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TY - CONF AU - Kurennoy, S.S. ED - Schaa, Volker RW ED - Pei, Guoxi ED - Chin, Yong Ho ED - Fu, Shinian ED - Zhao, Ning TI - Realistic Modeling of MEBT for the New LANSCE RFQ Injector J2 - Proc. of LINAC2018, Beijing, China, 16-21 September 2018 CY - Beijing, China T2 - Linear Accelerator Conference T3 - 29 LA - english AB - The new RFQ-based proton injector at LANSCE requires a specialized medium-energy beam transfer (MEBT) after the RFQ at 750 keV due to a following long (~3 m) existing common transfer line that also transports H⁻ beams to the DTL entrance. The horizontal space for MEBT elements is limited because two beam lines merge at 18-degree angle. The MEBT includes two compact quarter-wave RF bunchers and four short quadrupoles with steerers, all within the length of about 1 m. The beam size in the MEBT is large, comparable to the beam-pipe aperture, hence non-linear 3D fields at large radii and field-overlap effects become important. With CST Studio codes, we calculate buncher RF fields and quadrupole and steerer magnetic fields, and use them for particle-in-cell beam dynamics modeling of MEBT with realistic beam distributions from the RFQ. Our results indicate significant emittance growth in MEBT not predicted by the standard beam dynamics codes. Its origin is traced mainly to the quadrupole edge fields; the buncher RF fields also contribute noticeably. Proposed design modifications improve the MEBT performance. PB - JACoW Publishing CP - Geneva, Switzerland SP - 211 EP - 213 KW - DTL KW - emittance KW - quadrupole KW - rfq KW - proton DA - 2019/01 PY - 2019 SN - 2226-0366 SN - 978-3-95450-194-6 DO - DOI: 10.18429/JACoW-LINAC2018-MOPO096 UR - http://jacow.org/linac2018/papers/mopo096.pdf ER -