Terahertz intensity mapper focal plane and array design

TIM, the Terahertz Intensity Mapper, is a NASA balloon mission designed to perform [CII] intensity mapping of the peak of cosmic star formation. To achieve this, TIM has two longslit (1 degree slit length) grating spectrometers covering the 240-317 um and 317-420 um wavelength bands at R~250, respectively. We will present the design of the ~4000 pixel, horn-coupled kinetic inductance detector arrays servicing each of the spectrometer arms. Each pixel is a lumped-element superconducting resonator made from a 20 nm thick aluminum film, designed to achieve photon noise limited performance at 100 fW of loading. The inductor is a meandered narrow wire, designed to mimic a metal mesh grid at THz frequencies; it is optimized for absorption of both polarizations delivered by the circular waveguide. Each array will consist of four quadrants containing ~1000 pixels on a single microstrip readout line and will be mounted such that critical parameters of the absorber design are maintained.