X-ray Imaging Detector Using Silicon Field Emission Tip Array Energy Conversion

Existing x-ray detecting technologies can be classified as either photon-counting (digital) or integrating (analog). Multi-wire proportional counters (MVVPC) are digital detectors that have advantages such as high quantum sensitivity, high dynamic range, and high intrinsic energy resolution, and have a wide range of applications. However, most photon-counting detectors rely on gas conversion of the incident x-ray into pnmary electrons, and cannot attain both high count rate capability and high spatial resolution [I]. These have been replaced, in many cases, by analog integrating detectors, such as CCD-coupled cameras. Unfortunately, the latter are less sensitive, not real-time, have limited dynamic range and energy resolution [2]. There remains the need for faster photon-counting detectors. Although new "microgap" gas detectors and Si pixel array detectors have been developed for higher counting rates, the former has its maximum gain limited by discharges, while the latter requires a complex and expensive readout system [3]. We present here an x-ray detector based on Si field-emission tip technology. The x-ray is first converted to EIHPs in the substrate Si The electrons are emitted into vacuum from spatially-distinct nanoscale field emission tips fabricated on the back-side of the conversion layer, and detected using an imaging multi-channel plate (MCP). The imager is conceptually depicted in Fig. I..