at J-PARC and Integrated Detector System for High-Intensity Pulsed Muon Beam Experiment

Muonium is the bound state of a positive muon and an electron. In the standard model of particle physics, muonium is considered as the two-body system of structureless leptons. At J-PARC, we plan to measure muonium’s hyperfine splitting precisely. Our experiment has three major objectives: test of QED with the highest accuracy, precision measurement of the ratio of muon’s magnetic moment to proton’s magnetic moment, and search for CPT violation via the oscillation with sidereal variations. The experimental methodology is microwave spectroscopy of muonium. Figure 1 shows the conceptual overview of the experiment. Spectroscopy of the energy states can be performed by measurement of positron decay asymmetry. The uncertainty of the most recent experimental result[1] was mostly statistical (more than 90% of total uncertainty). Hence, improved statistics is essential for higher precision of the measurement. Our goal is to improve accuracy by an order of magnitude compared to the most recent experiment. For the improvement of precision, we use the J-PARC’s highestintensity pulsed muon beam and highly segmented positron detector with SiPM (Silicon PhotoMultiplier). After the improvement of statistical precision, reduction of systematic uncertainty becomes more important to reduce systematic uncertainty. Thus, we reduce the systematic uncertainty by using a longer cavity, a high-precision superconducting magnet, and an online/offline beam profile monitor. The detector system consists of several layers of hodoscopes and fast readout circuits with custom ASIC and FPGA-based multi hit TDC. Important requirements of the positron detector are high event rate capability and high detection efficiency. The designed muon beam intensity at J-PARC MUSE H-Line is 1 × 108 μ/s. To establish the optimal design of the positron detector, we developed GEANT4-based Monte-Carlo simulation tools. Figure 2 shows a simulated muon stopping distribution in the target gas chamber. Under realistic conditions, the highest instantaneous event rate is about 3 MHz/cm. The resonance lineshape was calculated numerically, and the systematic uncertainty of the resonance frequency due to the detector specification was evaluated as a function of the detector performance. Based on the results of the simulation study, a new prototype of the detector is under development

The Development of a Non-Destructive Analysis System with Negative Muon Beam for Industrial Devices at J-PARC MUSE

Motonobu Tampo1, Kouji Hamada1, Naritoshi Kawamura1, Makoto Inagaki2, Takashi U. Ito3, Kenji M. Kojima1, Kenya M. Kubo4, Kazuhiko Ninomiya2, Patrick Strasser1, Go Yoshida2 and Yasuhiro Miyake1 1Institute of Materials Structure Science, KEK, Tokai, Ibaraki 319-1195, Japan 2Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama Toyonaka, Osaka, 560-0043 Japan 3Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Naka, Ibaraki, 319-1195, Japan 4International Christian University, Mitaka, Tokyo, 181-8585, Japan

High-Precision Microwave Spectroscopy of Muonium for Determination of Muonic Magnetic Moment

The muonium atom is a system suitable for precision measurements for determination of muon’s fundamental properties as well as for the test of quantum electrodynamics (QED). A microwave spectroscopy experiment of this exotic atom is being prepared at J-PARC, jointly operated by KEK and JAEA in Japan, aiming at an improved relative precision at a level of 10−8 in determination of the muonic magnetic moment. A major improvement of statistical uncertainty is expected with the higher muon intensity of the pulsed beam at J-PARC, while reduction of various sources of systematic uncertainties are being studied: those arising from microwave power fluctuations, magnetic field inhomogeneity, muon stopping distribution and atomic collisional shift of resonance frequencies. Experimental strategy and methods are presented in this paper, with an emphasis on our recent development of apparatuses and evaluation of systematic uncertainties.

Muonic atom formation processes for carbon containing molecules

Muonic atom is an atomic system which has a negative muon substituted an electron. Muonic atom formation processes are strongly influenced by the chemical environment of muon capturing atom such as molecular structure, however, the initial processes of muon capture still have not been well investigated. In this study, we performed muon irradiation for gaseous carbon containing molecules to investigate the chemical environmental effect on muon capture processes.

Strongest Pulsed Muon Source at J-PARC MUSE

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.