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.

QUANTENELEKTRONIK

Laboca

Project purpose: Large Bolometer Camera (Laboca) with 300 pixel for sub-millimeter rangefor Atacama Pathfinder Experiment (APEX) on array of 12m-telescopes in Chili , Atacama

QUANTENELEKTRONIKBolometer Principles

Thermistor = transition edge sensor (TES)

Infrared power Peit T R I

QUANTENELEKTRONIK

Electro Thermal Feedback

Transition edge sensor with voltage bias

Resi

stance

TemperatureT0

Working point

Tc

Rw

• The transition temperature Tc is slightly above the bath

temperature T0 .

• Due to the power dissipation PBIAS = VBIAS

2/RW = (TC-T0)/Gthe thermistor warms up to TC .

•The working point is stable: T R PBIAS T

Electro-Thermal Feedback (ETF)

QUANTENELEKTRONIKSignal Response

)1(

1

)1(

1

iL

L

VP

IS

BIASi

)1()(

0iGT

PL BIAS

BIASi VS

1

)(log

)(log

Td

Rd

L>>1 ; << 1

Current response

Open loop gain Sharpness of the transition

10

L

Effective time constant

QUANTENELEKTRONIKTES Bilayer

Proximity bilayer with TC~ 0.5K

Mo (60 nm)

Au-Pd (8 nm)

QUANTENELEKTRONIK7-pixel Array

7-pixel array chip mounted in the Cu holder plate (1,5 cm x 1,5 cm)

Si waferSi N membrane ~1µm thick with Ti absorber film on the back side

Au ring

Nb wiring

Thermistor (TES)

QUANTENELEKTRONIKSQUID current sensors

SQUID holder with 4 mounted current sensorsµ-metal shield

SQUID current sensor chip

QUANTENELEKTRONIKMeasuring System

SQUID holder with 4 current sensors. The µ-metal shield is not installed.

Superconducting bolometer chamber (Al) with7-pixel horn array

3He stage with sorption pump (300mK)

1.5K pot of 4He cryostat

QUANTENELEKTRONIKFirst Light

30m - radiotelescope of IRAM on Pico Veleta in Spain, Sierra Nevada.

Cryostat with TES bolometers in telescope cabin

QUANTENELEKTRONIKFirst Results

0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3

1,0

1,5

2,0

RBIAS

= 90 mOhmChannel No.

1 2 3

Bol

omet

er S

igna

l, µA

Bias Current, mA

The whole system worked stable in the cabin.

But: bad weather (snow)

0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,360

70

80

90

100

110

120

RBIAS

= 90 mOhm

Channel No. 1 2 3

P, p

W

IBIAS

, mA

Response of the bolometers on the change of black body temperature (77K 300K)

Power calculated as IBIAS x RBIAS x Si

QUANTENELEKTRONIKNext Step

LABOCA: Large Bolometer Camera: 300 pixel on 4 inch wafer

Laboca should be ready in the middle of the year 2005!

QUANTENELEKTRONIKMultiplexing

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 !)

QUANTENELEKTRONIKTime Domain MUX

Amplifier SQUID

TES

RBIAS

TES

RBIAS

TES

RBIAS

TES

RBIAS

Digital control bias switches

FLL electronics,

Sinch

TES bias

Active SQUID

Out

Feedback 1.5K 0.3K 300K

RESET

Bias

QUANTENELEKTRONIKTest of the MUX Electronics

6 separate SQUIDs, SQUID-array as amplifier, the simplest FLL with two operational amplifiers

Sampling frequency 5 kHz Sampling frequency 100 kHz

QUANTENELEKTRONIKIntegrated Bolometer

First samples are fabricated. Tests in the laboratory will be performed in the next weeks.

QUANTENELEKTRONIKConclusions

•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.