Physics design of Quadrupole magnet triplet between IH LINAC 4 and 5 for VECC RIB accelerator project

An ISOL post-accelerator type of RIB facility is being developed at VECC. The post-acceleration scheme consists of RFQ, five IH LINACs and eight superconducting Quarter wave resonators (QWRs) along with other focusing and beam line elements. The final energy at the end of the complete acceleration scheme will be 2 MeV/u. This report presents the physics design of a quadrupole magnet triplet to be placed in between IH LINAC 4 and 5 for transverse focusing and acceptance matching. The 2-d design of this magnet triplet has been completed. Stringent dimension criteria along with lack of sufficient intertank space and need of very high magnetic field gradient make this design process quite challenging. The magnetic field gradient obtained from this design is about 6920 G/cm which is quite close to the value obtained from beam dynamics study. The field gradient uniformity is about 0.22% up to 60% of the magnet aperture. The outer diameter of the magnet has been kept only at 260 mm to cope well with the stringent transverse dimension requirement. The 2-d and 3-d design of this magnet triplet will be presented in this report. (author)