Source klystron

Source klystron laser tube nuclear decay... 

Besides the ambiguity of fitting simulated to experimental spectra, the instrumental limits (most conventional microwave sources — klystrons, Gunn diodes, etc. — operate only a limited band width within the octave, that is, they are not tunable) of the one frequency per octave approach does not assme one of being able to obtain the requisite number of spectra to begin with. For example, it is highly problematic to record cw-ENDOR of weakly coupled " N at the X-band... 

Waveguides are coimnonly used to transmit microwaves from the source to the resonator and subsequently to the receiver. For not-too-high-frequency radiation (<10 GHz) low-loss MW transmission can also be achieved usmg strip-lines and coaxial cables. At the output of a klystron an isolator is often used to prevent back-reflected microwaves to perturb the on-resonant klystron mode. An isolator is a microwave-ferrite device that pemiits the transmission of microwaves in one direction and strongly attenuates their propagation in the other direction. The prmciple of this device involves the Faraday effect, that is, the rotation of the polarization... 

Two-photon absorption has been observed in the microwave region with an intense klystron source but in the infrared, visible and ultraviolet regions laser sources are necessary. 

The simplest arrangement for a linear accelerator is shown in Fig. 5. Here a single source, either a self-oscillating magnetron or klystron amplifier with appropriate drive stages, feeds power into a single length of accelerator wave-... 

We have previously defined the relative dB scale in Equation 2.11. The power in EPR is expressed in decibels (dB) attenuation (or alternatively in -dB amplification) of a maximum value. X-band microwave sources (either klystrons or Gunn diodes) have a constant output that is usually leveled off at 200 mW. This value then corresponds... 

The basic features of an epr spectrometer are shown in Figure 2.95. The microwave source is a Klystron tube that emits radiation of frequency determined by the voltage across the tube. Magnetic fields of 0.1 — 1 T can be routinely obtained without complicated equipment and are generated by an electromagnet. The field is usually modulated at a frequency of 100kHz and the corresponding in-phase component of the absorption monitored via a phase-sensitive lock-in detector. This minimises noise and enhances the sensitivity of the technique. It is responsible for the distinctive derivative nature of epr spectra. Thus, the spectrum is obtained as a plot of dA/dB vs. 

A family of vacuum-tube MMW sources is based on the propagation of an electron beam through a so-called slow-wave or periodic structure. Radiation propagates on the slow-wave structure at the speed of the electron beam, allowing the beam and radiation field to interact. Devices in this category are the traveling-wave tube (TWT), the backward-wave oscillator (BWO) and the extended interaction oscillator (EIO) klystron. TWTs are characterized by wide bandwidths and intermediate power output. These devices operate well at frequencies up to 100 GHz. BWOs, so called because the radiation within the vacuum tube travels in a direction opposite to that of the electron beam, have very wide bandwidths and low output powers. These sources operate at frequencies up to 1.3 THz and are extensively used in THZ spectroscopic applications [10] [11] [12]. The EIO is a high-power, narrow band tube that has an output power of 1 kW at 95 GHz and about 100 W at 230 GHz. It is available in both oscillator and amplifier, CW and pulsed versions. This source has been extensively used in MMW radar applications with some success [13]. 

The setup for ESR spectroscopy is a cross between NMR and micro-wave techniques (Section 5.8). The source is a frequency-stabilized klystron, whose frequency is measured as in microwave spectroscopy. The microwave radiation is transmitted down a waveguide to a resonant cavity (a hollow metal enclosure), which contains the sample. The cavity is between the poles of an electromagnet, whose field is varied until resonance is achieved. Absorption of microwave power at resonance is observed using the same kind of crystal detector as in microwave spectroscopy. Sensitivity is enhanced, as in microwave spectroscopy, by the use of modulation The magnetic field applied to the sample is modulated at, say, 100 kHz, thus producing a 100-kHz signal at the crystal when an absorption is reached. The spectrum is recorded on chart paper. 

Microwave spectroscopy covers the frequency range from about 3 GHz to 300 GHz. The techniques used in the infrared, visible, and ultraviolet regions resemble one another closely, but the techniques of microwave spectroscopy differ considerably from those of optical spectroscopy. The source in microwave work is usually a klystron, which is an electronic tube... 

MICROWAVE SPECTROSCOPY. A type of adsorption spectroscopy used in instrumental chemical analysis that involves use of that portion of the electromagnetic spectrum hav ing wavelengths in the range between the far infrared and the radiofrequencies, i.e.. between 1 nun and. 111 cm. Substances to be analyzed are usually in the gaseous state. Klystron tubes are used as microwave source. 

Figure 29.9 shows a comparison between the components of a rudimentary EPR spectrometer and the corresponding elements of a more familiar apparatus for visible spectrometry. In EPR, the source of excitation radiation is a microwave device called a klystron. The microwaves would disperse in free space and must therefore be conducted to the sample by waveguide or coaxial cable. The sample, contained in the sample tube, is held in a microwave cavity between the poles of a magnet. The detector is usually a diode that produces a dc output propor-... 

Klystrons. The most commonly used radiation source is a klystron these tubes are available at discrete frequencies between 2.5 and 220 GHz. Many klystrons can be tuned over a range up to 3 % of the nominal frequency by a control that varies the physical dimensions of a resonant cavity inside the tube. Finer adjustment of the frequency is achieved by varying the voltage applied to the resonator and reflector electrodes. Thermal stability is obtained by immersion of the entire tube in an oil bath, or by water or air cooling. A feedback circuit provides automatic frequency control (AFC) to continuously correct the output frequency to the resonance frequency of the cavity. The power output of the klystrons used in EPR spectrometers is generally about 300-700 mW. The most widely used frequency for EPR spectrometers is 9.5 GHz, which is called X-band. 

The main types of microwave power sources are magnetrons and klystrons. Magnetrons which are commonly used in microwave ovens are mass produced thus cheap and easily available on the market. Therefore it is common practice to use the same magnetrons... 

The frequency source used for the study of CO+ was a klystron operating close to 120 GHz. The microwave radiation was launched through a microwave horn onto the Teflon lens at the source end of the discharge tube. The radiation emerging from the cell was focused by the second Teflon lens into a complementary horn for transmission to a diode detector. The mounting and precision adjustment of the horns was extremely important, and the whole assembly was mounted on an optical bench. The klystron... 

The magnetogyric ratio of a free electron is approximately 657 times that of a proton. Modem EPR spectrometers use a microwave generator (klystron) as the source of electromagnetic radiation (i.e., the oscillating magnetic field), with operating frequencies in the range 1-100 GHz (1 GHz = 103 MHz = 109 Hz) 9.5 GHz (the so-called A-band) is perhaps the most common. 

Fig. 3.1. Schematic diagram for a standard C.W. X-band spectrometer. The sample is placed vertically into the centre of the cavity in the region of maximum microwave magnetic field. Various forms of stationary waves are set up in the cavity, depending on its shape. The basis of the instrument is the Klystron as a source of monochromatic microwaves, the permanent electromagnet, giving a homogeneous field through the microwave cavity (or resonator). The field is swept to generate the spectrum, and the modulation coils provide a rapid sampling (often at ca. 100 kHz) to give phase-sensitive...

A schematic of an ESR spectrometer is shown in Fig. 3 more detailed discussion of construction and operation of the instrument can be found in Ref. 1 and in the citations therein, as well as in the manuals accompanying the spectrometer to be used. The microwave source is a vacuum-tube Klystron or a solid-state Gunn diode, which provides... 

Sources. The ultimate source for spectroscopic studies is one that is intense and monochromatic but tunable, so that no dispersion device is needed. Microwave sonrces such as klystrons and Gnnn diodes meet these requirements for rotational spectroscopy, and lasers can be similarly nsed for selected regions in the infrared and for much of the visible-ultraviolet regions. In the 500 to 4000 cm infrared region, solid-state diode and F-center lasers allow scans over 50 to 300 cm regions at very high resolution (<0.001 cm ), but these sources are still quite expensive and nontrival to operate. This is less trne... 

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