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Reviewing current efforts in X-ray source miniaturization reveals a broad spectrum of applications: Portable and/or
remote nondestructive evaluation, high throughput protein crystallography, invasive radiotherapy, monitoring fluid flow
and particulate generation in situ, and portable radiography devices for battle-front or large scale disaster triage
scenarios. For the most part, all of these applications are being addressed with a top-down approach aimed at improving
portability, weight and size. That is, the existing system or a critical sub-component is shrunk in some manner in order to
miniaturize the overall package.
In parallel to top-down x-ray source miniaturization, more recent efforts leverage field emission and semiconductor
device fabrication techniques to achieve small scale x-ray sources via a bottom-up approach where phenomena effective
at a micro/nanoscale are coordinated for macro-scale effect. The bottom-up approach holds potential to address all the
applications previously mentioned but its entitlement extends into new applications with much more ground-breaking
potential. One such bottom-up application is the distributed x-ray source platform. In the medical space, using an array
of microscale x-ray sources instead of a single source promises significant reductions in patient dose as well as smaller
feature detectability and fewer image artifacts. Cold cathode field emitters are ideal for this application because they can
be gated electrostatically or via photonic excitation, they do not generate excessive heat like other common electron
emitters, they have higher brightness and they are relatively compact. This document describes how ZnO nanowire field
emitter arrays are well suited for distributed x-ray source applications because they hold promise in each of the
following critical areas: emission stability, simple scalable fabrication, performance, radiation resistance and photonic
coupling.
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