Ultrafast Electron Diffraction Device for Time-Resolved Chemical Imaging

Generation and preservation of high-brightness electron beam is a major challenge of accelerator R & amp;D for time-resolved chemical imaging applications due to the importance of space-charge in this operating regime. The space-charge forces play a fundamental role in emittance degradation and bunch lengthening within the gun and subsequent emittance compensation drift. In order to generate and preserve the electron beam, transverse and longitudinal space-charge effects have to be precisely managed. Several different approaches, such as single-electrons at high repetition rate, and various velocity bunching and magnetic compression techniques, are being actively pursued. However, each has drawbacks that our proposed tabletop, single-shot, ultrafast, high-brightness system resolves. In a pump-probe setup with femtosecond resolution, our instrument enables the chemical imaging of surface dynamics on an atomic level. The technical objective of the present project is to develop a tabletop single-shot, ultrafast, high- brightness, Time-Resolved Chemical Imaging device utilizing an X-band RF gun that has a smaller footprint and is more economic than competing schemes. In Phase I, we have performed simulations that demonstrate the potential of our concept to deliver a 20 pC, & lt; 75 femtosecond electron bunch that is more than three times brighter than an equivalent S-band photocathode gun. We have completed the preliminary engineering analysis and design to demonstrate that the concept is robust and viable for near-term fabrication. In Phase II, we will complete the design and fabrication of the UED electron source. We have worked with the BNL/ATF Facility to develop a test program and received approval for the necessary facility modifications and schedule for completing Phase II validation experiments. The Phase II experimental setup will be a functional prototype UED device that will lead to near-term commercial sales. Commercial Applications and Other Benefits: The prototype X-band RF electron source we propose would find immediate application as a tabletop Ultrafast Electron Diffraction (UED) system for time-resolved chemical imaging, and as a resource for the pharmaceutical industry in drug-cell interaction analysis. Being compact and affordable with femtosecond temporal resolution, the instrument will deliver added value and increase the accessibility of smaller programs/users to existing ultrafast discovery science, and will also enable new applications with significant public benefit. As an advanced accelerator driver, significant future opportunities in medical systems and other commercial fields that require higher energy and seek highly compact devices, will emerge.