1. ConX – XEUS meeting Panu Helistö, Mikko Kiviranta Utrecht, 26-27.10.2004

2. VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT Board VTT Electronics VTT Information Technology VTT Industrial Systems VTT Processes VTT Biotechnology VTT Building and Transport Technical Research Centre of Finland (VTT) TTE Board Microelectronics Microsensing Tele- communications Networks Information Systems Media Human Interaction Technologies Information Technology (TTE) MEMS Sensors RF Sensors Quantronics Optical Sensors Biosensors Microsensing Thin film technology

3. VTT TECHNICAL RESEARCH CENTRE OF FINLAND Quantronics and thin film technology Quantronics Heikki Seppä Panu Helistö Juha Hassel Mikko Kiviranta Arttu Luukanen (at NIST until mid2005) Antti Niskanen Jari S Penttilä Hannu Sipola Topics 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) Thin film technology Ilkka Suni Markku Ylilammi Leif Grönberg Clean room technicians 1700 m 2 class 10/100 clean room

4. VTT TECHNICAL RESEARCH CENTRE OF FINLAND SQUID sensors SQUID (superconducting quantum interference device) is the most sensitive magnetic field sensor 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 – (low 4 power, impedance, noise, temperature) SQUID Amplified signal is fed into the readout electronics Superconducting ring, inner diameter ~ 2  m Josephson tunnel junctions Magnetic field in the loop changes the phase of the quantum wave function and changes the current through the ring Bias current Quantronics

5. VTT TECHNICAL RESEARCH CENTRE OF FINLAND 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of multiplexing methods for TES calorimeter readout Extensive theoretical evaluation in collaboration with SRON (mostly unpublished work) Conclusions: Frequency Division Multiplexing better than Time Division Multiplexing due to better scalability (in bolometer mode both are equal) XEUS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

6. VTT TECHNICAL RESEARCH CENTRE OF FINLAND SQUID readout for TES calorimeters mK SQUID design for XEUS X03 TRP

7. VTT TECHNICAL RESEARCH CENTRE OF FINLAND SQUID readout for TES calorimeters: dcSQUID Washer SQUID Flux noise about 0.1  0 /  Hz at 0.4 K

8. VTT TECHNICAL RESEARCH CENTRE OF FINLAND 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

9. VTT TECHNICAL RESEARCH CENTRE OF FINLAND SQUID readout for TES calorimeters: arraySQUID Arrays SQUID Flux noise about 0.35  0 /  Hz with direct RT readout

10. VTT TECHNICAL RESEARCH CENTRE OF FINLAND Low noise SQUID readout for multiplexing applications: bolometer readout 1.THz-range 4 K superconducting bolometer 2.Optimized, FDM compatible SQUID readout 3.Photon limited noise at room temperature NEP < 5 fW/Hz 1/2 => NETD <~ 10 mK/Hz 1/2 =>  T res ~ 0.3 K @1 kHz => video rate imaging feasible Univ. Jkl

11. VTT TECHNICAL RESEARCH CENTRE OF FINLAND 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/Hz 1/2 => bolometer noise limited, 2 fW/Hz 1/2

12. VTT TECHNICAL RESEARCH CENTRE OF FINLAND Low noise SQUID readout for multiplexing applications Room temperature AC LNAFlow cryostat with optical windows

13. VTT TECHNICAL RESEARCH CENTRE OF FINLAND 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 …

14. VTT TECHNICAL RESEARCH CENTRE OF FINLAND 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

15. VTT TECHNICAL RESEARCH CENTRE OF FINLAND Finland contribution to XEUS/ConX technology mK SQUID + LNA amplifiers, optimized to calorimeters FDM(/TDM) electronics development