1” Star Straw Neutron Detector Direct, drop-in replacement for up to 3.4 atm 1” 3He tubes

This 1” neutron detector is a direct, drop in replacement for 3He technology that relies on boron-coated straws (BCS) rather than the limited and expensive resource of 3He. This detector was tested at Pacific Northwest National Laboratory (PNNL), where it was shown to have an intrinsic efficiency for neutrons of 54%, equivalent to 3.4 atm of 3He in a 1” diameter form factor.

This detector is directly compatible with 3He electronics and the desired connector type can be requested to meet the needs of any application. These detectors rely on a close-packed array of star shaped BCS sealed inside an aluminum tube with an outer diameter of 1.0”. Each star straw is wired as a mini proportional counter with all outputs tied together for a single, simple readout. Detector lengths are available from 14 cm to 54 cm (5.5 inches to 21 inches) with 10 cm to 50 cm active lengths, respectively. In addition to testing at PNNL, these detectors have also undergone a battery of physical shock tests, surviving over 50 g peak acceleration.


  • Direct replacement of Helium-3 detectors
  • Easily integrates into existing instruments and monitors
  • Use existing calibration and counting electronics and software
  • Transport safe: no high pressure, no hazard
  • Ultra-low power electronics available
  • No user maintenance


  • First responders
  • Customs border agents
  • Military operations
  • Special Nuclear Material (SNM) search
  • Event monitoring
  • Radiological emergency response

Benefits of boron-coated straws

Each BCS detector contains 37 star-shaped copper straws coated with a ~1 m thick 10B enriched boron carbide, a neutron-sensitive material without the high costs and low supply that plague 3He detectors. Furthermore, BCS detectors are filled with an Ar/CO2 counting gas at only 0.7 atm, making them safer to transport and requiring minimal documentation compared to 3He or 10BF3 proportional detectors. Each star straw is wired as a proportional counter, supporting up to 10 times faster signals in the 1” tube than traditional 3He tubes.

Homeland Security

n-Defender series detectors are a new high performing neutron radiation detection product line specifically designed for security monitoring applications, with an emphasis on reliability, accuracy, and ease of use. These include the n-Defender Portal (PTI-110-NDM or PTI-101-NDM), the n-Defender Maritime (PTI-116-NDM), and the n -Defender Vehicle (PTI-119-VMD).The new n-Defender family of detection products represents a leap forward in the nuclear weapons detection market.  Developed for fixed, mobile, and portable radiation detection applications, n-Defender is designed to provide users with the most sensitive nuclear weapons and materials detection capability while at the same time ensuring a cost effective, high reliability product.

Preserving the basic advantages that made the 3He tube the dominant technology in the harsh security environment, n-Defender provides significant advantages over competitive neutron detectors for installations in fixed portal monitoring systems at ports and borders, mobile search systems for land and maritime missions, and portable radiation instruments such as backpacks and handhelds.  All n-Defender products utilize the powerful wire avalanche method of signal generation providing total immunity to temperature extremes, tolerance to harsh handling, and by far the best longevity in the field. Utilizing the patented boron-coated straw (BCS) technology, the n-Defender systems provide a simple and easily-deployed solution that provides users and instrument manufacturers with superior neutron detection with little to no modifications to their existing systems.

The n-Defender family of neutron detectors have been developed to leverage shared manufacturing, materials, and personnel resources.  All n-Defender modules utilize the same basic components, and can be resized quickly to support unlimited large variety of modules and solutions.

Portal DetectorMaritime Detector    Vehicle Mounted Detector


Neutron Science

Proportional Technologies, Inc.'s BCS technology is now offered in conveniently sealed packages that are readily scalable to replace position sensitive 3He tubes in neutron science instruments. Additionally, electronics for high rate & high resolution imaging are also available. Ongoing testing at national laboratories have shown that BCS detectors, like the 7-detector imaging panel pictured below, are equal to the task of replacing 3He detectors with minimal maintenance, reduced cost, and greater versatility.

Neutron imaging panel     Neuron imaging panel nat'l lab testing



Compact Neutron Detectors

PTI is pushing the limits in the size of neutron detection. Unlike 3He detectors, BCS detectors can operate at detector sizes smaller than 0.5" diameter tubes while remaining highly sensitive to thermal neutrons. PTI has developed pocket sized and hand-held personal radiation detectors that can be paired with a cell phone or tablet via Bluetooth for easy readout. PTI continues to advance the BCS technology by introducing the star straw detector - a 1" diameter detector with efficiency equivalent of a 3-atm 3He detector.

Personal radiation detector Star Straw Detector  Hand-held neutron detector   




Our portable Fission Meter and Multiplicity Counter offer solutions for the detection of fission neutron sources contained in illicit radioactive material. PTI also offers a BCS detector with extremely fast die-away times, compatible with active interrogation. Finally, PTI has developed a directional neutron detector, capable of mobile and real-time determination of the direction of a neutron source relative to the detector.



Click here to download slides to learn more about our Boron Coated Straw (BCS) detectors.

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