National Register of Historic Places

From Wikipedia, the free encyclopedia

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

National Register of Historic Places

Agency overview
Formed	1966; 56 years ago
Jurisdiction	United States
Annual budget	$16.8 million (2018)
Agency executive	Sherry A. Frear, Chief, National Register of Historic Places/National Historic Landmarks Program and Deputy Keeper of the National Register of Historic Places
Parent department	National Park Service
Website	www.nps.gov/subjects/nationalregister

The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance. A property listed in the National Register, or located within a National Register Historic District, may qualify for tax incentives derived from the total value of expenses incurred in preserving the property.

The passage of the National Historic Preservation Act (NHPA) in 1966 established the National Register and the process for adding properties to it. Of the more than one and a half million properties on the National Register, 95,000 are listed individually. The remainder are contributing resources within historic districts.

For most of its history, the National Register has been administered by the National Park Service (NPS), an agency within the United States Department of the Interior. Its goals are to help property owners and interest groups, such as the National Trust for Historic Preservation, as well as to coordinate, identify and protect historic sites in the United States. While National Register listings are mostly symbolic, their recognition of significance provides some financial incentive to owners of listed properties. Protection of the property is not guaranteed. During the nomination process, the property is evaluated in terms of the four criteria for inclusion on the National Register of Historic Places. The application of those criteria has been the subject of criticism by academics of history and preservation, as well as the public and politicians.

Occasionally, historic sites outside the country proper, but associated with the United States (such as the American Legation in Tangier) are also listed. Properties can be nominated in a variety of forms, including individual properties, historic districts and multiple property submissions (MPS). The Register categorizes general listings into one of five types of properties: district, site, structure, building or object.

National Register Historic Districts are defined geographical areas consisting of contributing and non-contributing properties. Some properties are added automatically to the National Register when they become administered by the National Park Service. These include National Historic Landmarks (NHL), National Historic Sites (NHS), National Historical Parks, National Military Parks, National Memorials and some National Monuments. (Federal properties can be proclaimed National Monuments under the Antiquities Act because of either their historical or natural significance. They are managed by multiple agencies. Only monuments that are historic in character and managed by the National Park Service are listed administratively in the National Register.)

History

Main article: History of the National Register of Historic Places

 

Old Slater Mill, a historic district in Pawtucket, Rhode Island, was the first property listed in the National Register, on November 13, 1966.

 

George B. Hartzog Jr., director of the National Park Service from January 8, 1964, until December 31, 1972

On October 15, 1966, the Historic Preservation Act created the National Register of Historic Places and the corresponding State Historic Preservation Offices (SHPO). Initially, the National Register consisted of the National Historic Landmarks designated before the Register's creation, as well as any other historic sites in the National Park system. Approval of the act, which was amended in 1980 and 1992, represented the first time the United States had a broad-based historic preservation policy. The 1966 act required those agencies to work in conjunction with the SHPO and an independent federal agency, the Advisory Council on Historic Preservation (ACHP), to confront adverse effects of federal activities on historic preservation.

U.S. Secretary of the Interior (1977–1981) Cecil Andrus removed the National Register from the jurisdiction of the National Park Service in 1978.

To administer the newly created National Register of Historic Places, the National Park Service of the U.S. Department of the Interior, with director George B. Hartzog Jr., established an administrative division named the Office of Archeology and Historic Preservation (OAHP). Hartzog charged OAHP with creating the National Register program mandated by the 1966 law. Ernest Connally was the Office's first director. Within OAHP new divisions were created to deal with the National Register. The division administered several existing programs, including the Historic Sites Survey and the Historic American Buildings Survey, as well as the new National Register and Historic Preservation Fund.

The first official Keeper of the Register was William J. Murtagh, an architectural historian. During the Register's earliest years in the late 1960s and early 1970s, organization was lax and SHPOs were small, understaffed and underfunded. However, funds were still being supplied for the Historic Preservation Fund to provide matching grants-in-aid to listed property owners, first for house museums and institutional buildings, but later for commercial structures as well.

A few years later in 1979, the NPS history programs affiliated with both the U.S. National Parks system and the National Register were categorized formally into two "Assistant Directorates". Established were the Assistant Directorate for Archeology and Historic Preservation and the Assistant Directorate for Park Historic Preservation. From 1978 until 1981, the main agency for the National Register was the Heritage Conservation and Recreation Service (HCRS) of the United States Department of the Interior.

In February 1983, the two assistant directorates were merged to promote efficiency and recognize the interdependency of their programs. Jerry L. Rogers was selected to direct this newly merged associate directorate. He was described as a skilled administrator, who was sensitive to the need for the NPS to work with SHPOs, academia and local governments.

Although not described in detail in the 1966 act, SHPOs eventually became integral to the process of listing properties on the National Register. The 1980 amendments of the 1966 law further defined the responsibilities of SHPOs concerning the National Register. Several 1992 amendments of the NHPA added a category to the National Register, known as Traditional Cultural Properties: those properties associated with Native American or Hawaiian groups.

The National Register of Historic Places has grown considerably from its legislative origins in 1966. In 1986, citizens and groups nominated 3,623 separate properties, sites and districts for inclusion on the National Register, a total of 75,000 separate properties. Of the more than one and a half million properties on the National Register, 95,000 are listed individually. Others are listed as contributing members within historic districts.

Nomination process

It is hereby declared to be the policy of the United States Government that special effort should be made to preserve the natural beauty of the countryside and public park and recreation lands, wildlife and waterfowl refuges, and historic sites.

— (49 USC 303)

Any individual can prepare a National Register nomination, although historians and historic preservation consultants often are employed for this work. The nomination consists of a standard registration form (NPS 10-900) and contains basic information about a property's physical appearance and the type of significance embodied in the building, structure, object, site, or district.

The State Historic Preservation Office (SHPO) receives National Register nominations and provides feedback to the nominating individual or group. After preliminary review, the SHPO sends each nomination to the state's historic review commission, which then recommends whether the State Historic Preservation Officer should send the nomination to the Keeper of the National Register. For any non-Federally owned property, only the State Historic Preservation Officer may officially nominate a property for inclusion in the National Register. After the nomination is recommended for listing in the National Register by the SHPO, the nomination is sent to the National Park Service, which approves or denies the nomination.

If approved, the property is entered officially by the Keeper of the National Register into the National Register of Historic Places. Property owners are notified of the nomination during the review by the SHPO and state's historic review commission. If an owner objects to a nomination of private property, or in the case of a historic district, a majority of owners, then the property cannot be listed in the National Register of Historic Places.

Criteria

S. R. Crown Hall is listed under criteria B and C for its association with architect Ludwig Mies van der Rohe and modernist design.

For a property to be eligible for the National Register, it must meet at least one of the four National Register main criteria. Information about architectural styles, association with various aspects of social history and commerce and ownership are all integral parts of the nomination. Each nomination contains a narrative section that provides a detailed physical description of the property and justifies why it is significant historically with regard either to local, state, or national history. The four National Register of Historic Places criteria are the following.

• Criterion A, "Event", the property must make a contribution to the major pattern of American history.
• Criterion B, "Person", is associated with significant people of the American past.
• Criterion C, "Design/Construction", concerns the distinctive characteristics of the building by its architecture and construction, including having great artistic value or being the work of a master.
• Criterion D, "Information potential", is satisfied if the property has yielded or may be likely to yield information important to prehistory or history.

The criteria are applied differently for different types of properties; for instance, maritime properties have application guidelines different from those of buildings.

Exclusions

There are specific instances where properties usually do not merit listing in the National Register. As a general rule, cemeteries, birthplaces, graves of historical figures, properties owned by religious institutions or used for religious purposes, moved structures, reconstructed historic buildings, commemorative properties and properties that have achieved significance during the last fifty years are not qualified for listing on the Register. There are, however, exceptions to all the preceding; mitigating circumstances allow properties classified in one of those groups to be included.

Properties listed

See also: United States National Register of Historic Places listings and List of U.S. National Historic Landmarks by state

 

A typical plaque found on properties listed in the National Register of Historic Places

 

An alternate series of plaques. Buildings on the National Register are often listed in local historic societies as well.

A listing on the National Register of Historic Places is governmental acknowledgment of a historic district, site, building, or property. However, the Register is mostly "an honorary status with some federal financial incentives." The National Register of Historic Places automatically includes all National Historic Landmarks as well as all historic areas administered by the National Park Service.

Landmarks such as these include National Historic Sites (NHS), National Historical Parks, National Military Parks/Battlefields, National Memorials and some National Monuments. Occasionally, historic sites outside the United States borders, but associated with the United States, such as the American Legation in Tangier, Morocco, also are listed.

Listing in the National Register does not restrict private property owners from the use of their property.

Some states and municipalities, however, may have laws that become effective when a property is listed in the National Register. If federal money or a federal permitting process is involved, Section 106 of the National Historic Preservation Act of 1966 is invoked. Section 106 requires the federal agency involved to assess the effect of its actions on historic resources. Statutorily, the Advisory Council on Historic Preservation (ACHP) has the most significant role by Section 106 of the National Historic Preservation Act. The section requires that the director of any federal agency with direct or indirect jurisdiction of a project that may affect a property listed or determined eligible for listing in the National Register of Historic Places must first report to the Advisory Council. The director of said agency is required to "take into account the effect of the undertaking" on the National Register property, as well as to afford the ACHP a reasonable opportunity to comment.

While Section 106 does not mandate explicitly that any federal agency director accept the advice of the ACHP, their advice has a practical influence, especially given the statutory obligations of the NHPA that require federal agencies to "take into account the effect of the undertaking."

In cases where the ACHP determines federal action will have an "adverse effect" on historic properties, mitigation is sought. Typically, a Memorandum of Agreement (MOA) is created by which the involved parties agree to a particular plan. Many states have laws similar to Section 106. In contrast to conditions relating to a federally designated historic district, municipal ordinances governing local historic districts often restrict certain kinds of changes to properties. Thus, they may protect the property more than a National Register listing does.

The Department of Transportation Act, passed on October 15, 1966, the same day as the National Historic Preservation Act, included provisions that addressed historic preservation. The DOT Act is much more general than Section 106 NHPA in that it refers to properties other than those listed in the Register.

The more general language has allowed more properties and parklands to enjoy status as protected areas by this legislation, a policy developed early in its history. The United States Supreme Court ruled in the 1971 case Citizens to Preserve Overton Park v. Volpe that parklands could have the same protected status as "historic sites."

• 

  Pecos Pueblo is one of a number of NRHP sites administered by the National Park Service.

• 

  The Illinois State Capitol is one of 44 U.S. state capitols listed on the NRHP.

• 

  College Hill Historic District is an example of a National Historic Landmark District.

• 

  The Robert C. Weaver Federal Building is an example of a modern building listed on the NRHP.

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  The American Legation, Tangier is the only site on the NRHP in a foreign nation.

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  Walden Pond is an example of a natural site listed on the NRHP.

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  The USS Wisconsin (BB-64) is one of a number of ships listed on the NRHP.

Multiple property submission

Round Barns in Illinois Thematic Resources is a Multiple Property Submission that includes 18 structures throughout the state.

A multiple property submission (MPS) is a thematic group listing of the National Register of Historic Places that consists of related properties that share a common theme and can be submitted as a group. Multiple property submissions must satisfy certain basic criteria for the group of properties to be included in the National Register.

The process begins with the multiple property documentation form which acts as a cover document rather than the nomination to the National Register of Historic Places. The purpose of the documentation form is to establish the basis of eligibility for related properties. The information of the multiple property documentation form can be used to nominate and register related historic properties simultaneously, or to establish criteria for properties that may be nominated in the future. Thus, additions to an MPS can occur over time.

The nomination of individual properties in an MPS is accomplished in the same manner as other nominations. The name of the "thematic group" denotes the historical theme of the properties. It is considered the "multiple property listing." Once an individual property or a group of properties is nominated and listed in the National Register, the multiple property documentation form, combined with the individual National Register of Historic Places nomination forms, constitute a multiple property submission.

Examples of MPS include the Lee County Multiple Property Submission, the Warehouses in Omaha, the Boundary Markers of the Original District of Columbia and the Illinois Carnegie Libraries. Before the term "Multiple Property Submission" was introduced in 1984, such listings were known as "Thematic Resources", such as the Operating Passenger Railroad Stations Thematic Resource, or "Multiple Resource Areas".

Types of properties

See also: National Register of Historic Places property types and Historic districts in the United States

 

From top to bottom: a building, a structure, an object and a site – all are examples of NRHP property types.

 

Example of a barn on the National Register of Historic Places; Cow Barn; Enfield Shaker Village, New Hampshire; built 1854.

Listed properties are generally in one of five broad categories, although there are special considerations for other types of properties that in any one, or into more specialized subcategories. The five general categories for National Register properties are: building, structure, site, district and object. In addition, historic districts consist of contributing and non-contributing properties.

Buildings, as defined by the National Register, are distinguished in the traditional sense. Examples include a house, barn, hotel, church, or similar construction. They are created primarily to shelter human activity. The term building, as in outbuilding, can be used to refer to historically and functionally related units, such as a courthouse and a jail or a barn and a house.

Structures differ from buildings in that they are functional constructions meant to be used for purposes other than sheltering human activity. Examples include an aircraft, a grain elevator, a gazebo and a bridge.

Objects are usually artistic in nature, or small in scale compared to structures and buildings. Although objects may be movable, they are generally associated with a specific setting or environment. Examples of objects include monuments, sculptures and fountains.

Sites are the locations of significant events, which can be prehistoric or historic in nature and represent activities or buildings (standing, ruined, or vanished). When sites are listed, it is the locations themselves that are of historical interest. They possess cultural or archaeological value regardless of the value of any structures that currently exist at the locations. Examples of types of sites include shipwrecks, battlefields, campsites, natural features and rock shelters.

Historic districts possess a concentration, association, or continuity of the other four types of properties. Objects, structures, buildings and sites in a historic district are united historically or aesthetically, either by choice or by the nature of their development.

There are several other different types of historic preservation associated with the properties of the National Register of Historic Places that cannot be classified as either simple buildings and historic districts. Through the National Park Service, the National Register of Historic Places publishes a series of bulletins designed to aid in evaluating and applying the criteria for evaluation of different types of properties. Although the criteria are always the same, the manner they are applied may differ slightly, depending upon the type of property involved. The National Register bulletins describe the application of the criteria for aids to navigation, historic battlefields, archaeological sites, aviation properties, cemeteries and burial places, historic designed landscapes, mining sites, post offices, properties associated with significant persons, properties achieving significance within the last fifty years, rural historic landscapes, traditional cultural properties and vessels and shipwrecks.

Property owner incentives

A National Register of Historic Places plaque at the Robert E. Howard Museum in Cross Plains, Texas

Properties are not protected in any strict sense by the Federal listing. States and local zoning bodies may or may not choose to protect listed historic places. Indirect protection is possible, by state and local regulations on the development of National Register properties and by tax incentives. By contrast, the state of Colorado, for example, does not set any limits on owners of National Register properties.

Until 1976, federal tax incentives were virtually non-existent for buildings on the National Register. Before 1976 the federal tax code favored new construction rather than the reuse of existing, sometimes historical, structures. In 1976, the tax code was altered to provide tax incentives that promote the preservation of income-producing historic properties. The National Park Service was given the responsibility to ensure that only rehabilitations that preserved the historic character of a building would qualify for federal tax incentives. A qualifying rehabilitation is one that the NPS deems consistent with the Secretary of the Interior's Standards for Rehabilitation. Properties and sites listed in the Register, as well as those located in and contributing to the period of significance of National Register Historic Districts, became eligible for the federal tax benefits.

Owners of income-producing properties listed individually in the National Register of Historic Places or of properties that are contributing resources within a National Register Historic District may be eligible for a 20% investment tax credit for the rehabilitation of the historic structure. The rehabilitation may be of a commercial, industrial, or residential property, for rentals. The tax incentives program is operated by the Federal Historic Preservation Tax Incentives program, which is managed jointly by the National Park Service, individual State Historic Preservation Offices and the Internal Revenue Service.

Some property owners may also qualify for grants, like the now-defunct Save America's Treasures grants, which apply specifically to properties entered in the Register with national significance or designated as National Historic Landmarks.

The NHPA did not distinguish between properties listed in the National Register of Historic Places and those designated as National Historic Landmarks concerning qualification for tax incentives or grants. This was deliberate, as the authors of the act had learned from experience that distinguishing between categories of significance for such incentives caused the lowest category to become expendable. Essentially, this made the Landmarks a kind of "honor roll" of the most significant properties of the National Register of Historic Places.

Recent past

The Portland Building was added to the NRHP only 29 years after its opening.

50-year rule

In American historic preservation, the 50-year rule is the generally held belief that a property must be at least 50 years old to be listed in the National Register of Historic Places. Actually, there is no hard rule. As stated by John H. Sprinkle Jr., deputy director of the Federal Preservation Institute, "this 'rule' is only an exception to the criteria that shape listings within the National Register of Historic Places. Of the eight 'exceptions' [or criteria considerations], Consideration G, for properties that have achieved significance within the past fifty years, is probably the best-known, yet also misunderstood preservation principle in America." Each year, a new group of resources crosses the 50-year threshold. The preservation of these "underage" resources has gained attention in recent years.

Limitations

The demolition of the Jobbers Canyon Historic District marked the largest National Register historic district lost to date.

As of 1999, there have been 982 properties removed from the Register, most often due to being destroyed. Among the properties that were demolished or otherwise destroyed after their listing are the Jobbers Canyon Historic District in Omaha, Nebraska (listed in 1979, demolished in 1989), Pan-Pacific Auditorium in Los Angeles, California (listed in 1978, destroyed in a fire in 1989), Palace Amusements in Asbury Park, New Jersey (listed in 2000, demolished in 2004), The Balinese Room in Galveston, Texas (listed in 1997, destroyed by Hurricane Ike in 2008), seven of the nine buildings included in the University of Connecticut Historic District in Storrs, Connecticut (listed in 1989, demolished in 2017), and the Terrell Jacobs Circus Winter Quarters in Peru, Indiana (listed in 2012, demolished in 2021).

Klystron

From Wikipedia, the free encyclopedia

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

400 kW klystron used for spacecraft communication at the Canberra Deep Space Communications Complex. This is a spare in storage.

 

5 kW klystron tube used as power amplifier in UHF television transmitter, 1952. When installed, the tube projects through holes in the center of the cavity resonators, with the sides of the cavities making contact with the metal rings on the tube.

A klystron is a specialized linear-beam vacuum tube, invented in 1937 by American electrical engineers Russell and Sigurd Varian, which is used as an amplifier for high radio frequencies, from UHF up into the microwave range. Low-power klystrons are used as oscillators in terrestrial microwave relay communications links, while high-power klystrons are used as output tubes in UHF television transmitters, satellite communication, radar transmitters, and to generate the drive power for modern particle accelerators.

In a klystron, an electron beam interacts with radio waves as it passes through resonant cavities, metal boxes along the length of a tube. The electron beam first passes through a cavity to which the input signal is applied. The energy of the electron beam amplifies the signal, and the amplified signal is taken from a cavity at the other end of the tube. The output signal can be coupled back into the input cavity to make an electronic oscillator to generate radio waves. The gain of klystrons can be high, 60 dB (an increase in signal power by a factor of one million) or more, with output power up to tens of megawatts, but the bandwidth is narrow, usually a few percent although it can be up to 10% in some devices.

A reflex klystron is an obsolete type in which the electron beam was reflected back along its path by a high potential electrode, used as an oscillator.

The name klystron comes from the Greek verb κλύζω (klyzo) referring to the action of waves breaking against a shore, and the suffix -τρον ("tron") meaning the place where the action happens. The name "klystron" was suggested by Hermann Fränkel, a professor in the classics department at Stanford University when the klystron was under development.

History

The first commercial klystron, manufactured by Westinghouse in 1940. Part of the tube is cut away to show the internal construction. On the left are the cathode and accelerating anode, which create the electron beam. In the center between the wooden supports is the drift tube, surrounded by the two donut-shaped cavity resonators: the "buncher" and the "catcher". The output terminal is visible at top. On the right is the cone shaped collector anode, which absorbs the electrons. It could generate 200 W of power at a wavelength of 40 centimeters (750 MHz) with 50% efficiency.

The klystron was the first significantly powerful source of radio waves in the microwave range; before its invention the only sources were the Barkhausen-Kurz tube and split anode magnetron, which were limited to very low power. It was invented by the brothers Russell and Sigurd Varian at Stanford University. Their prototype was completed and demonstrated successfully on August 30, 1937. Upon publication in 1939, news of the klystron immediately influenced the work of US and UK researchers working on radar equipment. The Varians went on to found Varian Associates to commercialize the technology (for example, to make small linear accelerators to generate photons for external beam radiation therapy). Their work was preceded by the description of velocity modulation by A. Arsenjewa-Heil and Oskar Heil (wife and husband) in 1935, though the Varians were probably unaware of the Heils' work.

The work of physicist W.W. Hansen was instrumental in the development of the klystron and was cited by the Varian brothers in their 1939 paper. His resonator analysis, which dealt with the problem of accelerating electrons toward a target, could be used just as well to decelerate electrons (i.e., transfer their kinetic energy to RF energy in a resonator). During the second World War, Hansen lectured at the MIT Radiation labs two days a week, commuting to Boston from Sperry Gyroscope Company on Long Island. His resonator was called a "rhumbatron" by the Varian brothers. Hansen died of beryllium disease in 1949 as a result of exposure to beryllium oxide (BeO).

During the Second World War, the Axis powers relied mostly on (then low-powered and long wavelength) klystron technology for their radar system microwave generation, while the Allies used the far more powerful but frequency-drifting technology of the cavity magnetron for much shorter-wavelength centimetric microwave generation. Klystron tube technologies for very high-power applications, such as synchrotrons and radar systems, have since been developed.

Right after the war, AT&T used 4 watt klystrons in its brand new network of microwave relay links that covered the US continent. The network provided long-distance telephone service and also carried television signals for the major TV networks. Western Union Telegraph Company also built point-to-point microwave communication links using intermediate repeater stations at about 40 mile intervals at that time, using 2K25 reflex klystrons in both the transmitters and receivers.

Operation

Klystrons amplify RF signals by converting the kinetic energy in a DC electron beam into radio frequency power. In a vacuum, a beam of electrons is emitted by an electron gun or thermionic cathode and accelerated by high-voltage electrodes (typically in the tens of kilovolts).

This beam passes through an input cavity resonator. RF energy has been fed into the input cavity at, or near, its resonant frequency, creating standing waves, which produce an oscillating voltage, which acts on the electron beam. The electric field causes the electrons to "bunch": electrons that pass through when the electric field opposes their motion are slowed, while electrons which pass through when the electric field is in the same direction are accelerated, causing the previously continuous electron beam to form bunches at the input frequency.

To reinforce the bunching, a klystron may contain additional "buncher" cavities.

The beam then passes through a "drift" tube, in which the faster electrons catch up to the slower ones, creating the "bunches", then through a "catcher" cavity.

In the output "catcher" cavity, each bunch enters the cavity at the time in the cycle when the electric field opposes the electrons' motion, decelerating them. Thus the kinetic energy of the electrons is converted to potential energy of the field, increasing the amplitude of the oscillations. The oscillations excited in the catcher cavity are coupled out through a coaxial cable or waveguide.

The spent electron beam, with reduced energy, is captured by a collector electrode.

To make an oscillator, the output cavity can be coupled to the input cavity(s) with a coaxial cable or waveguide. Positive feedback excites spontaneous oscillations at the resonant frequency of the cavities.

Two-cavity klystron

The simplest klystron tube is the two-cavity klystron. In this tube there are two microwave cavity resonators, the "catcher" and the "buncher". When used as an amplifier, the weak microwave signal to be amplified is applied to the buncher cavity through a coaxial cable or waveguide, and the amplified signal is extracted from the catcher cavity.

At one end of the tube is the hot cathode which produces electrons when heated by a filament. The electrons are attracted to and pass through an anode cylinder at a high positive potential; the cathode and anode act as an electron gun to produce a high velocity stream of electrons. An external electromagnet winding creates a longitudinal magnetic field along the beam axis which prevents the beam from spreading.

The beam first passes through the "buncher" cavity resonator, through grids attached to each side. The buncher grids have an oscillating AC potential across them, produced by standing wave oscillations within the cavity, excited by the input signal at the cavity's resonant frequency applied by a coaxial cable or waveguide. The direction of the field between the grids changes twice per cycle of the input signal. Electrons entering when the entrance grid is negative and the exit grid is positive encounter an electric field in the same direction as their motion, and are accelerated by the field. Electrons entering a half-cycle later, when the polarity is opposite, encounter an electric field which opposes their motion, and are decelerated.

Beyond the buncher grids is a space called the drift space. This space is long enough so that the accelerated electrons catch up with electrons that were decelerated at an earlier time, forming "bunches" longitudinally along the beam axis. Its length is chosen to allow maximum bunching at the resonant frequency, and may be several feet long.

Klystron oscillator from 1944. The electron gun is on the right, the collector on the left. The two cavity resonators are in center, linked by a short coaxial cable to provide positive feedback.

The electrons then pass through a second cavity, called the "catcher", through a similar pair of grids on each side of the cavity. The function of the catcher grids is to absorb energy from the electron beam. The bunches of electrons passing through excite standing waves in the cavity, which has the same resonant frequency as the buncher cavity. Each bunch of electrons passes between the grids at a point in the cycle when the exit grid is negative with respect to the entrance grid, so the electric field in the cavity between the grids opposes the electrons motion. The electrons thus do work on the electric field, and are decelerated, their kinetic energy is converted to electric potential energy, increasing the amplitude of the oscillating electric field in the cavity. Thus the oscillating field in the catcher cavity is an amplified copy of the signal applied to the buncher cavity. The amplified signal is extracted from the catcher cavity through a coaxial cable or waveguide.

After passing through the catcher and giving up its energy, the lower energy electron beam is absorbed by a "collector" electrode, a second anode which is kept at a small positive voltage.

Klystron oscillator

An electronic oscillator can be made from a klystron tube, by providing a feedback path from output to input by connecting the "catcher" and "buncher" cavities with a coaxial cable or waveguide. When the device is turned on, electronic noise in the cavity is amplified by the tube and fed back from the output catcher to the buncher cavity to be amplified again. Because of the high Q of the cavities, the signal quickly becomes a sine wave at the resonant frequency of the cavities.

Multicavity klystron

In all modern klystrons, the number of cavities exceeds two. Additional "buncher" cavities added between the first "buncher" and the "catcher" may be used to increase the gain of the klystron or to increase the bandwidth.

The residual kinetic energy in the electron beam when it hits the collector electrode represents wasted energy, which is dissipated as heat, which must be removed by a cooling system. Some modern 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.

Reflex klystron

Low-power Soviet reflex klystron from 1963. The cavity resonator from which the output is taken, is attached to the electrodes labeled Externer Resonator. Reflex klystrons are almost obsolete now.

 

cutaway: reflex klystron

 

Main article: Sutton tube

The reflex klystron (also known as a Sutton tube after one of its inventors, Robert Sutton) was a low power klystron tube with a single cavity, which functioned as an oscillator. It was used as a local oscillator in some radar receivers and a modulator in microwave transmitters the 1950s and 1960s, but is now obsolete, replaced by semiconductor microwave devices.

In the reflex klystron the electron beam passes through a single resonant cavity. The electrons are fired into one end of the tube by an electron gun. After passing through the resonant cavity they are reflected by a negatively charged reflector electrode for another pass through the cavity, where they are then collected. The electron beam is velocity modulated when it first passes through the cavity. The formation of electron bunches takes place in the drift space between the reflector and the cavity. The voltage on the reflector must be adjusted so that the bunching is at a maximum as the electron beam re-enters the resonant cavity, thus ensuring a maximum of energy is transferred from the electron beam to the RF oscillations in the cavity. The reflector voltage may be varied slightly from the optimum value, which results in some loss of output power, but also in a variation in frequency. This effect is used to good advantage for automatic frequency control in receivers, and in frequency modulation for transmitters. The level of modulation applied for transmission is small enough that the power output essentially remains constant. At regions far from the optimum voltage, no oscillations are obtained at all. There are often several regions of reflector voltage where the reflex klystron will oscillate; these are referred to as modes. The electronic tuning range of the reflex klystron is usually referred to as the variation in frequency between half power points—the points in the oscillating mode where the power output is half the maximum output in the mode.

Modern semiconductor technology has effectively replaced the reflex klystron in most applications.

Gyroklystron

The gyroklystron is a microwave amplifier with operation dependent on the cyclotron resonance condition. Similarly to the klystron, its operation depends on the modulation of the electron beam, but instead of axial bunching the modulation forces alter the cyclotron frequency and hence the azimuthal component of motion, resulting in phase bunches. In the output cavity, electrons which arrive at the correct decelerating phase transfer their energy to the cavity field and the amplified signal can be coupled out. The gyroklystron has cylindrical or coaxial cavities and operates with transverse electric field modes. Since the interaction depends on the resonance condition, larger cavity dimensions than a conventional klystron can be used. This allows the gyroklystron to deliver high power at very high frequencies which is challenging using conventional klystrons.

Tuning

Large klystrons as used in the storage ring of the Australian Synchrotron to maintain the energy of the electron beam

Some klystrons have cavities that are tunable. By adjusting the frequency of individual cavities, the technician can change the operating frequency, gain, output power, or bandwidth of the amplifier. No two klystrons are exactly identical (even when comparing like part/model number klystrons). Each unit has manufacturer-supplied calibration values for its specific performance characteristics. Without this information the klystron would not be properly tunable, and hence not perform well, if at all.

Tuning a klystron is delicate work which, if not done properly, can cause damage to equipment or injury to the technician due to the very high voltages that could be produced. The technician must be careful not to exceed the limits of the graduations, or damage to the klystron can result. Other precautions taken when tuning a klystron include using nonferrous tools. Some klystrons employ permanent magnets. If a technician uses ferrous tools (which are ferromagnetic) and comes too close to the intense magnetic fields that contain the electron beam, such a tool can be pulled into the unit by the intense magnetic force, smashing fingers, injuring the technician, or damaging the unit. Special lightweight nonmagnetic (or rather very weakly diamagnetic) tools made of beryllium alloy have been used for tuning U.S. Air Force klystrons.

Precautions are routinely taken when transporting klystron devices in aircraft, as the intense magnetic field can interfere with magnetic navigation equipment. Special overpacks are designed to help limit this field "in the field," and thus allow such devices to be transported safely.

Optical klystron

The technique of amplification used in the klystron is also being applied experimentally at optical frequencies in a type of laser called the free-electron laser (FEL); these devices are called optical klystrons. Instead of microwave cavities, these use devices called undulators. The electron beam passes through an undulator, in which a laser light beam causes bunching of the electrons. Then the beam passes through a second undulator, in which the electron bunches cause oscillation to create a second, more powerful light beam.

Floating drift tube klystron

The floating drift tube klystron has a single cylindrical chamber containing an electrically isolated central tube. Electrically, this is similar to the two cavity oscillator klystron with considerable feedback between the two cavities. Electrons exiting the source cavity are velocity modulated by the electric field as they travel through the drift tube and emerge at the destination chamber in bunches, delivering power to the oscillation in the cavity. This type of oscillator klystron has an advantage over the two-cavity klystron on which it is based, in that it needs only one tuning element to effect changes in frequency. The drift tube is electrically insulated from the cavity walls, and DC bias is applied separately. The DC bias on the drift tube may be adjusted to alter the transit time through it, thus allowing some electronic tuning of the oscillating frequency. The amount of tuning in this manner is not large and is normally used for frequency modulation when transmitting.

Applications

Klystrons can produce far higher microwave power outputs than solid state microwave devices such as Gunn diodes. In modern systems, they are used from UHF (hundreds of megahertz) up to hundreds of gigahertz (as in the Extended Interaction Klystrons in the CloudSat satellite). Klystrons can be found at work in radar, satellite and wideband high-power communication (very common in television broadcasting and EHF satellite terminals), medicine (radiation oncology), and high-energy physics (particle accelerators and experimental reactors). At SLAC, for example, klystrons are routinely employed which have outputs in the range of 50 MW (pulse) and 50 kW (time-averaged) at 2856 MHz. The Arecibo Planetary Radar used two klystrons that provided a total power output of 1 MW (continuous) at 2380 MHz.

Popular Science's "Best of What's New 2007" described a company, Global Resource Corporation, currently defunct, using a klystron to convert the hydrocarbons in everyday materials, automotive waste, coal, oil shale, and oil sands into natural gas and diesel fuel.

Human givens

From Wikipedia, the free encyclopedia

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

This is about psychotherapy. See Human condition for the general topic.

Human Givens is the name of a theory in psychotherapy formulated in the United Kingdom, first outlined by Joe Griffin and Ivan Tyrrell in the late 1990s. and amplified in the 2003 book Human Givens: A new approach to emotional health and clear thinking. The human givens organising ideas proffer a description of the nature of human beings, the 'givens' of human genetic heritage and what humans need in order to be happy and healthy. Human Givens therapy seeks to use a "client's strengths to enable them to get emotional needs met". It is advertised as "drawing from the best of person-centred counselling, motivational interviewing, cognitive behavioural therapy, psychoeducational approaches, interpersonal therapy, imaginal exposure and hypnotherapy". The Human Givens Institute has been accredited in the UK by the Professional Standards Authority for Health and Social Care (PSA).

Historical background

Abraham Maslow is credited with the first prominent theory which laid out a hierarchy of needs. The precise nature of the hierarchy and the needs have subsequently been refined by modern neuroscientific and psychological research.

Since Maslow's work in the middle of the twentieth century, a significant body of research has been undertaken to clarify what human beings need to be happy and healthy. The UK has contributed significantly to the international effort, through the ground breaking Whitehall Study led by Sir Michael Marmot, which tracked the lifestyles and outcomes for large groups of British civil servants. This identified effects on mental and physical health from emotional needs being met - for instance, it showed that those with less autonomy and control over their lives, or less social support, have worse health outcomes.

In the United States, the work of Martin Seligman, a psychologist at the University of Pennsylvania has been influential. Seligman has summarised the research to date in terms of what makes humans happy; again, this demonstrates themes about universal emotional needs which must be met for people to lead fulfilling lives.

At the University of Rochester, contemporaries of Seligman Edward Deci and Richard Ryan have conducted original research and gathered existing evidence to develop a framework of human needs which they call self-determination theory. This states that human beings are born with innate motivations, developed from our evolutionary past. They gather these motivational forces into three groups - autonomy, competence and relatedness. The human givens approach uses a framework of nine needs, which map onto these three groups.

Innate needs

The human givens model proposes that human beings come into the world with a given set of innate needs, together with innate resources to support them to get those needs met. Physical needs for nutritious food, clean water, air and sleep are obvious, and well understood, because when they are not met people die. However, the emotional needs, which the human givens approach seeks to bring to wider attention, are less obvious, and less well understood, but just as important to human health. Decades of social and health psychology research now support this.

The human givens approach defines nine emotional needs:

1. Security: A sense of safety and security; safe territory; an environment in which people can live without experiencing excessive fear so that they can develop healthily.
2. Autonomy and control: A sense of autonomy and control over what happens around and to us.
3. Status: A sense of status - being accepted and valued in the various social groups we belong to.
4. Privacy: Time and space enough to reflect on and consolidate our experiences.
5. Attention: Receiving attention from others, but also giving it; a form of essential nutrition that fuels the development of each individual, family and culture.
6. Connection to the wider community: Interaction with a larger group of people and a sense of being part of the group.
7. Intimacy: Emotional connection to other people - friendship, love, intimacy, fun.
8. Competence and achievement: A sense of our own competence and achievements, that we have what it takes to meet life's demands.
9. Meaning and purpose: Being stretched, aiming for meaningful goals, having a sense of a higher calling or serving others creates meaning and purpose.

These needs map more or less well to tendencies and motivations described by other psychological evidence, especially that compiled by Deci and Ryan at the University of Rochester. The exact categorisation of these needs, however, is not considered important. Needs can be interlinked and have fuzzy boundaries, as Maslow noted. What matters is a broad understanding of the scope and nature of human emotional needs and why they are so important to our physical and mental health. Humans are a physically vulnerable species that have enjoyed amazing evolutionary success due in large part to their ability to form relationships and communities. Getting the right social and emotional input from others was, in our evolutionary past, literally a matter of life or death. Thus, Human Givens theory states, people are genetically programmed only to be happy and healthy when these needs are met.

There is evidence that these needs are consistent across cultures, and therefore represent innate human requirements.

Innate resources

The Human Givens model also consists of a set of 'resources' (abilities and capabilities) that all human beings are born with, which are used to get the innate needs met. These constitute what is termed an 'inner guidance system'. Learning how to use these resources well is seen as being key to achieving, and sustaining, robust bio-psycho-social health as individuals and as groups (families, communities, societies, cultures etc.).

The given resources include:

• Memory: The ability to develop complex long-term memory, which enables people to add to their innate (instinctive) knowledge and learn;
• Rapport: The ability to build rapport, empathise and connect with others;
• Imagination: Which enables people to focus attention away from the emotions and problem solve more creatively and objectively (a 'reality simulator');
• Instincts and emotions: A set of basic responses and 'propulsion' for behaviours;
• A rational mind: A conscious, rational mind that can check out emotions, question, analyse and plan;
• A metaphorical mind: The ability to 'know', to understand the world unconsciously through metaphorical pattern matching ('this thing is like that thing');
• An observing self: That part of us which can step back, be more objective and recognise itself as a unique centre of awareness apart from intellect, emotion and conditioning;
• A dreaming brain: According to the expectation fulfilment theory of dreaming, this preserves the integrity of our genetic inheritance every night by metaphorically defusing emotionally arousing expectations not acted out during the previous day.

Three reasons for mental illness

A further organising idea proffered by the human givens approach is to suggest that there are three main reasons why individuals may not be getting their needs met and thus why they may become mentally ill:

1. Environment: something in our environment is interfering with our ability to get our needs met. Our environment is 'toxic' (e.g. a bullying boss, antisocial neighbours) or simply lacks what we need (e.g. community);
2. Damage: something is wrong with our 'resources' -- our 'hardware' (brain/body) or 'software' (missing or incomplete instincts and/or unhelpful conditioning such as posttraumatic stress disorder) is damaged;
3. Knowledge: we may not know what we need; or we may not have been taught, or may have failed to learn, the coping skills necessary for getting our needs met (for example, how to use the imagination for problem solving rather than worrying, or how to make and sustain friendships).

When dealing with mental illness or distress this framework provides a checklist that guides both diagnosis and treatment.

Key features

Key features of the human givens school include:

• A new model of therapeutic intervention (the APET model) based on the neurological finding that emotion precedes thought;
• New insights into trauma and how to treat it effectively - the 'rewind technique' (The human givens rewind technique has been evaluated in an international textbook on trauma.);
• An holistic understanding of the evolutionary origins and function of human dreaming (expectation fulfilment theory of dreaming) which is key to understanding the cycle of depression: how depression develops, is maintained and can be successfully treated;
• A neuroscience-based explanation for addiction and why withdrawal symptoms occur;
• A theory (called 'molar memories') which explains the mechanism that generates and maintains some instances of compulsive behaviour (such as sexual compulsions, anorexia and bulimia);
• A psychobiological explanation of clinical hypnosis, why it works and the mechanisms common to all forms of hypnotic induction;
• New understandings of the autistic spectrum disorder, including what has been termed ‘caetextia’;
• New insights into the nature of psychosis (waking reality processed through the REM state/dreaming brain);
• A clear protocol for conducting therapy sessions - the RIGAAR model: Rapport building; Information gathering; Goal setting (new, positive expectations related to the fulfillment of innate needs); Accessing the client's own strengths and resources (success templates); Agreeing a strategy (for achieving the needs-related goals); Rehearsing success (the enactment of the agreed strategies).

Research and evidence

There are now a number of independent studies evaluating the human givens approach:

• Human givens randomised controlled trial: There are no randomised-controlled trials (RCTs) to test the human givens approach. The first RCT is in process; The Bristol Randomised Controlled Trial Collaboration (a partnership between the University of Bristol and the National Health Service) has agreed to help design it.
• A 12–month evaluation of the human givens approach in primary care (2011): Peer reviewed evidence for the effectiveness of human givens therapy, published in Psychology and Psychotherapy: Theory, Research and Practice, showed that, of 120 patients treated by HG therapists in a GP's surgery, more than three-quarters were either symptom-free or reliably improved as a result of the therapy. This was accomplished in an average of only 3.6 sessions. This compares favourably with the recovery rate for the UK Government’s Improving Access to Psychological Therapies (IAPT) programme, which mainly uses therapists trained in cognitive-behavioural therapy (CBT) and expects therapy to take longer; less than half of its patients improve or recover.
• Using human givens therapy to support the wellbeing of adolescents (2011): An article for Pastoral Care in Education: An International Journal of Personal, Social and Emotional Development assessed the efficacy of an individual human givens intervention for three young people who reported high anxiety or depression and/or low self-concept. It found positive outcomes for the subjects which provided tentative evidence that human givens therapy might be useful to practitioners delivering therapeutic interventions in schools.
• Assessing the effectiveness of the “human givens” approach in treating depression (2012): A peer-reviewed research paper, published in Mental Health Review Journal found that treating people with mild to moderate depressed mood (measured using HADS) with human givens therapy had quicker results than the treatment provided to people in a control group.
• The Emotional Needs Audit: a report on its reliability and validity (2012): A peer-reviewed research paper published in the Mental Health Review Journal found that the Human Givens Institute’s Emotional Needs Audit (ENA) was a valid and reliable instrument for measuring wellbeing, quality of life and emotional distress. It also concluded that the ENA allows insight into the causes of symptoms, dissatisfaction and distress, complementing standardised tools when used in clinical practice.
• A 5–year evaluation of the human givens therapy using a Practice Research Network (2012): A peer-reviewed research paper published in the Mental Health Review Journal (2012) evaluated five year’s worth of practice-based evidence gleaned from a practice research network. The pre-post treatment effect size suggested that “clients treated using the HG approach experienced relief from psychological distress”.
• Evaluation of human givens ‘rewind’ treatment to treat trauma (2013): A poster presentation for a veteran lead research conference evaluated the effectiveness of a single human givens rewind treatment session to treat PTSD in the general psychiatric population and found that this treatment can be effective with severe, chronic and even multiple traumas in a single session, with some requiring no further treatment.

Organisations

The following constitute the main human givens organisations:

Human Givens Institute

The Human Givens Institute is a membership organisation open to those wishing to support and promote the human givens approach through all forms of psychological, educational and social interactions, and the professional body representing the interests of those in the caring and teaching professions who aim to work in alignment with the best scientific knowledge available about the givens of human nature. The Institute is accredited by the Professional Standards Authority for Health and Social Care. for the purposes of regulating practitioners who have completed training as Human Givens Therapists and who are Registered with the Institute.

Human Givens Foundation

The Human Givens Foundation is a charitable organisation devoted to spreading the human givens philosophy and information into organisations concerned with health, education, business, social work and the wider care system, the police, the armed forces, and, more widely, into social policy and government. It aims to support parents, families, couples and individuals to live more harmonious, satisfying and meaningful lives.

Human Givens College

Human Givens College is a training organisation offering psychotherapy courses as well as a full psychotherapy diploma course leading to qualification as a human givens practitioner. There are currently 226 Registered Members on the HGI Register – people who have achieved part 3 of the diploma course and are set up in private practice.