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ConX – XEUS meeting Panu Helistö, Mikko Kiviranta - PowerPoint PPT Presentation

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ConX – XEUS meeting Panu Helistö, Mikko Kiviranta. Utrecht, 26-27.10.2004. VTT Board. Thin film technology. TTE Board. VTT Electronics. Microelectronics. MEMS Sensors. VTT Information Technology. Microsensing. RF Sensors. VTT Industrial Systems. Tele- communications. Quantronics.

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ConX – XEUS meeting Panu Helistö, Mikko Kiviranta

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ConX – XEUS meetingPanu Helistö, Mikko Kiviranta

Utrecht, 26-27.10.2004

VTT Board

Thin film


TTE Board

VTT Electronics


MEMS Sensors

VTT Information



RF Sensors

VTT Industrial





VTT Processes


Optical Sensors






VTT Building

and Transport



Technical Research Centre of Finland (VTT)




Information Technology (TTE)


Heikki Seppä

Panu Helistö

Juha Hassel

Mikko Kiviranta

Arttu Luukanen (at NIST until mid2005)

Antti Niskanen

Jari S Penttilä

Hannu Sipola


Superconducting sensors, electronics and standards (SQUID, Josephson voltage, bolometers)

Mesoscopic electronics (BOT, sluice Cooper pair pump)

Optimised and integrated readout electronics (e.g. for MEMS sensors and bolometers)

R&D projects related to electricity metrology

STJ detectors (X-ray for ESTEC, protein flight-time mass spectroscopy)

Quantronics and thin film technology

Thin film technology

  • Ilkka Suni

  • Markku Ylilammi

  • Leif Grönberg

  • Clean room technicians

  • 1700 m2 class 10/100 clean room


Superconducting ring,

inner diameter ~ 2 mm

Josephson tunnel junctions

Bias current

Amplified signal

is fed into the

readout electronics

Magnetic field in the loop changes the phase of the quantum wave function and changes the current through the ring


SQUID sensors

  • Almost 20 year background in SQUID applications

  • Novel SQUID and readout concepts: unSQUID, hgSQUID, noise cancellation,…

  • Industrial standard SQUID process

  • World leader in biomagnetic SQUIDs

  • SQUID - ‘ideal’ for reading out cryogenic calorimeter and bolometer signals – (low4 power, impedance, noise, temperature)

  • SQUID(superconducting quantum interference device) is the most sensitive magnetic field sensor

Comparison of multiplexing methods for TES calorimeter readout

  • Extensive theoretical evaluation in collaboration with SRON (mostly unpublished work)

  • Conclusions: Frequency Division Multiplexing better than Time Division Multiplexing due to better scalability (in bolometer mode both are equal)

  • XEUS requirements difficult but feasible from readout point of view

SQUID readout for TES calorimeters

mK SQUID design for XEUS X03 TRP

SQUID readout for TES calorimeters: dcSQUID

Washer SQUID

  • Flux noise about 0.1 0 / Hz at 0.4 K

SQUID readout for TES calorimeters: unSQUID

(a) Schematics of the damping circuit for the un SQUID.

(b) Chip carrier with the SQUID chip and SMD components.

(c) The time trace of the SQUID current taken in the negative-resistance region indicates stable operation without parasitic oscillation.

Potentially lower noise, improved impedance matching

SQUID readout for TES calorimeters: arraySQUID

Arrays SQUID

  • Flux noise about 0.35 0 / Hz with direct RT readout

Low noise SQUID readout for multiplexing applications: bolometer readout

  • THz-range 4 K superconducting bolometer

  • Optimized, FDM compatible SQUID readout

  • Photon limited noise at room temperature

    • NEP < 5 fW/Hz1/2

    • => NETD <~ 10 mK/Hz1/2

    • => DTres ~ 0.3 K @1 kHz

    • => video rate imaging feasible



Low noise SQUID readout for multiplexing applications: bolometer readout

Room temperature LNA

  • 5 MHz center frequency

  • Noise temperature 26 K @ 50 Ohm

    SQUID amplifier

  • input current noise 2 pA/Hz1/2

  • => bolometer noise limited, 2 fW/Hz1/2

Low noise SQUID readout for multiplexing applications

Room temperature AC LNA

Flow cryostat with optical windows

XEUS/FDM readout challenges

  • Amplifier reading out the TES

    • Noise temperature <= 100 mK @ 10 MHz (SQUID)

    • Post-SQUID next stage easily dominates noise

  • AC biasing/multiplexing

    • Low impedance levels: very high Q-value filters required

    • Dynamic range/linearity

      • Idle current cancellation

      • Neg-FB with high loop gain when cable delay is present  FB at baseband, non-standard loop filters.

    • Effect of higher harmonics

    • Crosstalk

  • Others

    • Count rate/pileup management

Work division in ConX/XEUS technology development

Different possibilities

  • Instrument1: ESA

  • Instrument2: USA

  • TDM based path

  • FDM based path

  • calorimeter1SQUID1+LNA1FDM

  • calorimeter2(SQUID2)+LNA2TDM

  • etc

Finland contribution to XEUS/ConX technology

  • mK SQUID + LNA amplifiers, optimized to calorimeters

  • FDM(/TDM) electronics development

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