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Schematic of the test setup
Dhuley, Geelhoed | Al-Al contact resistance
4 K stage (OFHC) Adapter block (5N Al) Copper Tree
4 K heater
60 K stage (OFHC)
PT Reg.
Indium foil
ETP copper 22 AWG
Al-Al contact resistance: First results with the two-heater one- - - PowerPoint PPT Presentation
Al-Al contact resistance: First results with the two-heater one- - - PowerPoint PPT Presentation
Al-Al contact resistance: First results with the two-heater one- thermometer method Ram Dhuley, Michael Geelhoed Cryocooled-SRF group meeting 7 June 2017 Schematic of the test setup PT Reg. 60 K stage (OFHC) ETP copper 22 AWG 4 K heater
SLIDE 2
SLIDE 3
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Two-heater one-thermometer (2H-1T) method
Dhuley, Geelhoed | Al-Al contact resistance
Procedure
Step 1: QHU = Qin, QHD = 0, measure TU = T1 Step 2: QHU = 0, QHD = Qin, measure TU = T2
Al plates Upstream heater, HU Downstream heater, HD Thermometer, TU To cryocooler
Q
Method schematic
Thermometer, TD is optional
Result
(Rc = contact thermal resistance)
1 2 U c in in
T T T R Q Q
SLIDE 4
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Test assembly
Dhuley, Geelhoed | Al-Al contact resistance
4 K head Copper tree 2 x Al-Al contacts 2 x Al-Al contacts
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Details of Al-Al contacts
Dhuley, Geelhoed | Al-Al contact resistance
Joints J1 and J2 (distorted while tightening, one heater failed; no measurements were made) Joints J3 and J4
Copper tree connects here
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Details of joints J3 and J4
Dhuley, Geelhoed | Al-Al contact resistance
HU HD TD TU
Joint assembly (Oleg’s recipe)
- 1” x 1” contact
- 5/16-18 screw (steel) tightened to 75 in-lbf
- 5 mil indium interposer
Heaters
- Minco kapton film (37 ohm)
- Glued with GE-Varnish
- Taped around with copper adhesive tape
Thermometers
- Cernox CU packages
- Interposed with Apeizon N grease
- Finger tightened with 4-40 brass screws
HU HU TU
This being the first run with the 2H-1T method, we used a thermometer downstream for sanity check
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Results: Temperature data
Dhuley, Geelhoed | Al-Al contact resistance
Base T, offsets All heaters OFF HU-Joint 3 ON, Rest OFF HD ON, Rest OFF HU-Joint 4 ON, Rest OFF
𝛦𝑈𝑉-Joint 3 𝛦𝑈𝑉-Joint 4
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Results: Thermal resistance
Dhuley, Geelhoed | Al-Al contact resistance
- This test: Al-Al contact resistance = 0.68 - 0.73 K/W @ 4 K
- Oleg’s test (Run 10): Al-Al contact resistance = 0.55 K/W @ 4 K
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Next…
Dhuley, Geelhoed | Al-Al contact resistance
Develop recipe to make Al-Nb contacts
- without distortion
- with known tightening force
- using SRF compatible materials
- taking into account differential
thermal contraction of Al, Nb, bolt material
Distorted joint