A concept for a superconducting tunneling junction based spectrograph

We describe a multi-order spectrograph concept suitable for 8-m class telescopes, using the
intrinsic spectral resolution of superconducting tunnelling junction detectors to sort the spectral
orders. The spectrograph works at low orders, 1–5 or 1–6, and provides spectral coverage with
a resolving power of R 8000 from the atmospheric cut-off at 320 nm to the long-wavelength
end of the infraredH orK band at 1800 nm or 2400 nm. We calculate that the spectrograph would
provide substantial throughput and wavelength coverage, together with high time resolution
and sufficient dynamic range. The concept uses currently available technology, or technologies
with short development horizons, restricting the spatial sampling to two linear arrays; however,
an upgrade path to provide more spatial sampling is identified. All of the other challenging
aspects of the concept – the cryogenics, thermal baffling and magnetic field biasing – are
identified as being feasible.