 Main
Measurements of Secodary Cosmic Microwave Background Anisotropies with the South Pole Telescope
 Lueker, Martin Van
 Advisor(s): Holzapfel, William L
Abstract
The South Pole Telescope is a 10m millimeterwavelength telescope for finding
galaxy clusters via the thermal SunyaevZel'dovich (tSZ) effect. This thesis is divided into two parts. The
first part describes the development of the kilopixel SPTSZ receiver and the frequencydomain multiplexor
(fMUX). The second part describes the first SPT power spectrum measurement and the first detection of the
tSZ power spectrum.
The SPTSZ focal plane consists of 960 spiderweb coupled transitionedge sensors. Due to strong electro
thermal feedback, these devices have good sensitivity and linearity, though risk spontaneous oscillations.
Adding heat capacity to these devices can ensure stability, so long as the loopgain, $\mathcal{L}$, is less
than $G_\textrm{int}/G_0$, the ratio between the thermal conductances linking the TES to the heat capacity
and linking the heat capacity to the bath. I describe as experimental technique for measuring the
internal thermal structure of these devices, allowing for rapid sensor evaluation.
The fMUX readout system reduces wiring complexity in this receiver by ACbiasing each sensor at a unique
frequency and sending signals from multiple bolometers along one pair of wires. The Series SQUID Arrays
(SSAs) used to read changes in bolometer current are notably nonlinear and extremely sensititve to ambient
magnetic fields. The SSAs are housed in compact magnetic shielding modules which reduces their effective
area to 80 $\textrm{m}\Phi_0/\textrm{gauss}$. The SSA are fedback with a fluxlocked loop to improve their
linearity and dynamic range, and decrease their input reactance. The FLL is bandwidth of 1 MHz with a
measured loopgain of 10. In the current implementation, this bandwidth is limited between the SQUID input
coil and other reactances, which I study in Chapter \ref{chap:fllstab}.
In the second part of the thesis I present power spectrum measurements for the first 100~deg$^2$ field observed by the SPT. On angular scales where the primary CMB anisotropy is dominant,
$\ell \lesssim 3000$, the SPT power spectrum is consistent with the standard
$\Lambda$CDM cosmology. On smaller scales, we see strong evidence for
a point source contribution, consisteThe South Pole Telescope is a 10m millimeterwavelength telescope for finding
galaxy clusters via the thermal SunyaevZel'dovich (tSZ) effect. This thesis is divided into two parts. The
first part describes the development of the kilopixel SPTSZ receiver and the frequencydomain multiplexor
(fMUX). The second part describes the first SPT power spectrum measurement and the first detection of the
tSZ power spectrum.
The SPTSZ focal plane consists of 960 spiderweb coupled transitionedge sensors. Due to strong electro
thermal feedback, these devices have good sensitivity and linearity, though risk spontaneous oscillations.
Adding heat capacity to these devices can ensure stability, so long as the loopgain, $\mathcal{L}$, is less
than $G_\textrm{int}/G_0$, the ratio between the thermal conductances linking the TES to the heat capacity
and linking the heat capacity to the bath. I describe as experimental technique for measuring the
internal thermal structure of these devices, allowing for rapid sensor evaluation.
The fMUX readout system reduces wiring complexity in this receiver by ACbiasing each sensor at a unique
frequency and sending signals from multiple bolometers along one pair of wires. The Series SQUID Arrays
(SSAs) used to read changes in bolometer current are notably nonlinear and extremely sensititve to ambient
magnetic fields. The SSAs are housed in compact magnetic shielding modules which reduces their effective
area to 80 $\textrm{m}\Phi_0/\textrm{gauss}$. The SSA are fedback with a fluxlocked loop to improve their
linearity and dynamic range, and decrease their input reactance. The FLL is bandwidth of 1 MHz with a
measured loopgain of 10. In the current implementation, this bandwidth is limited between the SQUID input
coil and other reactances, which I study in Chapter \ref{chap:fllstab}.
In the second part of the thesis I present power spectrum measurements for the first 100~deg$^2$ field observed by the SPT. On angular scales where the primary CMB anisotropy is dominant,
$\ell \lesssim 3000$, the SPT power spectrum is consistent with the standard
$\Lambda$CDM cosmology. On smaller scales, we see strong evidence for
a point source contribution, consistent with a population of dusty, starforming galaxies.
I combine the 150 and 220$\,$GHz data to remove the majority of the point source power,
and use the point source subtracted spectrum to detect SunyaevZel'dovich (SZ) power at $2.6
\,\sigma$. At $\ell=3000$, the SZ power in the subtracted bandpowers is $4.2\,$$\pm$$\,1.5\,
\mu\rm{K}^2$, which is significantly lower than the power predicted by a
fiducial model using WMAP5 cosmological parameters. t with a population of dusty, starforming galaxies.
I combine the 150 and 220$\,$GHz data to remove the majority of the point source power,
and use the point source subtracted spectrum to detect SunyaevZel'dovich (SZ) power at $2.6
\,\sigma$. At $\ell=3000$, the SZ power in the subtracted bandpowers is $4.2\,$$\pm$$\,1.5\,
\mu\rm{K}^2$, which is significantly lower than the power predicted by a
fiducial model using WMAP5 cosmological parameters.
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