Search

The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne instrument that will probe the epoch of reionization and search for the signature of inflation through large angular scale measurements of the linear polarization of the cosmic microwave background in four frequency bands from 200 to 600 GHz. The PIPER receiver couples two 32x40 arrays of transition-edge sensors (TES) to cryogenic telescope optics. The optics are maintained at < 3 K using superfluid pumps in an open bucket of liquid helium. The receiver houses the detector arrays and sub-K cooler in a superfluid-tight enclosure. We describe several aspects of the receiver design and performance: 1) the thermal design of the receiver and cooling to 100 mK with a continuous adiabatic demagnetization refrigerator (CADR) 2) performance of the TES arrays in the integrated receiver, 3) design of the reimaging optics and superfluid-tight windows. The PIPER receiver is the first implementation of kilo-pixel TES bolometer arrays combined with a continuous ADR operating at 100 mK, which provide 10 uW cooling....

The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne instrument that will probe the epoch of reionization and search for the signature of inflation through large angular scale measurements of the linear polarization of the cosmic microwave background in four frequency bands from 200 to 600 GHz. PIPER consists of co-pointed twin cryogenic telescopes operating in an open liquid helium bucket dewar that upon achieving float altitude cool below a temperature of 3 K. Variable-delay polarization modulators (VPMs) provide sensitivity to circular polarization for systematic error control, along with one linear polarization component per telescope. The twin telescopes provide simultaneous sensitivity to Stokes I, Q, U, and V. On 14 October 2019, PIPER flew from Fort Sumner, NM, configured to observe in a band centered at 200 GHz. The flight lasted 13 hours, reaching an altitude of 30.2 km. Failure of an observation hatch to open upon reaching float altitude prevented astrophysical observations; however, the VPMs and telescope cryogenics were operated successfully. Here we report on the 2019 PIPER flight and the performance of these systems at float....

The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne instrument that will probe the epoch of reionization and search for the signature of inflation through large angular scale measurements of the linear polarization of the cosmic microwave background in four frequency bands from 200 to 600 GHz. The sky is imaged on to two 32x40 pixel arrays of time-domain multiplexed Transition-Edge Sensor (TES) bolometers operating at a bath temperature of 100 mK to achieve background-limited sensitivity. Each kilopixel array is indium-bump-bonded to a 2D superconducting quantum interference device (SQUID) time-domain multiplexer (MUX) chip and read out by warm electronics. Each pixel measures total incident power over a frequency band defined by bandpass filters in front of the array, while polarization sensitivity is provided by the upstream Variable-delay Polarization Modulators (VPMs) and analyzer grids. We present measurements of the detector dark parameters including transition temperature, saturation power, thermal conductivity, and time constants. We also present a summary of the pre-flight characterization of the detector arrays in the fully integrated flight receiver, describe the optimization of the integrated readout parameters, and the overall pixel yield of the arrays....