Gillette, P

Leboucher, C

Lecorché, E

Lemaître, E

Moscatello, M H

Savalle, A

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AUTOMATIC BEAM TUNING AT GANILA. Savalle, P. Gillette, E. Lemaitre, E. Lecorche, C. Leboucher, M.H. MoscatelloGrand Acclrateur National d’Ions Lourds, IN2P3(CNRS)-DSM(CEA), BP 5027, 14021 CAENCEDEX, FRANCEAbstractThe GANIL facility consists of 3 successive cyclotrons : C01 or C02, CSS1,CSS2. A fourth one : CIME, is to be added in 1999 (SPIRAL project). Thetuning of these cyclotrons, including the transfer beam lines, may be achievedin approximately 24 hours. Efforts must be made to reduce the time necessaryto set up the machine, and to improve beam intensity and quality.Thus, the tuning is progressively made automatic. As regards the beam lines,our programs have been written these two last years. Automatic transversematching and beam centering are now operational.The GANIL beam lines are composed of sections with separated functions.The matching section includes 4 magnetic quadrupoles and 3 beam profilemonitors. By construction, the beam is matched if the beam presents a cross-over on the central profiler, and if the beam size on the middle profile monitoris half of the value of the other ones. This disposition made the matching easyto check visually.The quadrupoles are initially set to theoretical values. The manual tuning con-sisted in varying one quadrupole, visualizing the effect on the beam sizes, thentrying another quadrupole, and so on.The automatic matching program uses now an on-line beam optics calculation.It first translates the beam sizes on the 3 profile monitors in terms of emittanceand betatron functions. The second step is to calculate the betatron functions atthe entrance of the first quadrupole, using the transfer matrix from one point toanother. The third step is to optimize this transfer matrix, so that the betatronfunctions correspond to a matched beam.Automatic matching is operationnal since the beginning of 1997, and reallymakes the tuning easier.Similarly, an automatic beam centering program is now used.The first step of the method is to measure the beam center of gravity as seenby the wire profile monitors.The second is to calculate the matrix M related to the effect of each steereron each monitor. Let P be the vector of the beam centers of gravity and Sbe the vector of the steerers intensities. It is desired that :   .Thus, the solution may be determined as : 	  with the transposition of the matrix M. This coresponds to a least-squares fit. Inaddition, the corrector values are simultaneously minimized.The results of the beam centering program are very convenient. The beamcenters of gravity in both planes after automatic beam centering are bellow 1mm, and the tuning is really faster and more reproducible.In writing these programs, the main work was to add all the data needed in thebeam optics calculation in the data base used for operation. This addition has48required some modification of the structure of this data base, and, thus, somemodification of other programs.49

Automatic beam tuning at GANIL

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