RUI: Electron Beam Production for Optical-Scale Accelerators using Pyroelectric Crystal Arrays

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This experimental research project aims to demonstrate a mechanism for producing miniature electron particle accelerators using unusual materials: pyroelectric crystals, which create strong electric fields during heating and cooling. Particle accelerators have been an essential part of scientific research into the fundamental properties of matter, but are also critical tools in modern medicine, defense applications, and industry. Typical accelerators are large and costly, but new types of accelerators which have the potential to provide electron beams using a tiny (millimeter-sized) device that can be built cheaply on a silicon wafer are now being developed. However, these microaccelerators also require new kinds of miniature electron beam sources: the injected beam should be about 1 micrometer (a millionth of a meter) wide, but have a speed near that of light. This research project aims to demonstrate a mechanism for producing such a beam using pyroelectric crystals. This project will be carried out at a small liberal-arts college, giving undergraduate students the opportunity to participate directly in cutting-edge research and contributing to the training of the next generation of scientists. The project will also enable development of new teaching tools for undergraduate lab courses.The technical objectives of this project are to demonstrate a novel injector scheme, capable of producing near-relativistic micron-scale electron beams that are suitable for use with dielectric-based microaccelerators and also potentially valuable as a small-footprint beam and radiation source. Fields provided by an array of pyroelectric crystals enable field emission from an array of nanoemitters and then accelerate the emitted beam to near-relativistic velocities. The use of pyroelectrics allows high accelerating fields and output energies without the need for large external voltages. This concept is supported by experimental measurements to date on lithium niobate crystals. The approach involves a narrow vacuum channel through the center of a three-crystal array, which is predicted to produce highly uniform accelerating fields of tens of MV/m, and in which a submillimeter patch of carbon nanotubes will be inserted. Projected output current is in the nanoampere range, with energy greater than 250 keV. Complete measurement of output beam parameters will be performed, enabling improved understanding of the physics and engineering principles of the pyroelectric accelerator, and leading to an optimized design for an application-ready injector module. This project will also yield more complete information about pyroelectric materials, including optimal heating modalities, internal and surface fields, and the time structure of their response.