Olin Student Projects 2007

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

2. USB X-ray Flux Meter X-ray Detector With Simple Preamp ~10 mV BNC • 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 ~10 nsec USB Controls Amplifier USB Controls Trigger Circuit FPGA? Comparator? USB Time, cnts/sec Or Time, pulseheight Computer

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: Detector X-rays in 2 d 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… Computer interface with event processing CCD control and readout electronics  Diffracted and fluoresced X-rays Four-dimensional event list: time, x, y, energy for each detected X-ray X-ray source x y CCD Apply geometry 2 Collimated X-ray beam  z time, , ,  for each event Sample at (xo,yo,zo) Apply Bragg’s law, n = 2d sin() An X-ray source producing Bremsstrahlung continuum X-rays (0.1-10 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. time, d-spacing,orientation, energy for each event.

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?