Single Pixel Performance of a 32 × 32 Ti/Au TES Array With Broadband X-Ray Spectra

We are developing a kilo-pixels Ti/Au TES array as backup option for Athena X-IFU. Here we report on single-pixel performance of 32$\times$32 operated in Frequency Division Multiplexing (FDM) readout system, with bias frequencies the range 1-5 MHz. have tested pixels response at several photon energies, by means $^{55}$Fe radioactive source (emitting Mn-K$\alpha$ 5.9 keV) and Modulated X-ray Source (MXS, providing Cr-K$\alpha$ 5.4 keV Cu-K$\alpha$ 8.0 keV). First, procedure used to perform detector energy scale calibration, usually achieving calibration accuracy better than $\sim$ 0.5 eV - 8.9 range. Then, present measured resolution different energies (best single pixel performance: $\Delta$E$_{FWHM}$ = 2.40 $\pm$ 0.09 @ keV; 2.53 0.10 2.78 0.16 keV), investigating also dependency from frequency count rate. Thanks long background measurements ($\sim$ 1 day), finally detected Al-K$\alpha$ line 1.5 keV, generated fluorescence inside experimental setup. analyzed this obtain first assessment low ($\Delta$E$_{FWHM}$ 1.91 0.21 evaluate linearity large band (1.5