Magnetic Measurements of Superconducting Insertion Devices by Stretched Wire with Direct Current

The main characteristics of multipole insertion devices (ID) are the first and second field integrals along an orbit trajectory in an accelerator. Such integrals of permanent magnets or traditional electromagnets insertion devices can be obtained by means of longitudinal scanning by Hall probes. Measurements of the magnetic field by Hall probes in superconducting IDs have obvious difficulties because of limited space, temperature deviation along the path, etc. Measurements of the integrals by Hall probes, especially when the integrals has to be equal to zero, it is very difficult to make with a necessary accuracy. At Budker INP along with Hall probes the system of magnetic measurements on the basis of the tense wire with a direct current is used. The method is based on similarity of interaction of a direct current in a stretched wire and an electron beam in an accelerator with magnetic field. The stretched wire with current is a good model to describe behavior of an electron beam when passing through a magnet. Especially the method is useful at measurement of superconducting IDs where it isn't enough space for other probes. The method provides a dynamic control of the field integrals in different modes of a magnet operation (field ramp up or down), allows to measure the integrals quickly and rather precisely.