Measurements of temperature on LHC thermal models

Measurements of temperature on LHC thermal models Christine Darve 1, Juan Casas 2, Moyses Kuchnir 1 1 : Fermi National Accelerator Laboratory, Batavia, IL, USA 2 : CERN, European Laboratory for Particle Physics, Geneva, CH

Measurements of temperature on LHC thermal models Thermal measurements on models Presentation of both projects Sensors implementation Results Use of cryogenic thermometers at Fermilab and at CERN Uncertainty evaluations Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 2

Introduction to LHC thermal models Inner Triplet heat exchanger test unit (US-IT-HXTU) Validation of the Inner Triplet cooling scheme Heat transfer based on the exchange between the two-phase saturated He II used to extract heat loads generated in the stagnant pressurized He II bath. Extreme heat loads due to the detector proximity : nominal Q =7 W/m. Investigation in a linear model-based predictive control Reduce requirements on temperature sensor, cryogenic sys. performance Self-regulating process Related project: Small scale heat exchanger test Material property measurements: Kapitza resistance. Results used to estimate the wetted area of the full-scale model. Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 3

From the LHC Inner Triplet to the Inner Triplet heat exchanger test unit IT to Thermal model Four modules Magnet simulators Full helium capacity Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 4

Inner triplet heat exchanger test unit Modules 8 cryogenic thermometers 2 heaters Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 5

Inner triplet heat exchanger test unit Piping system Heat exchanger tube Pressurized He circuit Shield cooling pipes Sat He II supply Magnet simulator Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 6

Instrumentation port flange Inner triplet heat exchanger test unit Feed-box---- ----Turnaround Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 7

Inner triplet heat exchanger test unit Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 8

Thermal measurements on the US-IT-HXTU Why do we perform thermal measurements? To measure the temperature rise along the He II heat load path, for different LHC heat load scenarios-> maximum: heat load, Tsat. To understand the behavior of He II (co-current two-phase flow, wetted area). To calibrate and measure the performance of the HX tube. To validate the theoretical model->ultimate LHC condition (472W). Function of temperature measurements Display the transport of the heat load from pressurized to saturated He II. Indicator to check the evolution towards steady-state conditions. Variable parameter, Tsat, for various measurements of the HX tube performance. Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 9

Thermal measurements on the US-IT-HXTU How are they implemented? Pressurized He II temperature Glued to printed circuit board (PCB) card. Thermometers immersed in pressurized He II bath along the HX tube (pressurized side) and magnet simulator pipes. Thermometer wires routed through a 3 m long feedthrough from the pressurized He II bath to the room temperature. Saturated He II temperature Measurement of the saturated temperature provided from the pressure measurement. To reduce air leaks through the instrumentation feedthrough (subatmospheric circuit). Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 10

Thermal measurements on the US-IT-HXTU HX Saturated He II Pressurized He II Outer shell of the HX Connector @ Room temperature Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 11

Thermal measurements on the US-IT-HXTU DT1: from the Module thermal center, From JT valve to the module end within the pressurized He II DT6 DT5 Tsat9214 DT2: within the connecting pipe TT4121 TT4151 TT5121 TT4121B TT4151B DT4 TT5121B RB DT3 DT3: between connecting pipe and He II HX DT4: within the pressurized He II side of He II HX TT4221 TT4251 DT2 TT5221 DT5: across the He II heat exchanger wall TT4221B TT4251B DT1 TT5221B DT6: due to the vapor pressure drop. Vapor V= 448 cm/sec Y4203 Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 12

Thermal measurements on the US-IT-HXTU Heat transfer into and through pressurized He II (DT 1-4) One-dimension model In steady-state, heat flux Q is given by: X Q' = S ( Tc ) X ( Tw ) l 0.29 ( ( 3 (2.16 T ) X ( T ) = 520 1 e ) ) 2.5 X(Tc) - X(Tw) [(W.cm -2 ) 3.4 ] 600 500 400 300 200 100 Q Tw l He II Tc S 0 1.5 1.7 1.9 2.1 Temperature [K] Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 13

US-IT-HXTU- Small scale HX Kapitza Resistance and DT 5 Rth=(Tpres-Tsat)/Qelec Rth=2.Rkapitza+Rcu=α(1/Tpres 3 )+b α 2 Ckapitza. S Rkapitza β e S. Ccu Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 14

Thermal measurements on the small-scale heat exchanger test unit - results 70 12 Tpres - Tsat (mk) 60 50 40 30 20 10 0 1.75K 1.80K 1.85K 1.90K 1.95K 2.00K 0 2 4 6 8 10 Q (watt) Rth (10-3 K. W -1 ) 10 8 6 4 2 OFHC+ HCl 0.12 0.14 0.16 0.18 0.20 Tsat -3 (K -3 ) Bronze (95%Cu-5% Sn) OFHC-US-IT-HXTU #1 - OFHC #2 OFHC + HCl #3 - Bronze Characteristics OD/ ID (mm) 97/86 97/86 123/101 Wall thickness (mm) 0.7 0.7 0.5 Corrugation depth (mm) 5 5 11 Corrugation pitch (mm) 12.4 12.4 11.7 Surface (cm 2 ) for one side 416 416 978 Shape of the corrugated pipe Helical Helical Bellows Surface treatment None Hydrochloric acid None Results CKapitza (W K -4 m -2 ) 893 1138 565 Kapitza conductance @ 1.85 K (W K -1 cm -2 ) 0.565 0.72 0.357 Thermal conductivity @ 1.85 K (W K -1 m -1 ) 88 88 2.4 Relative performance Ref. 27% -37% Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 15 #1 #2 #3

US-IT-HXTU - Nominal Condition: 248 W Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 16

US-IT-HXTU - Ultimate Condition: 315 W Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 17

US-IT-HXTU - Some results T-Tsat (mk) 68 58 48 38 28 18 8 HX side @ middle of the module HX side @connecting pipe Magnet side @ connecting pipe Magnet simulator pipe @ middle Tsat ~ 1.90 K P~21 mbar Ultimate condition @ 315 W P=24.1 mbar 4 5 6 7 8 9 10 11 Power applied (W/m) C/C: The difference of temperature on the heat exchanger interface < 50 mk. The thermal gradient within the heat exchanger pipe is still to be measured in december at CERN. Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 18

Thermal measurements on the US-IT-HXTU Heat loads on the US-IT-HXTU extrapolated from the heat load in the Inner Triplet at IP5 or IP1, by Tom Peterson. Example for Tsat= 1.915 K, Q tot= 315 W 90.0 80.0 70.0 Predicted Measured Equations: dt/dx=-f(t) q m => T=q 3 L/1200 60.0 50.0 40.0 30.0 20.0 10.0 0.0 DT1 DT2 DT3 DT4 DT5 DT6 Total DT Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 19

Introduction to LHC thermal models Cryostat thermal model (CTM) Measurements of the LHC cryostat dipole performance + Heat loads to the actively cooled shield and to the dummy cold mass. + Components performance: Multi-Layer Insulation, support posts, beam screen, cryogenic thermometers. Conditions under investigation Steady-state and transient modes for the LHC conditions Insulation vacuum degradation Adoption of an actively cooled screen @ 5-10 K (CTM3)? Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 20

Thermal measurements on the CTM Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 21

Thermal measurements on the CTM View of the radiation screen View of the dummy cold mass Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 22

Thermal measurements on the CTM Carbon composite spacer cold mass Vacum vessel Thermal shield Radiation screen Support post MLI 50-75 K supply line carbon composite spacer 50-75 K Return line 5-10 K Return line Simulated cold mass 890 5-10 K supply line 960 LHC accelerator cross-section CTM3 cross section Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 23

Thermal measurements on the CTM Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 24

Thermal measurements on the CTM Performance of the thermal shield (50-75K) and radiation screen(5-10k) The temperature is measured at each extremity of the helium pipes Q = m H m = mass-flow, H = enthalpy difference Heat load to the dummy cold mass Heat load to the dummy cold mass is measured with the boil-off method Q 1.9 K = m L m = mass-flow, L = latent heat of vaporization Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 25

Implementation of sensors on the CTM On a pipe On the cold mass On the shield Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 26

Implementation of sensors on the CTM In the MLI Thermalization of the instrumentation wires Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 27

Some results - CTM2 Total heat load measured: Heat inleak [W/m] @ 50-75 K / Line E+F error: ± 5% 5-20 K / Line C+D error: ± 4.7% @ 1.9 K error: ± 2.5% measured calculated measured calculated measured calculated CTM1 4.78 4.58 0.23 0.24 0.18 0.19 CTM2 4.32 4.12 0.48 0.33 0.16 (1) 0.12 The contribution of the feed box on the measured He in-leak at 1.9 K is estimated to 390 mw. Q ts [W] 50 40 30 20 Line E Line F Total 10 0 50 70 90 110 130 150 Temperature at the rear section of the Thermal Shield [K] Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 28

CTM3 - Some results Influence of the insulation vacuum degradation Averaged heat loads (Watts): Insulation vacuum 7.5 10-5 Pa 100 Component Average Temperatures K 50-75 K 5-10 K 1.9 K CTM1 CTM2 CTM3 w/o actively cooled shield @5-10K w/ partial cooled shield @5-10K w/ actively cooled shield @5-10K 90 80 70 60 50 40 Supply and return boxes 0.300 Thermal shield 68 43.2 Radiation screen 8.7 3.1 Cold-mass 1.8 0.441 Support System 14.9 1.1 0.129 Total CTM Cryostat 28.3 2.0 0.012 0 1.E-03 1.E-02 1.E-01 Pressure [Pa] 30 20 10 = CTM3, dummy cold mass experienced He leaks -> results difficult to interpret. = MLI qualification on an horizontal cryostat was performed. = Choice of the shield assembly: welded to the extruded pipe C/C: Since the cost of a radiation screen material is dominant and even if a better performance with a 5K cryostat was measured, the LHC cryostat will only consider to wrap 10 layers of MLI around the cold mass. No rigid radiation screen (5-10 K) will be used in the LHC accelerator. Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 29

Some cryogenic thermometers used at Fermilab - US-IT-HXTU Thermometer immersed into He II bath Commercial sensors Printed circuit board Calibration facility Chebychev polynom Pro and cons + Cryogen true value - Implementation - Feedthrough&Connector Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 30

Some cryogenic thermometers used at Fermilab Allen-Bradley Cernox on cards Cernox+copper Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 31

Calibration of the thermometer Fermilab facility Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 32

Some cryogenic thermometers used at CERN - CTM Under vacuum: Industrial-type cryogenic thermometers with built-in heat intercept Sensor implementation Thermometric bloc Accessories Copper blocs Radiation protection Thermalization foil Pro and cons + Easy-to-use - Thermal anchoring Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 33

Some cryogenic thermometers used at CERN Layout of the cryogenic thermometer Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 34

Some cryogenic thermometers used at CERN // foil Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 35

Uncertainty evaluations Measurement string Cryogenic thermometer wire, conditioner control system and acquisition calibration fit Environmental factor Thermo-cycling Moisture Magnetic field Irradiation Systematic error Calibration: fit Effect of the liquid level gauge Statistical error Stability of the bath temperature Stability of (Tpres-Tsat) Error ± 5 mk at 1.8 K Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 36

Overheating Check US-IT-HXTU thermal measurements: Thermometers calibrated with a 0.2 µa current but used with a 1 µa. Implementation on the PCB High resistance at low temperature (40 k Ω at 1.8 K) Large dispersion of resistance (40-12 kω at 1.8K) Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 37

Overheating - Resistance influence 18 16 14 Influence of the self-heating {R=39kohm @1.8K, I=0.2microA} T1.5 T1.6 T1.7 To = Temperature out of the calibration fit relative to a current of 0.2 µa used for the calibration data. Error (T-To/To) [%] 12 10 8 6 4 2 T1.8 T1.9 T2 T2.1 T2.2 T2.3 T3 T4.1 If : R=32 KΩ @ 1.8 K I=1 µ A then Error = 0.1% 0 T4.3 0 1 2 3 4 5 6 7 8 9 10 Current [microamp] Influence of the self-heating {R=12kohm @1.8K, I=0.2microA} 8 If : R=12 KΩ @ 1.8 K I=1 µ A then Error = 0.02% Error (T-To/To) [%] 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 Current [microamp] T1.4 T1.5 T1.6 T1.7 T1.8 T1.9 T2 T2.1 T2.2 T2.3 T3 T4.1 T4.3 Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 38

Overheating - fitting expression Fit = Chebychev polynomial 0.5microAmp Fit = simple polynomial 1microAmp 16 2microAmp 5microAmp 16 (T-To)/T [%] 12 8 10microAmp (T-To/To) [%] 12 8 4 4 0 T=1.4 K Z= log (R) T=1.5 K T=1.6 K T=1.7 K T=1.8 K T=1.9 K T=2.0 K T=2.1 K T=2.2 K T=2.3 K 10microAmp 0 0.5microAmp X=((Z-Zl)-(Zu-Z))/(Zu-Zl) T= Σ Ai X i T=Σ Ai COS (i ARCCOS(X)) T=1.5K T=1.6K T=1.7K T=1.8K T=1.9K T=2K T=2.1K T=2.2K T=2.3K Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 39 0.5uA 10uA

Overheating - Current influence Temperature drift vs. current 600 0.5 microamp 1 microamp 500 2 microamp Calibration fit: (T-To) [mk] 400 300 200 5 microamp 10 microamp 20 microamp w/ R@ 0.2 microamp T=Cherb Cherb(R0.2) To: R w/ 0.2 microamp T: R w/ 0.5-20 microamp 100 0 To=1.4 K To=1.6 K To=1.8 K To=2.0 K To=2.2 K To= 2.4 K To=2.6 K To=2.8 K To=3.0 K To=3.2 K 20 microamp 0.5 microamp Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 40

Overheating Drift of temperature vs. current 140 120 100 0.5 microamp 1 microamp (T-To) [mk] 80 60 40 Drift =1.3 mk for To=1.8 K I=1 microamp 2 microamp 5 microamp 20 0 To=1.4 K To=1.6 K To=1.8 K To=2.0 K To=2.2 K To= 2.4 K To=2.6 K To=2.8 K To=3.0 K To=3.2 K 5 microamp 0.5 microamp Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 41

Conclusion Measurement of thermal model performances Temperatures rise in He II => US-IT-HXTU Heat loads => CTM Improvement of techniques for measurements of temperature Better reliability Ch. D. 12/05/00 Measurements of temperature on LHC thermal models 42