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935A Quad 200-MHz Constant Fraction Discriminator

ORTEC 584 Constant Fraction DiscriminatorIn fast-timing applications, such as gamma-spectroscopy, nuclear physics and Medical and Industrial Imaging, the timing of detected events is crucial. However, any variation in amplitude of input pulses can give rise to inaccuracies.

The ORTEC 935A is a high-performance Quad 200-MHz Constant-Fraction Discriminator (CFD), designed for ultra-fast timing applications that requires exceptional accuracy and minimal pulse walk. With four independently adjustable timing discriminators in a single-width module, the 935A model delivers exceptional timing resolution, making it ideal for use with microchannel plates, fast photomultiplier tubes, fast scintillators and fast silicon detectors. Its constant-fraction technique ensures timing accuracy independent of input pulse amplitude, setting a new standard in timing precision.

The 935A model is a versatile and powerful tool that empowers researchers and technicians across a wide range of applications. 

  • Literature +


    935A Brochure

  • More Information +


    Key Features of 935A Quad 200MHz Constant-Fraction Discriminator

    Whether working with microchannel plates, fast photomultiplier tubes, or fast scintillators, the 935A empowers scientists to achieve precise timing measurements with ease and confidence. Its constant-fraction timing technique ensures accurate measurements regardless of input pulse amplitude, making it indispensable in high-speed experiments.

    - Four independent channels in a compact NIM module
    - Can handle up to 200-MHz of High-Speed Performance
    - Fast negative NIM outputs with adjustable widths (2 ns to 500 ns)
    - Exceptional timing resolution, with walk <50 ps
    - Wide threshold range (-15 to -1000 mV) for flexible signal discrimination
    - Pulse-pair resolution <4 ns for high-speed applications
    - Front-panel LED indicators for real-time activity monitoring
    - Common Veto and Independent Gate settings for advanced trigger control
    - Robust design with low transmission delay and temperature stability

  • Specifications +


    Inputs
    Quantity
    		 4 independent LEMO Fast Negative analogue inputs 
    Impedance 50 Ω 
    Max Voltage -10 V 
    Threshold Range -15 mV to -1000 mV 
    Rise Time <1 ns 
    Constant Fraction 20% of max input pulse amplitude

     Outputs
    Timing Output 3 bridged fast negative NIM outputs (Updating/Blocking Modes) 
    Amplitude -800 mV on 50 Ω load 
    Output Width Adjustable from 2 ns to 500 ns 
    Transmission Delay <7 ns (with 3 ns external delay) 
    Temperature Sensitivity <±10 ps/°C (0 to 50°C) 
    Activity Indicators Front-panel LEDs per channel 
     
    Electrical & Mechanical
    Power Requirements
    		 –6V (1600 mA), +6V (300 mA), –12V (100 mA)
    Operating Temperature 0 to 50°C 
    Weight ~1 kg (Net) / ~2 kg (Shipping) 
    Dimensions NIM-standard single-width module (3.43 x 22.13 cm)

  • Ordering Information +


    Model Description
    935A Quad 200MHz Constant Fraction Discriminator