Measurement of thermal conductivity of sapphire rods ii
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Measurement of thermal conductivity of sapphire rods II. Takafumi Ushiba The university of Tokyo at Hongo Tsubono Laboratory. Contents. Purpose of the measurement How to measure Result D iscussion Summary. Purpose of the measurement. Final goal

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Measurement of thermal conductivity of sapphire rods II

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Measurement of thermal conductivity of sapphire rodsII

TakafumiUshiba

The university of Tokyo at Hongo

Tsubono Laboratory

KAGRA Cryogenic Payload Meeting


Contents

  • Purpose of the measurement

  • How to measure

  • Result

  • Discussion

  • Summary

KAGRA Cryogenic Payload Meeting


Purpose of the measurement

  • Final goal

    measure the thermal conductivity of Moltech and INPEX sapphire rods with nail head.

  • Near goal

    measure thermal conductivity of polished Photoran’s sapphire rods near peak temperature to confirm the purity of sapphire rods is well or not.

KAGRA Cryogenic Payload Meeting


How to measure

Heat bath

  • Sample size

    diameter :

    sample length : 100mm

  • One dimensional approximation.

    :thermal conductivity

    L :length between two temperature sensors,

    Q:heat flow,A :sample cross section,

    :difference of values of two temperature sensors

temperature

sensor

L

Q

temperature

sensor

heater

KAGRA Cryogenic Payload Meeting


How to measure

  • Sample size

    diameter :

    sample length : 100mm

  • One dimensional approximation.

    :thermal conductivity

    L :length between two temperature sensor,

    Q:heat flow,A :sample cross section,

    :difference of values of two temperature sensor

heat bath

temperature

sensor

heater

KAGRA Cryogenic Payload Meeting


Result

This time, I take three data near 30K.

KAGRA Cryogenic Payload Meeting


Discussion

  • Error bars

    uncertainty of offset voltage of thermometer

  • Peak’s shape

    If the offset voltage of thermometer does not depend on temperature, the shape of peak of thermal conductivity is same as the real peak.

KAGRA Cryogenic Payload Meeting


Summary

  • I measure thermal conductivity near 30K

  • The result has too large error bars because of the offset voltage of the temperature sensor.

  • In this measurement, I do not confirm the purity of sapphire rod is well or not.

  • So, I need to measure thermal conductivity of sapphire rod again near 30K.

KAGRA Cryogenic Payload Meeting


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