CUORE Detector Calibration System - Wright Laboratoryneutrino.physics.wisc.edu/talks/2011-08-CUORE-DOE/CUORE_Heeger_DOE... · Karsten Heeger, Univ. of Wisconsin LBNL, August 2-3,

Karsten Heeger, Univ. of Wisconsin LBNL, August 2-3, 2011

CUORE Detector Calibration System

Karsten M. HeegerUniversity of WisconsinDetector Calibration System Leader

US CUORE Annual ReviewLBNL, August 2-3, 2011

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Outline

• Calibration system requirements• Scope and system elements• Progress at Wisconsin since 2010

– improved DCS failsafe system and positioning– integration work– system testing– hardware for 4K test– readiness and optimization for DCS fabrication – cleaning, assembly, and installation planning

• Schedule and personnel• DCS milestones and CD-4 requirements

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Calibration of CUORE Bolometers

I. Gain StabilizationFor each bolometer an energy pulse generated by a Si resistor is used to correct pulse amplitudes for gain instabilities (→ every 5 min).

III. Voltage-Energy ConversionFit of a calibration measurement with a gamma source (e.g. 232Th) of known energy. Energy calibration performed regularly. (~ monthly).

II. Calibration of individual bolometer

energy [keV]500 1000 1500 2000 2500 3000

[co

un

ts/(

ke

V k

g y

r)]

0

1000

2000

3000

4000

5000

energy [keV]500 1000 1500 2000 2500 3000

[co

un

ts/(

ke

V k

g y

r)]

0

1000

2000

3000

4000

5000

583keV 208Tl

911keV 228Ac

969keV 228Ac 2103keV

single escape

2615keV 208Tl

1592keV double escape

511keV

Sum calibration spectrum of Cuoricino with 232Th source

ββ0ν

• calibrate with γ-sources• need 5+ lines visible in calibration spectrum• energy accuracy goal: < 0.05 keV

Detector Calibration SystemProvide absolute energy calibration of energy spectrum in each bolometer

Summed spectrum from all detectors

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CUORE Detector Calibration System

need to place sources next to crystals to allow calibration of all bolometers

Key Issues• Thermal loads meet heat load requirements of cryostat• Calibration rate of < 150mHz for each bolometer to avoid pile-up• Sources can be replaced. Other source isotopes can be used if necessary (e.g. 56Co has been studied)• Shortest possible calibration time (< 1 week), minimize loss in detector livetime.• Negligible contribution to radioactive background in the ββ0ν region•Minimize the uncertainty in the energy calibration (< 0.05 keV)

Calibration uncertainty - affects the resolution of the detectors- is one of the systematic errors in the determination of the 0νββ half life

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Calibration Source Simulations

radioactive sources: 56Co and/or 232Th

56Co: proton activated Fe wire; 232Th: Thoriated Tungsten wire

both have been used in Cuoricino

~100 events over background per peak are required for successful calibration

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radioactive sources: 56Co and/or 232Th

56Co: proton activated Fe wire; 232Th: Thoriated Tungsten wire

both have been used in Cuoricino

calib

ratio

n tim

e (d

ays)

Number of counts in peak

Calibration time vs counts in peak ~100 events over background per peak are required for successful calibration

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Detector Calibration System - Simulations – 06 Dec 2007

MC HEX

STILL

EXT SOURCES (symmetric)

INT SOURCES

60°

0°


Optimization of Source Strength, Position, and Distribution

source positions

• achieve uniform illumination of all crystals with internal/external sources

• determine max source activity, minimize calibration time

external sources

internal sources

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Detector Calibration System - Simulations – 06 Dec 2007

MC HEX

STILL

EXT SOURCES (symmetric)

INT SOURCES

60°

0°


Optimization of Source Strength, Position, and Distribution

source positions

• achieve uniform illumination of all crystals with internal/external sources

• determine max source activity, minimize calibration time

external sources

internal sources

Activity per discrete source:– internal/external sources: 130 mBq/633 mBq

– internal/external sources (top/bottom) : 131 mBq/728 mBq (higher activity to compensate for z-variation)

Max hit rate of 150 mHz per crystal to avoid pile-up, based on Cuoricino experience

layer 6

event rate in crystals (2615 keV)

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Detector Calibration System

insertion of 12 γ sources that move under own weight

vertical cross section of the cryostat

Pb shield

300K

40K

4K

0.7K80mK

10mK

detectors@ ~10mK

Pb shield

motion systeminsertion and extraction of sources in and out of cryostat

guide tubes no straight vertical access

source stringsmove under own weight in guide tubes

top view of detector array with source positions

source locations

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Detector Calibration System

insertion of 12 γ sources that move under own weight

Lead shield

40K

300K

4K

0.7K70mK10mK

guide tubes

detector support plate

bolometers@ ~10 mK

motion systeminsertion and extraction of sources in and out of cryostat

guide tubes no straight vertical access

source stringsmove under own weight in guide tubes

top view of detector array with source positions

source locations

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Cryogenic Considerations

• Calibration system must be integrated with complex detector cryostat

• Must meet available cooling power requirements at all thermal stages

→ Cooldown of source string→ Friction heat during insertion/extraction→ Static heat load of guide tubes: thermal conductance&radiation emission

Stage T [K]Cooling power

available to calibration [W]

Static heat load from

guide tubes

Radiation from source string at 4K

40K 40 – 50 ~ 1 ~1 --

4K 4 – 5 0.3 0.02 --

0.7K 0.6 – 0.9 0.55m 0.13m 0.08µ

70mK 0.05 – 0.1 1.1µ negligible 0.3µ

10mK 0.01 1.2µ 1.07µ 0.08µ

detector 0.01 < 1µ -- 0.25µ

Stainless SteelCopper

Perfect thermal coupling

Weak thermal couplinginternal external

Guide Tubes and Thermal Coupling

• Thermal conductivity of guide tubes• Radiation heat inflow from 300 K• Heat radiated by the source strings• Thermal conductivity of the source strings• Frictional heat during source string motion

40K

300K

4K

0.7K

70mK

10mK

Lead shield

Detector region9


Calibration Motion System Motion Box

vacuum feedthrough with shaft

vacuum flangemotor, gears, and encoder

electrical feedthrough

drive spools can be removed with clean bag for individual source exchange

Drive Spool

source string spool

string guide

load cellhome limit switch

emergency switch

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Calibration Source & Guide Tubes

radioactive source wire•232Th: Thoriated Tungsten wire• 56Co: proton activated Fe wire

Kevlar string

PTFE heat shrink

• flexible, moves under gravity in guide tube

• small mass: < 5 grams• vertical distribution of

source activity can be adjusted

• 30 capsules crimped and evenly spaced over 85 cm of Kevlar string

Source String

Guide Tubes• stainless and/or machined from solid, low-background copper• can use teflon tubes for bends

~10mm

source wire

Cu crimp

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40K

300K

4K

0.7K70mK

10mK

Lead shield

Lead shield

Detector region

solenoid linear actuator

source string pushing blade

Magneto-mechanical 4K thermalization mechanism

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CUORE cryostat

Thermalization at 4K Flange

Calibration Thermalization to 4K• Sources must be cooled to < 4K to meet heat load requirements• Strong mechanical contact is needed between the source carrier

and a heat sink at 4K


Failsafe and Positioning Systems

Induction-based proximity sensors detects position of source capsules and counts them.

Emergency switch protects mechanically against excess tension.

Encoder measures spooling of source string.

Home limit switch provides mechanical zero position of source home position.

Gate valve closes motion box during regular data taking Failsafe during power and pressure failure, with mechanical and software switch.

Load cell measures tension in string. Allows rough position determination in cryostat. Monitors insertion and retraction. Software limits for automatic shut-off.

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Improved Failsafe Positioning


Integration Effort at Wisconsin

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DCS Integration Effort at Wisconsin and with CUORE Integration TeamCUORE cryostat is complex

In early 2011 UWisc integrated DCS model into up-to-date cryostat model.

4 interferences above 300K:- 3 solved by rotating/customizing DCS parts- 1 solved by changing pulse tube part

cryostat model incomplete below 4K:- top support, bottom support plates missing- outdated detector frames

Frascati integration team working on many critical CUORE issues, cryostat is one of them


Outstanding Integration Issues

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Top Support Plate+DCS+Wiring Reveals InterferencesFurther integration work needed in detector region- Italian integration team proposes to change guide tube routing:original routing, proposed new routing- Monte Carlo studies of backgrounds in progress - decision by end of August 2011?

Connection to bottom plate to be finalized


Calibration System TestingPhased System Testing ProgramMotion/mechanical tests at 300K extensive tests performed to date, verified and characterized motion and instrumentationcomplete but ongoing

Motion/mechanical tests at 77K tests mechanical operation of thermalization mechanism and cryostat parts for > 5 year lifetimecomplete but ongoingMotion/thermal tests at 4K (in CUORE cryostat at LNGS)hardware built for test of 1 motion box and typical guide tube routing, integrated test of thermalization, depends on CUORE cryostat schedulein preparation, planned for early 2012

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Calibration System TestingPhased System Testing ProgramMotion/mechanical tests at 300K extensive tests performed to date, verified and characterized motion and instrumentationcomplete but ongoing

Motion/mechanical tests at 77K tests mechanical operation of thermalization mechanism and cryostat parts for > 5 year lifetimecomplete but ongoingMotion/thermal tests at 4K (in CUORE cryostat at LNGS)hardware built for test of 1 motion box and typical guide tube routing, integrated test of thermalization, depends on CUORE cryostat schedulein preparation, planned for early 2012

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Motion/thermal tests at 4K (standalone)- setting up independent 4K test chamber in Wisconsin (He bath and pulse tube)- tests in fall 2011

will allow UWisc to make measurements with thermalizaton mechanism and learn and prepare for 4K testing at LNGS


Calibration System Testing & Schedule

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Figure: Peterson



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Figure: Peterson

start of cryostat assembly = start of UWisc presence at LNGS



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Figure: Peterson

start of cryostat assembly = start of UWisc presence at LNGS

cryostat assembly procedure under development,expect 4K test in early 2012


System Testing at Wisconsin

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Outgassing measurements and bakingMechanical motion test stand at 300K

System tests at 77K

Setting up independent 4K pulse tube


load cell

guide tubes

webcam

proximity sensor

source moves reliably under its own weightposition accuracy ~ 1-2 mmreproducible load cell pattern allows safe operation

load cell data

profile limits

load cell data shows unique geometry of guide tube system

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up

down

Load Cell DataMechanical motion test stand at 300K


Improved Positioning with Limit Switch

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home reset switch

emergency kill switch

- Home position from encoder drifts over time by about ~2mm - home switch resets home position to increase positioning precision- engages at low force ~0.3N

Time (hrs)

Pos

ition

(cm

)drift of home position over time without home reset switch


Mechanical Testing at 77K

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Thermalization Mechanism Prototype Testing source string & capsule

thermalization blade

CUORE requirements- expect calibration ~ 1/month- 60 cycles per string over 5 years- 180 cycles per mechanism over 5 years- expect < 500 cycles including commissioning

Testing> 27000 cycles for 1 s push and 1 s release at 300K > 15000 cycles for 1 s push and 1 s release at 77K> 400 cycles for 30 s push and 30 s release at 77K > 9000 cycles for 1 s push and 1 release on top edge of blade at 77K> 800 cycles for 1 s push and 1 s release on undersized capsule at 77K

no jamming, no wear of mechanism, no significant wear on capsules


Calibration System Test at 4K

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Integrated test of one motion box and inner and outer guide tubes at 4K in CUORE cryostat at LNGS→ test of the key DCS components in empty CUORE cryostat

motion box above 300K

thermalization mechanism

thermal Cu shunt to improve thermalization

- requires CUORE cryostat at LNGS, DCS schedule follows on-site work- uses “old” guide tube routing around lead shield- hardware designed and built for 4K test does not reflect proposed change of guide tube routing through lead shield.


Hardware for 4K LNGS Test

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see demonstration hardware at review


Readiness for DCS Production

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Building and optimizing jigs for guide tube production

customized jig for bending, welding, and leak checking 300K-4K stainless guide tubes

developed procedure for precision bending of copper guide tubes

- meet bending radius to < 1mm- determine radius with digital image and Autocad radius fitting - max elliptical deviation of inner radius ~0.006” (0.15mm)

Gundrilling method for guide tube fabrication

- built 300mm length for 4K test, can increase to 500-800mm length if needed. would eliminate segmentation of guide tube in detector region- fabrication tools easily reconfigurable for new routing in cryostat


Cleaning and Assembly at Wisconsin

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- New class-1000 cleanroom at Wisconsin with cleaning capabilities. Meets UHV requirements. - Will be used for source fabrication and final cleaning of motion box parts and for cleaning of DCS cryostat components. - Will be used for final acceptance testing just before shipment.


Installation Planning at Wisconsin

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1:0.75 model printout of cryostat

1:1 wooden model of cryostat flanges

300K

40K

4K


Installation Planning at Wisconsin

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1:0.75 model printout of cryostat

1:1 wooden model of cryostat flanges

300K-4K guide tubes in jig

- visualize and develop installation procedure before installation at LNGS- practice installation of guide tubes and indium seal


Calibration Team

Scientists– K. Heeger (faculty)– Daniel Lenz (postdoctoral fellow, UWisc)– L. Ejzak (graduate student, 5th year)– A. Dally (graduate student, 2th year on CUORE)– S. Sangiorgio (postdoctoral fellow, now at LLNL)Engineer/Designer (UWisc)– Ken Kriesel (mechanical engineer) – Glen Gregerson (designer

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Communication (Wisconsin and CUORE cryostat group)– weekly meetings with Wisconsin

engineer– phone meetings with cryostat

group in Milan– integration meetings at time of

collaboration meetings

Current

Planned in FY2012-13Scientists– K. Heeger (faculty)– Daniel Lenz (postdoctoral fellow, at UWisc)– A. Dally (graduate student, 2th year on CUORE) Researcher– T. Wise (senior researcher) Engineering as needed

→ on-site for DCS testing→ on-site long-term for cryostat assembly and DCS testing

→ on-site installation and testing


Calibration System Milestones

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completed

achievable if DCS 4K test at LNGS by Spring 2012

need to commit to building remaining DCS hardware in summer 2012


Revised CD-4 Requirements

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based on vacuum requirement from cryostat

Objectives for Revised CD-4 Criteria:

1. ensure DCS functionality to greatest extent possible 2. make deliverable independent of cryostat and on-site work as much as possible

Proposed Change to Calibration System CD4 Deliverables

all requirements have essentially been met with 4K test hardware


Summary

• Wisconsin has completed design, mechanical tests, and vacuum testing of motion box. Developed source fabrication procedure. Continue long-term motion testing.

• Built hardware for 4K calibration test in cryostat at LNGS. • Optimizing fabrication procedures for remaining DCS hardware.• Addressing outstanding integration challenges together with

CUORE integration team in Italy. Will finalize DCS integration in detector region in Fall 2011.

• Develop independent capabilities at Wisconsin for cleaning, assembly, and mechanical and thermal testing of DCS components to greatest extent possible.

• Developing installation plans and procedures utilizing 1:1 model of cryostat at Wisconsin.

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Karsten Heeger, Univ. of Wisconsin LNGS, March 28-29, 2011

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Documents

CUORE Detector Calibration System - Wright Laboratoryneutrino.physics.wisc.edu/talks/2011-08-CUORE-DOE/CUORE_Heeger_DOE... · Karsten Heeger, Univ. of Wisconsin LBNL, August 2-3,