User:The Original Wildbear/Sandbox

Depressed Collector
The efficiency of a TWT or a klystron can be improved by the use of a so-called depressed collector. With a single collector, a significant fraction of the power input to the tube is dissipated as heat in the collector. If the voltage on the collector is reduced (depressed) below the body voltage, the velocity of the electrons striking the collector is reduced and so is the heat generated in the collector. Thus, the collector recovers some of the power in the spent electron beam. The use of multiple depressed collectors at intermediate voltages, rather than a single collector, allows catching each spent electron at a voltage near optimum. Up to ten collector sections have been used in some communication tubes, but three sections are more typical for high-power TWTs for radar systems. The several different voltages needed for the depressed collectors add complexity to the high-voltage power supply, but these voltages need not be as well regulated as the main-beam voltage. It is usually easier to design a depressed collector for a TWT than for a klystron since the spent electron beam of a TWT might have a 20% spread in velocity, but the klystron might have a velocity spread of almost 100%. Because the efficiency in a conventional TWT is usually lower than than that of a klystron, the increase in efficiency in the TWT provided by a depressed collector has a greater relative effect than with a klystron.

-- Collector

After the RF energy has been extracted from the electron beam, the beam is destroyed in a collector. Some klystrons include depressed collectors, which recover energy from the beam before collecting the electrons, increasing efficiency. Multistage depressed collectors enhance the energy recovery by "sorting" the electrons in energy bins. Klystron

-- Net efficiency of microwave devices can be enhanced by recovering energy from the spent electron beam. Depressed collectors are commonly used for low to medium voltage (<100 kV), CW microwave tubes to achieve this objective. Designs of single-stage depressed collectors for high-power, high-voltage, pulsed gyroklystron amplifiers are presented here. Theoretical velocity distributions of the spent beams from 17.14 and 35.0 GHz relativistic gyroklystron designs are used as input to the particle trajectory simulations. The entire spent beam is collected at the cylindrical collector held at a depressed potential with respect to the interaction cavities. The magnetic field profile is adjusted to achieve collection of electrons at the maximum depressed value of the collector potential. A significant improvement in the device efficiency is estimated for both designs. A possible implementation scheme for the energy recovery using a double anode electron gun is described in detail

http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel3%2F16%2F14512%2F00662816.pdf%3Farnumber%3D662816&authDecision=-203 -- A TWTA consists of a traveling-wave tube coupled with its protection circuits (as in klystron) and regulated power supply (EPC, electronic power conditioner), which may be supplied and integrated by a different manufacturer. The main difference between most power supplies and those for vacuum tubes is that efficient vacuum tubes have depressed collectors to recycle kinetic energy of the electrons and therefore the secondary winding of the power supply needs up to 6 taps of which the helix voltage needs precise regulation. The subsequent addition of a linearizer (as for inductive output tube) can, by complementary compensation, improve the gain compression and other characteristics of the TWTA; this combination is called a linearized TWTA (LTWTA, "EL-tweet-uh").

Traveling-wave_tube -- Latest versions of IOTs achieve even higher efficiencies (60%-70%) through the use of a Multistage Depressed Collector (MSDC) (one manufacturer's version is called Constant Efficiency Amplifier (CEA) or another manufacturer's version ESCIOT (Energy Saving Collector IOT)).

Inductive_output_tube --

MDC Multistage Depressed Collector (electron beam technology): Invented in 1971 by Dr. Henry Kosmahl of the NASA Lewis Research Center (LeRC). Led to two Emmys. The first Emmy was to NASA and the Canadian Department of Communication for pioneering work on direct broadcast of television from space by means of the Communications Technology Satellite (CTS). The second Emmy was to the Public Broadcasting System (PBS) for application of NASA technology to develop a highly effective klystron for UHF television transmission.

http://images.google.com/imgres?imgurl=http://ranier.hq.nasa.gov/Sensors_page/GenGIF/MAMA.GIF&imgrefurl=http://ranier.hq.nasa.gov/sensors_page/terms.html&usg=__37rarrqlU3iR7xTQ0UOgjI0t7i8=&h=716&w=864&sz=27&hl=en&start=40&tbnid=49gvY4yfd2E2RM:&tbnh=120&tbnw=145&prev=/images%3Fq%3D%2522depressed%2Bcollector%2522%26gbv%3D2%26ndsp%3D18%26hl%3Den%26safe%3Doff%26sa%3DN%26start%3D36

Applications
The development group sought a way to make available to UHF operators power amplifying devices with efficiencies comparable to VHF. The indicated line of approach was to incorporate into UHF transmitters a power amplifying device known as the Multistage Depressed Collector (MDC) developed a decade earlier at Lewis Research Center to enhance the efficiency of communications satellite transmissions; the MDC allowed satellites to transmit more powerful signals, thus enabling the use of smaller, less costly Earth stations for signal reception.

The klystron is a vacuum tube used to generate and amplify ultrahigh frequencies. It draws radio frequency energy from a high voltage electron beam but does so at very low efficiency levels; most of the energy is dissipated as waste heat. The concept behind the Lewis/Varian development was that the MDC could recover much of the wasted energy by recycling a large part of the electron beam energy, in effect doubling the amount of the beam energy being converted to radio frequency energy.

Volumetric efficiency (capacitor)
Volumetric efficiency in capacitors refers to the density of energy storage, and it is measured in capacitance-volts per volume:
 * $$energy\ density = \frac{C\;W_{V\!DC}}{volume}$$

Longer capacitors tend to have greater volumetric efficiency than shorter units. This is because volume is used by encapsulation and unused dielectric at the capacitor ends.

The call for a new investigation
Polls have indicated that a significant portion of the population desires a new investigation into the events of September 11, 2001. A 2004 Zogby poll found that two in three (66%) New Yorkers (and 56.2% overall) desired another full investigation.

Prominent persons calling for a new investigation include Arizona state senator Karen S. Johnson, U.K. Member of Parliament Michael Meacher, British M.P. George Galloway, Japanese Diet member Yukihisa Fujita, former Italian President Francesco Cossiga, former German Defense Secretary Andreas von Bülow, and U.N. Human Rights Council official and professor emeritus of international law at Princeton University Richard A. Falk. Individuals calling for a new investigation are collectively known as the 9/11 Truth movement.

On Wednesday, June 24, 2009, the New York City Coalition for Accountability Now (NYC CAN) filed a petition containing 52,000 signatures calling for a referendum on the creation of a New York City independent commission to investigate the events of September 11, 2001. If the initiative is passed into law, an independent commission with subpoena power will be formed to fully investigate the 9/11 matter.

Joule Effect
Joule Effect is a term commonly used to refer to any of several different physical effects discovered or characterized by English physicist James Prescott Joule. These physical effects are not the same, but they are all frequently or occasionally referred to in literature as the "Joule effect". These physical effects include:
 * Joule's first law, a physical law expressing the relationship between the heat generated and current flowing through a conductor.
 * Magnetostriction, a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field.
 * The Joule–Thomson effect, which describes the temperature change of a gas or liquid when it is forced through a valve or a porous plug. This principle is also known as the Joule–Kelvin effect, or the Kelvin–Joule effect.
 * The Gough-Joule effect or the Gow-Joule effect, which is the tendency of elastomers to contract when heated if they are under tension.

Joule's first law
Between the years 1840 and 1843 Joule made a careful study of the heat produced by an electric current. From this study, he developed Joule's laws of heating, the first of which is commonly referred to as the Joule effect. Joule's first law expresses the relationship between heat generated in a conductor and current flow, resistance, and time.

Magnetostriction
The magnetostriction effect describes a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field. Joule first reported observing change in the length of ferromagnetic rods in 1842.

Joule–Thomson effect
The Joule–Thomson effect describes the temperature change of a gas or liquid when it is forced through a valve or a porous plug. The effect is named for James Joule and William Thomson (1st Baron Kelvin), who discovered it in 1852 following earlier work by Joule on Joule expansion, in which a gas undergoes free expansion in a vacuum.

Gough-Joule effect
If an elastic band is first stretched and then subjected to heating, it will shrink rather than expand. This effect was first observed by John Gough in 1802, and was investigated further by Joule in the 1850s, when it then became known as the Gough-Joule effect.

Test
On November 20, 2008, NIST released its final report on the collapse of 7 World Trade Center. In the report, NIST explains that fire was the main reason for the collapse, along with lack of water to fight the fire. Fires continued to burn throughout the afternoon on the lower floors. At 5:20 pm. a critical column buckled, leading to the collapse of floor 13, which triggered a cascade of floor failures and global collapse. From collapse timing measurements taken from a video of the north face of the building, NIST observed that the building fell at free fall acceleration through a distance of approximately 8 stories (32 meters, or 105 feet.) The entire building above the buckled-column region moved downward as a single unit, until completion of the global collapse sequence.

Reference Testing
The New American Mill Valley Air Force Station test Benjamin Franklin's capacitor experiments. Battery of Cannon