📝 SummarXiv

Abstract

In preparation for HL-LHC operation, a number of new detector systems are being constructed with timing precision on physics objects of $\leq50$ picoseconds. These time stamps will reduce the level of pileup induced backgrounds as the number of interactions per crossing will reach of order 100-200\cite{Shiltsev}. In this report we note that this high pileup level will necessitate a new approach to calibration of these large timing arrays (typically with several $\times10^5$ channels) . Since the usual tools required for walk correction (a single t$_{0}$ reference and tracking) may not be readily available on Day-1, an initial calibration technique using only data internal to the timing array would be a benefit. We demonstrate that enhancing the usual pair of timing ASIC data (ie threshold time and amplitude or time-over-threshold) with a 2nd threshold time greatly simplifies the analysis of amplitude walk. Walk dependence on the slope at threshold (derived from the two thresholds) is quite generally given by a single linear expression. Furthermore the Amplitude Walk Coefficient (AWC) can usually be determined in advance, as we will show. While this technique results in calibration precision equivalent to the familiar brute force technique it should be emphasized that it is applicable when the tools required for the latter technique are not available.