IPAC'23 - Student Poster Session Guide

IPAC’23 / STUDENT POSTER SESSION GUIDE 23 Student Poster Session sextupole separating magnet structure will be described in detail; the numerical simulation of the method of adiabatic passage, the design and testing of the RFT units will also be discussed. SUPM035 Design of a 10.156 MHz Pre-buncher for a heavy ion RFQ Yu Tang , Yao Yang, bo2 zhang, Yuhan Zhai, Zehua Jia, Liangting Sun (Institute of Modern Physics, Chinese Academy of Sciences). LEAF (Low Energy heavy ion Accelerator Facility) is a low-energy high-intensity heavy-ion LINAC complex for multidiscipline research. At present, the beam repetition rate is the same as the LINAC frequency of 81.25 MHz. A lower frequency would be desirable for many types of exper- iments employing time of fight data acquisitions. A method of increasing the bunch spacing to 98 ns by combining a 10.156 MHz pre-buncher before the RFQ and an RF chopper after the RFQ has been proposed. This paper reports the design studies of such a low-frequency pre-bunch- er. A resonator-based buncher is the best choice since lumped circuit-based buncher cannot provide the high voltage we expect for the efficient bunching of ion beams with an A/q of 7. Ac- cording to the simulation result, the bunching efficiency of a 3-harmonic buncher will merely in- crease by 1% compared to a 2-harmonic buncher. We decide to design a two-harmonic buncher based on the little improvement in bunching efficiency. We optimize the length of electrodes so that the utilization of the parasitic field is maximized. The beam dynamics analysis indicates that the voltage amplitude and the RF power can be lowered by 1.3 times and 2.2 times by op- timizing the electrode length. SUPM036 The mechanism of non-uniform distribution of tin sites on the surface of niobium Shuai Wu (Institute of Modern Physics, Chinese Academy of Sciences) . A uniform distribution of nucleation tin sites is essential to the growth of high quality Nb3Sn thin film by vapor diffusion method. The less-nuclear zones were commonly observed in previ- ous nucleation experiments. However, a fully understanding of the occurrence of less-nuclear zones has not yet been achieved. Here, the adsorption energy of nuclear agent SnCl2 on differ- ent crystal planes of niobium (Nb) including Nb (110), Nb (100), Nb (211) are studied through density functional theory (DFT) calculations and several types of adsorption configurations are optimized. The large differences of calculated adsorption energy of SnCl2 on three different crystal planes reveal strong crystal direction selectivity during nucleation stage. In addition, the phenomenon of nucleation experiment on large grain samples further consolidates the accuracy of the calculation results. The calculation results explain the presence of less-nucle- ar zones during nucleation process and provide guidance for the subsequent suppression of these regions.