epic cooling the epic telescope and focal plane path to cmb pol workshop university of chicago july...

EPIC

Cooling The EPIC Telescope and Focal Plane

Path to CMB Pol Workshop

University of ChicagoJuly 3, 2009

Jamie Bock (JPL) Study leader

Talso Chui (JPL) Spacecraft

Jeff Raab (NGAS) 4K Cooler

Warren Holmes (JPL) Sub-K

EPIC

EPIC-ized Planck Cooling Chain

Use ~15KPulse Tube for EPIC

Sunshields Added to V-Groove Radiators

ADR Baselined

4.4K Joule-Thompson(maybe 4.4K + 1.7K Stage)

EPIC

EPIC Configuration

April 24, 2009 3

Launch Configuration

Solar Illumination and the Scan Pattern

4th shield

Deployed Configuration

•“4K” Telescope Design Includes 4th Shield•“30K” Telescope Design Omits 4th Shield

EPIC

Mechanical Design (4K Telescope Focal Plane Shown)

4K Shield(reddish)

InterceptShield(orange)

DetectorStage(orange)

Tiled Blocking Filters on Each Shield4K Telescope = 11094 Detectors30K Telescope = 2022 Detectors

Herschel-SPIRE Focal Plane

Planck

EPIC

5

Radiator Thermal Model

First Shield

Fourth Shield

SC

(c) Silver Teflon film (green)

Aluminized Kapton

Aluminized Kapton

Aluminized Kapton

Silver Teflon

Black Paint

Black Paint

Aluminized Kapton

(a)

Indium Tin Oxide for charge controlTeflonSilver with Inconel protective coatAdhesiveKaptonAluminum

Acrylic overcoat

Acrylic overcoat

Acrylic overcoat

Aluminum

AluminumKapton

(b) Doubled Aluminized Kapton film (red)

EPIC

6

Conductor Properties

0 50 100 150 200 250 300 35010

-2

10-1

100

101

102

103

T (K)

The

rmal

con

duct

ivity

k (

w/m

-K)

Gold, high disordered state

Al 6061-T6

Manganin

Red - -aluminaBlue – Effective k of strut

Teflon

HTS wire

Brass

Effective kstrut and wires

strut

i

iiieff LA

LAkk

EPIC

7

Modelling Technique

• Thermal Desktop – uses finite difference method to solve a 2D thermal equivalent electrical network.

• Uses RADCAD module of Thermal Desktop for Monte Carlo Ray Trace analysis.

– 50,000 rays per node.

• 2,900 nodes in model.

• Takes ~ 8 minutes to run on a 3.59 GHz Pentium CPU on Windows XP operating system.

EPIC

8

Model Output – steady state, no active cooling, four-shields option

T(K) Radiative Heat Transfer to

Next Stage (W)

Conductive Heat Transfer to Next

Stage (W)

Radiative Heat Transfer to Space (W)

Thermal Resistance to

next stage (K/W)1st Shield 231 69.5 3.91 16,300 29.32nd Shield 116.5 5.89 1.07 75.44 52.43rd Shield 60.39 0.685 0.264 6.00 85.84th Shield 37.75 0.0299 0.0266 0.892 323

Optical Box 29.15 0.00282 0.01213 0.0294 580Telescope 22.12 NA NA 0.0232 NA

Model summary of temperatures, thermal resistances, radiative and conductive heat transfer.

System 3D view Telescope

EPIC

9

Model Output – steady state-four-shields option

Optical Box

4th Shield

3rd Shield

2nd Shield

1st Shield

Spacecraft

EPIC

10

Spin SC at 0.5 rpm, Time Dependent Analysis

1st Shield T = 1.2 K pp

2nd Shield T = 0.3 mK pp

3rd Shield T not observable at 3 K level

Digitization noise

• Thermal isolation 4000 per stage.

• Implies 19 pico K variation at 4th shield.

EPIC

11

Moonshine

• Moon Shine Energy Flux

2cos dASq MoonMoon Earth

Moon

Lunar Orbit

L2 d

Scaled Position of Earth, Moon and L2. Dimensions are in units of 106 km.

S = Solar constant = 1350 W/m2

Amoon= rMoon2 = disk area of the Moon = 9.49x106 km2

d = distance between L2 and the Moon = 1.54x106 kmdegree90% of qMoon is infra red, 10% is visible light.

2mW/m 1.33Moonq

• At Apogee - Small Amount of Moon Shine Illuminates Back of Telescope

• Heating From Moon Is Negligible

At Apogee Moon shine touches red-purple area

EPIC

• Software Tool Assumption – Absorptivity/Emissivity Is Independent of Wavelength.

• Metal Coated Surfaces

• Colder Surface Emissivity () Always Less Than Absorptivity ()

• Software Tool Under Estimates Heat Transfer from Hot to Cold Side in V-Grooves

• The actual temperature should be 10% higher.

• The error is about the size of uncertainties in material properties.

12

“Greying” of Radiative Coatings

4Tq o

%104

1

q

q

T

T

5.0)()(

4.15.0

cold

hot

cold

hot

T

T

q

q%40or

q

q

EPIC

13

EPIC 4.4K Cooler – Extension of MIRI Cooler Design

• The approach to the Experimental Probe of Inflationary Cosmology (EPIC) cryocooler is to define low-risk hardware and software with minimal changes from flight heritage designs. This approach minimizes cost, schedule, and risk by adapting the very similar design developed for the Mid InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST) to the EPIC requirements

J - T

CCERed.15

53

Cooler Tower Assembly

(CTA)

Cooler ControlElectronics (CCE)

Cold Head Assembly (CHA)

HCC

Comp.

(PT)

RSAJ -T

CCEPrimary15

53

PT

CCERed.15

53

RSAPT

CCEPrimary15

53

JT

OMS

HX

Precooler Coldhead

MIRI

engineering

Flight

qual ’edKey

Spac

ecra

ft

JT Compressor

Precooler Environmental

Shield

R1RLDAR4 R3 R2

HEC

Comp.

Reed

Valve

Assy.

Cooler Compressor Assembly(CCA)

Bypass

De - Contamination Comp.

Reed

Valve

Assy.

Cooler Compressor Assembly(CCA)

Bypass

-

ValveValve

J - T

CCERed.15

53

Cooler Tower Assembly

(CTA)

Cooler ControlElectronics (CCE)

Cold Head Assembly (CHA)

HCC

Comp.

(PT)

J -TCCE

Primary1553

PT

CCERed.15

53

RSA

PT

CCEPrimary15

53

JT

OMS

HX

MIRI

engineering

Flight

qual ’edKey

Spac

ecra

ft

JT Compressor

R1RLDAR4 R3 R2

HEC

Precooler Environmental

Shield

Precooler Coldhead

EPIC<18K

EPIC4.4K

2X forEPIC

J-T

PT – Pulse tube JT – Joule Thompson CCE – Cryocooler Control Electronics HEC – High eff. compressor HCC – High capacity compressor RX – Recuperators

EPIC changes

De Contamination Field Joint

EPIC

14

Cryocooler Flight History and Reliability

(X) Number of Flight Units

Flight Project Electronics '98 '99 '00 '01 02 '03 '04 '05 '06

CX (2) Mini-Pulse Airs Class (2)

HTSSE (1) Stirling Custom

MTI (1) Airs Class Airs Class

HYPERION (1) Mini-Pulse Hyperion Class

SABER (1) Mini-Pulse Demo

STSS (4) Mini-Pulse Airs Class (4)

AIRS (2) Airs Class Airs Class (2)

TES (2) Airs Class Airs Class (2)

GOSAT(1) HEC Hyperion Class (1)

JAMI (2) HEC Hyperion Class (2)

OPAL (2) HEC Hyperion Class (4)

Hybrid 2 Stage (2) HEC ACE (2)

Cooler '07 '08

OCO (1) Airs Class Airs Class (1)

ARGOS host satellite failed

GOES ABI (8) HEC ACE (8)












OPAL (2) HEC Hyperion Class (4)

Hybrid 2 Stage (2) HEC ACE (2)

Cooler '07 '08


ARGOS host satellite failed













HTP (2) HEC ACE (2)

In Orbit

Cooler '07 '08


ARGOS host satellite reached EOL


NEWT (2) HEC ACE (2)

MIRI (1) HCC/HEC-JT 10K ACE (2)

'09

NGAS Flight Coolers Are Reliable- All performing nominally

EPIC

15

4.4K Cryocooler Cooling Loads for MIRI and EPIC Applications

• The EPIC requirements with 100% cooling margin are well with-in the capability of the MIRI cooler

MIRI EPIC

Temperature (K)

Heat Load (mW)

Temperature (K)

Heat Load (mW)

Stage 4 6.2 65 4.4 42

Stage 3 17-18 78 <18 134

Reject Temperature 313 K 300 K

Bus Power (steady state) 400 W 270 W

Bus Power (cooldown) 475 W TBD

EPIC

16

Measured JT Cooling at 4.4K using MIRI EM Cooler

• Demonstrated performance at 4.4K and anchored model used to predict the EPIC cases for “4K” and 30K optics cases

0

10

20

30

40

50

60

0 50 100 150 200 250 300 350

Heat Lift at 15K (mW)

He

at

Lif

t a

t 4

.4K

(m

W)

Measurement

anchored model

367 W measured input power to compressors

EPICMargined Load

4.4K Optics

EPICMargined Load

30K Optics

Test Facility

EPIC

17

4.4K Cooler Bus Power Estimates for Different Operating Points

• Parametric combinations of 4.4K and 15K loads versus bus power various loads for the optical bench/cavity (15K) and ADR/sensor assembly (4.4K)

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

100 200 300 400 500

Bus Power (W)

Lif

t at

4.4

K (

W)

0 mW intercept load, Model




Reference point

EPIC

Sub-K Cooler Method of Analysis

• Define Structure and Focal Plane Mass

– 4.4K Shield, Thermal Intercept Stage, Detector Stage

– CAD Model + Mag Shields Scaled from SPIDER Actual Mass

– Size “Magic” Ti 15-3-3-3 Struts for Launch Loads

• Compute Direct Heat Loads

– “Non Signal” Thermal IR Transmitted or Emitted by Blocking Filters

– Detector and SQUID Bias Loads

– Cable Heat Leak (SPIRE-Like Cables, Nb-Ti Wires)

• Compute Performance for Different Coolers

– ADR + 4.4K Cryocooler

– Planck Like Closed Cycle Dilution + 1.7K + 4.4K Cryocooler

– Parallel 3He + ADR + 1.7K + 4.4K Cryocooler Stage

• Gas Gap heat Switches >1K, Superconducting Heat Switches <1K

• Vandium Permendur Flux Return Magnet Shield

EPIC

Adiabatic Demagnetization Refrigerator (ADR)

– ‘On State’ During Magnetization (AB) Reject Heat at High T

– ‘Off State’ During Adiabatic Demag (BC)

– Isothermal Demagnetization (CD) Absorb Heat at Low T

– Warm Up (AD) and Repeat Cycle A-B-C-D

EPIC

Continuous Cooling (Serial Method Shown)

•Paired ADRs Alternate Cycling to Maintain Constant Temperature at 1200mK and 100mK Stages

•1200mK Is Heat Intercept Stage•100mK Is Detector Stage

•~30% Swing in Total Power to Cryocooler•4 Heat Switches

EPIC

Continuous Magnet Cycling

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 5 10 15 20 25

Time (hours)

Po

we

r to

1.7

K (

mW

)

0

1

2

3

4

5

6

7

8

9

10

Mag

net

Cu

rren

t (A

)

Intercept AMagnet

Intercept BMagnet

Power to 1.7K

Duty Cycle ~60%Balances Power Load to 1.7KCryocooler

Cryocooler

Cry

oco

ole

r

Serial Continuous ADRBlack Curves Only

EPIC

Intercept Temperature Tuning

Lo

ad a

t H

eat

Sin

k (a

rb u

nit

s)

AD

R C

ycle

Per

iod

(ar

b u

nit

s)

Intercept Temperature (arb units)

Example Intercept Tuning

00 0

Tsink

Ti for Minimum Cryocooler Load

Ti for Maximum Recycle Time

•Optimum Temperature of Intercept (Ti) Depends on Parasitics So Is Unique for Configuration•Each Configuration Has Choice of Optimum Ti - Maximum Cycle Time or Lowest Cryocooler Load

EPIC

• Cooler to Focal Plane Heat Strap Design Important Regardless of Cooler

• Heat Strap Mass Fully Constrained

– m=ljAs=Pd ld2/(0f Td

2)

– Pdand Td Fixed by Detector Requirements and Instrument Design

– For a Metallic Heat Strap Pd Td2 = Constant

– With No Intercept Stage Heat Straps >7kg

• Lightweighting of Isothermal Detector Holders a Special Job for EPIC

– Ground Based Strategy Is “Just Add More Copper”

– In Plane Thermal Spreaders Are ~10kg for SCUBA II

– Space Designs Need Optimization

Heat Straps and Detector Holder Thermal Engineering

EPIC

0

5

10

15

20

25

0 1 2 3 4 5 6

CB

E M

ass

(kg

)

Hold Time (hr)

4K Telescope Cooler System Mass Estimate

dashed lines - optimized for minimum reject powersolid lines - optimized for maximum hold timedashed lines - optimized for minimum reject powersolid lines - optimized for maximum hold timered - parallel cyclingblue - serial cycling

0

5

10

15

20

25

0 1 2 3 4 5 6

CB

E M

ass

(kg

)

Hold Time (hr)

30K Telescope Sub K Cooler System Mass Estimate

dashed lines - optimized for minimum reject powersolid lines - optimized for maximum hold timedashed lines - optimized for minimum reject powersolid lines - optimized for maximum hold timered - parallel cyclingblue - serial cycling

Mass Estimates

•Serial Operated ADR, Optimized for Longest Cycle Time, Is Least Massive (Baseline)•Sub K Cooler for 4K and 30KTelescope Options Differ by <2kg•Baseline Mass Set By Cycle Time of 1Hour ~2X Gas Gap Heat Switch Cycle Time

EPIC

Heat Load Table

Units 4K Telescope 30K Telescope

Detector System Power W 1.76 0.34

IR Loading (Detector/Intercept) W 2.8/3.0 2.2/6.4

Detector Stage Heat Lift W 8.1 5.0

Intercept Temperature K 1.03 0.996

Intercept Stage Heat Lift W 205 142

Heat Strap Mass kg 1.1 0.71

ADR System Mass kg 7.2 6.0

ADR Cooler Load at 4.4K mW 5.5 4.3

•Serial Cycled CADR Used for Mass Estimate

EPIC

Planck Dilution Principle of Operation

-4He flow Sets Cooling at 100mK-P = 33 n4 f(T) T2 (mW/(mmol/sec))-f~6.8% Saturation of 3He in 4He-Prefactor 34 In Ideal Dilution Is 82

-Undiluted 3He flow Provides Additional Cooling ofParasitic Loads Upto Tricritical Point ~860mKP~10-15microW As Pure 3He DropletsDissolve in 4He Rich Phase

n4

n3

JT Expansion ProvidesMore Additional CoolingPlanck JT at <1.4K~200-300mircoW + Parasitics

10-20bar Input

~ 0bar Output

0.097K

EPIC

Lab Demo Closed Cycle Planck Dilution

n4

n3

-T < Superfluid Transition-Magic 4He Purifier-Dominant Power Source

<1bar Input 0.097K

-Pump in S/C Bus-<100Torr Compressed to >800 Torr

-JT Expansion Moved to 3He “Input” Line

0.3-0.35K

-Lift ~5microW at 100mK in Prototype Test-39mK Prototype Base Temperature

EPIC

Continuous Cooling (3He + ADR Parallel Only)

•Replace “High Temperature ADR with Herschel-Like 3He Sorption Cooler•Feasible if Cryocooler Stage at 1.7K•Used Cycling Powers from L. Duband, et al Cryogenics (2006)•Near Constant Power to Cryocooler•8 Heat Switches•20mW Lift Needed at 1.7K•~ Mass of ADR/ ADR System•Removes “High Field” ADRs •Single Shot Option?

3He 3He

300mK

3He 3He

300mK

EPIC

Sub-K Cooler - Conclusions

Sized Different Coolers Technologies For EPIC ADR Mass and Power Performance Within Prototype Capabilities Closed Cycle Planck Dilution Cooler Feasible

Units ADR/ADR Closed Planck Dilution

3He + ADR

Cryocooler Temeprature (K) 4.4 or 1.7 1.7 1.7

Cryogenic Mass kg 9.5 or < 9.5 ~5 <9.5

Cryogenic Magnetic Field yes no yes

Heat Switches 4 0 8Heat Load to Cryocooler mW 8 or ~3 <10 >20

Cryogenic Fault Tolerance Partial Ice Plug Heater Partial

Warm Electronics – Cooler Operation Only

W 20 150-200 12

EPIC

30

Summary of Results

• Detailed Radiative Modelling of Spacecraft with “Systematics” Checks– Model Accuracy ~0.5%

– Non-Axial Temperature Variations Negligible (at 0.5rpm Spin Rate)

– Moon Shine Is Negligible

– Greying of Emissivity and Absorptivity ~10% Corrections to Model Results

• Cryocooler Requirements Within Reach of Current Technology

– Characterizations Performed at 4.4K on ‘Flight Like Cooler’– 4.4K Cooler Based on Current MIRI Cooler (for James Webb Space Telescope)

4K 30K

100mK Lift (mW) ADR/ADR 0.008 0.005

4.4K Lift (mW) Joule-Thompson 20 11

~15K Lift (mW) Pulse Tube 68 ~0

Spacecraft Power (mW) Radiator 290000 185000

Sub-K Cooler (kg) Cryo-mass only 7.2 6.0

Cryocooler (kg) Cryo+pumps+readout 79.4 67.7

EPIC

Planck Launch

PLANCK is now a "stellar object" of an estimated magnitude 18.5 in theOphiuchus constellation.

EPIC

32

Backups

EPIC

33

Optical Properties

0 50 100 150 200 250 3000.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

0.055

0.06

T (K)

Em

issi

vity

Emissivity of Aluminized Kepton versus T

Inherited from SAFIR

Coating Solar Absorptivity

Infrared Emissivity

Specularity Thermal Conductivity (W/m-K)

Silver Teflon 0.14 0.75 95% NAAluminized Kapton

0.14 0.056 * 95% NA

Black Paint 0.94 0.9 100% NAMLI NA Effective = 0.05 NA 1.2x10-6

Optical properties of coating materials at 300 K

EPIC

34

EPIC Cryocooler Properties Summary

Instrument Capabilities4.4K Optics

Capabilities30K Optics

Mass (Best Estimate)Cooler Assembly (JT/ PT Pre-cooler)Electronics (JT/Pre-cooler/Switch box) Total

(Kg)49.2 30.279.4

(Kg)49.2 17.867.0

Nominal Operating ConditionCooling Load @ 4.4KHeat Reject TemperatureBus Power at steady statePeak cool down power

42mW3000K270W

TBD W

22mW3000K165W

TBD W

Operating Temperature Range (PT and JT coolers) -20 to 50oC

Non-operating Temperature Range (PT and JT coolers) -40 to 70oC

Operating Temperature Range (CCE) -20 to 60oC

Non-operating Temperature Range (CCE) -35 to 75oC

Launch Vibration (PT and JT coolers) 14.2 Grms, 1 min

Launch Vibration (CCE) 14.2 Grms, 1 min

Launch Vibration JT cooler 18K to 4.4K component 25.8 Grms, 1 min

Bus Voltage Range 21V to 42V

Ripple Current 100 dB micro amps

Communication Protocol RS422/1553B

Lifetime >10 years

EPIC

35

Optical Properties

0 50 100 150 200 250 3000.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

0.055

0.06

T (K)

Em

issi

vity

Emissivity of Aluminized Kepton versus T

Inherited from SAFIR

Coating Solar Absorptivity

Infrared Emissivity

Specularity Thermal Conductivity (W/m-K)

Silver Teflon 0.14 0.75 95% NAAluminized Kapton

0.14 0.056 * 95% NA

Black Paint 0.94 0.9 100% NAMLI NA Effective = 0.05 NA 1.2x10-6

Optical properties of coating materials at 300 K

EPIC

ADR Heat Load Breakdown

•Serial Cycled CADR4K - TDM 30K - TDM

Detector Stage Loads (in W)

Telescope IR 2.8 2.2

Thermal IR 0 0

Heat Switch 2.1 1.8

Struts 0.91 0.56

Wires 0.43 0.1

Intercept Stage Loads (in W)

Optimum Temperature 1.03 0.996

Telescope IR 3 6.4

Thermal IR 72 35

Heat Switch 57 58

Struts 60 41

Wires 16 4

EPIC

Heat Load Table

Units 4K Telescope 30K Telescope Planck

Intercept Temperature mK 145 180 ~300

Detector Stage Dissipation W 4.6 2.5 <0.1(temp reg)

dn3/dt mole/s 15 9.7 6.7

dn4/dt mole/s 197 110 20

Cooling at 1.7 K mW 4.7 2.6 -0.2

3He per year if open cycle ℓ(STP) 10550 6870 4730

•Cryogenic Mass ~ 5kg Less Than ADR System•Required Heat Lift Not Far from Prototype Demo•No Heat Switches – 100mK Lift Is Lower•No Magnets or Magnet Leads•Requires Warm Pump (Like SPICA and MIRI JT Cooling Stages

EPIC

Generic ADR Cooler Sizing

• Compute Heat Loads Fixed as Driven by Science Goals

• Gas Gap Heat Switch for Intercept Stage

– Off State from SS Canister

– On State <50mW/K (JPL Design)

– 60% Duty Cycle for Continuous

• Superconducting Heat Switches for Detector Stage

– Switch Design Based on Mueller et al Rev Sci Inst (49) 515 (1978)

– On State Fixed for 1% Gradient at Operating Point

– Off State Phonon Conduction ~T3

• Mueller Used Al – Which Won’t Work for T>~200mK

• Use V or “Switching Ratio” ~500 Used in Model

• Pb Switching Ratio ~100 Backup, But Would Lower Ti (Heer, et al, Rev. Sci. Inst. 25, 1088 (1954)

• Maximum Field ~2.2Tesla at 6.5Amps (“Easy” to Achieve B/I Ratio)

• Flux Return Shield with Soft Ferromagnetic Material

epic cooling the epic telescope and focal plane path to cmb pol workshop university of chicago july...

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