Grant: Research Tools and Instruments - Category 1 (<$150,000)

We are requesting funds to build receiver electronics for a novel, one-dimensional Fourier transform telescope which we will install on the radio-quiet campus of the Dominion Radio Astrophysical Observatory. This instrument is a pathfinder experiment for a baryon acoustic oscillation experiment called CHIME. The most surprising discovery in cosmology in recent times, awarded the 2011 Nobel Prize in Physics, is the accelerating expansion of the Universe. This either signals that a previously unknown component called Dark Energy dominates the energy density of the Universe, or that our understanding of gravity on large scales is incorrect. The implications for fundamental physics are profound, and advancing our understanding requires new, higher-quality data. More precise observations of expansion history would better constrain the physics of Dark Energy. Measurement through cosmic time of ""baryon acoustic oscillations"" (BAO), the remnant of sound waves in the primordial plasma, provides the most reliable probe of expansion history. A novel technique for mapping matter, called hydrogen intensity (HI) mapping, has recently been demonstrated by a team led by co-applicant Pen, and allows one to measure the BAO signal as a function of redshift without the cumbersome intermediate step of detecting individual galaxies. This is what CHIME is designed to do. The full CHIME instrument will survey half the sky and reach definitive sensitivity in 2 years of observing. The pathfinder instrument, with 10% of the ultimate collecting area, will still be sensitive enough to produce the largest volume hydrogen redshift survey to date. With it we will advance the intensity mapping technique, demonstrate galactic foreground suppression, and probe the matter power spectrum. The electronics requested here will allow us to build the CHIME pathfinder and will poise Canada to play a leading role in Dark Energy research.