Cooldown data: Cernox thermometers on a niobium plate Ram Dhuley, - - PowerPoint PPT Presentation

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Cooldown data: Cernox thermometers on a niobium plate Ram Dhuley, - - PowerPoint PPT Presentation

Dec 17, 2022 547 likes •658 views

Cooldown data: Cernox thermometers on a niobium plate 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 Manganin 32 AWG 4 K heater 4 K stage

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SLIDE 1

Cooldown data: Cernox thermometers

  • n a niobium plate

Ram Dhuley, Michael Geelhoed Cryocooled-SRF group meeting 7 June 2017

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SLIDE 2

6/7/2017 2

Schematic of the test setup

Dhuley, Geelhoed | Calibration cooldown

4 K stage (OFHC) Adapter block (5N Al) Niobium plate

4 K heater Cernoxes

60 K stage (OFHC)

PT Reg.

Indium foil

Manganin 32 AWG ETP copper 22 AWG

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SLIDE 3

6/7/2017 3

Setup details

  • 17 calibrated Cernox thermometers

(CU package)

  • 3 x 3 array, 0.6” x 0.6” spacing
  • 9 sensors on top face, 8 on the bottom
  • 4-40 screws finger-tight
  • augmented with Apeizon N grease

Dhuley, Geelhoed | Calibration cooldown

  • Niobium plate
  • 2 inches wide x 2.8 mm thick
  • 8.5 inches long
  • Plate wrapped with 10 layers
  • f MLI
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SLIDE 4

6/7/2017 4

Cooldown

Dhuley, Geelhoed | Calibration cooldown

Shield ≈ 59 K Nb plate (17 Cernoxes) ≈ 3.4 - 3.5 K Cooler start Heating cycles Vacuum start

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SLIDE 5

6/7/2017 5

Cooldown around 9 K

Dhuley, Geelhoed | Calibration cooldown No noticeable change in the cooldown rate around NC-SC transition

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SLIDE 6

6/7/2017 6

Spread near base temperature

Dhuley, Geelhoed | Calibration cooldown Thermometers T1 - T9 on the face touching the cooler Thermometers T10 - T17 on the back face

T1 T16

  • Thermometers from the same row bunch up; spread ≈ 25 mK (similar to with the copper plate);

T1 and T16 are outliers of their bunches

  • A heat flow appears along the plate towards the cooler with Row 1 being the warmest

and Row 3 the coldest.

1, 10 4, 13 7, 15 2, 11 5, - 8, 16 3, 12 6, 14 9, 17 0.6” x 0.6” array

Thermometer layout on the Nb plate

Heat flow path Row 1 Row 2 Row 3

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SLIDE 7

6/7/2017 7

Heat flow rate estimation

Dhuley, Geelhoed | Calibration cooldown

1, 10 4, 13 7, 15 2, 11 5, - 8, 16 3, 12 6, 14 9, 17 0.6” x 0.6” array

Heat flow path

Row 1 Row 2 Row 3

L = 1.2”, dT = 60 mK 2” 2.8 mm

qNb ≈ 14 mW with kNb = 50 W/m-K

Along the Nb plate... If our copper plate was seeing the same heat flow…

Δ𝑈𝐷𝑣 ≈ 2 mK (<< 40 mK spread)

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SLIDE 8

6/7/2017 8

Heating cycles

Dhuley, Geelhoed | Calibration cooldown No noticeable change during warm up or cooldown

NC SC

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SLIDE 9

6/7/2017 9

Summary

  • Outliers exist but majority of the Cernox thermometers

(15 of 17) show spread similar to when they were on the copper plate

Dhuley, Geelhoed | Calibration cooldown

  • There does not appear a fundamental limitation that would

limit the Cernox CU package from measuring SC niobium temperature

  • All 17 thermometers pass smoothly through NC-SC transition

temperature of niobium