実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF Experimental Report

提出日 Date of Report

課題番号 Project No. 2014A0001

装置責任者 Name of responsible person

実験課題名 Title of experiment

Yasuhiro Miyake

Development of a new elemental analysis system using negative

装置名 Name of Instrument/（BL No.）muon capture

D2

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Takahito OSAWA

May 14 to 17, 2014

所属 Affiliation
Quantum Beam Science Center, Japan Atomic Energy Agency
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
Carbon (Graphite)
Imilac Meteorite (pallasite)
Brown Filed Meteorite (H3 chondrite)
JP-1 (peridotite)

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

The new elemental analysis system using negative muon beam developed in 2014 is mainly composed of awater-cooled electromagnet, an Al flight tube, an Al sample chamber, a lead shielding body, and a Ge detector.
The electromagnet was designed to generate magnetism up to 0.43 T to bend muon beam with the momentumof 45 MeV/c. Curvature radius of the magnet and the flight tube is 350 mm. The muon beam is bent below withan angle of 45 degree in the Al flight tube and irradiates a sample that is set in the Al sample chamber. The
installation of the sample can be made easy by bending the muon beam with the magnet below. The flight tube
and the sample chamber are made by A5052 and A1070 aluminum alloys, respectively. A beam incident port of
the Al flight tube is a polyimide foil supported by an Al trellis window and most of muon beam can penetrate
the polyimide foil. Therefore, muon beam passes through air between a beam outlet and the beam incident port
and the distance is 140 mm. The muon beam is collimated by an Al collimator set under a mounting adaptor
that is installed between the flight tube and sample chamber and the collimators can be exchanged easily.
Three Al collimators were prepared in this work and the sizes of a round hole of them were φ30, φ50, and
φ70. The sample chamber has a loading hatch which is used to exchange sample easily.
12. 実験方法及び結果（つづき） Experimental method and results (continued)
A sample is put on a beryllium plate and the plate set in the sample chamber. All the muons which do notirradiate a sample pass through the beryllium plate (10×10 mm) and stop at the bottom of the chamber. Alead shielding body sheathed by copper with the thickness of 3 mm is installed upon the sample chamber anda Ge detector is set in the shielding body. Muonic X-rays emitted from the collimator and from the bottom of
the sample chamber can be shielded by the lead shielding body. Therefore, the geometry of the analysis
system can effectively reduce the background level. The Al chambers are exhausted by a turbo molecularpump before measurement and the pressure is lower than 0.05 Pa. Ultra-high vacuum is not required in themeasurement. The alignment of the analysis system can be adjusted using a three-axis movable mechanism.
Excitation current of the electromagnet is supplied by a DC stabilization power supply which is externallycontrolled by a multifunction DAQ and a control program produced by LabVIEW.
Beam profile can be recorded through an acrylic fiber flange installed to the sample chamber. A plastic
scintillator (2T×120×120 mm) was horizontally put on a sample holder in the sample chamber and the pictureof the luminescence from the scintillator was taken by a CCD camera equipped with an image intensifier. TheCCD camera was installed with its optical axis inclined to the scintillator by 45 degree. Reflecting light fromthe inner surface of the sample chamber is prevented by a black film that is treated by alumite. The beamprofiles were recorded in twelve conditions; the momentums of muon beam were 30, 35, 40, 45 MeV/c andcollimators were φ30, φ50, and φ70. Recording duration depended on the momentum; such as 300, 60, 20,and 20 seconds for 30, 35, 40, and 45 MeV/c, respectively. Excitation current was gradually changed and theprofiles were taken in each condition. The best excitation current can be determined by the profilesempirically. The effect of the beam collimators was checked in the next step. The spread of muon beam isunrelated to the momentum of muon beam and it is controlled only by the size of the hole of collimator. It
became clear that the muon beam widely spread and not only the sample but also the aluminum sample holder
is irradiated when the size of collimator’s hole is large. φ30 collimator is, therefore, the most suitable among
the three collimators to measure the sample.
Four samples, carbon (graphite, 5T×50×50 mm), a standard reference material of peridotite (JP-1),
Brownfield meteorite (H3 ordinary chondrite, ca. 40×30 mm), and Imilac meteorite (pallasite, ca. 30×20 mm)
were measured after the background analysis. An aluminum dish with 50 mm diameter was filled with JP-1
powder and it was wrapped by aluminum foil to prevent the powder from overflowing out of dish in the vacuum
chamber. Negative muon completely penetrates the aluminum foil and no X-ray is emitted from the foil
because its thickness is only 15 μm. Other three samples were not wrapped by aluminum foil. The momentum
was 40 MeV/c and φ30 collimator was used for all analyses. Only Be plate was measured in the blankanalysis. Background level and S/N ratio are obviously improved compared with the previous work because
the peaks of Al found in the spectrum of Murchison meteorite was mostly derived from the background noise.
In all cases of our experiment, beautiful spectra were recorded and all major elements were detected. In theblank analysis no Be peak was found, indicating negative muon penetrate the plate completely. The resultshows that muonic X-ray analysis using the new analysis system is available to the measurement of theextraterrestrial materials.

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