Title :
Observation of a periodic pattern in the persistent-current fields of the superconducting HERA magnets
Author :
Brück, H. ; Gall, D. ; Krzywinski, J. ; Meinke, R. ; Preissner, H. ; Halemeyer, M. ; Schmüser, P. ; Stolzenburg, C. ; Stiening, R. ; ter Avest, D. ; van de Klundert, L.J.M.
Author_Institution :
DESY, Hamburg, Germany
Abstract :
During an experimental study of the time dependence of a HERA dipole, it was found that the sextupole field exhibits a sinusoidal structure along the axis of the magnet. A similar periodic structure was found for the main dipole field with the help of a nuclear magnetic resonance probe. The wavelength of the periodic pattern is compatible with the transposition pitch of the Rutherford-type cable in the magnet coils. The effect is related to superconducting currents in the cable because it vanishes when the magnet is warmed up above its critical temperature. The structure was found to exist in all HERA dipoles measured afterwards ( approximately 10) and also in a superconducting coil without iron yoke. With a specially developed 2-cm-long pickup coil, it was found that all accessible multipole components in dipole and quadrupole magnets are modulated along their axis.<>
Keywords :
beam handling equipment; electron accelerators; magnetic field measurement; storage rings; superconducting magnets; 2 cm; HERA dipole; Rutherford-type cable; magnet coils; main dipole field; periodic pattern; persistent-current fields; pickup coil; quadrupole magnets; sextupole field; sinusoidal structure; superconducting coil; superconducting currents; superconducting magnets; Iron; Magnetic modulators; Magnetic resonance; Nuclear magnetic resonance; Periodic structures; Probes; Superconducting cables; Superconducting coils; Superconducting magnets; Temperature;
Conference_Titel :
Particle Accelerator Conference, 1991. Accelerator Science and Technology., Conference Record of the 1991 IEEE
Conference_Location :
San Francisco, CA, USA
Print_ISBN :
0-7803-0135-8
DOI :
10.1109/PAC.1991.164895
