A small high sensitivity neutron detector using a wavelength shifting fiber

Area of Science:

• Nuclear instrumentation
• Particle detection
• Optical physics

Background:

• A previous optical fiber neutron detector offered excellent spatial resolution (<1mm) and access to confined spaces for reaction rate measurements.
• However, the detector's small size resulted in low neutron sensitivity, limiting its application in certain research reactor and accelerator environments.

Purpose of the Study:

• To develop a novel optical fiber neutron detector with significantly improved neutron sensitivity.
• To enhance the detector's capability for accurate reaction rate measurements, particularly in low neutron flux conditions.

Main Methods:

• Development of a new optical fiber neutron detector incorporating wavelength shifting fibers.
• Measurement of reaction rate distribution within a reactor core to evaluate detector performance.
• Comparison of the new detector's sensitivity with conventional optical fiber detectors and BF(3) proportional counters.

Main Results:

• The new detector design allows for an increased effective detector length, leading to higher neutron sensitivity compared to previous models.
• Sensitivity was enhanced by utilizing longer wavelength shifting fibers.
• The improved neutron sensitivity approaches that of a typical small BF(3) proportional counter.

Conclusions:

• The developed wavelength shifting fiber optic neutron detector offers high sensitivity suitable for low neutron flux fields.
• This advancement enables more effective reaction rate measurements in research reactors and accelerator facilities.
• The detector's design overcomes the sensitivity limitations of earlier optical fiber neutron detectors.