‘thermal’ and ‘fast’ refer to the energy level of the neutron incident on a detector. Thermal neutrons are typically defined as having energy <.025 eV. These lower energy neutrons are more likely to be absorbed by neutron sensitive materials, meaning thermal neutron detectors tend to have higher overall sensitivity. Thermal neutron detectors are designed to generate the majority of their usable signal from interactions with thermal neutrons, where fast neutron detectors are primarily capable of measuring high energy neutrons (>1 MeV). This has applications for research, where it may be important to use multiple detectors to differentiate between neutron energies, or in reactor applications where measurable neutron flux is primarily in high energy neutrons.

Detector operation can be significantly affected as the ambient temperature they are exposed to increases above 400 C, by several different mechanisms. The internal gases used to ensure linear operation of the detector must be carefully chosen to ensure they can remain chemically unchanged at these high temperatures. Further, as temperature rises above 400 C the internal resistance of the detector may decrease, causing a rise in leakage current which could limit the functional range or decrease the accuracy of the detector. For these concerns Photonis has designed high temperature detectors, utilizing the appropriate gases, materials, and guard ring construction to allow accurate and reliable operation up to 600 C.

A detector is usable so long as it remains sensitive to neutrons and capable of transmitting sufficient signal to be used by the electronics. The sensitivity of the detector will gradually decrease over time as it is exposed to thermal neutron flux, and the detector will remain viable as long as the electronics allow for the decrease in sensitivity. For B-10 lined proportional counters the gas internal to the detector is vital to linear performance of the detector and is subject to degradation during operation in high radiation environments. Photonis proportional counters may include an additional reservoir of proportional gas which extends detector life (up to ~5 x 1018 n/cm2) substantially, making total lifetime greater than the life of similar detectors without this reservoir and significantly longer than BF3 counters.

Auto-Gating provides a better reaction time when sudden bright light events occur, such as explosions or car headlights. The benefits can easily be seen not only during day-night-day transitions, but also under dynamic light conditions when rapidly changing from low light to high light conditions, such as sudden illumination of dark room or shooting at night (muzzleflash). 

The ATG maintains the optimum performance of the Image Intensifier Tube (IIT) while continuously revealing mission critical details, safeguarding the IIT from additional damage and protecting the user from temporary blindness.

Gain, also referring to brightness gain or luminance gain, is defined as the number of times the image intensifier tube amplifies the light. This characteristic should match the Night Vision Device (NVD) into which it is integrated. Providing a NVD with an External Gain Control (EGAC) allows the user to have a more versatile system, this allows him to dim the brightness.

In military applications, Night Vision Devices (NVD) are developed with the ability to provide a clear image thanks to the contribution of light coming from external sources such as stars, moon or artificial light of the cities. While choosing NVDs, a lot of important performance parameters need to be considered and particularly the FOM because it is used to determine the overall performance of the Image Intensifier Tube (IIT) and is calculated as a product of the IIT resolution by the Signal-to-Noise Ratio (SNR).

• The SNR typically defines how much system noise interferes with the image.
• Limiting resolution measured in line pairs per mm (lp/mm) refers to contrast allowing to gives more details

The phosphor screen of the Image Intensifier Tube (IIT) converts the electron avalanche from the microchannel plate back into photons, resulting in the green image that has become the signature view in night vision technology.

White phosphor, or P45, provides excellent recognition and has similar decay time properties as the P43 (green) phosphor. In night vision, there are no « lab » performance differences between P43 & P45. Furthermore, during trial of soldiers, no combat effectiveness difference was found. That’s why phosphor color is often a personal preference, the most important criteria being for the operator to have as less eye fatigue as possible.

Black spots are cosmetic blemishes that may originate from fixed tiny particles inside the Image Intensifier Tube (IIT) or in the fiber optic of the screen. Small size black spots are inherent to the manufacturing process and do not affect the performance or reliability of the device. Black spots can be acceptable as long as they don’t interfere with the viewing of the image to be observed and therefore specifications of tubes should be fine-tuned to match the constraints of the end-use application.

The IIT is sensitive to light if you expose this device to daylight such as sunlight, but also cloudy skies or direct light such as car headlights. So you will damage the night vision system. More especially, using an IIT when bright light hits the photocathode might seriously damage the photocathode itself. The key to avoid any damage it’s to systematically cover the night vision device (NVD) with their protective caps even if the NVD is off, raised on the helmet.

Reducing the load on a soldier is a constant challenge. We can notice a real evolution concerning the size and weight of our image intensifier tubes (IIT). We talk about SWaP: Size Weight and Power.

Reduction of SWaP contributes to enhance the efficiency and effectiveness of armed forces. Night vision devices that are designed around the 16mm IIT offer the tremendous advantage of having the same level of performance as those based upon the 18 mm tube, but with significantly reduced weight.