実験報告書様式（一般利用課題・成果公開利用）

MLF Experimental Report

提出日 Date of Report
8/22/2012

課題番号 Project No.

装置責任者 Name of responsible person

2012A0072

Yasuhiro Miyake

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

muSR study on the behavior of trace hydrogen in high-pressure

D1silicate minerals

実施日 Date of Experiment

実験責任者名 Name of principal investigator

5/5/2012-5/9/2012

Nobumasa Funamori
所属 Affiliation
Department of Earth and Planetary Science, University of Tokyo
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.
Quartz, Powder in aluminum capsule, SiO2
Coesite, Powder in aluminum capsule, SiO2
Stishovite, Powder in aluminum capsule,
Basalt, Plate of natural rock,

SiO2

SiO2 50% MgO 10% FeO 10% CaO 10% Al2O3 15% Na2O 5%Gabrro, Plate of natural rock, SiO2 50%

MgO 10% FeO 10% CaO 10% Al2O3 15% Na2O 5%

Peridotite, Plate of natural rock, SiO2 40%

MgO 40% FeO 10% CaO 5% Al2O3 5%Chondrite, Plate of natural meteorolite, SiO2 35% MgO 35% FeO 20% CaO5% Al2O3 5%

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 purpose of our study is to clarify the behavior of hydrogen atoms in mantle silicates. As the firststep, we have measured the yield of muonium, an isotope of hydrogen, in the silicate samples irradiated bymuon beam.
First, we conducted measurements on silver and holmium to estimate the full asymmetry of muSR signal
for the sample having a diameter of about 20 mm, the size of our samples. The full asymmetry has been
estimated to be 0.175. Then, we measured the asymmetry (the magnitude of diamagnetic oscillation) for
our samples to determine the missing fraction, which may correspond to the yield of muonium in thematerials. We also tried to measure the missing fraction for smaller samples having a diameter of about 5mm but we could not make it (the S/N was too bad). The measurements were conducted at TF = 20 G atroom temperature. Experimental results are given in Table 1.

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2. 実験方法及び結果（つづき） Experimental method and results (continued)
Two major conclusions are obtained:(1) The yield of muonium in a six-fold coordinated SiO2 crystal, stishovite, may be comparable to those infour-fold coordinated SiO2 crystals, quartz and coesite. This means that large interstitial voids instructure may not be required for high yields.
(2) The yield of muonium may increase with increasing SiO2 content in silicates.
To confirm the conclusions and understand the physical background for them, we have to conduct moredetailed experiments and/or first principles theoretical calculations.

Table 1.

Missing fraction of muSR signal in silicates.

MaterialForm

SiO2 content

Asymmetry

Missing fraction

SilverPlate

N.A.

0.175

0Quartz

Powder in aluminum capsule

100%

0.044

0.75

CoesitePowder in aluminum capsule

100%

0.016

0.91

Stishovite

Powder in aluminum capsule

100%

0.036

0.79

BasaltNatural rock plate

50%

0.075

0.57

GabbroNatural rock plate

50%

0.098

0.44

Natural rock plate

40%

0.145

0.17

Natural meteorolite plate

35%

0.134

0.33

Peridotite
ChondriteAA

having a larger size. The full asymmetry was measured to be 0.200.

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