863 QUAD TIMING FILTER AMPLIFIER

• Optimum pulse shaping and amplification for timing with germanium and other solid-state detectors
• Four amplifiers in a single-width NIM for experiments with a large number of detectors
• Selectable cable clipping of the input signal 
• Rise time <10 ns for outputs from 0 to ±5 V on a 50-W load
• Front-panel pole-zero adjustment
• Selectable integration and differentiation filters

The ORTEC Model 863 Quad Timing Filter Amplifier incorporates four separate timing filter amplifiers in a single-width NIM module. This design provides a compact and cost-effective solution for experiments where timing is required on a number of detectors. Together with an ORTEC Model 935 Quad Constant-Fraction Timing Discriminator, the Model 863 can provide optimum timing for up to four germanium detectors. The unit can also be used for timing with other solid-state detectors, or operate as a general-purpose wideband amplifier with selectable bandwidth.

The signals from germanium or silicon detectors at the preamplifier output are not always optimum for achieving good timing resolution. Before presentation to a timing discriminator, the signals normally require amplification with a wideband amplifier, and they may need additional pulse shaping to minimize the noise contribution to the time resolution. The Model 863 provides a flexible approach in serving these two functions in order to handle a wide variety of solid-state detector types.

The Gain can be selected as either inverting or noninverting and is adjustable over the nominal range from 2 to 250. The Fine Gain is adjustable from 2 to 50 using a front-panel screwdriver potentiometer, while a printed wiring board (PWB) jumper selects a Coarse Gain of either 1 or 5. The output will drive a 50-W load to ±5 V with good linearity. This ensures that the full –50 mV to –5 V dynamic range of a constant-fraction timing discriminator can be used. Excellent dc stability of the output is maintained by a continuous baseline restorer.

Several means of bandpass limiting are included to achieve the pulse shaping that yields the optimum time resolution. With all jumpers in the Out position, the Model 863 is a wideband amplifier with an output rise time <10 ns. To reduce low frequency noise and shorten the output pulse width, the CR differentiation time constant can be decreased from 0.1 ms (Out position) to 200 ns using a PWB jumper. Alternatively, two front-panel connectors can be employed (using a 50-W coaxial cable) to add delay line clipping. This results in a more abrupt termination of the output pulse duration while reducing low frequency noise. Both the CR differentiation and the cable clip can be used together to yield a bipolar output signal for fast, zero-crossing timing.

In some cases it is beneficial to select a 50-ns RC integration time constant using the PWB jumper provided for that purpose. This reduces the high frequency noise while slowing the output rise time to 110 ns.

In addition to the two standard jumper selections incorporated into each of the Differentiation and Integration controls, a third position is provided for both jumpers. By adding the appropriate components to each third position, it is possible for the user to select a customized set of integration and differentiation time constants.

In order to ensure that the output pulse returns to baseline as quickly as possible, the differentiation circuit includes a front-panel pole-zero trimmer. This control permits compensation for the preamplifier decay time constant.

Each section of the Model 863 has five sets of PWB jumpers to control the various functions of the unit. These jumpers are accessible by removing the left side panel of the module.

ORDERING INFORMATION