BS EN IEC 61788-7:2020 pdf free.Superconductivity.Electronic characteristic measurements – Surface resistance of high-temperature superconductors at microwave frequencies.
BS EN IEC 61788-7 It is the responsibility of the user of this document to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use. Hazards exist in this type of measurement. The use of a cryogenic system is essential to cool the superconductors to allow transition into the superconducting state. Direct contact of skin with cold apparatus components can cause immediate freezing, as can direct contact with a spilled cryogen. The use of an RF generator is also essential to measure high-frequency properties of materials. If its power is too high, direct contact to human bodies can cause an immediate burn.Figure 2 shows a schematic of a typical measurement apparatus (closed type resonator) for the Rs of HTS films deposited on a substrate with a flat surface. The upper HTS film is pressed down by a spring, which is made of phosphor bronze. The plate type spring should be used for the improvement of measurement uncertainty. This type of spring reduces the friction between the spring and the other part of the apparatus, and allows the smooth movement of superconductor films due to the thermal expansion of the dielectric rod. In order to minimize the measurement uncertainty, the sapphire rod and the copper ring shall be arranged coaxially. Two semi-rigid cables for measuring transmission characteristics of the resonator shall be attached on both sides of the resonator in an axial symmetrical position (φ= 0 and π，where φ is the rotational angle around the central axis of the sapphire rod). Each of the two semi-rigid cables shall have a small loop at the ends. The plane of the loop shall be set parallel to that of the superconductor films in order to suppress the unwanted Transverse Magnetic Wave Modes (TMmn0 modes). The coupling loops shall be carefully checked for cracks in the spot weld joint that may have developed upon repeated thermal cycling. These cables can move right and left to adjust the insertion attenuation (IA). In this adjustment, coupling of unwanted cavity modes to the interested dielectric resonance mode shall be suppressed. Unwanted, parasitic coupling to the other modes reduces the high Q-value of the Transverse Electro-Magnetic Mode (TE mode) resonator. For suppressing the parasitic coupling, special attention shall be paid to designing high-Q resonators. Two other types of resonators along with the closed type shown in Figure 2 can be used. They are explained in A.4. BS EN IEC 61788-7 pdf download.