BS 61788-8:2010 pdf download – Superconductivity Part 8: AC loss measurements — Total AC loss measurement of round superconducting wires exposed to a transverse alternating magnetic field at liquid helium temperature by a pickup coil method

BS 61788-8:2010 pdf download – Superconductivity Part 8: AC loss measurements — Total AC loss measurement of round superconducting wires exposed to a transverse alternating magnetic field at liquid helium temperature by a pickup coil method 5 Apparatus 5.1 Testing apparatus The testing apparatus shall be constructed such that the pickup coils and a coiled specimen are arranged in a uniform alternating magnetic field applied by a superconducting magnet. The coils of the testing apparatus are arranged as described below. Typically, the main pickup and compensation coils are coaxially positioned on the outside and inside of the coiled specimen, respectively. The applied alternating magnetic field shall have a high uniformity as shown in 7.1 .5. The testing apparatus has a sub-system that calculates the magnetization and the AC loss of the specimen by integrating the signal of the pickup coils. A typical electrical circuit for the AC loss measurement is given in Figure 2. 5.2 Pickup coils Pickup coils shall be made of very fine insulated wire, such as insulated copper wire with a diameter of 0,1 mm, to avoid eddy currents at low temperatures. The pickup coil formers shall be made of non-metallic and non-magnetic material such as glass fiber reinforced plastic, phenol resin, etc. The main pickup coil shall be arranged coaxially and adjusted concentrically outside the compensation coil. The standard arrangement is shown schematically in Figure 1 , where the height of the compensation coil is the same as that of the main pickup coil. The number of turns in the compensation coil shall be usually adjusted to be a little larger than the balance level in which the total interlinkage flux of the applied magnetic field into the compensation coil is equal to that into the main pickup coil. The pickup coil system shall be constructed so that the coiled specimen can be taken in and out easily from the system. The pickup coil method has geometrical errors in relation with the arrangement of the coiled specimen and the pickup coils. The geometrical error is mentioned briefly in Annex C. To achieve a low uncertainty due to geometrical effects of less than 1 %, the following arrangement for the coiled specimen and the two pickup coils shall be the standard one; a height of 30 mm for the coiled specimen, a height of 1 0 mm for the pickup coils, a coil radius of 1 8...