Search

The gradient method for measuring the transversal emittance of a high current ion beam in the injection channel of the cyclotron DC-72 is considered. The standard scanner is proposed for measuring the transversal dimensions of the beam. The formulae for determination of the mean square beam dimensions by current signals from the scanner needle are adduced. The method of the emittance recovery for axial-symmetric ion beam is set for the case when the space charge effect is essential. The algorithm for tuning of the quadrupole lenses in the injection channel of the cyclotron DC-72 for obtaining the axial-symmetric ion beam is proposed. The evaluations of the expected accuracy of the proposed method for the emittance recovery have been carried out.

The methods of measuring of the transversal emittance of ion beams in the cyclotron DC-72 injection channel with the help of the 'pepper-pot' and gradient means are discussed in this work. Two ways for the reconstruction of the ion beam transversal emittance are proposed for the 'pepper-pot' method. The first one can be used for beams having the uniform distribution of particles in the phase space. At that the values of the Twiss matrix and the full beam emittance are reconstructed according to the measurement results with the help of the phase ellipse fitting by the least-squares method. The corresponding FORTRAN code was created. On simulation the beam emittance was reconstructed with accuracy of 5%. The second method of the beam emittance reconstruction can be used in the common case at the arbitrary particle distribution in the phase space. It is based on calculation of the mean-square parameters of the beam according to the measurement results in the plane of the 'pepper-pot' mask. The mean-square emittance of the model-based beam was reconstructed with the help of this method with an accuracy of 2%. It was shown that taking into account the beam magnetization does not insert any essential error in the value of the reconstructed emittance. Both methods gave the emittance value of the magnetized ion beam, divergent from its calculated value, not more than on 5% also. The simulation of the beam emittance measurement was also carried out with the help of the gradient method. The fulfilled calculations showed that when the beam current in the injection channel is up to 100 mu A its transversal emittance can be reconstructed according to the measurement results with the accuracy not more than 10%. For the beam currents exceeding the mentioned value it is necessary to take into account its space charge when working on the measurement results.