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Noise Analyser NA4


The NA4 Noise Analyser provides a convenient way to test fission chambers that are used in the Mean Square Voltage mode (also known as Campbell mode or fluctuation mode). The Mean Square Voltage (MSV) technique uses the property that the mean of the square of the signal from a fission chamber, within a fixed bandwidth, is proportional to the neutron flux. When combined with a conventional pulse counting technique this enables a single fission chamber to cover ten or more decades of neutron flux.

The NA4 provides in one portable instrument, everything required to measure the spectrum from an in-service chamber. It can also be used to test newly manufactured or spare fission chambers using a research reactor or accelerator. An integral low-noise EHT supply polarises the chamber. Measurement frequencies can then be selected manually, or the process can be run automatically. In the automatic mode, the start frequency, stop frequency, number of points per decade and averaging time for each result are selected. On pressing the Run button, the instrument averages the signal at each frequency point and stores the results on a USB flash drive. Results have the units A2/Hz and are therefore proportional to neutron flux. The file format is suitable for importing into Excel for graph plotting and further analysis. The stored file also contains the time and date of the measurement and the instrument settings.


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