M. D. Niemack, et al., P03

A kilopixel array of TES bolometers for ACT:

Development, Testing, and First Light

Low Temperature Detectors 12, P03

July 26, 2007

M. D. Niemack,

Princeton University

Y. Zhao, E. Wollack, R. Thornton, E. R. Switzer, D. S. Swetz, S. T.

Staggs, L. Page, O. Stryzak, H. Moseley, T. A. Marriage, M. Limon, J. M. Lau, J. Klein, M. Kaul, N. Jarosik, K. D. Irwin, A. D. Hincks, G. C. Hilton,

M. Halpern, J. W. Fowler, R. P. Fisher, R. Dunner, W. B. Doriese, S. R. Dicker, M. J. Devlin, J. Chervenak, B. Burger, E. S. Battistelli, J. Appel, M.

Amiri, C. Allen, and A. M. Aboobaker

¼ array

M. D. Niemack, et al., P03Columbia Haverford

U. KwaZulu-NatalRutgers U. TorontoU. CatolicaCardiff

UMass

CUNYUBC

Cluster (SZ, KSZ

X-rays, & optical) Diffuse SZ

OV

CMB to l~10,000

Lensing

Observations:

Collaboration:

Science: Growth of structure

Eqn. of state

Neutrino mass

Ionization history

ACT Atacama Cosmology Telescope

Optical

X-ray

TheoryNIST

Power spectrum

INAOE PrincetonNASA/GSFC

UPenn U. Pittsburgh

wwwphy.princeton.edu/act

M. D. Niemack, et al., P03

Kilopixel Array Overview

• Detector Parameter Selection

• Screening and assembly

• Dark bolometer measurements

• Optical time constants

• First light!

• Current status

M. D. Niemack, et al., P03

Parameter Selection

• Critical Parameters: Noise level, Psat , f3dB

• SQUID noise– Time-domain multiplexing aliasing

select low TES resistance

so high current noise dominates SQUID noise

• Saturation power, Psat

– Predicted load at 145 GHz < 2 pW saturation power for biasing uniformity and f3dB

de Korte, et al. (2003)

M. D. Niemack, et al., P03

Pre-screening and Assembly

• Pre-screen mux chips and shunt chips• Assemble components into columns

Light

Det chip (32 pixels)

Shunt chipNyquist chipMux chip

• Assemble columns into array

¼ filled array

8x32 bolometer array

thermometer

M. D. Niemack, et al., P03

Array Assembly and Si Coupling Layer

Evanescently coupled Si layer matches bolometer impedance

to free space

…also protects

array

…currently

being tested

Light

M. D. Niemack, et al., P03

Pre-Assembly Column Screening

• Test every pixel– V-phi, Tc, I-V, Rshunt, noise

• Repairs– Disconnect oscillating and

problematic detectors– Short failed SQUIDs

• ~90% yield on first ¼ arrayDewar Flange

4He Bath

Vacuum Can

Vacuum Ports,

Electronics

1 m

SRDP

4He Pot

3He Pot

FlexColumn

(1x32TES)3 cm

M. D. Niemack, et al., P03

Noise and Nyquist Inductor Selection

• Compare noise and aliasing estimates pre- and post-Nyquist inductor

• Find maximum decrease in aliasing after adding inductor, without causing oscillations

(R. Dunner & T. Marriage)

TES

AbsorberSi

Aliasing Estimate

Bolometer Model

M. D. Niemack, et al., P03

Optical time constants – CCam prototype

• Chopper wheel measurements

• 3 bolometer types follow trend

• Consistent f3dB between 0.25 – 0.75 * Rn

• Drives us to select higher Psat

CCam

isothermal, no L

• ACT scans in azimuth 5o p2p during observationsLight

M. D. Niemack, et al., P03

First Light!

• CCam prototype on ACT

• Scanning Obs. of JupiterCaveats:

– Mirror alignment

– Non-ideal optics

– Ladder

– Focus

• Plate scale looks good ~38’/mm

M. D. Niemack, et al., P03

Status & Thanks

• Completed majority of testing of remaining columns for array

• Finishing last MBAC receiver tests

• Testing data acquisition with more CCam observations

• Aligning mirrorsThank you:

Cardiff Univ. for supplying CCam filters

A. Dahlen, B. Harrop, T. Essinger-Hileman, K. Martocci, L. Parker, and A. Sederberg for help with detector screening and assembly

All other members of the ACT Collaboration