Fission chambers

Name: Fission chambers
Brand: Exosens

When precision matters most, trust the detectors built for the world's most demanding nuclear environments.

Designed for performance, certified for safety, and trusted across the nuclear industry.

Precise Detection Across Wide dynamic range of Neutron Fluxes

Exceptional reliability and extended operating life

Flexible customization to meet specific user applications - Customization according to the user’s needs

Guarded designs to maximizes signal-to-noise ratio

Thermal and fast neutron detection capabilities

Fission chambers

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Technical information

Product ^[a]	Diameter^[b] (mm)	Sensitive Length^[b] (mm)	Thermal Neutron Sensitivity^[b][c][d]		Fast Neutron (2.5MeV) Sensitivity^[b][d][e]	Typical Material	Type^[i]
			Pulse (cps/nv)	D.C. (A/nv)	Pulse (cps/nv)
FC165	25.4	57	0.12	^[g]	2.86x10^{-4 [f]}	Stainless Steel^[h]	Coaxial
FC167	25.4	127	0.14	^[g]	2.90x10^{-4 [f]}	Stainless Steel^[h]	Coaxial
CFUM	25.4	120	x10^-1	x10^-14	-	Aluminium	Coaxial
FC550	36.8	116	0.48	^[g]	9.54x10^{-4 [f]}	Stainless Steel^[h]	Coaxial
CFUL	48	211	1	2.00x10^-13	-	Aluminium	Coaxial
FC1400	50.8	508	1.16	3.38x10^-13	2.43x10^{-3 [f]}	Aluminium	Coaxial
FC1199	50.8	900	1.22	2.46x10^-13	2.08x10^{-3 [f]}	Aluminium	Coaxial
CFUG	80	220	4	8.0x10^-13	-	Aluminium	Coaxial
CFUC	48	220	0.6	9.00x10^-14	-	Inconel^[h]	Guard Ring
FC765	76.2	213	0.6	1.20x10^-13	1.33x10^{-3 [f]}	Aluminium	Guard Ring
FC1330	76.2	371	2	4.0x10^-13	-	Aluminium	Guard Ring
CFUP	76.5	180	0.7	1.40x10^-13	-	Aluminium	Guard Ring

PFC16	66.3	[44.4]^[j]	0.0011	^[g]	2.77x10^{-5 [f]}	Stainless Steel^[h]	Parallel Plate
PFC82	124.2	[101.6]^[j]	0.0057	^[g]	1.42x10^{-4 [f]}	Stainless Steel^[h]	Parallel Plate
PFC338	61	52.8 [32.8]^[j]	^[g]	^[g]	5.85x10^-4	Stainless Steel^[h]	Parallel Plate

[a] Significant catalogue of fission chamber designs and variants available. Table shows the most popular variants
[b] Nominal values stated
[c] At 1000µg/cm2 of 235U unless otherwise stated. Alternative coating materials and densities are available which will alter performance.
[d] Standard tolerance on these devices is ±20%
[e] At 1000µg/cm2 of 238U unless otherwise stated. Alternative coating materials and densities are available which will alter performance.
[f] Estimated from mono-energetic neutron testing of PFC338/450/U238 and theoretical sensitivity factor determined from cross-section ratio (≈9x10-4)
[g] Simple reconfiguration required to optimise performance for this operational mode.
[h] May be suitable for high temperature (300°C to 600°C) or very high temperature (>600°C) operations, subject to specific configurations.
[i] Design, materials and manufacturing process are common among most of these devices. Consequently, operation capability is common and may be transferable.
[j] Active length [window diameter], where applicable.

Description

Exosens fission chambers are capable of operating in pulse, fluctuation (Campbell or Mean-Squared-Voltage), or current modes to deliver accurate, reliable neutron flux measurements across startup, operational, and safety-critical conditions. Engineered for resilience in high-radiation and high-temperature applications, we offer a full range of high-sensitivity and high-flux models — including custom solutions tailored to your needs.

Fission chambers are highly sensitive neutron detectors designed to measure neutron flux in environments, such as nuclear reactors, research facilities, fusion power and nuclear fuel cycle facilities. They operate by detecting fission reactions initiated by incoming neutrons interacting with a fissile material deposited within the chamber. The resulting fission fragments ionize the gas inside the chamber, generating electrical pulses proportional to the neutron flux.

Gas-filled neutron detectors are designed to operate in three modes:

Pulse mode analyzes and counts individual detector pulses.
Fluctuation, or Campbell / Mean-Squared-Voltage mode, is used to analyze the fluctuations in the signal.
Current mode is used to measure the mean of the direct current from the detector.

Fission chambers offer a robust solution for a wide range of neutron flux levels and maintain performance stability, even in harsh radiation and high-temperature conditions. Their fast response time, wide dynamic range, and resilience make them critical for reactor monitoring, safety systems, and experimental applications.

What We Offer:

We supply a comprehensive range of fission chambers optimized for demanding applications. Our portfolio includes:

High-sensitivity chambers for low-flux measurements.
High-flux capable chambers for power reactor monitoring and control.
Customized designs tailored to specific reactor conditions or experimental needs.
Harsh environment models for extended lifetimes in high temperatures and radiation levels.

Our expertise ensures reliability, precision, and safety in all neutron detection applications, supporting the operational excellence and regulatory compliance of nuclear facilities worldwide.

Custom fission chambers

With full control of the following processes, Exosens can supply custom Exosens fission chambers with the highest quality and reliability levels:

Adaptation of industrialized fission chambers to customer-specific requirements utilizing significant operational experience
Development of new fission chambers with our experienced research and development teams.
Long-term collaboration with internationally renowned organizations for modeling, qualification tests in research reactors and development.
Complete manufacturing and test process on site.
Support from all the Exosens group activities, experience, and knowledge.
Highly regulated Quality Assurance programs adapted to the customer’s environment.
Expertise in design and manufacture of nuclear instrumentation to solve customer challenges. .
Export control, as an Authorized Economic Operator, Exosens acts in accordance with the EU international regulations.
Fissile material management & product storage
Calibration measurements in high radiation flux

Examples of custom versions from basic types

Neutron and gamma sensitivity tailored to individual requirements.
Guard-ring (2 outputs) or unguarded (1 output) designs, as well as coaxial and parallel plate configurations
Materials for high temperature (>3000°C) and very high temperature (>600°C) operation.
Adapted mechanical interface for installation (Customized external dimensions, springs, threads, hooks).
LOCA (Loss Of Coolant Accident) and post-LOCA protection.
Ruggedized structure for harsh environment (radiation, temperature, humidity, mechanical stress).
Integral cables or integral connectors.
Coaxial or triaxial mineral-insulated cable, as well as organic cables.
Customized connector type (BNC, HN, SHV and many others)

Main features

Structure configuration: Coaxial, parallel plate, unguarded or guard-ring.

Structure material: Various material types utilized including aluminium, stainless steel, titanium and nickel alloy.

Integral cable: Integral mineral insulated, or organic cables options are available.

Connector: Customized connector type (BNC, HN, SHV and many others)

Insulators: Exosens only uses high-grade, radiation-resistant insulators from qualified suppliers to ensure the measurement of extremely low currents.