P.R. Sarma

OPTIMIZATION OF THE PARAMETERS OF AN ION BEAM BUNCHER

To maximize the ion current in a bunch coming out of a beam buncher several parameters have to be optimized. In this paper an analytical method has been developed to optimize these parameters for a sinusoidal buncher and a buncher excited by a combination of the first and second harmonics. Expressions have been given for maximum obtainable bunching efficiency as a function of phase acceptance. The shape of the bunched beam is discussed.

Improvement of field quality of Glaser magnets used for focusing ion beams

Abstract Glaser magnets used for focusing charged particle beams show appreciable aberrations. These aberrations can be reduced by increasing the pole gap, which, however, reduces the focal power also. We have shown that a better way of improving the field quality in Glaser magnets is to taper the poles outwards. The saturation characteristics also are better in tapered poles.

Generating the effect of six harmonics in beam bunchers using only two harmonics

Abstract Bunching efficiency in multi-harmonic bunchers and double-drift bunching systems increases as the number of harmonics is increased. We have proposed a double-drift bunching scheme where one can obtain a bunching effect equal to that of a six-harmonic buncher by using only two harmonics mixed in optimum proportions. The linear programming technique used in optimizing the buncher parameters has been described.

Improvement of field quality in passive magnetic channels by using linear programming technique

Abstract The geometry of the magnetic channels used in cyclotrons for beam extraction and focusing has been optimized by using linear programming technique to produce good field quality. By this procedure we have reduced the deviation in the field gradient not only in the median plane but also in the planes above and below it within the beam aperture.

A Glaser magnet of improved field quality

Abstract Glaser magnets are used for focusing low-energy charged particle beams. But these magnets show appreciable aberrations which cause an increase in the beam emittance. We have designed and fabricated an improved Glaser magnet which reduces these aberrations. This has been achieved by tapering the pole pieces of the magnet.

The measurement of the RMS emittance of an ion beam with an arbitrary density profile

A simple method to evaluate the RMS beam emittance is described. We obtained a relation between the beam parameters and the RMS width of the profile which can be measured by a beam profile monitor and this relation was used to determine the RMS beam emittance. This method is applicable to beams with any kind of density distribution in the phase space.

Optimization of collimating slit sizes to maximize beam transmission

Abstract A method has been worked out to optimize the sizes of a pair of collimators to maximize the beam transmission for nuclear physics experiments. The mathematical treatment takes into account a Gaussian distribution in space as well as angle for the beam. Considerations for choosing the inter slit distance and the second slit to the target distance are given.

A proposed new type of radially and azimuthally varying magnetic field in cyclotrons for enhanced focusing

Abstract For vertical focusing of ions in cyclotrons generally an azimuthal variation is given to the magnetic field with the help of a straight sector geometry or a spiral sector geometry. In the present work a new type of magnetic field, which varies azimuthally and has a periodic radial variation as well, has been proposed. It has been shown that the vertical focusing obtained with the proposed geometry is much stronger than what can be obtained with straight sector geometries.