KNI-MDL Seminar

The TIME-Pilot CII Intensity Mapping Experiment, Abigail Crites

I will present and overview of the science and instrumentation for a new instrument, TIME-Pilot.  TIME-Pilot is designed to make measurements from the Epoch of Reionization (EoR), when the first stars and galaxies formed and ionized the intergalactic medium. This will be done via measurements of the redshifted 157.7 um line of singly ionized carbon ([CII]). In particular, TIME-Pilot will produce the first detection of [CII] clustering fluctuations, a signal proportional to the integrated [CII] intensity, summed over all EoR galaxies. TIME-Pilot is thus sensitive to the emission from dwarf galaxies, thought to be responsible for the balance of ionizing UV photons, that will be difficult to detect individually with JWST and ALMA. TIME-Pilot will employ a linear array of spectrometers, each consisting of a parallel-plate diffraction grating. The spectrometer bandwidth covers 185-323 GHz to both probe the entire redshift range of interest and to include channels at the edges of the band for atmospheric noise mitigation.  The 1840 detectors will be Transition Edge Sensor bolometers read out with the NIST time-domain-multiplexing (TDM) scheme and cooled to a base temperature of 250 mK with a 3He sorption refrigerator. 

Detectors of Electromagnetic Radiation Based on Superconducting Magnesium Diboride, Boris Karasik

Magnesium Diboride (MgB₂) is a remarkable superconducting material with a critical temperature T_C ≈ 40 K. Since its discovery in 2001, numerous studies have been carried out revealing many puzzling characteristics of the material, especially the coexistence of two superconducting gaps. However, the progress in achieving electronic devices (tunnel junctions, bolometers, SQUIDs, etc) has been hampered by the unavailability of high quality thin films and the high reactivity of the material. A recent progress in fabrication and processing of thin (~ 10 nm) films of MgB₂ using the Hybrid Physical Chemical Vapor Deposition (HPCVD) process triggered the development of novel radiation sensors which are expected to significantly advance the state-of-the-art.

JPL is currently using MgB₂ films for development of hot-electron bolometer (HEB) mixers for application in high-resolution THz heterodyne spectrometers and Single-Photon Superconducting Nanowire Detectors (SSNPD) for optical communication in space and quantum information applications. Magnesium diboride films bring the ability to operate such detectors without using liquid helium that is especially important for operation in space. Another benefit of thin-film MgB₂ is the high thermal relaxation rate (~ 10 ps) determining the speed/bandwidth of the detector. Future directions for sensor development may include kinetic inductance detectors (KID) and bolometers and also Josephson junction based structures for achieving broadly tunable THz generators.

In my talk, I will discuss the approaches to radiation detectors based on MgB₂ and present the results obtained to date. I will also discuss the technological challenges in achieving large wafers of this material that are needed for detector array fabrication.