Author: Goswami, A.
Paper Title Page
WEPPT004 Feasibility Study of Intense Beam Matching at the Spiral Inflector Using Elliptical Solenoid 326
  • A. Goswami, V.S. Pandit, P. Sing Babu
    VECC, Kolkata, India
  Simulation results on a spiral inflector for compact cyclotron, indicate that convergent phase ellipses with different orientations in x and y planes and a comparatively smaller width in the y plane gives better beam transmission through the inflector. In order to transform the axisymmetric beam to a non-axisymmetric beam for matching at the entrance of the inflector one needs either an elliptical solenoid or a quadrupole doublet. The injection system of 10MeV-5mA proton cyclotron being developed at VECC consists of a 2.45GHz (80keV) microwave ion source and two solenoids to transport and match the beam at the spiral inflector. Due to space constraint we have planned to use an elliptical solenoid just before the spiral inflector for transverse matching of the beam. In this work the beam optical properties of an elliptical solenoid have been studied, including the effect of space charge. An envelope model based on the canonical description of motion has been developed and utilized to study the feasibility of using an elliptical solenoid for transverse matching of a space charge dominated beam to the acceptance of a spiral inflector.  
WEPPT019 Investigation on the Transverse Emittance Growth of Intense Beam during Bunching 361
  • P. Sing Babu, A. Goswami, V.S. Pandit
    VECC, Kolkata, India
  Bunchers are widely used in the injection system of cyclotrons to transform dc beam into a bunched beam in a desired phase width. In the case of low beam current, the longitudinal compression of beam has very little effect on the transverse dynamics. However in the case of high current bunching the increase of current in the specified bunch width as the beam advances affects the transverse behavior. A 2D particle-in-cell code has been developed to study the transverse dynamics during beam bunching in the injection system of 10MeV, 5mA compact proton cyclotron. We have used a linear increase of beam current in the specified bunch width from the buncher position to the time focus. In the PIC method this effect is introduced by reweighting the charge and mass of the macroparticles during the transport with longitudinal compression. The evolutions of beam envelope and emittance growth have been estimated for various initial particle distributions. It is observed that the rms beam size is independent of particular beam distribution whereas rms emittance grows with nonuniformity of the distribution and peaks near the time focus.