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Olin Student Projects 2007 Keith Gendreau NASA/GSFC 301-286-6188.

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Presentation on theme: "Olin Student Projects 2007 Keith Gendreau NASA/GSFC 301-286-6188."— Presentation transcript:

1 Olin Student Projects 2007 Keith Gendreau NASA/GSFC

2 USB X-ray Flux Meter Will have MANY uses at GSFC –X-ray source stability monitor at 600m beamline –Calibrator of new X-ray Diffractometer/Fluorescence Instrument Design and build a USB connected pulse counter that can be connected to a fast X- ray detector for purposes of monitoring X- ray flux. Project would involve circuit design –FPGA developer boards with USB interface? –Other USB developer boards –Pulse Processor Simple comparotr trigger? Multiple Pulseheight Triggers (eg build up spectrum AND countrate) Pulse Profile Fitting? – Input from “Generic” X-ray Detector APD (Simple to implement anywhere) Proportional Counter Software design –USB Driver –Pulseheight Analysis X-ray Detector With Simple Preamp BNC Amplifier Trigger Circuit FPGA? Comparator? USB Computer USB Controls USB Controls ~10 mV ~10 nsec Time, cnts/sec Or Time, pulseheight

3 Material Identification using a simultaneous X- ray diffractometer/Fluorescence instrument. GSFC has developed a new type of X-ray Diffractometer (XRD) using instruments and techniques developed for X-ray astrophysics XRD measures the spacing between atomic planes in materials using X-rays as rulers Data sets are very rich Q: what is the minimum number of photons needed to ID a material with this instrument? This will take longer to explain, but is VERY cool

4 Material analysis with X-rays: fluorescence (XRF) and diffraction (XRD) XRF — Elemental abundances through spectroscopy XRD — Bragg's law describes how atomic plane spacings may be measured: d 22 X-rays in Detector Traditional monochromatic XRD methods must vary sample-detector geometry, or randomize crystal orientations by powderizing the sample: destructive!

5 Multidimensional XRD CCDs provide energy (wavelength) and position information for individual photons. Using continuum radiation literally opens up a new dimension. The richness of the resulting data is surprising… CCD control and readout electronics Computer interface with event processing Four-dimensional event list: time, x, y, energy for each detected X-ray time, , , for each event time, d-spacing, orientation, energy for each event. Apply geometry Apply Bragg’s law, n = 2d sin(  ) An X-ray source producing Bremsstrahlung continuum X-rays ( keV) sends a collimated beam toward a sample. The X-rays either diffract from atomic planes in the sample or excite characteristic line emission. A photon-counting, energy-resolving CCD captures some of the resulting X-rays, producing an event list that can be transformed into both fluorescence (elemental composition) and diffraction (mineral atomic-plane spacing) information on an event-by-event basis. Sample at (x o,y o,z o ) CCD X-ray source Collimated X-ray beam Diffracted and fluoresced X-rays x y z 22  

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7 The $15 X-ray CCD Camera Go to K-mart or someplace and buy a cheap webcam. Carefully remove housing Using a razor and knife, carefully remove the glass cover of the CMOS detector Put in a dark box with a radioactive X-ray source See X-rays Q: can we hack the software of these camera to process the frames to extract X-ray events?


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