TES Bolometer ArrayFor the APEX-SZ Camera

Jared MehlUniversity of California, Berkeley

LTD 12, Paris, 2007

CollaboratorsU. C. BerkeleyBill HolzapfelZigmund KermishAdrian LeeMartin LuekerJared MehlTom PlaggePaul RichardsDan SchwanMartin White

MPIfRRolf GuestenRuediger KneisslErnst KreysaKarl MentenDirk MudersPeter SchilkeAxel Weiss

McGill UniversityMatt DobbsTrevor LantingJames Kennedy

University of ColoradoNils HalversonDan BeckerAmy Bender

LBNLHelmuth Spieler

NISTHsiao-Mei Cho

Cardiff UniversityPeter Ade

University of BonnKaustuv BasuFrank Bertoldi Martin Nord Florian Pacaud

MPEHans Boehringer

APEX-SZ• 12 m antenna, ALMA prototype

• 5100 m Atacama Plateau, Chile

• 320 element TES bolometer array

• Frequency domain SQUID

multiplexer readout

• Pulse-Tube Cooler (PTC)

• Use Sunyaev-Zel’dovich effect to

study galaxy clusters

• Operating and taking data

TES Array

• Horn-coupled

• 55 Pixels Per Wedge

• 6 Wedges Per Array

TES Array

• Horn-coupled

• 55 Pixels Per Wedge

• 6 Wedges Per Array

TES Bolometer

• Al/Ti Bilayer TES

R ~ 1.2 normal

T ~ 450 mKC

• Au Thermal Link

G ~ 200 pW / K

• low-stress Si N substrate, released with XeF etch3 4 2

• Au spiderweb absorber

R ~ 200 / sq

~ 9 msoptical

Bolometer Cavity Design

Invar Backshort

SiliconWafer

Spiderweb Absorber

Airgap

WaveguideFeed Horn

TES

Band-defining filters

Bolometer Cavity Simulation150 GHz Simulation, 200 Ohm/sq Abs, λ/4 Backshort

Absorbed Power

Reflected Power

Radiated Power

• Optimize bolometer cavity• HFSS - Ansoft Corporation - 3D finite-element electromagnetic sims

Frequency Domain Multiplexer

AC bias bolometers from 200 kHz – 1 MHz

Frequency Domain Multiplexer

• Zero power dissipation

at sub-Kelvin stage

• Strong rejection of time- varying B-fields

• Simple shielding requirements

• Reduced vibration sensitivity

AC bias bolometers from 200 kHz – 1 MHz

Frequency Domain Multiplexer

SQUID arraymade by NIST

= / (Loopgain + 1) > 300 μs

Bolometer Stability

bias

sensor[ Irwin, JAP,1998 ]

5.8Conservative Stability Criterion:

bias = 2L

R~ 50 μs

For current fMUX (AC bias) at 50% bolometer superconducting transition:

With conservative stability criterion we can tolerate:

sensor 0

Early bolometers:

= ~ 100 μs C

G

Too fast for stable operation0

MUX

Increasing Heat Capacity

Current Bolometers:

0 ~ 30 ms

• Add 3 μm thick gold ring

• Slow down detectors

• Critical for heat capacity to be strongly coupled to TES

• Allows operation deep into transition

Noise Performance

120 aW / Hz1/2

Cluster MapAbell 2163 ~1 hour integration

Courtesy T. Lanting

South Pole TelescopeSub-millimeter Wavelength Telescope:• 10 meter telescope (1’ FWHM beam at

150 GHz)1st Generation Camera:• 1 sq. deg FOV• ~1000 pixels• Observe in 3+ bands between 95-220

GHz simultaneously with a modular focal plane

Funded by NSF

220 GHz 150 GH

z

150

GH

z150 GH

z

95 G

Hz

95 GHz

The End.