Cavity Shunt Research Articles

Syringobulbia in Patients with Chiari Malformation Type I: A Systematic Review.

This study aimed to summarize the clinical features, diagnosis, and treatment of Chiari malformation type I- (CM-1-) associated syringobulbia. We performed a literature review of CM-1-associated syringobulbia in PubMed, Ovid MEDLINE, and Web of Science databases. Our concerns were the clinical features, radiologic presentations, treatment therapies, and prognoses of CM-1-associated syringobulbia. This review identified 23 articles with 53 cases. Symptoms included headache, neck pain, cranial nerve palsy, limb weakness/dysesthesia, Horner syndrome, ataxia, and respiratory disorders. The most frequently involved area was the medulla. Most of the patients also had syringomyelia. Surgical procedures performed included posterior fossa decompression, foramen magnum decompression, cervical laminectomy, duraplasty, and syringobulbic cavity shunt. Most patients experienced symptom alleviation or resolution postoperatively. A syringobulbic cavity shunt provided good results in refractory cases. Physicians should be aware of the possibility of syringobulbia in CM-1 patients, especially those with symptoms of sudden-onset brain-stem involvement. The diagnosis relies on the disorder's specific symptomatology and magnetic resonance imaging. Our review suggests that the initial therapy should be posterior fossa decomposition with or without duraplasty. In refractory cases, additional syringobulbic cavity shunt is the preferred option.

Beam-cavity interaction physics for mildly relativistic, intense-beam klystron amplifiers

We examine beam-cavity interaction physics relevant to mildly relativistic, intense-beam klystron amplifiers. This is an interesting but difficult regime of operation, because of the combination of high beam current and low voltage. The advantage of this regime is that it is relatively easy to access high beam powers (and potentially high microwave output powers) at relatively low beam energy. We calculate the effect of the extremely high beam loading in the input and idler cavities. The output cavity's shunt impedance must match the low beam impedance in order to prevent high output gap voltages that will reflect electrons back upstream. This leads to very low cavity Q factors (<10). We derive expressions for mode purity for such low-Q cavities and show that acceptable cavities can be designed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of a long-pulse 1.3 GHz relativistic klystron amplifier

A research approach for obtaining kilojoule microwave pulses of microsecond duration at 1.3 GHz from the relativistic klystron amplifier is described. Achieving kilojoule microwave pulses requires extending electron beam pulse durations and maximizing the microwave extraction efficiency at the fundamental frequency. An electron beam diode has been constructed that delivers peak currents in excess of 5 kA with a monotonically increasing current pulse exceeding durations of 1 mu s at beam kinetic energies above 400 keV. Close attention has been given to minimizing the current losses from the diode. Maximum microwave extraction efficiency at the fundamental frequency has been related to the beam bunching amplitude and output cavity shunt impedance in terms of a simple circuit theory. The circuit theory predictions have been tested by particle-in-cell code calculations of the electron beam interactions with the proposed cavity structures. The successful cavity structures have been constructed and are awaiting testing. >

Generation and Distribution of Radio-Frequency Power in LEP

The beam energy in LEP Phase I at maximum luminosity is 55 GeV. With a circulating current of 3 mA per beam, an effective cavity shunt impedance of 40 M..cap omega../m and RF power losses in the waveguide system of 7.5%, a total of 14.9 MW RF generator power is required for achieving this energy, the respective values for injection being 20 GeV and about 0.26 MW. This RF power is generated by 16 klystrons and supplied to the 128 accelerating structures via a WR 2300 waveguide system. Two klystrons, together with 16 accelerating structures, the controls and associated waveguide system, form an RF unit.

Optical Frequency Mixing in Semiconductors

Abstract The paper is concerned with a theoretical study of photoconductive mixing phenomena. The output power at the difference frequency is obtained in terms of the applied optical input power, cavity shunt resistance and the physical properties of the semiconductor. The dependence on the length of the semiconductor is investigated and it is shown that a short length is preferable if ωτ≫ 1 (τ=recombination time, ω=difference frequency). If ωτ<1 the output power is found to be independent of length until the equivalent shunt resistance of the semiconductor becomes comparable with the shunt resistance of the cavity.

The Q of a Microwave Cavity by Comparison with a Calibrated High-Frequency Circuit

A comparison method has been developed for the direct measurement of cavity Q at microwave frequencies. It is particularly useful for high values of Q, such as 5,000 to 15,000. The over-all error in the measurement is estimated to be less than ±3 per cent. A two-channel superheterodyne technique is used, in which both channels are driven by the same frequency-swept oscillator, and both channels use the same local oscillator. The cavity is inserted in the radio-frequency stage of the first channel, and a comparison circuit is inserted in the intermediate-frequency stage of the parallel channel. The two resonance curves are displayed on the same oscilloscope for alternate sweeps of the oscillator. When the resonance curves are made to coincide, the Q of the cavity is n times the Q of the comparison circuit, where n is the ratio of radio frequency to intermediate frequency. Cavity shunt resistances can be measured on the same apparatus.