Observations of Cosmic Microwave Background (CMB) polarization are a powerful probe of cosmology and will eventually probe the standard model of physics at ultrahigh energy. With this award, Dr. Adrian Lee, University of California at Berkeley, will lead a new project called POLARBEAR (POLARization of the Background Radiation) which will use a dedicated telescope equipped with a powerful 1,200-bolometer array receiver to produce maps of CMB polarization with unprecedented accuracy. The most exciting possibility is that POLARBEAR will detect the signature of gravitational waves from the end of the inflationary period, 10-38 seconds after the Big Bang. If detected, these signals will provide an independent verification of the inflationary paradigm and test specific models for inflation.
Another important scientific motivation is to characterize the gravitational lensing of the CMB polarization. An accurate lensing measurement will yield constraints on Dark Energy. POLARBEAR can verify, or rule out, models with a strongly time-dependent Dark Energy equation of state w. In fact, POLARBEAR can provide information on w", the time derivative of w, which is comparable and complementary to that from a space-based supernovae search. The lensing signal is also sensitive to neutrino masses because massive neutrinos act as "hot" dark matter changing the formation of the lensing large scale structure.
POLARBEAR introduces unprecedented levels of instrumental sensitivity and control of systematic errors. The high sensitivity is achieved with an array of planar-antenna-coupled Transition-Edge Sensor (TES) bolometers operated at 250 mK. Dr. Lee and his colleagues have built and conducted tests of prototypes of these arrays. POLARBEAR's final configuration will include 1,200 bolometers distributed among three frequency bands at 90, 150, and 220 GHz.
Members of the collaboration have played key roles on many of the best CMB experiments to date. They are also playing a key role in bringing the next generation of large TES focal plane instruments. These experiments will be reaching maturity as POLARBEAR starts, and the collaboration members will be focused on building POLARBEAR. There will be significant international funding contributions from Canada on the readout electronics, from the UK on optical filters, and from France and the UK on data analysis.
POLARBEAR is the most ambitious CMB polarization experiment to date, and it will explore the ultimate limit of ground-based CMB polarimetry. POLARBEAR's unique combination of high sensitivity and stringent control of systematic errors will result in a search for inflationary gravitational waves over most of the experimentally accessible range.
POLARBEAR will explore new technologies and methods that will carry forward to future CMB experiments such as NASA's CMBPOL mission. At UCSD, the team will connect POLARBEAR with the 'TRITONCAM' project that uses a radio telescope and polarimeter to teach physics to San Diego high school students.
Observations of Cosmic Microwave Background (CMB) polarization are a powerful probe of cosmology and will eventually probe the standard model of physics at ultrahigh energy. With this award, Dr. Adrian Lee, University of California at Berkeley, has led a new project called POLARBEAR (POLARization of the Background Radiation) which will use a dedicated telescope equipped with a powerful 1,274-bolometer array receiver to produce maps of CMB polarization with unprecedented accuracy. The most exciting possibility is that POLARBEAR will detect the signature of gravitational waves from the end of the inflationary period, 10^(-36) seconds after the Big Bang. If detected, these signals will provide an independent verification of the inflationary paradigm and test specific models for inflation. Inflation is a hypothesized exponential, faster-than-light, expansion of the Universe just after the Big Bang. Another important scientific motivation is to characterize the gravitational lensing of the CMB polarization. An accurate lensing measurement will yield constraints on Dark Energy. POLARBEAR can verify, or rule out, models with a strongly time-dependent Dark Energy equation of state w. In fact, POLARBEAR can provide on the time derivative of w, which is comparable and complementary to that from supernovae searches, baryon acoustic oscillations studies, and optical weak lensing measurements. The lensing signal is also sensitive to neutrino masses because massive neutrinos act as "hot" dark matter changing the formation of the lensing large scale structure. POLARBEAR is sited at 17,000 ft (5150 m) elevation in the Chilean Andes 6 km away from the ALMA interferometer. POLARBEAR introduces unprecedented levels of instrumental sensitivity and control of systematic errors. The high sensitivity is achieved with an array of planar-antenna-coupled Transition-Edge Sensor (TES) bolometers operated at 250 mK. Dr. Lee and his colleagues have developed and matured these arrays. POLARBEAR's final configuration include 1,274 bolometers observing a center frequency of 150 GHz. POLARBEAR is an ambitious CMB polarization experiment that will explore the ultimate limit of ground-based CMB polarimetry. POLARBEAR's unique combination of high sensitivity and stringent control of systematic errors will result in a search for inflationary gravitational waves over most of the experimentally accessible range. Also, there are more advanced versions of POLARBEAR under development using new multichroic pixel technology. These new versions will increasethe mapping speed of the experiment by more than one order of magnitude. POLARBEAR will explore new technologies and methods that will carry forward to future candidate space-based CMB experiments such as NASA's CMBPOL mission, JAXA's LiteBIRD mission, and ESA's CORE.
