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Cosmology with ACT. Mark Halpern, UBC. Photo of the Atacama Cosmology Telescope by Michele Limon. A tacama C osmology T elescope. A program designed to measure the high- l features of the CMB.

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slide1
Cosmology with ACT

Mark Halpern, UBC

Photo of the Atacama Cosmology Telescope by Michele Limon

slide2
AtacamaCosmologyTelescope

A program designed to measure the high-l features of the CMB

ACT is a 3-color off-axis 6m telescope. Beam sizes are 1-2 arc minutes, corresponding to 400< l <7000

X-ray

Theory

Optical

Collaboration:

Cardiff

Columbia

Haverford

NIST

CUNY

Princeton

INAOE

NASA/GSFC

Rutgers

UBC

UPenn

U. Toronto

U. Catolica

U. KwaZulu-Natal

UMass

U. Pittsburgh

slide3
The CMB is still a scientific gold mine.

Small scale anisotropy

Polarization at all angular scales

Better known parameters

Measure w(z)

Neutrino mass?

Non-gaussianity?

Something new?

Non-adiabatic modes ?

Formation and growth of cosmic structure.

Tests of field theories at 10-35 s.

slide5
One example…

Tilt of the Angular Power Spectrum.

The overall tilt of the spectrum--- encoded in the “scalar spectral index” ns--- is a new handle on inflation.

ACT and other small scale measurements will resolve ns.

Polarization experiments will help resolve r.

Expect results from Planck, Clover, Spider, Ebex, Spud, Bicep, Poincare, bPol, CMB-pol. This is an active field.

Expts in red use UBC TES electronics and NIST-style multiplexors.

slide6
Comparison of WMAP and ACT spectra will provide a useful measurement of ns.

A 2% variation in ns produces a 5% variation in primary anisotropy at l = 2500.

The relative calibration of WMAP and ACT must be known to <1% to provide useful data. This is easier than knowing the WMAP beam shape well enough.

slide7
ACT will also probe secondary anisotropies which arise during the epoch of structure formation

Sunyaev Zeldovich effect from clusters

Gravitational Lensing of the CMB

Vishniac Effect and Kinetic SZ

Foreground point sources

Epoch of cluster formation

Measure w(z)

Measure mass spectrum

Star formation history

Photo from Act towards llano de Chajnantor by Michele Limon

sz signature non cmb spectrum
SZ Signature: Non-CMB spectrum

Hot electron gas imposes a unique spectral signature:

photon number is preserved while photons scatter to higher energy

145 GHz

decrement

220 GHz

null

270 GHz

increment

1.4°x 1.4°

NO SZ Contribution in Central Band

slide9
Thomson Scattering and structure in either the velocity or the density of free electrons produce a secondary anisotropy.

The frequency spectrum (color) of the anisotropy matches the CMB.

Valageas, Balbi &Silk Astro-ph 0009040

slide10
ACT will measure the matter power spectrum in both linear (Ostriker-Vishniac) and non-linear (kinetic Sunyaev-Zel’dovich) growth regimes.

Non-linear: kSZ

Clusters have formed. Cluster velocity produces signal

Linear Effects: OV

Structure in ne not correlated with bulk v.

From Wayne Hu, Astro-ph 9907103

slide11
The ACT angular resolution is needed to study SZ.

150 GHz

SZ Simulation

MBAC on ACT

Planck

Burwell/Seljak

2X noise

1.7’ beam

WMAP

MAP

ACT

PLANCK

Statistical uncertainties based on 1 season with best measured noise.

de Oliveira-Costa

panels installed
Panels Installed

Each panel of the primary mirror is adjusted by hand and locked in place.

slide15
Large sensitive arrays of superconducting Transition Edge Sensor bolometers are at the heart of ACT.

We build the control and readout electronics for these arrays.

slide17
Load curves
  • Also plot as power in detector vs voltage
  • Power constant in superconducting transition
  • Power proportional to V2 in normal state
  • Responsivity (S) in transition proportional to 1/V

Decreasing heater power

slide18
Optical response of five bolometers:

Feedback

Error signal

This is 10 kHz readout of a sub-pW optical signal.

(Data collected at UBC on a cryostat in New Jersey. by Elia Batastelli.)

slide19
UBC and ACT

Mandana Amari

Elia Batastelli

Bryce Burger

Matthew Hasselfield

slide20
240square degrees in circle
  • 100 square degrees for CMB

Cross Linked Scan Strategy is Crucial to Making Maps on Degree Angular Scales

slide21
An image of Jupiter taken in drift scan with an 8x32 camera, taken before primary surface alignment, in fact taken before the ladder was removed from in front of the primary!
observing
2007 Season Complete: 30 Days with 1000-element 145 GHz detector array
  • 2008 Season to commence in June for 6 months with 145, 215, (and 280) GHz arrays
  • 2009 Season: Another 6 months with three arrays
observing
bullet cluster sz
Bullet cluster SZ

6 minutes effective observing time..0.03% of our data

ACT

2007 Data

Previous Generation SZ

-55.8

ACT Inset

-55.9

-56.0

-56.1

104.875 104.75 104.625 104.5

Gomez et al. 2003

Black contours are show dark matter distribution

derived from weak lensing and brown contours show

gas distribution derived from X-rays. (Clowe et al. 2006)

thank you
Thank You!

Photo by Elia Batastelli, 7 Oct. 2007.

slide25
General relation of MBAC to ACT Telescope

Scanning is performed by rotating the entire structure about a vertical axis passing through the cryostat.

800 lbs

slide26
The TT power spectrum is now cosmic-variance limited out to l =400.

The sharp “snake bites” at l=180 and 205 are slightly smaller, but still present.

Notice how little difference there is l by l between 1-year and 3-year data.

WMAP-3yr (Black)

WMAP-1 yr (Grey)

Cosmic Variance

mbac layout
MBAC Layout

Cylindrically shaped

aligned along optical axis

Liquid-Cryogen Free

Pulse Tube Coolers

1st stage: 80W @ 45K

expected: 30W @ 40K

2nd stage: 2W @ 4.2K

expected: 0.2W @ 3K

Helium-4 and Helium-3

Sorption Fridges

270 mK temp w/

60 hour hold time

with 15 μW load

Window

4He Fridge

Pulse Tube

3He Fridge

Detectors

40K Shield

3 feet

3K Shield

slide28
Regions of the Sky covered

BCS

GALEX, XRAY

The bands are the areas

Of sky we observe in CMB

slide31
ALMA Support

APEX

Devlin

ACT –

5200 meters

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