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QUANTENELEKTRONIK TES Bolometer Array with SQUID readout for Apex V. Zakosarenko, T. May, R. Stolz, H.-G. Meyer, Institute for Physical High Technology, Jena E. Kreysa, W. Esch, Max Planck Institute for Radioastronomy, Bonn The work is supported by the German BMBF under the contract No. 05 AA2PC1/3. Laboca Project purpose: Large Bolometer Camera (Laboca) with 300 pixel for sub-millimeter range for Atacama Pathfinder Experiment (APEX) on array of 12m-telescopes in Chili , Atacama QUANTENELEKTRONIK Bolometer Principles QUANTENELEKTRONIK Infrared power Peiwt T R I Thermistor = transition edge sensor (TES) Electro Thermal Feedback Transition edge sensor with voltage bias QUANTENELEKTRONIK • The transition temperature Tc is slightly above the bath temperature T0 . Resistance • Due to the power dissipation PBIAS = VBIAS2/RW = (TC-T0)/G the thermistor warms up to TC . Working point Rw •The working point is stable: T R PBIAS T Electro-Thermal Feedback (ETF) T0 Tc Temperature Signal Response I 1 L 1 Si P VBIAS ( L 1) (1 iw ) PBIAS L(w ) GT (1 iw 0 ) d (log R) d (log T ) Open loop gain Sharpness of the transition Si 1 VBIAS L>>1 ; w << 1 QUANTENELEKTRONIK Current response 0 L 1 Effective time constant TES Bilayer QUANTENELEKTRONIK Au-Pd (8 nm) Proximity bilayer with TC~ 0.5K Mo (60 nm) 7-pixel Array Si wafer QUANTENELEKTRONIK Si N membrane ~1µm thick with Ti absorber film on the back side Au ring Thermistor (TES) Nb wiring 7-pixel array chip mounted in the Cu holder plate (1,5 cm x 1,5 cm) SQUID current sensors QUANTENELEKTRONIK SQUID current sensor chip µ-metal shield SQUID holder with 4 mounted current sensors Measuring System SQUID holder with 4 current sensors. The µ-metal shield is not installed. Superconducting bolometer chamber (Al) with 7-pixel horn array 3He stage with sorption pump (300mK) QUANTENELEKTRONIK 1.5K pot of 4He cryostat First Light 30m - radiotelescope of IRAM on Pico Veleta in Spain, Sierra Nevada. Cryostat with TES bolometers in telescope cabin QUANTENELEKTRONIK First Results QUANTENELEKTRONIK The whole system worked stable in the cabin. But: bad weather (snow) 120 Channel No. 1 2 3 RBIAS = 90 mOhm 110 100 P, pW Bolometer Signal, µA 2,0 1,5 RBIAS = 90 mOhm 90 Channel No. 1 2 3 80 70 1,0 0,4 0,5 0,6 0,7 0,8 0,9 1,0 Bias Current, mA 1,1 1,2 1,3 60 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 IBIAS, mA Power calculated as IBIAS x RBIAS x Si Response of the bolometers on the change of black body temperature (77K 300K) Next Step QUANTENELEKTRONIK LABOCA: Large Bolometer Camera: 300 pixel on 4 inch wafer Laboca should be ready in the middle of the year 2005! Multiplexing QUANTENELEKTRONIK Two possibility: a) parallel readout 300 current sensors each in separate packaging, ~1250 wires to room temperature electronics, 300 FLL electronics. low risk (familiar way) mechanical complexity, thermal last, too expensive ! b) multiplexing 300 SQUID integrated on the wafer with bolometers, ~30 SQUID amplifier in separate packaging, ~200 wires to room temperature, 30 FLL electronics, and digital controller . less expensive new development (challenge !) Time Domain MUX QUANTENELEKTRONIK TES bias Digital control bias switches TES RBIAS TES RBIAS Bias TES Active SQUID RBIAS Sinch Amplifier SQUID RESET FLL electronics, TES RBIAS 0.3K Feedback 1.5K 300K Out Test of the MUX Electronics Sampling frequency 5 kHz QUANTENELEKTRONIK Sampling frequency 100 kHz 6 separate SQUIDs, SQUID-array as amplifier, the simplest FLL with two operational amplifiers Integrated Bolometer QUANTENELEKTRONIK First samples are fabricated. Tests in the laboratory will be performed in the next weeks. Conclusions QUANTENELEKTRONIK • 7 pixel TES bolometer array with SQUID readout shows stable operation in real environment in telescope cabin. • 7 pixel TES bolometer array with integrated SQUID is ready for test. • Time domain multiplexing operates. Optimization of bandwidth and noise figure is in progress. • Great challenge to perform the proposed schedule.