9327 1-GHz Amplifier and Timing Discriminator

• For picosecond timing with mV signals from: Microchannel Plate Detectors
  Microchannel Plate PMTs
  Fast Photodiodes
  Fast Photomultiplier Tubes
• 1-GHz Amplifier and Timing Discriminator are internally matched for minimum walk and timing jitter
• Walk typically <±40 ps over the top 90% of full scale
• Jitter <20 ps FWHM at 50% of full scale
• Optimized for pulse widths from 250 ps to 1 ns; accepts pulse widths up to 5 ns
• Selectable input pulse height range: 0 to –30 mV, or 0 to –150 mV full scale
• 2:1 Fine Gain control
• Over-Range LED for precise gain adjustment without an oscilloscope

The Model 9327 1-GHz Amplifier and Timing Discriminator combines into one compact preamplifier sized package the two functions normally needed for picosecond timing with ultra-fast detectors. It is ideal for Fluorescence/Phosphorescence Lifetime Spectrometry (Fig. 1), Time-of-Flight Mass Spectrometry (Fig. 2) and LIDAR applications. The Model 9327 is optimized for use with the millivolt signals produced by microchannel plate detectors, microchannel plate photomultiplier tubes, fast photodiodes, and fast, discrete-dynode photomultiplier tubes. The compact package avoids degradation of the sub-nanosecond signals from these detectors by enabling an exceptionally short cable connection between the detector and the amplifier. The timing discriminator output logic pulse can be transmitted over much longer cables to the rest of the time spectrometer without compromising the picosecond time resolution.

The amplifier provides a 1-GHz bandwidth to minimize the noise and rise time contributions to timing jitter on detector pulses having widths as narrow as 250 ps. The 50-W amplifier input includes diode clamps to protect against overload pulses. A PC-board-mounted jumper controls the coarse gain to yield two ranges for full-scale input pulse amplitudes: 0 to –30 mV and 0 to –150 mV. A fine gain control permits varying the gain over nominally a 2:1 range. An oscilloscope is not needed to adjust the gain, because an over-range LED indicates when pulse amplitudes have exceeded the full-scale limit of the amplifier. Detector and/or amplifier gain can be increased until the over-range LED turns on, and then decreased until the LED just turns off. This ensures that the pulses utilize all of the amplifier’s linear range.

The timing discriminator employs a zero-crossing technique that processes pulse widths from 250 ps to 5 ns without the need to adjust pulse-shaping cables. The zero-crossing technique results in minimal timing jitter and walk as a function of pulse amplitude. It is optimized for sub-nanosecond pulse widths, but will accommodate pulses up to 5 ns wide. The shift in the timing output (walk) as a function of pulse amplitude is typically less than ±40 ps over the top 90% of full scale when employing a 300-ps input pulse width (Fig. 3). The typical contribution of the 9327 to timing jitter is illustrated in Figure 4. With such a small contribution from the 9327, the detector normally becomes the dominant source of timing jitter. The Model 9327 includes a noise discriminator adjustable over a major fraction of full scale. With the source of detector events turned off, the discriminator threshold can be adjusted until the associated LED is turned on by triggering on noise. Subsequently, the threshold is adjusted until the LED just turns off, thus ensuring that the discriminator will not trigger on noise.

The Model 9327 provides two fast-negative NIM logic signals suitable for operating other timing instruments with picosecond time resolution. A 100-ns wide TTLoutput is also provided for counting applications. In addition to excelling in high-resolution time spectrometry, the Model 9327 can be used for single-photon and single-ion counting applications.

A 3-meter long captive power cord terminated in a 9-pin, D connector supplies power to the unit. Power can be derived from the mating connectors on a 9308 or 9328 picosecond TIME ANALYZER, a 4002P Portable Power Supply, a 4003 Preamp power output module, or any ORTEC spectroscopy amplifier. Alternatively, a dc power source in the range of +12 to +15 V at 350 mA can be connected to the designated pins on the power connector.

Fig. 1. Typical Block Diagram for a Fluorescence Lifetime Spectrometer (with reversed start/stop assignments).

Fig. 2. The Model 9327 in a Simplified Illustration of a Time-of-Flight Mass Spectrometer. The Model 9308 picosecond TIME ANALYZER functions as a multiple-stop time spectrometer.

Fig. 3. Typical Walk vs. Pulse Amplitude. Full scale is denoted by the Over Range LED turning on. Measured with a pulse width of 300 ps FWHM.

Fig. 4. Timing Jitter vs. Pulse Amplitude. Measured with the system in Fig. 1 by replacing the detectors with a pulser having a pulse width of 300 ps FWHM. Full scale is denoted by the Over Range LED turning on.

ORDERING INFORMATION