Since the invention of nuclear power, there have been numerous “accidents.” From Three Mile Island and Chernobyl to the more recent problems in Fukushima, it would seem nuclear power is not fully under our control. Recently a Chinese scientist has warned that the single mountain under which North Korea most likely conducted its five most recent nuclear bomb tests, including the latest and most powerful could be at risk of collapsing. Wang Naiyan, the former chairman of the China Nuclear Society and senior researcher on China’s nuclear weapons program, said that if Wen’s findings were reliable, there was a risk of a major environmental disaster. Another test might cause the whole mountain to cave in on itself, leaving only a hole from which radiation could escape and drift across the region, including China, he said. Terrorist attacks involving the use of radiological and nuclear materials also pose a potential threat to U.S. citizens and service members.
Early detection of these materials and devices made from them is a critical part of the U.S. strategy to prevent attacks. Sensitive, compact, real-time, and low-cost detectors, along with innovative deployment and networking strategies, would significantly enhance detection
and deterrence of such an attack. One of thrust areas of DARPA is to counter CBRNE threats by developing and testing networked, mobile and cost-effective nuclear- and radiological-weapons detectors that can easily be deployed to provide real-time surveillance over city-scale areas.
Current handheld radiological detectors are expensive and lack networking capability. In addition, existing neutron detectors used
for nuclear materials detection at, for example, ports of entry, are large, expensive, and rely on exotic materials, such as helium-3, a rare isotope of helium that can capture a neutron from radiating nuclear sources. These limitations have prohibited widescale and continuous deployment of radiation detection systems. Adding further complexity to the situation, abundant sources of non-threatening radiation
in hospitals, on sites, and in industry settings can trick existing detectors, causing false alarms.
The SIGMA program began in 2014 with the challenge to the technology community of transforming nuclear and radiological threat detection for city-scale monitoring. It was designed to investigate new technologies that have the potential to protect city-and metropolitan-sized areas from radiological and nuclear-based terror threats through large-scale deployment of low-cost, high-capability radiation sensors and automated detection algorithms to provide real-time alerts of potential threats.
Key components of the SIGMA system include small and large form-factor mobile and static radiation sensors intended to support agile deployment strategies; the network infrastructure to connect thousands (up to ten thousand) of these sensors; the cloud-computing infrastructure to automatically analyze streaming spectroscopic data from these sensors in real-time as well as store—in an easily retrievable manner—many billions of these spectra for spatiotemporal and forensic analyses.
The task required fundamental advances in a range of fields including sensing, data fusion, analytics, and social and behavioral modeling. Realizing this capability required significant advances in:
• low-cost, high-capability detectors that can be networked together;
• scalable network architecture using commercial cellular communications and open-source network infrastructure that can handle tens of thousands of realtime sensor feeds; and
• efficient algorithms that maximize detection and source-tracking capabilities while minimizing false alarms and system latency that can
prolong detection times.
Even so, within just a few years, innovative performers contracted to work in the program had developed and demonstrated an automated, low-cost, networked radiation detection capability for counter-terrorism and continuous cityto-region scale radiation monitoring. SIGMA program has successfully created high quality, handheld radiological sensors—the size of an average smart phone—at a fraction the cost of today’s devices. SIGMA developed not only that hardware but also the software to monitor thousands of those mobile detectors in real time—an essential capability to discern the movement of nuclear materials before they can be incorporated into a terrorist’s weapon. In addition, the sensors retain local detection capabilities in the event of a network outage. Lastly, these sensors are inventoried, managed, and displayed to analysts to reveal individual and collective device status and sensor output. DARPA has achieved these core components and their integration into the SIGMA system. SIGMA has succeeded in making large-scale radiation sensor networks technically feasible and operationally practical , and it is now being operationally deployed.
In April 2018, DARPA’s performer teams partnered with the Indianapolis Metropolitan Police Department, Indianapolis Motor Speedway, and the Marion County Health Department to deploy the network on-site at the Indianapolis Motor Speedway. “With this network, we’re able to use just the chemical sensor outputs and wind measurements to look at chemical threat dynamics in real time, how those chemical threats evolve over time, and threat concentration as it might move throughout an area.”
The December 2019 exercise marked the capstone for DARPA’s SIGMA program, culminating a five-year effort to develop and deploy an automated, high-performance, networked radiation detection capability for counterterrorism and continuous city-to-region scale radiological and nuclear threat monitoring. On a blustery winter day last December, a car carrying radioactive material approached one of the Port Authority of New York and New Jersey’s major transportation hubs. As the car got closer, an alarm flashed and sounded on a large monitor in the police operations center, identifying on a digital map the exact location of the vehicle and the specific radioactive isotope radiating from the car – Cesium-137. Within minutes, officers in the Port Authority Police Department – equipped with vehicle-mounted and pocket-sized radiation sensors displaying the same real-time digital map – tracked the vehicle and apprehended the suspects in a parking lot. “We want to thank the Port Authority for their outstanding support throughout the SIGMA program and their continued support as we test SIGMA+ sensors,” said Mark Wrobel, DARPA program manager in the Defense Sciences Office. “Being able to test and refine the system in the country’s largest metropolitan region was invaluable in taking SIGMA from a research project to an operationally deployed system in just five years.”
The transition of the radiation-detection system took place prior to the coronavirus disease (COVID-19) pandemic. In the eight months since the SIGMA transition, DARPA has been developing and testing additional sensors under its SIGMA+ effort to detect chemical, biological and explosive threats as well. In its five years, the now-completed SIGMA program progressed from a basic and applied research program to a deployed operational system, providing revolutionary radiationdetection capability at multiple locations in the United States and overseas. Arktis, Silverside, Kromek, and Two Six Labs now all offer SIGMA sensors and networking capabilities as commercial products, which will drive down the cost or radiological detection and monitoring for the Department of Defense and other U.S. Government users.
DARPA has greenlit an automated, networked radiation detection system known as SIGMA for use by the Port Authority of New York and New Jersey, promising new protections for the region. “New York City and Northern New Jersey have some of the nation’s most critical transportation infrastructure – heavily trafficked tunnels, bridges, airports, train and bus stations, and ferry terminals,” Dave Warrington, senior manager for strategic preparedness in the Port Authority’s Office of Emergency Management, said. “This unique partnership with DARPA was mutually beneficial – DARPA had access to our transportation nodes to collect real background radiological data for developing the system, and the Port Authority now has a network of high-performance stationary, vehicle-mounted, and wearable sensors providing enhanced, 24-hour nuclear and radiological threat detection.”
According to users of the system, it’s user friendly, based on an app-like Android interface. Officials and first responders can use it to track alerts and threats in real-time, allowing for enhanced coordination. The system also doesn’t sacrifice power for portability. It’s versatile, based in worn, portable sensors, vehicular mounted sensors, and stationary sensors at key transportation nodes. It can also be constantly improved through regular software updates.
DARPA is currently extending the capabilities for networked chemical detection by investigating additional sensor modalities, including short-range point sensors based on, for example, mass spectrometry, and long-range spectroscopic systems. As these systems are further developed, they will be integrated into the SIGMA+ network architecture to increase the system’s capabilities for city-scale monitoring of
chemical and explosive threats as well as threat precursors. In 2020, DARPA directed some of the SIGMA effort directly to the challenge of detecting SARS-CoV-2, the virus at the heart of the COVID-19 pandemic, in buildings and other environmental settings.
A key element of SIGMA, which began in 2014, has been to develop and test low-cost, high-efficiency, radiation sensors that detect gamma and neutron radiation. As part of the overall system, the SIGMA program called for the development of highly sensitive, low-cost neutron detectors using alternative materials to helium-3. Neutron detectors play a critical role in the identification of plutonium-based nuclear threats and are valuable in reducing false alarms by being able to discriminate threatening nuclear sources from common industrial sources of radiation such as density gauges used in civil construction. Helium-3-based radiation detectors have traditionally been the standard, but the global supply of the isotope is diminishing, leading to higher costs. Specifically, SIGMA sought to develop neutron detector technologies with sensitivities twice that of a standard helium-3 portal monitor and with a price point of $5,000 per unit at a quantity of 200 units.
U.S. ‘s Defense Advanced Research Projects Agency (DARPA) had asked industry to design a pocket-sized radiation detector to help foil terrorists attempting to detonate concealed dirty bombs or full-blown nuclear weapons in or around U.S. cities and crucial government and industrial infrastructure. Direct measurement of gamma and neutron emission remains one of the few definitive to detect and identify special nuclear materials and radiological sources, DARPA officials say.
SIGMA’s research funding also enabled development of a low-cost, highly sensitive, pocket-sized detector –wearable by troops and first responders. SIGMA made early fundamental research investments in this area with two companies, Arktis Radiation Detectors and Silverside Detectors. Both companies, with additional investments, developed practical technologies and products that are now deployed and providing added security at critical sites around the world.
Silverside Detectors working with Onshape to make Nuclear radiation Sensors
Silverside Detectors, a Massachusetts-based company specializing in nuclear security, is using tools from Onshape, a cloud-based CAD software provider. The objective is to develop low-cost compact-sized nuclear radiation detectors. Philip Taber, Silverside VP of Hardware Engineering, praised the efficiency of Onshape software, “We switched to Onshape because we urgently needed help with data management.”
Program Manager and Applied Physicist at DARPA, Dr. Vincent Tang, states, “The SIGMA program aims to revolutionize detection and deterrent capabilities for countering nuclear terrorism.” Tang further elaborates, “A key component of SIGMA thus involves developing novel approaches to achieve low-cost, high-efficiency, packaged radiation detectors with spectroscopic gamma and neutron sensing capability.”
Nuclear radiation detection
Helium-3 is an isotope of the helium gas. It is non-radioactive and is used in the detection of nuclear radiation. In recent years, due to the increased threat of nuclear terrorism, the demand of helium-3 has peaked, which has resulted in a shortage of the isotope. In 2001, the demand of helium-3 was 8,000 liters per year, whereas in 2008 it went up to 80,000 liters/year, decreasing the accumulated stockpile of the isotope.
One way to counter this problem is using elements other than the helium-3 and developing smaller radiation sensors. Silverside Detectors, working on the SIGMA program and partly funded by DARPA, has a solution. The company wants to build a lithium-based (Li-6) neutron detectors, which is compact in size and cost-effective.
Leveraging 3D technology
Now, Onshape with its 3D software capabilities will help Silverside Detectors speed up the development of the Li-6 nuclear radiation detector. Jon Hirschtick, CEO of Onshape further added, “Silverside Detectors is genuinely making the world a much safer place … We’re proud that Onshape is playing a role in speeding up the production of their nuclear radiation detectors and getting them deployed on the ground as quickly as possible.” “Onshape probably cuts our design time in half because we’re designing our parts together in one place versus flipping back and forth between files. We can make changes without worrying about breaking the assembly.”
Kromek to support DARPA’s SIGMA dirty bomb detection programme
Kromek, one of the contracted performers in the program, shrunk the dimensions and cost of existing portable detectors from a $10,000 shoe-boxsized unit with no networking capability to a lightweight, networked handheldsized device that costs $400 per unit (at a quantity of 10,000). UK-based radiation detection company Kromek had secured two separate contracts from the US Department of Defense (DoD) to support the Defense Advanced Research Projects Agency’s (DARPA) SIGMA programme. Valued at $6m, the deal requires the company to supply spectroscopic personal radiation detectors (D3S) in support of the programme.
The SIGMA programme aims to develop an advanced personal detection system for gamma and neutron radiation that can be combined with other such systems to form large networks to detect radiation signatures over an extended area. The technology used could provide early warning about acts of terrorism such as a ‘dirty bomb’. The second contract, which is valued at $0.75m, covers the supply of 12,000 inductive charging packs for D3S detectors and associated mobile devices. The inductive charging pack provides a long battery life for the detectors, and can be recharged and recalibrated when necessary.
Kromek CEO Arnab Basu said: “The D3S is the world’s first fully approved combined gamma and neutron detector available in volume shipment and at a market leading unit price of $400, which is also available to other user organisations buying over 10,000 detectors in a single procurement.
Needed are belt-worn, pocket-size, wearable, and large-area radiation detectors that represent an order of magnitude less expensive with substantially increased detection capability than what is available today, researchers say. DARPA is interested in new packaged dual-mode gamma and neutron detector concepts with an order of magnitude reduction in cost per unit while achieving 5 x and 10 x greater sensitivity in gamma and neutron detection, respectively, compared to the state-of-the art. For gamma detection, spectroscopy is required, whereas for neutron detection, counting is sufficient. The user interface is expected to be provided by a user-owned mobile device with both USB and wireless secure connection options, and the detector is expected to be worn (e.g., on a belt or in pocket), not held.
At the heart of these detectors is a small thalliumactivated cesium iodide crystal. When the crystal absorbs the characteristic
radiation energies of specific isotopes in its vicinity, it responds by emitting light particles. These, in turn, are converted into electrical signals that serve as signatures the detector system can use to identify the radiating substance and help determine if it poses a threat.
Physical Sciences Inc.
The system that has emerged from SIGMA research relies on advanced spectroscopic algorithms developed by Physical Sciences Inc. to process the information provided by the detectors and determine if a potential threat exists. These algorithms run within the Two Six framework and intelligently combine information to reduce false alarms and improve sensitivity.
The detectors, which do not themselves emit radiation, are networked via smartphones to provide city, state, and federal officials real-time awareness of potential nuclear and radiological threats such as dirty bombs, which combine conventional explosives and radioactive material to increase their disruptive potential. The Kromek detectors, which can attach to a belt or fit in a backpack’s outer pocket, are networked with the larger Arktis and Silverside sensors providing city-wide threat awareness via smartphone, tablet, or web-based user interfaces.
Two Six Labs
Continuous threat monitoring over large areas requires thousands of detector feeds to be collected, aggregated, and processed in real time to provide overall situational awareness to end users. Another performer, Two Six Labs, developed and operationalized a framework that incorporates open source tools to ingest and process the data. Two Six Labs also developed the user interfaces to display results to operators.
Existing Data Ingestion, Streaming Analysis, Storage and Situational Awareness Network Products and Services
In order to plan appropriate follow-on efforts, DARPA is interested in any software products and network infrastructure that may have demonstrated capabilities similar to the SIGMA system.
Invincea Labs, LLC leads these networking and integration efforts within the SIGMA program.
- Ability to ingest, analyze, and store data for thousands (up to ten thousand) spectroscopic sensors reporting full spectral data and device status at 1 Hz, via ~kilobyte sized compressed and encrypted packages transmitted directly through wifi, cellular, or other communication means to a cloud-based network backbone;
- Ability for bidirectional communication with these sensors;
- Ability to run multiple computationally-intensive detection, identification, tracking and sensor fusion algorithms in real-time with minimal reporting latency (~seconds);
- Ability to manage inventory and device status (including sensor health, calibration data and other metadata) for many thousands of heterogeneous sensors;
- Ability to display and report device status, sensor output, and location in real-time to analysts and commanders through web-based Command and Control (C2) interface designed for thousands (up to ten thousand) sensors, providing real-time threat monitoring, situational awareness, and blue-force tracking capability;
- Ability to query recent historical data (~month) with minimal latency (~10-100 ms);
- Storage of multiple years of sensors data (~10 TB/year);
- Ability to simulate many thousands of sensors to demonstrate scalability and to replay historical sensor data through the system for multiple purposes, including for example testing of new algorithms or development of new concepts-of-operation;
- Security and encryption appropriate for national security information systems (e.g., NIST 800-53);
- Ability to deploy on multiple commercial cloud infrastructures (e.g., Amazon Web Services (AWS), Azure) or locally on premise;
- Ability to support expansion into novel sensor modalities, detection algorithms, and data fusion;
- Code base with unlimited rights.
DARPA is also more generally interested in production and operational grade software and Internet of Things (IoT) development organizations with expertise (or planned expertise) in the following areas:
- Massive sensor networks reporting in real-time;
- Advanced data analytics with very stringent performance guarantees;
- Familiarity with the challenges presented by heterogeneous sensor physics and sensor fusion approaches;
- Unique security and privacy concerns inherent in a distributed national-security system, including cybersecurity requirements.
Testing, Transitioning and Depoyment
SIGMA developed and networked thousands of high-capability, low-cost detectors to demonstrate large-scale, continuously streaming physical sensor networks for the RN interdiction mission. In collaboration with officials in the Washington, D.C., metropolitan area and the Port Authority of New York and New Jersey, DARPA in 2016 tested the devices and networking system at critical transportation hubs and on a city-wide scale involving 1,000 detectors. That test showed the system could fuse the data provided by all those sensors to create minute-to-minute situational awareness of nuclear threats. Working in close cooperation with the Department of Homeland Security, DARPA’s technology has been on track for deployment in multiple locations. SIGMA capabilities have been tested and operationalized with federal, state, and international partners.
Working through the Joint Program Executive Office for Chemical, Biological, Radiological, and Nuclear Defense (JPEOCBRND), 1,000 wearable SIGMA radiation detectors are being deployed to U.S. Forces in the Republic of Korea. In 2019, the Department of Homeland Security awarded a commercial contract that specifies Silverside neutron detectors, developed under the SIGMA program, as
replacements for current U.S. radiation portal monitors. These monitors provide screening at critical locations, such as border entries and ports.
SIGMA is also operational with the Port Authority of New York and New Jersey, providing advanced radiation threat detection at key locations in the greater New York City area. Overseas, SIGMA technology has transitioned to the United Kingdom’s Home Office, and
Arktis neutron detectors are deployed and operating at the Port of Antwerp, Belgium, Europe’s second-largest port.
DHS S&T Transitions Next-Generation Explosives Trace Detection Technology to DARPA
The Department of Homeland Security (DHS) Science and Technology Directorate (S&T) transitioned technology to the Defense Advanced Research Projects Agency (DARPA) that is representative of S&T’s deep body of work in cataloging, detecting and thwarting explosive threats. Now this body of work will help keep our warfighters and our nation safe from weapons of mass destruction (WMD) threats.
The technology—a Next-Generation Mass Spectrometry Explosive Trace Detector (Next-Gen Mass Spec ETD)—was developed due to emerging explosive threats and evolving tactics by terrorists to evade detection. For the past decade, S&T has made it a top priority to equip and enhance DHS security personnel with next-generation capabilities that can rapidly identify and defeat these threats.
For example, we all know that explosive threats are a major concern in aviation security. They are the reason we remove our shoes as we go through airport checkpoints and why the Transportation Security Administration (TSA) scans every piece of luggage and cargo before loading them onto planes. The sheer variety of explosive materials, the many vehicles for deploying them, and the increasing tactics used to avoid detection pose a tremendous risk not only to American (and global) aviation, but across the entire homeland security enterprise.
References and Resources also include: