Title :
Suppression of the main LEP coupling source
Author :
Billan ; Gourber, J.P. ; Koutchouk, J-P. ; Remondino, V.
Author_Institution :
CERN, Geneva, Switzerland
Abstract :
An unexpected magnetisation of the thin nickel layer of the LEP dipole vacuum chamber has been identified as the main cause of the large horizontal to vertical optical coupling found during the LEP commissioning. Even though the betatron coupling could be much weakened by changing the difference between the tunes from 8 to 6, it was decided, after some tests, to suppress the source itself by demagnetizing the nickel layer of every chamber. An “in situ” method avoiding a removal of the chambers has been developed. The coupling has been reduced by more than a factor 5. The demagnetization suppresses a constraint on the betatron tunes and weakens the horizontal betatron spin resonances
Keywords :
beam handling techniques; particle beam diagnostics; LEP commissioning; LEP dipole vacuum chamber; Ni layer demagnetisation; betatron coupling; betatron tune constraint; horizontal betatron spin resonances; large horizontal to vertical optical coupling; main LEP coupling source suppression; thin Ni layer magnetisation; Aluminum; Demagnetization; Lead; Magnetic field measurement; Magnetic flux; Magnetic hysteresis; Nickel; Resonance; Saturation magnetization; Testing;
Conference_Titel :
Particle Accelerator Conference, 1993., Proceedings of the 1993
Conference_Location :
Washington, DC
Print_ISBN :
0-7803-1203-1
DOI :
10.1109/PAC.1993.309013
