22 July 2014 Canadian Hydrogen Intensity Mapping Experiment (CHIME) pathfinder
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A pathfinder version of CHIME (the Canadian Hydrogen Intensity Mapping Experiment) is currently being commissioned at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC. The instrument is a hybrid cylindrical interferometer designed to measure the large scale neutral hydrogen power spectrum across the redshift range 0.8 to 2.5. The power spectrum will be used to measure the baryon acoustic oscillation (BAO) scale across this poorly probed redshift range where dark energy becomes a significant contributor to the evolution of the Universe. The instrument revives the cylinder design in radio astronomy with a wide field survey as a primary goal. Modern low-noise amplifiers and digital processing remove the necessity for the analog beam forming that characterized previous designs. The Pathfinder consists of two cylinders 37m long by 20m wide oriented north-south for a total collecting area of 1,500 square meters. The cylinders are stationary with no moving parts, and form a transit instrument with an instantaneous field of view of ~100 degrees by 1-2 degrees. Each CHIME Pathfinder cylinder has a feedline with 64 dual polarization feeds placed every ~30 cm which Nyquist sample the north-south sky over much of the frequency band. The signals from each dual-polarization feed are independently amplified, filtered to 400-800 MHz, and directly sampled at 800 MSps using 8 bits. The correlator is an FX design, where the Fourier transform channelization is performed in FPGAs, which are interfaced to a set of GPUs that compute the correlation matrix. The CHIME Pathfinder is a 1/10th scale prototype version of CHIME and is designed to detect the BAO feature and constrain the distance-redshift relation. The lessons learned from its implementation will be used to inform and improve the final CHIME design.
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Kevin Bandura, Kevin Bandura, Graeme E. Addison, Graeme E. Addison, Mandana Amiri, Mandana Amiri, J. Richard Bond, J. Richard Bond, Duncan Campbell-Wilson, Duncan Campbell-Wilson, Liam Connor, Liam Connor, Jean-François Cliche, Jean-François Cliche, Greg Davis, Greg Davis, Meiling Deng, Meiling Deng, Nolan Denman, Nolan Denman, Matt Dobbs, Matt Dobbs, Mateus Fandino, Mateus Fandino, Kenneth Gibbs, Kenneth Gibbs, Adam Gilbert, Adam Gilbert, Mark Halpern, Mark Halpern, David Hanna, David Hanna, Adam D. Hincks, Adam D. Hincks, Gary Hinshaw, Gary Hinshaw, Carolin Höfer, Carolin Höfer, Peter Klages, Peter Klages, Tom L. Landecker, Tom L. Landecker, Kiyoshi Masui, Kiyoshi Masui, Juan Mena Parra, Juan Mena Parra, Laura B. Newburgh, Laura B. Newburgh, Ue-li Pen, Ue-li Pen, Jeffrey B. Peterson, Jeffrey B. Peterson, Andre Recnik, Andre Recnik, J. Richard Shaw, J. Richard Shaw, Kris Sigurdson, Kris Sigurdson, Mike Sitwell, Mike Sitwell, Graeme Smecher, Graeme Smecher, Rick Smegal, Rick Smegal, Keith Vanderlinde, Keith Vanderlinde, Don Wiebe, Don Wiebe, "Canadian Hydrogen Intensity Mapping Experiment (CHIME) pathfinder", Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 914522 (22 July 2014); doi: 10.1117/12.2054950; https://doi.org/10.1117/12.2054950

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