Naohito Saito

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

J-PARC MUSE H-line optimization for the g-2 and MuHFS experiments

Significant deviation of the anomalous magnetic moment value (g-2) observed by the muon g-2 experiment should be confirmed by the other experiment. This value is experimentally determined by frequency difference observed by the g-2/EDM experiment and muon magnetic moment observed by the muonium hyperfine splitting experiment (MuHFS). Both two experiments are planned to be performed at H-line of the J-PARC/MUSE under construction. We optimized the beamline layout for each experiment with G4beamline. For both experiments, statistics is the most important, thus beamline transmission efficiency should be maximized. Especially for the g-2, the purpose of the present effort is to compromise between small beam size and small leakage field. For the MuHFS, it is crucial to minimize leakage field at around final focus position, and to get all stopped muons within good field region of MuHFS magnet. Conceptual design of the several final focusing systems will be presented. contribution (or invited paper) to NUFACT 11, XIIIth International Workshop on Neutrino Factories, Super beams and Beta beams, 1-6 August 2011, CERN and University of Geneva

Study on Field Measurement and Ground Vibration for Superconducting Solenoid of New g-2 Experiment at J-PARC

Basic R&Ds of a superconducting solenoid for a new g-2 experiment at J-PARC are on going. High uniformity of magnetic field below 0.1 ppm is required for the g-2 experiment within a storage region of 33.3±5 cm in radius and ±10 cm in height. Two R&Ds have been started to develop the magnet with such high uniformity; a development of a precise field monitoring system and a study of seismic ground vibration. The prototype monitoring system using continuous wave type NMR probe for horizontal MRI solenoid has been built and tested. Cross-check between NMR and Hall probe has been also carried out. The seismic ground vibration has been measured at Materials and Life science Facility, MLF, in J-PARC. Based on the measured results, the spectrum analysis of the iron yoke has been performed using ANSYS.

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

New μSR spectrometer at J-PARC MUSE based on Kalliope detectors

We developed a new positron detector system called Kalliope, which is based on multi-pixel avalanch photo-diode (m-APD), application specific integrated circuit (ASIC), field programmable gated array (FPGA) and ethernet-based SiTCP data transfer technology. We have manufactured a general-purpose spectrometer for muon spin relaxation (μSR) measurements, employing 40 Kalliope units (1280 channels of scintillators) installed in a 0.4 T longitudinal-field magnet. The spectrometer has been placed at D1 experimental area of J- PARC Muon Science Establishment (MUSE). Since February of 2014, the spectrometer has been used for the user programs of MUSE after a short commissioning period of one week. The data accumulation rate of the new spectrometer is 180 million positron events per hour (after taking the coincidence of two scintillators of telescopes) from a 20×20 mm sample for double-pulsed incoming muons.

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

Superconducting Magnet Design for the Hyperfine Structure Measurement of Muonium at the J-PARC

A superconducting magnet system for a new muonium hyperfine structure, MuHFS, measurement at J-PARC is being developed. This experiment requires a magnetic field strength of 1.7 T with high homogeneity below 1 ppm. The overall mechanical design including helium and vacuum vessels was almost completed. In order to evaluate the influence of coil vibration on the error field, the modal analysis was performed. The conceptual design of superconducting shim coils was carried out. The zonal and radial shim coils were designed by using the conventional spherical harmonics method and the singular value decomposition method, respectively.

Development of High-Rate Positron Tracker for the Muonium Production Experiment at J-PARC

1 Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan 2 Institute of Materials Structure Science, KEK, 1-1 Oho, Tsukuba, Ibaraki, Japan 3 Institute of Particle and Nuclear Studies, KEK, 1-1 Oho, Tsukuba, Ibaraki, Japan 4 Advanced Meson Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama, Japan 5 Department of Physics, Korea University, 145, Aman-ro, Seongbuk-gu, Seoul, 137-713, Korea 6 Department of Physics, Tokyo University of Science, 1-3, Kagurazaka, Sinjuku-ku, Tokyo, Japan

Optimal crossed overlap of coherent vacuum ultraviolet radiation and thermal muonium emission for μSR with the Ultra Slow Muon

For μSR with ultra slow muon, we are constructing U line in materials and life science facility (MLF), J-PARC at present. Generation of ultra slow muon requires thermal muonium generation and laser resonant ionization process with vacuum ultraviolet radiation (1S→2P) and 355-nm radiation (2P→unbound). For laser resonant ionization, the coherent radiations and the thermal muonium emission must be coincident in time and space. The radiations can be steered in a chamber for reasonable overlap in space, and they can be easily overlapped in time because they are generated from one laser source. The trigger signal of the accelerator is useful for stable overlap in time.

Development status of superconducting solenoid for the MuHFS experiment at the J-PARC

The development of a superconducting solenoid for a new Muonium HyperFine Structure, MuHFS, measurement at J-PARC has been underway since 2010. High homogeneity of magnetic field below 1 ppm is required for this experiment. Superconducting main coils were designed and error fields caused by the main coil misalignment were evaluated for designing superconducting shim coils. The coil deformation by the coil winding, thermal contraction and hoop stress due to the magnetic force was also estimated. A quench protection study was performed to determine the required parameters of the superconducting strand.