A New Type of Pulsed Air-Core Multipoles of Simple Construction

Because of the rising cost of electric energy, pulsed magnets for beam transport systems attract increasing interest. Especially pulsed air-core systems are advantageous because of their very low weight, small volume and the possibility to install them inside the vacuum system utilizing the good insulating properties of vacuum. This paper describes some general theoretical aspects of pulsed air-core systems as well as two given examples in form of a pulsed quadrupole and a kicker magnet operating at DESY. It is well known that magnetic multipole fields of the order of n may be generated by an axial current on the surface of a circular cylinder with a current distribution of the form I_ocos(n/2·φ). Since for beam optical applications only the integral field over the system length counts, it is a straightforward method to use periodic filamentary conductors on the cylindrical surface with a contour which, on averages, gives a cosine distribution. Due to the skin-effect, thin conducting sheets of the same contour are equally suitable. A rather good approximation is already attainable with comb-like conducting sheets, as will be shown in detail. It is evident that this concept leads to air-core systems of extremely simple construction.