Nikiya Anton Bettey 2021: 09-24-2021-1233 - backward wave oscillator (BWO) carcinotron

Friday, September 24, 2021

09-24-2021-1233 - backward wave oscillator (BWO) carcinotron

The Disco Ball (TV Special 2003) - IMDb

A backward wave oscillator (BWO), also called carcinotron (a trade name for tubes manufactured by CSF, now Thales) or backward wave tube, is a vacuum tube that is used to generate microwaves up to the terahertz range. Belonging to the traveling-wave tube family, it is an oscillator with a wide electronic tuning range.

An electron gun generates an electron beam that interacts with a slow-wave structure. It sustains the oscillations by propagating a traveling wave backwards against the beam. The generated electromagnetic wave power has its group velocity directed oppositely to the direction of motion of the electrons. The output power is coupled out near the electron gun.

It has two main subtypes, the M-type (M-BWO), the most powerful, and the O-type (O-BWO). The output power of the O-type is typically in the range of 1 mW at 1000 GHz to 50 mW at 200 GHz. Carcinotrons are used as powerful and stable microwave sources. Due to the good quality wavefront they produce (see below), they find use as illuminators in terahertz imaging.

The backward wave oscillators were demonstrated in 1951, M-type by Bernard Epsztein ^[1] and O-type by Rudolf Kompfner. The M-type BWO is a voltage-controlled non-resonant extrapolation of magnetron interaction. Both types are tunable over a wide range of frequencies by varying the accelerating voltage. They can be swept through the band fast enough to be appearing to radiate over all the band at once, which makes them suitable for effective radar jamming, quickly tuning into the radar frequency. Carcinotrons allowed airborne radar jammers to be highly effective. However, frequency-agile radars can hop frequencies fast enough to force the jammer to use barrage jamming, diluting its output power over a wide band and significantly impairing its efficiency.

Carcinotrons are used in research, civilian and military applications. For example, the Czechoslovak Kopac passive sensor and Ramona passive sensor air defense detection systems employed carcinotrons in their receiver systems.

https://en.wikipedia.org/wiki/Backward-wave_oscillator

https://en.wikipedia.org/wiki/mirror_matter

https://en.wikipedia.org/wiki/mirror

The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second.^[1] It is named after Heinrich Rudolf Hertz (1857-1894), the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (10³ Hz, kHz), megahertz (10⁶ Hz, MHz), gigahertz (10⁹ Hz, GHz), terahertz (10¹² Hz, THz), petahertz (10¹⁵ Hz, PHz), exahertz (10¹⁸ Hz, EHz), and zettahertz (10²¹ Hz, ZHz).

Some of the unit's most common uses are in the description of sine waves and musical tones, particularly those used in radio- and audio-related applications. It is also used to describe the clock speeds at which computers and other electronics are driven. The units are sometimes also used as a representation of energy, via the photon energy equation (E=hν), with one hertz equivalent to h joules.

Hertz
Unit system	SI derived unit
Unit of	Frequency
Symbol	Hz
Named after	Heinrich Hertz
In SI base units	s⁻¹

Definition[edit]

The hertz is defined as one cycle per second. The International Committee for Weights and Measures defined the second as "the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom"^[2]^[3] and then adds: "It follows that the hyperfine splitting in the ground state of the caesium 133 atom is exactly 9192631770 hertz, ν(hfs Cs) = 9192631770 Hz." The dimension of the unit hertz is 1/time (1/T). Expressed in base SI units it is 1/second (1/s). Problems can arise because the units of angular measure (cycle or radian) are omitted in SI.^[4]^[5]^[6]^[7]

In English, "hertz" is also used as the plural form.^[8] As an SI unit, Hz can be prefixed; commonly used multiples are kHz (kilohertz, 10³ Hz), MHz (megahertz, 10⁶ Hz), GHz (gigahertz, 10⁹ Hz) and THz (terahertz, 10¹² Hz). One hertz simply means "one cycle per second" (typically that which is being counted is a complete cycle); 100 Hzmeans "one hundred cycles per second", and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz.

The occurrence rate of aperiodic or stochastic events is expressed in reciprocal second or inverse second (1/s or s⁻¹) in general or, in the specific case of radioactive decay, in becquerels.^[9] Whereas 1 Hz is one cycle per second, 1 Bq is one aperiodic radionuclide event per second.

Even though angular velocity, angular frequency and the unit hertz all have the dimension 1/s, angular velocity and angular frequency are not expressed in hertz,^[10] but rather in an appropriate angular unit such as radians per second. Thus a disc rotating at 60 revolutions per minute (rpm) is said to be rotating at either 2 $π$ rad/s or 1 Hz, where the former measures the angular velocity and the latter reflects the number of complete revolutions per second. The conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second is

\omega =2\pi f\,

and

f={\frac {\omega }{2\pi }}\,

The hertz is named after Heinrich Hertz. As with every SI unit named for a person, its symbol starts with an upper case letter (Hz), but when written in full it follows the rules for capitalisation of a common noun; i.e., "hertz" becomes capitalised at the beginning of a sentence and in titles, but is otherwise in lower case.

History[edit]

The hertz is named after the German physicist Heinrich Hertz (1857–1894), who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission (IEC) in 1935.^[11] It was adopted by the General Conference on Weights and Measures (CGPM) (Conférence générale des poids et mesures) in 1960, replacing the previous name for the unit, cycles per second (cps), along with its related multiples, primarily kilocycles per second (kc/s) and megacycles per second (Mc/s), and occasionally kilomegacycles per second (kMc/s). The term cycles per second was largely replaced by hertz by the 1970s.^[12]

Sometimes the "per second" was omitted, so that "megacycles" (Mc) was used as an abbreviation of "megacycles per second" (that is, megahertz (MHz)).^[13]

Applications[edit]

A sine wave with varying frequency

A heartbeat is an example of a non-sinusoidal periodic phenomenon that may be analyzed in terms of frequency. Two cycles are illustrated.

Vibration[edit]

Sound is a traveling longitudinal wave which is an oscillation of pressure. Humans perceive frequency of sound waves as pitch. Each musical note corresponds to a particular frequency which can be measured in hertz. An infant's ear is able to perceive frequencies ranging from 20 Hz to 20000 Hz; the average adult human can hear sounds between 20 Hz and 16000 Hz.^[14] The range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtohertz^[15] into the terahertz range^[16] and beyond.^[17]

Electromagnetic radiation[edit]

Electromagnetic radiation is often described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz.

Radio frequency radiation is usually measured in kilohertz (kHz), megahertz (MHz), or gigahertz (GHz). Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz. Electromagnetic radiation with frequencies in the low terahertz range (intermediate between those of the highest normally usable radio frequencies and long-wave infrared light) is often called terahertz radiation. Even higher frequencies exist, such as that of gamma rays, which can be measured in exahertz (EHz). (For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum.)

Computers[edit]

In computers, most central processing units (CPU) are labeled in terms of their clock rate expressed in megahertz (10⁶ Hz) or gigahertz (10⁹ Hz). This specification refers to the frequency of the CPU's master clock signal. This signal is a square wave, which is an electrical voltage that switches between low and high logic values at regular intervals. As the hertz has become the primary unit of measurement accepted by the general populace to determine the performance of a CPU, many experts have criticized this approach, which they claim is an easily manipulable benchmark. Some processors use multiple clock periods to perform a single operation, while others can perform multiple operations in a single cycle.^[18] For personal computers, CPU clock speeds have ranged from approximately 1 MHz in the late 1970s (Atari, Commodore, Apple computers) to up to 6 GHz in IBM POWER microprocessors.

Various computer buses, such as the front-side bus connecting the CPU and northbridge, also operate at various frequencies in the megahertz range.

SI multiples[edit]

SI multiples of hertz (Hz)
Value	SI symbol	Name	Value	SI symbol	Name
Submultiples			Multiples
10⁻¹ Hz	dHz	decihertz	10¹ Hz	daHz	decahertz
10⁻² Hz	cHz	centihertz	10² Hz	hHz	hectohertz
10⁻³ Hz	mHz	millihertz	10³ Hz	kHz	kilohertz
10⁻⁶ Hz	µHz	microhertz	10⁶ Hz	MHz	megahertz
10⁻⁹ Hz	nHz	nanohertz	10⁹ Hz	GHz	gigahertz
10⁻¹² Hz	pHz	picohertz	10¹² Hz	THz	terahertz
10⁻¹⁵ Hz	fHz	femtohertz	10¹⁵ Hz	PHz	petahertz
10⁻¹⁸ Hz	aHz	attohertz	10¹⁸ Hz	EHz	exahertz
10⁻²¹ Hz	zHz	zeptohertz	10²¹ Hz	ZHz	zettahertz
10⁻²⁴ Hz	yHz	yoctohertz	10²⁴ Hz	YHz	yottahertz
Common prefixed units are in bold face.

Higher frequencies than the International System of Units provides prefixes for are believed to occur naturally in the frequencies of the quantum-mechanical vibrations of high-energy, or, equivalently, massive particles, although these are not directly observable and must be inferred from their interactions with other phenomena. By convention, these are typically not expressed in hertz, but in terms of the equivalent quantum energy, which is proportional to the frequency by the factor of Planck's constant.

Hertz: Unicode characters.^[19]
Symbol	Name	Unicode number
㎐	Hertz (Square HZ)	U+3390
㎑	Kilohertz (Square KHZ)	U+3391
㎒	Megahertz (Square MHZ)	U+3392
㎓	Gigahertz (Square GHZ)	U+3393
㎔	Terahertz (Square THZ)	U+3394

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