Caption: Throughput of 10 eV resolution events in the 5 to 8 keV range for a Crab-like spectrum as a function of source flux expressed in mCrab. The curves are computed without (red) and with (blue) a Be filter. The 100 µm Be filter blocks most of the < 3 keV photons. Its transmission in the 5 to 8 keV is about 90%, explaining the difference between the two curves at low fluxes. The requirement derived from black hole wind science is to have a throughput larger than 50% in the 5 to 8 keV range at 1 Crab. The addition of a Be filter enables the X-IFU to meet its requirement with satisfactory margins.

Additional comments: The Crab spectrum assumed in the simulation is a power law with a photon index of 2.1, a normalization of 9.5 and an N_H of 3x10²¹ cm^-2. A limited resolution event is defined as an event for which the time since the previous event is ≥ 3.2 ms, the time to the next event is ≥ 1.6 ms, and for which the crosstalk error is below 4 eV.

Reference: The X-IFU throughput budget, P. Peille, T. Dauser, R. den Hartog, C. Kirsch, E. Cucchetti, M. Lorenz, 2018, X-IFU internal note, XIFU-TN-SYS-00175-CNES, version 2.1.

Creation date: 25/11/2018. Version #: 3.

Credits: X-IFU Consortium. Copyrights: © DB/X-IFU.