Post on 11-Jan-2016
Nobuhiro Fukumoto, Yukinori Onoa, Masahiro Horia, Ryo Chikaokaa, Yosuke Hayakawaa, Shigenori Moriwaki and Norikatsu Mio
Photon Science Center, Univ. of Tokyoa Graduate School of Science and Engineering Univ. of Toyama, Toyama
Electron spin resonance measurement of sapphire for KAGRA mirrors
Japanese gravitational wave detectionproject KAGRA
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Gravitational wave Propagating as space strain Strain is very small No evidence of direct observation
Gravitational wave interferometer Huge Michelson interferometer Efforts for decreasing noises ・ mono-crystal sapphire mirror
space strain(plus mode)
Sapphire mirrorKAGRA interferometer
Mono-crystal sapphire mirror
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We need information about impurities in Mono-crystal sapphire
Merit・ low mechanical loss（ lower at cryogenic measurement ）・ high thermal conductivity
Demerit・ IR (infrared) absorption By impurities （ Fe3+ , Cr3+ ,Ti3+ … ） Sample IR absorption → 30~680ppm /cm KAGRA requirement →50ppm /cm
𝑯𝟎
Theory・ Solve degeneracy by external field absorption condition
Electron Spin Resonance （ ESR ）
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Energy level transition(Free Electron)
𝑔=h𝜐𝛽𝐻 0
： Energy of microwave： Lande - factor： magnetic moment
Electron Spin Resonance （ ESR ）
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Setup・ Cavity Excite standing microwave・ Electromagnet Sweep external field
Inside of cavityStanding microwave fields
High sensitive measurement observing each spin
Instruments Setup
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ESR measurement instruments（ Graduate School of Science and Engineering Univ. of Toyama ,Ono.lab ） microwave frequency ： 9.38 GHz （ X-band ） Sweeping magnetic Field ： 0 ～ 10 kG
Electromagnet and cavityESR instrument
Sample preparation
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Crystals for IR absorption measurement High IR absorption crystal(680 ppm/cm): AC150 Low IR absorption crystal (30 ppm/cm): P401
Cut samples for ESR measurement Cut into 27 blocks(from A1 to C9)
C-axis
Sample cuttingIR absorption crystal diameter: 10mm length: 40mm
Measurement Summary
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ESR peak summary
ESR peaks at 3 regions around 2 kG around 3 kG around 5 kG
Comparison of peaks between samples among blocks
Measurement conditionTemperature: room temperatureMicrowave power: 1mWMicrowave frequency: 9.38GHz
We have measured 27 x 2=54 samples.
Around 2kG
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Inte
nsity
(a.u
.)
Field(G)Each peak position is different→ different origin
P401_A8AC150_A3
Peak1930G
Peak 1705G
Around 3kG
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Inte
nsity
(a.u
.)
P401_A8
AC150_A3
Peak: 3345G
Peak: 3345G
Peak at the same positionField(G)
Around 3kG, another block
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Inte
nsity
(a.u
.)
No peak→ depend on position
P401_C8
AC150_C3
Field(G)
Around 5kG
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Inte
nsity
(a.u
.)
Field(G)
Peak: 5233G
Only high absorption sample has peak→possibility of contribution to IR absorption
P401_A1
AC150_A3
Peak intensity distribution around 3 kG
Ａ ＣＢ
AC150
Ａ ＣＢ
P401
Intensity is largest at red part and decreases with distance→possibility of local impurity/affix in cutting
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Peak intensity distribution diagram Red: HighYellow: MiddleBlue: Low
Identification of impurity
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Around C1 and C2, high IR absorption sample has peak, but around C2 it has no peak.
Around F3, both samples has peak , but around F1 and F2, they has no peak.
𝑔=h𝜐𝛽𝐻 0
(b):RT
Around Ti3+ peak, samples have peak, but, these peaks are same as Fe3+ case.
Cr3+
Fe3+
R. S. de BIAS1 and D. C. S. RODRIGUES J. Am. Cerum. Soc., 68 [7] 409 (1985)
HighLowBoth
9.50GHzRT
Conversion peak position(calculated from g-value) Ti3+
Radiation Measurements 43 (2008) 295 – 299
Summary
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We observed ESR signals of the samples fabricated from the mono-crystals of different IR absorptions.
We observed peaks with intensity dependence on the block position around 3kG. It may come from local impurity or affix in cutting.
We observed peaks from only high IR absorption crystal sample around 5kG. It can be related to IR absorption.
Future work
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We have not identified the impurity yet.
In order to do so, we will prepare mono-crystal samples in which impurities (Fe3+, Ti3+ Cr3+…) are intentionally doped and measure them for impurity identification.
Thank you for your attention
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