Access to famous persons, too, became more and more restricted ; potential visitors would be forced through numerous different checks before being granted access to the official in question, and as communication became better and information technology more prevalent, it has become all but impossible for a would-be killer to get close enough to the personage at work or in private life to effect an attempt on his or her life, especially given the common use of metal and bomb detectors.

They also tend to have much lower junction capacitance than p – n diodes, which provides for high switching speeds and their use in high-speed circuitry and RF devices such as switched-mode power supply, mixers, and detectors.

This covers all radiation instrument technologies, and is a useful comparative guide to the use of GM detectors.

Scintillation-type detectors use a radiation-sensitive crystal, most commonly thallium-doped sodium iodide ( NaI ( Tl )), which emits light when struck by gamma photons.

Modern systems with a higher time resolution ( roughly 3 nanoseconds ) also use a technique ( called " Time-of-flight ") where they more precisely decide the difference in time between the detection of the two photons and can thus localize the point of origin of the annihilation event between the two detectors to within 10 cm.

Thermistors differ from resistance temperature detectors ( RTD ) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals.

Success, however, had to wait until after World War II, during which the attempt to improve silicon and germanium crystals for use as radar detectors led to improvements both in fabrication and in the theoretical understanding of the quantum mechanical states of carriers in semiconductors and after which the scientists who had been diverted to radar development returned to solid state device development.

Besides its use in the superheterodyne circuit which is found in almost all radio and television receivers, it is used in radio transmitters, modems, satellite communications and set-top boxes, radar, radio telescopes, telemetry systems, cell phones, cable television converter boxes and headends, microwave relays, metal detectors, atomic clocks, and military electronic countermeasures ( jamming ) systems.

Some robotic lawn mowers will adapt their programming by detecting the speed in which grass grows as needed to maintain a perfect cut lawn, and some vacuum cleaning robots have dirt detectors that sense how much dirt is being picked up and use this information to tell them to stay in one area longer.

Magnetic anomaly detectors employed to detect submarines during World War II harnessed the fluxgate magnetometer, an inexpensive and easy to use technology developed in the 1930s by Victor Vacquier of Gulf Oil for finding ore deposits.

Both fields also use solid state detectors, though the specific type of solid state detectors used are different.

Businesses use a variety of options for physical security, including security guards, electric security fencing, cameras, motion detectors, and light beams.

Daytime talk shows, such as Maury Povich and Steve Wilkos, frequently use lie detectors to tell if someone is cheating on their significant other.

More recent spectrographs use electronic detectors, such as CCDs which can be used for both visible and UV light.

Their use as particle detectors is still at the developmental stage.

Their use as particle detectors was proposed from the beginning of the 20th century, but the first regular, though pioneering, use was only in the 1980s because of the difficulty associated with cooling and operating a system at cryogenic temperature.

Commercially, geophysical prospecting companies also use magnetic detectors to identify naturally occurring anomalies from ore bodies, such as the Kursk Magnetic Anomaly.

Later scintillator detectors were used, and still later " channeltron " electron multipliers have found particularly wide use.

Compared to just a decade ago, detectors are lighter, deeper-seeking, use less battery power, and discriminate better.

's 1969 derivation was oriented towards the use of " two-channel " detectors, and indeed it is for these that it is generally used, but under their method the only possible outcomes were + 1 and − 1.

In the case of neutron detectors, high efficiency is gained through the use of scintillating materials rich in hydrogen that scatter neutrons efficiently.

Darkly pigmented butterflies Pachliopta aristolochiae and Troides rhadamathus use specialized heat detectors to avoid damage while basking.

Metal detectors use electromagnetic induction to detect metal.

Weather systems such as weather radar ( typically Arinc 708 on commercial aircraft ) and lightning detectors are important for aircraft flying at night or in instrument meteorological conditions, where it is not possible for pilots to see the weather ahead.

Lightning detectors like the Stormscope or Strikefinder have become inexpensive enough that they are practical for light aircraft.

This is supported by the fact that adenylate cyclases are coincidence detectors, meaning that they are activated only by several different signals occurring together.

Photomultiplier tubes are the most frequently used detectors in LS AAS, although solid state detectors might be preferred because of their better signal-to-noise ratio.

Cryogenic temperatures, usually well below 77 K (− 196 ° C ) are required to operate cryogenic detectors.

They are also used as large volume ionizing radiation detectors and as photodetectors.

Semiconductor detectors for high-energy particles are used in large numbers.

The delayed-choice experiment and the quantum eraser are sophisticated variations of the double-slit with particle detectors placed not at the slits but elsewhere in the apparatus.

The resulting energy emissions are observed with particle detectors and are studied in particle physics.

Currently the detectors for the project are being upgraded, and new results are not expected until at least 2012.

Geiger detectors are still used as a general purpose alpha / beta portable Radioactive contamination measurement and detection instrument, owing to their relatively low cost, their robustness and their relatively high detection efficiency ; particularly with high energy beta particles.

In 2005, the Tohono O ' odham Nation brought suit against the National Science Foundation to stop further construction of gamma ray detectors in the Gardens of the Sacred Tohono O ' odham Spirit I ' itoi, which are just below the summit.

These scintillators are already widely used commercially in detectors of neutrons or gamma rays.

The most common types of gamma detectors encountered in NAA are the gas ionisation type, scintillation type and the semiconductor type.

Both Ge ( Li ) and HPGe detectors have excellent sensitivity and resolution, but Ge ( Li ) detectors are unstable at room temperature, with the lithium drifting into the intrinsic region ruining the detector.

Particle detectors can also be used to detect the emission of alpha ( α ) and beta ( β ) particles which often accompany the emission of a gamma photon but are less favourable, as these particles are only emitted from the surface of the sample and are often absorbed or attenuated by atmospheric gases requiring expensive vacuum conditions to be effectively detected.

The raw data collected by a PET scanner are a list of ' coincidence events ' representing near-simultaneous detection ( typically, within a window of 6 to 12 nanoseconds of each other ) of annihilation photons by a pair of detectors.

Rhodium detectors are used in nuclear reactors to measure the neutron flux level.