Manufacturer:  Hamner Electronics Model:  Nuclear Scaler Year:  1966 Schematic:  RE

Functions:  Nuclear Scaler Display:  1-of-10 Incandescent Logic:  Discrete Transistor

Hamner Electronics was a 1960s manufacturer of nuclear instrumentation, located in Princeton, New Jersey. This is a NIM bin populated with modules to form a nuclear scaler.

NIM (Nuclear Instrumentation Module) is a standard created in the late-1950s defining dimensions and requirements for a card cage (bin) accepting plug-in modules and backplane providing power to the modules.

The modules here are:

• LA-110 Amplifier:
  A first-stage detector amplifer accepting input from a Geiger or Scintillation detector.

• NA-15 Amplifier / Discriminator:
  Two functional units in one module: Amplifier and Pulse-Height Threshold Discriminator.

• NC-20 Spectrum Stabiliser:
  Two functions: Pulse-Height Window Discriminator and Spectrum Stabiliser.

  The spectrum stabiliser apparently interacts in a loop arrangement with the radiation source / experiment. A third level is established between the min-max levels of the window discriminator, thus defining two regions (over/under) within the window. Detected radiation-event pulses occurring within the two regions pump a charge-pump up or down. The output from the charge-pump is fed back to the experiment to perform some control function. The overall functional operation is much like a phase-locked-loop.

• NS-10 Scaler:
  Basically a 7-decade counter with gate and start-stop flip-flop. The least-significant 3 decades are electronic with 1-of-10 displays, the most-significant 4 decades are a solenoid-triggerred mechanical odometer-style module.

  The gate is manually controlled by pushbuttons. Additionally, a 'preset' switch can select one of several decades upon which to automatically stop counting, e.g. close the gate after 1000 or 10,000, etc. pulses.

• NT-15F-1 Timer/Scaler:
  Much like the NS-10 Scaler but 4-decades (all electronic) and including a timebase of 0.1S or 0.1 Minutes.

These modules are all held together in an:

• NH-84A NIM Bin: 12-slot rack-mounted card cage and backplane

with an:

• SPS-521 Power Supply: Provides regulated +/-24V, +/-12V up to 72VA max.

The Scaler and Timer/Scaler are interconnected such that their respective start/stop gate-controls interact in synchronism. The idea then, is one can start an experiment by pressing Start, then have it stop automatically after some time period or upon reaching some event count. At the end, the respective variable number of events in a fixed period, or the variable time needed for a fixed number of events to occur, is presented.

Simple test procedure: Enable 60Hz TEST on scaler; TIMER, 0.1S and 10^2 PRESET on Timer. After pressing START, activity should stop after 10S. Displays should present Scaler=600, Timer=100.

Closer view of front panel. The photo was taken with a long exposure time resulting in many numerals appearing lit simultaneously. Each decade actually has only one numeral on at any instant.

NC-20 Spectrum Stabiliser NIM module.

NS-10 Scaler NIM module.