Evaluation of 6N Aluminum Heat-Link Tomohiro Yamada ICRR, - - PowerPoint PPT Presentation

Evaluation of 6N Aluminum Heat-Link

Tomohiro Yamada

ICRR, University of Tokyo Takayuki TomaruA, Toshikazu SuzukiA and the KAGRA Cryogenic Payload Group

High Energy Accelerator Research OrganizationA

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

Heat-Links & Payload System

Heat-links are the main path to cool down the cryogenic payload system. Heat-links are connected from the cryocooler to the payload system. We need to evaluate how much vibration is transmitted by the heat-links.

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

by Ayako Hagiwara

PT Cryocooler

What we must investigate about the Heat-link

◇ High thermal conductivity

・To reduce the number of the Heat-links

• > High purity material

◇ Small spring constant :

・To reduce the transmission of vibration

• > Thin wire

These properties must be compatible with the requirements of the KAGRA Heat-link. => We use very thin ultra high purity aluminum ( 99.9999% (6N) ) wires.

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

KAGRA Heat-link & Size effect

Small diameter wire ・Small thermal conduction compare to large diameter wire ・Difficulty to handle them => Stranded cable 1 Heat-link = Φ 0.15 mm × 7 × 7 × 7 ( Total cross sectional area ～ 6 mm2 )

Size effect :

Electron mean-free-path limited by diameter of each heat-link wire.

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

Evaluation of 6N Aluminum Heat-Link

It takes a long time to measure the thermal conductivity.

We can estimate the thermal conductivity from the RRR. ◇ What is RRR?

• RRR = Residual Resistivity Ratio

RRR =

$%&&' $(.*'

• RRR is an indicator of the purity of material.

RRR measurement is the easiest and simplest one.

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

𝑆 : electric resistance

We measure the RRR as a preliminary experiment.

RRR measurement

◇ 4 wire measurement

Current : ±100 mA Sample : 5N, φ0.15 mm wire 6N, φ0.15 mm wire

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

Ⓥ

Keithly Nanovoltmeter 2182

Ⓐ

Keithly DC and AC current source 6221

sample Liquid Helium RRR = 𝑆1223 𝑆4.53

Results & Estimation

◇ RRR results

5N φ0.15mm : 3100 6N φ0.15mm : 3500

◇Estimation of thermal conductivity

𝜆 = 1 1.83×10:;×𝑈5 + 1.09 RRR/𝑈 ⁄

〈 6N φ0.15mm 〉

8K : 𝜆 ~ 20000 W m ⁄ /K 20K : 𝜆 ~ 11000 W m ⁄ /K

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

20 10 8 4 101 10E 104

5N 6N

8K

FGH FIH → 110%

Thermal conductivity [W/m/K] Temperature [K]

Effects of Bending

◇ During installation of heat-links to the cryogenic payload, we’ll need to handle heat-links. We tried to evaluate the effects of bending caused by handling. ◇ How to evaluate ・wind a wire around a glass beaker 50 times ・Then, measure the RRR ◇ Results 6N : 3500 -> 2700 23% worse 5N : 3100 -> 2300 26% worse WE MUST HANDLE HEAT-LINKS CAREFULLY !!

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica

Φ 45 mm

Conclusion

• Vibration transmitted by heat-links could be an issue.

We need very soft material for the heat-link and

• ne which has a high thermal conductivity.
• 6N aluminum heat-links are the suitable material.
• RRR measurement of 6N aluminum is on-going.
• Evaluation of the thermal conductivity and the spring

constant will be done in the near future.

• A calculation of cooling down time and an estimation
• f transmission of vibration must be done after those

measurements.

The 3rd KAGRA International Workshop 21st, May, 2017 @ Academia Sinica