Features

• Independent ULD, LLD, and SCA outputs
• Precise threshold discrimination
• Exceptional stability – dc-coupled input
• External baseline sweep input
• Dynamic range 1000:1
• LLD monitored by LED display
• Source matched logic outputs

Description

The CANBERRA Model 2030 analyzes the peak amplitude of energy pulses from nuclear pulse shaping amplifiers, and generates its primary logic output (SCA) for input analog pulses between the levels referenced by the Lower Level (E) and Window (ΔE) front panel ten-turn controls. Auxiliary outputs from the Lower Level Discriminator (LLD) as set by (E), and the Upper Level Discriminator (ULD) as set by (E + ΔE) are also provided. Timing of these logic outputs is set as the trailing edge of the input signal crosses the (E) reference.

The several outputs may be used together or individually to assist in a wide variety of applications from simple noise removal to extraction of a narrow energy range from a wide spectrum of signals for energy analysis. The sharp, precise threshold discrimination levels are exceptionally stable (drift is less than ±0.005%/°C, full scale). The dc coupled input allows excellent baseline stability limited only by the shaping amplifier’s restorer. These significant features permit excellent amplitude discrimination, even in high count rate spectra.

The Lower Level (E) threshold is calibrated by reference to the regulated NIM supply voltages, and is usable over the range from +0.001 V dc to +10.0 V dc. Linearity of control is limited only by the specified ±0.25% maximum nonlinearity of the front panel potentiometer. A front panel mounted LED is useful in visually monitoring the setting of the Lower Level (E) reference just above the shaping amplifier’s noise level (the LED will fade off).

The Window (ΔE) threshold is also calibrated by reference to the regulated NIM supply voltages, and is usable over the range from the Lower Level (E) setting to +10.0 V dc. A front panel ΔE Range switch allows use of a 1.0 V full scale range for very fine adjustments of the desired window.

An external lower level discriminator (LLD) input on the rear panel may be used in place of the front panel control for applications requiring a ratioed or sweeping baseline reference over the energy range. This input requires a positive polarity reference voltage, and is linear over the full scale of 0 to +10.0 V dc. A locking toggle switch is used to select this input.

All output logic signals are positive logic, and are adjustable in peak amplitude for compatibility with interfacing instruments. All outputs are source matched with 50 Ω series resistive terminations to prevent ringing due to reflections on unterminated cables, and the resulting multiple counting frequently experienced.
The instrument is shipped with a socketed resistor which limits the output to +5 V nominal (open circuit) for direct interface with common TTL circuitry. The resistor (1 for each output) can be removed to obtain a +8 V nominal open circuit voltage for instruments requiring the NIM pulse level, or +4 V nominal into the 50 Ω load termination which some other instruments provide. This flexibility adapts the output signal to various needs without risking the problem encountered with improperly driven cables. Load end terminations are not necessary.

Careful attention has been paid to minimize reflections of the fast logic pulses back to the analog input. Thus all logic outputs are isolated from chassis to prevent circulating pulse currents in the instrument bin.