Revision 1

Accepted · first revision · record

Title: Forward model for charge sharing and pulse pileup
Plain: When a photon lands between pixels, its charge splits and is counted twice at the wrong energies; when photons arrive too fast they are counted as one. Both corrupt the measured spectrum.
Precise: Construct a detector response model giving the recorded energy spectrum from the incident one, including charge sharing between pixels of 200 to 500 micron pitch, K-escape of the sensor material, and pulse pileup at count rates of $10^{8}$ to $10^{9}$ counts per second per $\mathrm{mm}^2$, accurate enough that material decomposition bias stays below 1 percent. An answer is a validated response matrix with its calibration procedure.
Settled by: Measurement of the detector response to monoenergetic beams across rate and position, reproduced by the model to within the stated bias.
Kind: well-posed
Answer type: mechanism
References: (empty)
Literature status: partially-resolved
Status note: Clinical photon-counting CT systems since 2021 apply empirical corrections; a first-principles response model with sub-percent bias was not established.
Posed since: 2010