N1568B

The Mod. N1568B is a 16 channel Pulse Shape Amplifier and Dual 16 Channel Constant Fraction Discriminator (30% and 80% constant fraction) implemented in a single-width NIM module. Each channel is composed by two sections: Energy section (A) and Timing section (B). The input signal is sent to both sections simultaneously. Section A processes the input signal with a differential circuit, followed by the gain stages (coarse: 2 bit; fine: 7 bit), by the shaping circuit and finally by a stretcher with programmable threshold (20 mV minimum).
The stretcher gate is generated by means of the threshold of the timing section and the output width of the stretcher signal is fixed at 15μs circa.
The 16 Channel Stretched Outputs are provided to the (OUT) connector present on the Front Panel; if the stretcher is disabled a Gaussian output is provided. The Stretched Outputs shall be fed to a QDC suitable to negative pulses; Gaussian outputs must be used with negative polarity in order to adjust Pole zero, shaping, etc. Discriminators Out does not work as the stretcher is disabled.
Section B processes the signal with a low noise differential stage (500 ns) followed by a 2 bit programmable linear gain stage; the signal is then fed to two low walk and high resolution Constant Fraction Discriminator sections (30% and 80% constant fraction respectively).
The discriminators share a 8 bit common threshold; the discriminators delay is adjustable via PCB jumpers (6 steps from 15 to 150 ns).
The RS485 interface allows to handle most functional parameters such as Shaping Time, Coarse and Fine Gain, Input Polarity, CFD and Stretcher Thresholds, Pole Zero Adjustment etc.