The horizontal dimension of the image is produced by moving either the truck or the scanning hardware. The cobalt-60 units use gamma photons with a mean energy 1.25 MeV, which can penetrate up to 15–18 cm of steel.
The systems provide good quality images which can be used for identifying cargo and comparing it with the manifest, in an attempt to detect anomalies. It can also identify high-density regions too thick to penetrate, which would be the most likely to hide nuclear threats.
They also deliver about 1000 times higher dose of radiation to potential stowaways. All three systems are based on neutron interactions with the inspected items and examining the resultant gamma rays to determine the elements being radiated.
FNA and PNA use fast neutron scattering to generate the gamma rays. The method was re-discovered and improved upon by a research team at Los Alamos National Laboratory, muon tomography is completely passive, exploiting naturally occurring cosmic radiation.
This makes the technology ideal for high throughput scanning of volume material where operators are present, such as at a marine cargo terminal. In these cases, truck drivers and customs personnel do not have to leave the vehicle or exit an exclusion zone during scanning, expediting cargo throughput.
Radiological materials emit gamma photons, which gamma radiation detectors, also called radiation portal monitors (RPM), are good at detecting. Systems currently used in US ports (and steel mills) use several (usually 4) large PVT panels as scintillators and can be used on vehicles moving up to 16 km/h.
They provide very little information on energy of detected photons, and as a result, they were criticized for their inability to distinguish gammas originating from nuclear sources from gammas originating from a large variety of benign cargo types that naturally emit radioactivity, including bananas, cat litter, granite, porcelain, stoneware, etc. Those naturally occurring radioactive materials, called NORMs account for 99% of nuisance alarms.
Some radiation, like in the case of large loads of bananas is due to potassium and its rarely occurring (0.0117%) radioactive isotope potassium-40, other is due to radium or uranium that occur naturally in earth and rock, and cargo types made out of them, like cat litter or porcelain. Those types of shields do not stop fission neutrons produced by plutonium sources, however.
Radiation Portal Monitors often use Helium-3 based detectors to search for neutron signatures. However, a global supply shortage of He-3 has led to the search for other technologies for neutron detection.
^ a b “Technical Specifications of Mobile Pakistan Cards Inspection System” (PDF). “Protecting our Borders while Ensuring Radiation Safety” (PDF of PowerPoint Presentation).
Presentation to the Northern California Chapter of the Health Physics Society. “Processing of interlaced images in 4–10 MeV dual energy customs system for material recognition”.
^ “Secrets of the pyramids” ^ “Muon radiography” by Brian Fishing from Los Alamos National Laboratory ^ “Muons for Peace” by Mark Overton in Scientific American ^ “Dr. Stanton D. Sloane of Decision Sciences looks at how passive detection systems can play their part in protecting the global supply chain” by Cargo Security International ^ “Decision Sciences Awarded Atomic Weapons Establishment (AWE) Contract for Nuclear Detection System.” ^ “Cosmic Rays to pinpoint Fukushima cores” by World Nuclear News ^ “Overview of Exploration's AT-980 Radiation Portal Monitor (RPM)”.
Heck, a bright light bulb can be seen through an inch of non-tinted wax. Whenever someone calls for the infrared camera on TV shows and film these days, either the handheld version or one mounted on Spy Satellites, the device will have amazing qualities, chief among them being able to see through walls.
It's incredibly convenient for the good guys being able to make out what's happening inside the building. In fact an infrared camera meant for thermal imaging (as opposed to near-infrared), the kind most often seen on TV and movies, cannot even see through a sheet of regular glass that's perfectly clear to anyone using the Mark One Eyeball (this is the effect greenhouses are based on).
Steam is not good for IR either, but any light fog (which is usually cool) could be penetrable to an extent. The truth is plainly obvious from all those televised high-speed chases in Los Angeles where the chase takes place at night so the Forward Looking Infrared camera on the police helicopter gets to show the Cool High Tech imagery.
You can see the heat of the car engine, the tires, the ground where something hot has been, even the reflection of heat off the ground, yet you can 't see the driver and his passengers although the few millimeters of metal making up the car body is a lot thinner than the several inches of material making up the average house wall. One can therefore conclude that either writers and directors don't watch Fox, or that it's yet another case of technology gone awry in the service of the plot.
Note, however, that there theoretically exist wavelengths on which the electromagnetic radiation behaves similarly to this trope. Just one example would be the terahertz radiation (T-rays), which sits uncomfortably on the border between infrared and microwaves.
Terahertz sensors (which, as noted above, have more in common with radars, rather than with the cameras), are already being used for airport security in a number of countries, and known as nude scanners “. Fate/Zero : Kiritsugu Emily, the Magus Killer “, uses infrared goggles to detect Magi, since their body temperature rises higher than normal when they use their Mage craft.
A character also hides in the bucket of a backhoe which, as the monsters are short, they can 't look over the sides to see into while milling around. Dutch realizes that the creature sees in infrared when it can 't spot him covered in (cooler) mud which temporarily disguised his body heat.
When the film shows scenes from the Predator's point of view, the body heat of the humans is blocked by cooler objects in the foreground such as vegetation, just like it really would be. However, in real life, the mud would warm up due to the body heat pretty quickly, as demonstrated by the MythBusters.
It's also done as a bit of a gag at this trope's expense, as the Marines realize this while the Aliens are right in front of their faces, and completely invisible. This was definitely popularized by, and may have come from, both the movie and television versions of Blue Thunder, where the helicopter mounts IR sensors that do precisely this.
The camera Q issues to Bond just lets him take pictures of the '' Disco Vol ante's exterior. The SEAL Team sniper uses a .50 caliber rifle with a thermal scope with these miraculous capabilities.
It's notable that anyone can see the green spotlight that is, basically, the weapon's equivalent of the red dot. Done somewhat correctly, as it's used to track magi, who when using mage craft will have an increased body temperature from the Circuits.
This was subverted in the NCIS: Los Angeles episode, The Watchers when we find out that Betty installed heaters in the roof of the boat shed to prevent this. On the other hand, another episode showed a thermal infrared camera was able to see through a dust cloud that obscured visible light.
NUMB3RS used a variant when body-heat signatures pinpointed survivors trapped in the wreckage of a train crash. Arguably might've been justified, in that Charlie sent small camera-armed robots into the wreck to observe the trapped victims directly, rather than through intervening walls.
Unfortunately, the signatures of two unlucky victims vanished within seconds of their demise, whereas a real body's heat would take many minutes to disperse. The infrared scanner could see through walls and showed the results on the usual color-coded display screen in the cockpit.
One notable example had the camera looking through the wooden walls of an old barn to detect an aircraft with a suspiciously warm engine. On an episode of Burn Notice where Team Western deals with a Mafia human-trafficking ring, Fiona uses one of these to scope out the interior of a Russian restaurant.
In another episode a regular digital camera is used to spot the infrared laser being bounced off one of the apartment's windows in order to eavesdrop on Michael (in such a system the laser can measure vibrations in the glass and output it as sound from inside the room. A Law & Order episode used infrared scanner imaging to secure a search warrant on a mosque.
The defendant's lawyer successfully argued that the technology violated the Fourth Amendment without a warrant specifying its use and got the evidence seized there thrown out. Episode “Fallen Angel” from The X -Files featured invisible aliens and one of them was seen through a heat-source sensing device through walls.
The album cover of Frank Zappa's Hot Rats (1969) was shot with this color technique. The album cover and the music video of Emotional Rescue (1980) by The Rolling Stones were both shot making use of thermal imagery.
Dark vision is itself unrealistic, as it apparently shows shapes just fine but lacks color information... which actually acts more like sonar than anything else! Mutants & Masterminds averts this trope, noting that it works largely like regular sight and is blocked by walls (although they fail to note that glass blocks it), only allowing Infra vision as an alternative to regular sight.
Infrared goggles and thermal scopes don't see through anything solid, and the vision gets less distinct as distance increases. Enemies further away will be only slightly brighter colors than the background haze, and if sufficiently far will blend in entirely.
Of course, you'd never see that (one of the cool things infrared can do) on TV or in the movies... Metro id is apparently in The Future after all. The infrared goggles allow you to see people and dogs (and nothing else) in range as bright red silhouettes, even through walls.
In Ghost Squad, you can actually use the infrared goggles to snipe through the walls of a straw hut. Possibly for the same reason actual military forces keep night vision goggles on them, even on day missions.
On the other hand, one soldier in Black Hawk Down decided to forgo night vision in favor of grabbing extra ammo, along with many others. They paid dearly for this when they ended up stuck on the battlefield all the way into the night, without one of their greatest tactical advantages.
FEAR 2's elite power armor has a fairly realistic false color thermal imaging mode; it doesn't exclusively show people, as fire and other power armor (which are incredibly heat inefficient) also shows up. The Steyr AUG in Siphon Filter: The Omega Strain has a false-color infrared scope with this effect.
Provision in Crisis 2 is a combination of night and infrared visions that can see through dust and smoke (not perfectly, but still better than the naked eye). The thermal vision in Ghost Recon: Advanced War fighter doesn't see through cover, although the HUD can display the silhouettes of concealed enemies that have already been spotted by other means.
Averted in Shadow of the Tomb Raider, where the game explicitly says that IR-equipped enemies can 't see Lara through walls. At one point it's implied that the enemy has them as well, as Street Robin watches them redeploy on the roof in response to his own movements.
Some materials are transparent to infrared, but opaque to the visible spectrum, so this trope is in play some time. Thermal imaging cameras make use of long-wave infrared to detect the temperature of objects, which often allows the user to see things hidden to the naked eye.
While they can 't see through objects, this sense allows them to hunt prey and avoid predators at night. Some Sony cameras feature “Nightspot” modes, that allow to take images in absolute darkness using infrared wavelengths.