ASTROHN terahertz technology as the basis of a metro passenger screening system

THERZ-7A small-sized terahertz system

ASTROHN terahertz technology as the basis of a metro passenger screening system

One of the main targets of terrorist attacks among transport facilities is the metro. That fact has been borne out by specialists of the National Terrorism Consortium at the University of Maryland (USA). The metro has a huge passenger flow, so the attacks lead to a large number of victims, which is what modern terrorism seeks. In order to protect the transport infrastructure facilities and metro vehicles from terrorist attacks in our country, like in many others, in recent years, active work has been carried out to create transport security systems.

The metro territory is divided into zones of:

  • transport safety, accessed through checkpoints (inspection zones) in accordance with the established procedure;
  • free access, not restricted for individuals and material objects.

The transport safety zone, in turn, is divided into the transportation and technological sectors. Most of the engineering security systems installed in the metro are designed to equip checkpoints (inspection zones). Zones are located in the lobby between the entrance and the turnstiles. Currently, active work is underway in the metros of Russia to create and equip these zones.

As part of the Federal Target Program, ASTROHN Technology ltd. has developed THERZ-7A small-sized terahertz system to detect prohibited items hidden under clothing. The system scans passengers for “terahertz” waves naturally emitted by their bodies, whose frequencies are in the infrared and microwave ranges. If a person carries a prohibited object (weapons or explosives, metallic or non-metallic), it blocks emission and becomes revealed.

What is terahertz radiation?

The terahertz (THz) frequency range is somewhere in between the infrared (IR) and microwave regions of the electromagnetic spectrum. Conventionally, the frequencies of 0.02 THz and 10 THz are considered to be the boundaries of the THz range. This frequency range is often also called the far infrared or submillimeter range.

Terahertz radiation is non-ionizing, unlike x-ray radiation. Different biological tissues have different absorption in this range, which allows for the contrast of images. The terahertz range includes the spectra of complex organic molecules (molecules of proteins and DNA, explosives, etc.). Compared to visible and infrared radiation, terahertz is long-wavelength, i.e. it is less prone to scattering. As a result, many dry dielectric materials such as fabrics, wood, paper, and plastics are transparent in this range. Therefore, terahertz radiation can be used for non-destructive testing of materials, scanning at airports, etc. At the same time, the radiation wavelength is small enough to provide submicron spatial resolution for freely propagating radiation. The terahertz range is where the resonances of rotational and vibrational transitions of many molecules occur. This allows molecules to be identified by their spectral “imprints”. In combination with obtaining images in the terahertz range, this makes it possible to determine both the shape and the composition of the studied object.

Electromagnetic radiation spectra

Electromagnetic radiation spectra

THERZ-7A advantages

THERZ-7A allows for quick and effective contactless checks of the flow of people. This system can be easily adapted to the existing security system and does not affect its performance. THERZ-7A detects hidden objects by distinguishing between the natural energy of the human body in the millimeter range and the energy of non-living objects such as explosives and weapons, even if they are hidden under clothing.

The detection mechanism frames a potentially dangerous object and triggers an alarm, which will notify the guard of a possible danger, so that security personnel can additionally check the suspect or turn off the alarm. The system accurately identifies metal, ceramic, plastic, composite items, liquids and gels.

The device neither irradiates objects nor poses a risk to human health, including those with pacemakers or pregnant women. The system does not cause claustrophobia, as it is completely open. THERZ-7A does not display the anatomical structures, thereby protecting personal integrity and observing moral standards. The system works in real time, does not cause long queues at the entrance and exit.

Installation and operation of a small-sized system is possible without preliminary preparation of checkpoints. Preparation for work takes 15 minutes and requires one person only.

Image example for THERZ-7A Operator

Image example for THERZ-7A Operator

THERZ-7A consists of:

  • a camera unit (terahertz camera, video surveillance camera, thermal imaging camera);
  • uninterrupted power supply;
  • automated workstation.

THERZ-7A technical specifications

  • The detection range of large objects (hidden under clothing) – min. 15 m.
  • The throughput in the pass mode – min. 150 people/hour.
  • The maximum output time of the screening result (the presence or absence of objects provided that the object of inspection is immovable) does not exceed 2 sec.
  • The screening results presented to the THERZ-7A operator on the AWS monitor screen visualize the hidden object with the reference to its location on the inspected person.
  • THERZ-7A can operate both autonomously (independently) and as part of an integrated set of technical security equipment via Ethernet.
  • Storage time of recorded video information – 30 days.
  • Recording of stored data on external media (removable hard drive or solid-state storage medium).
  • THERZ-7A operates from a common industrial AC network 220V (±10%), 50Hz (±1).
  • Gross electrical power does not exceed 150W.
  • Operating temperature range from +5 to +40 °C inside heated rooms without moisture condensation, ingress protection degree – IP20.
  • Overall dimensions of the camera unit – 660×650×245 mm.

Possible arrangement of a security zone checkpoint using THERZ-7A

Possible arrangement of a security zone checkpoint using THERZ-7A

Synergetic effect

New security systems allow metro law enforcement bodies to check passengers in continuous crowded traffic and take preventive measures if suspicious objects, explosive devices, or weapons are detected.

The use of THERZ-7A at the facilities will ensure the following effects:

  • early remote detection of hidden objects on the approach to the system;
  • detection of hidden non-metallic objects;
  • better efficiency of operational organizational and technical measures;
  • harmless to people;
  • non-invasive (doesn’t display the anatomical structures);
  • high-quality and effective remote screening of people at the facilities;
  • improvement of the overall performance of existing and newly created integrated complexes and physical protection systems of metros of the Russian Federation.

V.V. Startsev, V.I. Voitov