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| TUPSA006 | Experiment on RF Heating of the Copper Cavity - the Imitator of the CLIC High-Gradient Accelerating Structure | controls, electron, vacuum, radiation | 47 | ||
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The facility for joint experiments of JINR-IAP RAS has been commissioned to investigate the lifetime dependence of the CLIC high-gradient accelerating structure* on the surface damage by repetitive high-power RF pulses. The facility is based on the 30 GHz JINR free-electron maser, which uses an electron beam of the induction linear accelerator LIU-3000 **. Intermediate optical observations of the central ring allowed us to control the process of the damage evolution. The first damage of the copper surface have been observed after 16000 pulses with the pulse heating of 240°C. After 63000 pulses the damage of the surface of the oxygen-free copper cavity became strong enough to cause regular breakdowns inside the test cavity.
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* I. Wilson – CERN AB-2004-100, CLIC Note 617, Dec. 2004, 12pp. |
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| TUPSA007 | Thermal Balance of Multilayered Tunable Dielectric Loaded Wakefield Accelerating Structure | acceleration, vacuum, radiation, electromagnetic-fields | 50 | ||
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Funding: Ministry of Education and Science of Russia, “Scientific and scientific-pedagogical personnel of innovative Russia” and the Russian Foundation for Basic Research (09-02-00921) |
Thermal balance of a cylindrical tunable multilayer dielectric-filled accelerating structure is considered. One ceramic layer of the structure possesses ferroelectric properties, which allow the waveguide frequency spectrum to be tuned by varying the permittivity of the ferroelectric layer. Dielectric and induction losses in ferroelectric layer and a metal shell leads to a structure warming up and increasing temperature of the ferroelectric layer. Because of a temperature sensitivity of dielectric permittivity of ferroelectric layer this effect may detune the accelerating structure. On the basis of the analysis of a thermal regime of multilayered wakefield structure the medium and pulse temperature deviations are determined. A repetition rate of electronic bunch series should be chosen to limit temperature detuning. |
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| TUPSA035 | Shapes of Nuclear Induction Signals under Inhomogeneous Magnetic Fields | resonance, radio-frequency, site, acceleration | 119 | ||
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The influence of the inhomogeneous magnetic field on the shape of nuclear induction signals is analyzed. The most frequent five of magnetic field distributions: Lorentz, Gaussian, exponential, triangular and ideal “square”- are described. Nonideal "square" distributions that have finite duration pulse edges variable by Lorentz, Gaussian, exponential and triangular dependences are considered. The signal change as a result of placing of nuclear spins under the constant gradient magnetic field is studied. All results have been found in the analytical form taking into an account the magnetic screening effect of atomic nuclei.
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| TUPSA036 | Advance of the Marginal Oscillator | resonance, feedback, impedance, electron | 122 | ||
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The advance of the transistor marginal oscillator (TMO) circuits are considered. The various TMO circuits, the features of their functioning and the simple NMR magnetometers based on them are reviewed.
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| THPSC008 | Superconducting Transformers for Study of High-Current Superconducting Cables | dipole, superconducting-magnet, cryogenics, power-supply | 340 | ||
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A facility for measurement of critical current and minimal quench energy of Rutherford-type superconducting cables for accelerator magnets is created. The sample current is energized by a superconducting transformer circuit using an inductive method, where the sample conductor is a part of the secondary circuit. Two superconducting transformers were built; one of them is a solenoid type coil. The transformer consists of two concentric solenoids; the secondary coil is placed inside the primary coil. External magnetic field up to 6.5 T is provided by a superconducting solenoid with the aperture diameter of 60 mm. The second superconducting transformer with race-track coils has been designed and taken into operation. Short-circuited sample, fixed on a special holder, is placed in the aperture of a superconducting dipole magnet such way that the plane of sample loop is perpendicular to direction of external magnetic field, which can reach up to 6 T. The critical current of the secondary superconducting coil is 18 kA. The equipment for measurements of characteristics superconducting cable versus magnetic field is described.
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