Code-division multiplexing for x-ray microcalorimeters
  We demonstrate the code-division multiplexed (CDM) readout of eight transition-edge sensor microcalorimeters. The energy resolution is 3.0 eV (full width at half-maximum) or better at 5.9 keV, with a best resolution of 2.3 eV and a mean of 2.6 eV over the seven modulated detectors. The flux-summing CDM system is described and compared with similar time-division multiplexed (TDM) readout. We show that the sqrt(Npixels) multiplexing disadvantage associated with TDM is not present in CDM. This demonstration establishes CDM as both a simple route to higher performance in existing TDM microcalorimetric experiments and a long-term approach to reaching higher multiplexing factors. 
G. M. Stiehl, W. B. Doriese, J. W. Fowler, G. C. Hilton, K. D. Irwin,   C. D. Reintsema, D. R. Schmidt, D. S. Swetz, J. N. U...
physics.ins-det astro-ph.IM