John Smedley

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A real-time LightCycler assay for Legionella pneumophila was evaluated with 120 water samples potentially contaminated with PCR inhibitors. Results were obtained within five hours, with a detection limit equivalent to 800 cells/L. However, 11 of 22 culture-positive samples containing < 100 CFU/L were also positive by LightCycler assay, indicating the(More)
This paper reviews the requirements and current status of cathodes for accelerator applications, and proposes a research and development plan for advancing cathode technology. Accelerator cathodes need to have long operational lifetimes and produce electron beams with a very low emittance. The two principal emission processes to be considered are thermionic(More)
Business and information technology are highly compatible curriculum partners for academic study, providing a multitude of opportunities for enterprise and entrepreneurship. However, training students to successfully operate in today's international, fast-moving technology world requires more than merely curricula encompassing such topics. Appropriate(More)
Fabrication and testing of a prototype transmission-mode pixelated diamond X-ray detector (pitch size 60-100 µm), designed to simultaneously measure the flux, position and morphology of an X-ray beam in real time, are described. The pixel density is achieved by lithographically patterning vertical stripes on the front and horizontal stripes on the back of(More)
Metal photocathodes are commonly used in high-field RF guns because they are robust, straightforward to implement and tolerate relatively poor vacuum compared to semiconductor cathodes. However these cathodes have low quantum efficiency (QE) even at UV wavelengths, and still require some form of cleaning after installation in the gun. A commonly used(More)
Two transmission-mode diamond X-ray beam position monitors installed at National Synchrotron Light Source (NSLS) beamline X25 are described. Each diamond beam position monitor is constructed around two horizontally tiled electronic-grade (p.p.b. nitrogen impurity) single-crystal (001) CVD synthetic diamonds. The position, angle and flux of the white X-ray(More)
The diamond amplifier (DA) is a new device for generating high-current, high-brightness electron beams. Our transmission-mode tests show that, with single-crystal, high-purity diamonds, the peak current density is greater than 400  mA/mm², while its average density can be more than 100  mA/mm². The gain of the primary electrons easily exceeds 200, and is(More)
We report on the status of an electron RF-gun made of two superconductors: niobium and lead. The presented design combines the advantages of the RF performance of bulk niobium superconducting cavities and the reasonably high quantum efficiency of lead, as compared to other superconducting metals. The concept, mentioned in a previous paper, follows the(More)
Diamond sensors are evaluated as incident beam monitors for X-ray absorption spectroscopy experiments. These single crystal devices pose a challenge for an energy-scanning experiment using hard X-rays due to the effect of diffraction from the crystalline sensor at energies which meet the Bragg condition. This problem is eliminated by combination with(More)
Electron emission from the negative electron affinity (NEA) surface of hydrogen terminated, boron doped diamond in the [100] orientation is investigated using angle resolved photoemission spectroscopy (ARPES). ARPES measurements using 16 eV synchrotron and 6 eV laser light are compared and found to show a catastrophic failure of the sudden approximation.(More)