TES Bolometer Array
For the APEX-SZ Camera
Jared Mehl
University of California, Berkeley
LTD 12, Paris, 2007
Collaborators
U. C. Berkeley
McGill University
MPIfR
Bill Holzapfel
Zigmund Kermish
Adrian Lee
Martin Lueker
Jared Mehl
Tom Plagge
Paul Richards
Dan Schwan
Martin White
Matt Dobbs
Trevor Lanting
James Kennedy
Nils Halverson
Dan Becker
Amy Bender
Rolf Guesten
Ruediger Kneissl
Ernst Kreysa
Karl Menten
Dirk Muders
Peter Schilke
Axel Weiss
Cardiff University
University of Bonn
LBNL
Peter Ade
Kaustuv Basu
Frank Bertoldi
Martin Nord
Florian Pacaud
Helmuth Spieler
NIST
Hsiao-Mei Cho
University of Colorado
MPE
Hans 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
• Au spiderweb absorber
R ~ 200  / sq
t
optical
~ 9 ms
• Al/Ti Bilayer TES
R normal ~ 1.2 
T C ~ 450 mK
• Au Thermal Link
G ~ 200 pW / K
• low-stress Si 3 N4 substrate, released with XeF2 etch
Bolometer Cavity Design
Band-defining filters
Feed Horn
Waveguide
Spiderweb
Absorber
TES
Silicon
Wafer
Airgap
Invar Backshort
Bolometer Cavity Simulation
150 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
AC bias bolometers from 200 kHz – 1 MHz
• Zero power dissipation
at sub-Kelvin stage
• Strong rejection of timevarying B-fields
• Simple shielding
requirements
• Reduced vibration
sensitivity
Frequency Domain Multiplexer
SQUID array
made by NIST
Bolometer Stability
Conservative Stability Criterion:
t sensor
t bias
> 5.8
[ Irwin, JAP,1998 ]
For current fMUX (AC bias) at 50% bolometer superconducting transition:
t bias
2L MUX
=
~ 50 μs
R
Early bolometers:
t0
=
C
G
~ 100 μs
Too fast for stable
operation
With conservative stability criterion we can tolerate:
t sensor
=
t0
/ (Loopgain + 1) > 300 μs
Increasing Heat Capacity
Current Bolometers:
• Add 3 μm thick gold ring
• Slow down detectors
t0
~ 30 ms
• Allows operation deep into transition
• Critical for heat capacity to be
strongly coupled to TES
Noise Performance
120 aW / Hz1/2
Cluster Map
Abell 2163
~1 hour integration
Courtesy T. Lanting
South Pole Telescope
Sub-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
The End.