SAXS and SANS facilities and experimental practice Clement Blanchet - PowerPoint PPT Presentation

SAXS and SANS facilities and experimental practice Clement Blanchet – EMBL Hamburg

Small Angle Scattering experiment Detector Sample X-ray or neutron 2 θ 2 θ Beam s Buffer The beam hits the sample, X-rays/neutrons interact with the sample and are scattered, providing structural information on the sample. Same formalism but different scattered particles  Different instrument. 10/15/2019 SAXS and SANS facilities 2 Clement Blanchet

Outline • X-rays / neutrons • SAS instruments • Sample environment • Sample requirements and collection strategy 10/15/2019 SAXS and SANS facilities 3 Clement Blanchet

X-rays and neutrons 10/15/2019 SAXS and SANS facilities 4 Clement Blanchet

X-rays Roengten, 1895 10/15/2019 SAXS and SANS facilities 5 Clement Blanchet

Electromagnetic wave 10/15/2019 SAXS and SANS facilities 6 Clement Blanchet

How are X-ray produced? • Brehmstrahlung – When a charge is accelerated charge, electromagnetic radiation is produced 10/15/2019 SAXS and SANS facilities 7 Clement Blanchet

X-ray sources - Synchrotron • Synchrotrons 10/15/2019 SAXS and SANS facilities 8 Clement Blanchet

X-ray sources - synchrotron • Synchrotron radiation – Insertion devices 10/15/2019 SAXS and SANS facilities 9 Clement Blanchet

Insertion devices Undulator (PetraIII) Dipole bending magnet (APS) 10/15/2019 SAXS and SANS facilities 10 Clement Blanchet

Synchrotrons around the world 10/15/2019 SAXS and SANS facilities 11 Clement Blanchet

X-ray sources - FEL • Free electron laser – Electrons are accelerated and send into a long undulator (several 100s meters) – Self amplified spontaneous emission: electrons group themselves into small bunches. – Production of very short and intense X-ray pulses 10/15/2019 SAXS and SANS facilities 12 Clement Blanchet

X-ray sources - FEL • Free electron laser 10/15/2019 SAXS and SANS facilities 13 Clement Blanchet

Lab sources 10/15/2019 SAXS and SANS facilities 14 Clement Blanchet

Lab sources • Principle : electrons, produced by heating a cathode are accelerated in an electric field and projected on a metallic anode. – Brehmstrahlung – Fluorescence 10/15/2019 SAXS and SANS facilities 15 Clement Blanchet

X-ray sources • Lab source (rotating anode, liquid jet) 10/15/2019 SAXS and SANS facilities 16 Clement Blanchet

10/15/2019 SAXS and SANS facilities 17 Clement Blanchet

Neutron James Chadwick λ= h/mv 10/15/2019 SAXS and SANS facilities 18 Clement Blanchet

Neutron production • Nuclear reaction 10/15/2019 SAXS and SANS facilities 19 Clement Blanchet

Neutron production • Spallation source – Accelerated protons hit a heavy metal target. 10/15/2019 SAXS and SANS facilities 20 Clement Blanchet

Neutrons Facilities 10/15/2019 SAXS and SANS facilities 21 Clement Blanchet

SAXS and SANS Instruments 10/15/2019 SAXS and SANS facilities 22 Clement Blanchet

Optics Monochromatic Polychromatic focused (parallel) divergent beam beam for SAS from the source 10/15/2019 SAXS and SANS facilities 23 Clement Blanchet

Monochromatic X-ray • Bragg diffraction on a crystal n λ = 2 d sin θ 10/15/2019 SAXS and SANS facilities 24 Clement Blanchet

Monochromator • Before • Polychromatic • After • One wavelength + harmonics 10/15/2019 SAXS and SANS facilities 25 Clement Blanchet

Focusing/low divergence 2 θ 2 θ • Small beam at the detector position • Small beam at the sample position 10/15/2019 SAXS and SANS facilities 26 Clement Blanchet

Focusing X-ray • Compound refractive lenses • X-ray mirrors 10/15/2019 SAXS and SANS facilities 27 Clement Blanchet

Focusing X-ray • Focussing mirror 1,0 • Reflectivity 0,8 Transmission 0,6 0.15 Degree 0.25 Degree 0,4 1 Degree 0,2 0,0 10000 Energy [eV] 10/15/2019 SAXS and SANS facilities 28 Clement Blanchet

Focussing mirror – harmonics filter Monochromatic, focused x-ray beam 10/15/2019 SAXS and SANS facilities 29 Clement Blanchet

Monochromatic neutrons • De Broglie equation: λ=h/mv The wavelength of a neutron is related to its velocity. • Velocity selector ∆λ/λ =5-10% • For pulsed source, TOF 10/15/2019 SAXS and SANS facilities 30 Clement Blanchet

Collimation neutrons • The collimator is used to obtain a parallel beam 10/15/2019 SAXS and SANS facilities 31 Clement Blanchet

Get rid of parasitic scattering: slits Beam defining slits Guard or anti-scatter slits

Hybrid slits • Idea: use a crystal for the tip of the blade:  no scattering but diffraction 10/15/2019 SAXS and SANS facilities 33 Clement Blanchet

Hybrid slits • On the P12 beamline 10/15/2019 SAXS and SANS facilities 34 Clement Blanchet

Sample environment 10/15/2019 SAXS and SANS facilities 35 Clement Blanchet

Flight tube 10/15/2019 SAXS and SANS facilities 36 Clement Blanchet

Beamstop • Prevent the direct beam from hitting the detector – Big enough to stop the direct beam – Small enough to collect the small angle • Measure transmitted beam 10/15/2019 SAXS and SANS facilities 37 Clement Blanchet

Active Beamstop • SAXS images needs to be accurately scaled to allow for proper buffer subtraction and extraction of the solute SAXS pattern 10/15/2019 SAXS and SANS facilities 38 Clement Blanchet

Detectors Gas detector X-ray film X-rays ionize a gas (argon) producing of ions and free X-rays interacts with silver halide crystals, electrons. electrons are produced by photoelectric effect. A voltage applied to the gas chamber, ions and electrons They gather around crystal defects, dragging the are moved in opposite direction and produce a detectable silver atoms that can be revealed during the current. development phase. 10/15/2019 SAXS and SANS facilities 39 Clement Blanchet

Photostimulated luminescence X-rays interacts electrons of a photostimulable phosphore plate. After exposure, the electrons are trapped in a high energy state. They can be untrapped by laser illumination and go back to their initial state. While doing so, they produce light that can be detected

Hybrid pixel detectors • Each pixel is readout individually: – No readout noise – Fast readout – high frame rate – High dynamic range

Pilatus Eiger 10/15/2019 SAXS and SANS facilities 42 Clement Blanchet

 Count rate capability 10 7 photons/s/pixel  High spatial resolution with 75 µm pixel size  Kilohertz frame rate with dead-time-free readout  Two energy discriminating thresholds  Gateable detection for pump & probe experiments  Large active area for wide angular coverage  Single-pixel point-spread function  No readout noise or dark current  Compact housing  Room temperature operation of all components 10/15/2019 SAXS and SANS facilities 43 Clement Blanchet

Up to 2000 Hz for smaller detectors 10/15/2019 SAXS and SANS facilities 44 Clement Blanchet

Neutron detection • He3 detector: n + 3 He → 3 H + 1 H + 0.764 MeV 10/15/2019 SAXS and SANS facilities 45 Clement Blanchet

Sample environment 10/15/2019 SAXS and SANS facilities 46 Clement Blanchet

Samples SAS applicable to many type of samples. Metal alloys Sufactants Tissues Polymers Nanomagnetic materials Bio-macromolecules in solution 10/15/2019 SAXS and SANS facilities 47 Clement Blanchet

Sample environment Heating stages Magnetic field system Rapid mixing device Sample changers Example ID02 (ESRF) multipurpose beamline 10/15/2019 SAXS and SANS facilities 48 Clement Blanchet

Sample environment • Bio-macromolecules in solution are weakly scattering sample. • For biological macromolecules in solution: – fragile – Preferably in vacuum – Thermostated 10/15/2019 SAXS and SANS facilities 49 Clement Blanchet

Sample cell • Cell material: low absorption and scattering – Mica, quartz, polycarbonate • Sample thickness (t): compromise between scattering and absorption – Scattering α t – absorption α exp(-ut) • For neutron, cell are rather thin (<1mm to avoid multiple scattering) 10/15/2019 SAXS and SANS facilities Clement Blanchet 50

Solution SAXS 15 years ago: Manual sample loading  Buffer and sample should be measured in the same cell  Difficult to implement in vacuum  10-15 minutes per measurement  High sample consumption  Non-optimized cleaning procedure  Tedious, energy and attention consuming 10/15/2019 SAXS and SANS facilities 51 Clement Blanchet

SAXS sample changer @EMBL Hamburg 10/15/2019 SAXS and SANS facilities 52 Clement Blanchet

SAXS sample changer 10/15/2019 SAXS and SANS facilities 53 Clement Blanchet

Sample changer performances • Large storage capacity • Full cycle time (loading, exposure, flushing, cleaning, drying) ≈ 1 min • Volume 5-20 microliter • Very efficient cleaning • Flow measurement 10/15/2019 SAXS and SANS facilities 54 Clement Blanchet

Online size exclusion column 10/15/2019 SAXS and SANS facilities 55 Clement Blanchet