- Records time of pulses at input over time spans from 51.2 ns to 6.7 ms
- 512 to 67 M time bins
- Digital resolution selectable from 100 ps to 13 us
- Dead time correction function enables a factor of 10 higher event rates
- Complete with data acquisition, control, display and analysis software running under Windows? 98, NT, 2000 and XP
- 1 GHz Burst Rates: Multiple Stop capability with 1 ns pulse-pair resolving time
- Compact, half-length PCI card; up to 4 units in the same computer
- Histogramming, List, Trend, and Chromatograph Modes implemented in software
- ActiveX?controls provide an easy-to-use programmer‘s toolkit
The Model 9353-P 10 GHz Time Digitizer / MCS is a plug-in PCI card that functions as a time digitizer or a multichannel scaler. It measures the arrival times of Start pulses and multiple Stop pulses with a precision of 100 ps. Exceptional digitizing precision, speed and time span make it ideal for Electrospray Time-of-Flight Mass Spectrometry, Orthogonal- Acceleration MALDI TOF-MS, LIDAR, and Fluorescence/Phosphorescence Lifetime Spectrometry.
It measures the arrival times of multiple Stop pulses after the most recent Start pulse. Deep, cascaded FIFO buffers accommodate burst rates up to 1 GHz and sustained rates up to 10 MHz. The pulse-pair resolving time for Stop events is 1 ns. A dead time correction algorithm, implemented in software, permits increasing the Stop event rate by an order of magnitude, while keeping dead time distortions of the time spectrum insignificant.
The time span following each Start pulse can be as short as 51.2 ns or as long as 6.7 ms, with the selected span distributed over as few as 512 time bins, or as many as 67,000,000 bins. The maximum time span can be extended to infinity utilizing the auto roll-over monitoring with customized software. The width of each time bin can be adjusted from 0.1 ns to 13.1072 us.
The Time Digitizer / MCS can store the time information using either of two modes. In the List Mode, the Start and Stop events are streamed to the supporting computer and onto hard disk as a list of 32-bit time stamps. This is a productive way to produce a compact file when the Stop event rates are low, and changes in the time spectrum occur over periods shorter than a few seconds. Each time stamp in the list marks the arrival time of a Start or Stop pulse with a precision of 0.1 ns. The time stamp for each Start pulse is referenced to the time at which the data acquisition commenced. For Stop pulses, the time stamp is referenced to the most recent Start pulse. The maximum value of the time stamp is approximately 6.7 ms for Stop pulses, and 125 hours for Start pulses. Either during or after acquisition, specific segments of the list can be selected and histogrammed by the software to display a time spectrum.
The Histogramming Mode, on the other hand, produces a more compact file size when the data rates are high. In this mode, the software in the PC sorts and combines the Stop events following multiple Start pulses to form a spectrum of the number of Stop events versus their Start-to-Stop time. This spectrum is a histogram, because the horizontal axis is grouped into bins of 100-ps width. The resulting histogram is saved on hard disk. When the time digitizer is measuring the flight times of photons or charged particles over a fixed distance, this histogram is called the time-of-flight (TOF) spectrum.
More specifically, each Start pulse marks the beginning of a scan through the selected time span. The time stamps for the Stop pulses are expressed with zero time corresponding to the arrival of the prior Start pulse. The arrival time of a Stop pulse determines the appropriate bin in the histogram to which one count is added. This process of adding Stop events to the histogram is repeated for each scan until the desired number of scans has been completed. The resulting histogram is displayed as the number of Stop events (vertical axis) versus Start-to-Stop time (horizontal axis); in TOF-MS applications the horizontal axis represents m/z.
