IPAC'23 - Student Poster Session Guide

IPAC’23 / STUDENT POSTER SESSION GUIDE 34 Student Poster Session Dielectric wakefield acceleration (DWA) is a promising approach to particle acceleration, offer- ing high gradients and compact sizes. However, beam instabilities can limit its effectiveness. In this work, we present the result of a DWA design that uses alternating gradients to counteract quadrupole-mode induced instabilities in the drive beam. Through simulation and experimen- tal results, we show that this approach is effective at suppressing beam breakup, allowing for longer accelerating structures. We have designed and fabricated a new apparatus for positioning the DWA components in our setup. This allows us to precisely and independently control the gap in both transverse dimen- sions and consequently the strength of the destabilizing fields. Our results show that the use of alternating gradient structures in DWA can significantly im- prove its performance, offering a promising path forward for high-gradient particle accelera- tion. SUPM059 Correlations between cesium antimonide crystallinity and photocathode performance Chad Pennington (Cornell University (CLASSE)) . Elena Echeverria (Cornell University (CLASSE)), John Smedley (SLAC National Accelerator Laboratory), Mengjia Gaowei (Brookhaven National Laboratory), Pallavi Saha, Siddharth Karkare (Arizona State University), Jared Maxson (Cornell University). Thin film alkali antimonide photocathodes are high-efficiency photo-emitting sources for elec- tron accelerators and photon detectors. To date, all alkali antimonide photocathodes used as electron sources in actual accelerators are polycrystalline and disordered. In this proceeding, we demonstrate the synthesis of epitaxial Cs3Sb films with a high degree of crystallinity on silicon carbide substrates using the Pulsed Laser Deposition (PLD) growth method. Films less than 5 nm thin are grown in vacuum and exhibit percent level quantum efficiencies at 532 nm. We find a positive correlation between quantum efficiency and improved crystallinity of the photocathode film, particularly in the longer wavelengths of the visible spectrum. We present a model describing the optical interference effects observed in the SiC - Si substrate multilayer that enhance quantum efficiency of the thin film photocathodes by almost a factor of two at particular wavelengths. Additionally, we characterize the surface and bulk crystallinity of epitax- ial Cs3Sb films using both X-ray diffraction (XRD) and refection high energy electron diffraction (RHEED) to identify relationships between crystalline phases and photocathode performance. SUPM060 First demonstration of spin-polarized electrons from gallium nitride photocathodes Samuel Levenson (Cornell University (CLASSE)) . Debdeep Jena, Huili Xing, Jared Maxson, Jimy Encomendero, Vladamir Protasenko (Cornell Universi- ty), Ivan Bazarov, Matthew Andorf (Cornell University (CLASSE)). For the first time, photoemission of spin-polarized electron beams from gallium nitride (GaN) photocathodes are observed and characterized. The spin polarizations of the emitted electrons from epitaxially grown hexagonal and cubic GaN photocathodes activated to Negative Electron Affinity (NEA) via cesium deposition are measured in a retarding-field Mott polarimeter.