Speaker
Dr
Kurtis Nishimura
(University of Hawaii)
Description
A general procedure for precision timing calibration of giga-sample/s
waveform digitizing ASICs is presented. These devices are increasingly
used in a number of high-energy physics experiments to perform
waveform sampling of front-end detector signals. Waveform digitizing
ASICs have considerable advantages over traditional TDC/ADC systems,
such as high channel density and low power consumption, but have
irregularly spaced timing intervals between samples due to process
variations at the production level. The procedure presented here
exploits the known correlation between nearby samples of a sine wave
function to obtain the time difference between them. As only the
correlations are studied, the procedure can be performed without
knowledge of the phase of the input signal, and converges with smaller
data samples than other common techniques. It also serves as a
valuable diagnostic tool, allowing a fast, visual, qualitative check
of ADC linearity, gain mismatches between sampling cells, and other
ADC artifacts. Work is continuing to extend the procedure to fit for
timing intervals in the face of such non-idealities.
We present both the algorithm and example calibration results from
multiple ASICs. In particular, using the PSEC3 ASIC, we show
improvement in timing performance for readout of a stripline MCP-PMT,
which serves as a prototype for moving toward large (order m^2)
photodetectors. Due to the anode geometry, the calibration technique
improves both the timing resolution and the spatial resolution
of the device.
Authors
Dr
Andres Romero-Wolf
(Jet Propulsion Laboratory)
Dr
Kurtis Nishimura
(University of Hawaii)
