What if you use a capillary, small specimen or transmission technique “Gun” Mount - Forensic Science Courtesy Forensic Science Laboratory - Germany Film Mount Courtesy Forensic Science Laboratory - Germany Transmission – Combinatorial Analysis - Courtesy Bruker-AXS

Glass Capillary Mount Courtesy of PANalytical

Number of Particles - Reflection Volume of sample in X-ray beam V= (area of beam) (2x half-depth of penetration) Assume area = 1cm x 1cm = 100mm2 t1/2 = 1/m,where m = linear absorption coefficient mSiO2 = 97.6 cm-1 ~ 100 cm-1 = 10 mm-1 V = (100) (2) (10-1) mm3 = 20 mm3

Number of Particles – Capillary Volume of sample in X-ray beam V= (width of beam) (cross-sectional area of capillary) For a 0.7 mm internal diameter capillary V= (width of beam) (0.1225 mm2)  For a 1 cm-wide beam, V = 3.85 mm3 For a 1 mm-wide beam, V = 0.385 mm3 ! However, capillary rotation brings many more particles into Bragg alignment

{ What is usually going to cause you trouble? Texture/orientation effects - affects peak intensity Sample displacement - affects peak 2q position { Bad particle statistics with thin films, small specimens and capillaries Well aligned capillary, film, or transmission system can greatly reduce displacement errors. These systems frequently have an alignment telescope or laser.

Cue for capillary sample preparation movies

Collimators, Slits, Mirrors, Capillaries Control Divergence Tube Tube Glass Capillary Mount Courtesy of PANalytical Transmission – Combinatorial Analysis - Courtesy Bruker-AXS Collimators, Slits, Mirrors, Capillaries Control Divergence

Capillary Technique / Goniometer Head Mark Tubes for μg Specimen : Adjusting the Specimen with the Crosshair and the Laser Spot of the Video Sample Alignment System In most cases the Mark tubes are fastened to a goniometer head. This is screwed onto an additional Phi-circle, which is fastened to the XYZ-stage. The Phi – circle is a particularly attachment of our GADDS system. The specimen is adjusted with the crosshair of the video microscope and the laser spot of the video sample alignment system to the instrument center. Mark Tube on a Goniometer Head Additional Φ-Circle, Fastened to the XYZ - Stage

Fixed / Rotated Specimen Sample Fixed: Sample Rotated: This image shows the data frame from a fixed and from a rotated specimen. Due to the non-isotropic specimen structure - large grains and preferred orientation- the intensity distribution along the Debye-Scherrer cones is inhomogenous in the case of the fixed specimen. In order to obtain better statistics, we prepare most powder specimen with the capillary technique and we use the rotation mode with the phi-circle. Courtesy Forensic Science Laboratory - Germany

I = I e I = Transmitted Intensity I = Incident Intensity - ut o I = Transmitted Intensity I = Incident Intensity u = mass absorption coefficient t = sample thickness o 0.1 cm or less thick, u most organics <10 cm-1

Test of influence of capillary diameter Sample: tetracycline hydrochloride Set of different capillaries: 0.3 mm, 0.5 mm, 0.7 mm, 1 mm, 2 mm Goal: determine influence of capillary diameter on resolution and intensity Data Courtesy of PANalytical

Zoom-in of first peak Data Courtesy of PANalytical Counts 0.3 mm 40000 22500 10000 2500 Data Courtesy of PANalytical 8.40 8.60 8.80 9 Position [°2Theta]

Optimum capillary diameter Sample Absorption Insufficient Volume of specimen in the beam Data Courtesy of PANalytical

Comparison with parabolic mirror   Parallel Beam Parabolic mirror Data Courtesy of PANalytical

Capillaries and Small Specimens Accurate d-spacings Intensity fluctuations Increase collection area (2D detector) Rotate specimen

Summary Experimental Goals and Specimen Parameters Specimen for accurate d-spacing Ideal: Thin specimen Grain size ~ 20-40 mm Purpose: Low penetration Sharp well-resolved peaks Uses: Identification Accurate cells

Summary Experimental Goals and Specimen Parameters Specimen for accurate intensities Ideal: Thick specimen Grain size ~ 1mm Purpose: Avoid preferred orientation Produce smooth profiles Uses: Quantification Structure analysis

Summary Special specimen problems Solid specimens Residual stresses may cause line shifts Large solid specimens Special supports and shielding Thin layers Grazing beam limits penetration Special attachment collimators diffracted rays Reactive specimens Protect from atmosphere Toxic specimens Confine sample

Summary Special specimen problems Radioactive specimens Confine sample and block radiation Small specimens Limited non-specimen scattering Shaped particles Deliberately orient particles Dust specimens Collect on filters