Triaxial cable extensions & connectors

Triaxial cable extensions & connectors

In severe operating conditions, and when the use of detectors with an integral cable is not preferred, an alternative is to use a triaxial mineral insulated cable extension connected to the detector.

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High level of resistance against radiation and electromagnetic parasitic signals
Watertight, mineral insulated cables and connectors
Customization according to the user’s needs

Triaxial cable extensions & connectors

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Technical information

Similar to coaxial cable extensions & connector but in triaxial configuration


Basic typeMI Cable External diameter (mm)Signal transmissionConnector type
EXT-HN6Pulse, fluctuation (Campbell) and current modesHN


Such mineral insulated cable extensions are terminated by two adapted HN or specific triax-connectors (plugs or jacks). Triaxial cable extensions & connectors can work for pulse and current transmissions.

Custom triaxial cable extensions & connectors

By full control of the following processes, Photonis Nuclear Instrumentation can supply custom triaxial cable extensions & connectors with the highest quality and reliability levels

  • Adaptation to customer specific requirements.

  • Development of new triaxial cable extensions & connectors with our experienced R&D team.

  • Long term collaboration with the French Alternative Energies and Atomic Energy Commission / CEA (theoretical approach, modeling, qualification tests in research reactors.

  • Complete manufacturing process on site.

  • Support from all the Photonis Group activities, experience and knowledge.

  • Certifications & Quality Assurance programs adapted to the customer environment.

  • Technical support, applying our expertise in the design and manufacture of nuclear instruments to solve customer challenges.

  • Export control, as an Authorized Economic Operator, Photonis acts in accordance with the EU international regulations.

Examples of customization of standard parts

  • Mechanical interface with the equipment (Customized external dimensions, cable curvature radius).

  • Electrical characteristics (characteristic impedance, capacitance, line resistance, attenuation, transfer impedance).

  • Cable insulator material (Al2O3, MgO, SiO2).

  • LOCA (Loss Of Coolant Accident) and post-LOCA protection.

  • Ruggedized structure for harsh environment (radiation, temperature, humidity, mechanical stress).

  • Coaxial Mineral insulated connector type (HN, BNC, BNC HT or specific). Reinforced types are available for high pressure, high temperature conditions.

  • External mechanical and/or electrical protection around the cable and/or the connectors (folded spiral seam, radiation resistant heat-shrink sleeve).

  • Connectors can also be delivered in mating connector or tight feedthrough versions.

Main features

Structure configuration: Triaxial (one central conductor, two external envelopes).

Cable materials: Multi metallic cable envelope for high immunity to electromagnetic parasitic signals. Magnesia (MgO) cable insulator.

Connector Material: Stainless steel and Nickel structure and high-grade Alumina (Al2O3) insulator.


The French Atomic Energy Commission (CEA) selected Photonis as its technological partner for a co-operative development of neutron and gamma detectors when the French nuclear power program took shape in the sixties.

Our references

PWR – Safety critical signal transmission in reactor building – Mineral insulated cable extension – EXT-HN - France