142PC Preamplifier

• Ideal for proportional counters
• Accepts 0 to ±3 kV bias
• High sensitivity and very low noise for soft x-ray and low-energy gamma spectroscopy

The ORTEC Model 142PC Preamplifier is a low-noise charge-sensitive unit especially designed for use with proportional counters requiring up to ±3000 V detector bias.

The high sensitivity of this unit often allows operating the proportional counter at reduced voltages, thus greatly minimizing peak position shifts and peak broadening with changing count rates.

The low-noise performance for this type of preamplifier greatly improves the resolution of the spectroscopy system. The separate energy and timing outputs enhance instrument flexibility.

The Model 142PC incorporates a protection circuit for the input FET to prevent damage from inadvertently applied overvoltages. The unit is shipped with the protection circuit in place; better resolution, however, will be obtained when the protection is removed (Fig. 1).

Fig. 1. Noise as a Function of Input Capacitance, Measured with an ORTEC Model 572 Amplifier and 2-µs Time Constant.

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