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. 6/20/2016 SAXS and SANS facilities 2 Clement Blanchet

Outline • X-rays / neutrons • SAS instruments • Sample environment • Sample requirements and collection strategy 6/20/2016 SAXS and SANS facilities 3 Clement Blanchet

X-rays and neutrons 6/20/2016 SAXS and SANS facilities 4 Clement Blanchet

X-rays Roengten, 1895 6/20/2016 SAXS and SANS facilities 5 Clement Blanchet

Electromagnetic wave 6/20/2016 SAXS and SANS facilities 6 Clement Blanchet

How are X-ray produced? • Brehmstrahlung – When a charge is accelerated charge, electromagnetic radiation is produced (from Maxwell equation) 6/20/2016 SAXS and SANS facilities 7 Clement Blanchet

X-ray sources - Synchrotron • Synchrotrons 6/20/2016 SAXS and SANS facilities 8 Clement Blanchet

X-ray sources - synchrotron • Synchrotron radiation – Insertion devices 6/20/2016 SAXS and SANS facilities 9 Clement Blanchet

Insertion devices Undulator (PetraIII) Dipole bending magnet (APS) 6/20/2016 SAXS and SANS facilities 10 Clement Blanchet

Synchrotrons around the world 6/20/2016 SAXS and SANS facilities 11 Clement Blanchet

X-ray sources - FEL • Free electron laser – Electrons are accelerated and send to 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 6/20/2016 SAXS and SANS facilities 12 Clement Blanchet

X-ray sources - FEL • Free electron laser 6/20/2016 SAXS and SANS facilities 13 Clement Blanchet

Lab sources 6/20/2016 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 6/20/2016 SAXS and SANS facilities 15 Clement Blanchet

X-ray sources • Lab source (rotating anode, liquid jet) 6/20/2016 SAXS and SANS facilities 16 Clement Blanchet

6/20/2016 SAXS and SANS facilities 17 Clement Blanchet

Neutron James Chadwick λ= h/mv 6/20/2016 SAXS and SANS facilities 18 Clement Blanchet

Neutron production • Nuclear reaction 6/20/2016 SAXS and SANS facilities 19 Clement Blanchet

Neutron production • Spallation source – Accelerated protons hit a heavy metal target. 6/20/2016 SAXS and SANS facilities 20 Clement Blanchet

Neutrons Facilities 6/20/2016 SAXS and SANS facilities 21 Clement Blanchet

SAXS and SANS Instruments 6/20/2016 SAXS and SANS facilities 22 Clement Blanchet

Optics Monochromatic Polychromatic focused (parallel) divergent beam beam for SAS from the source 6/20/2016 SAXS and SANS facilities 23 Clement Blanchet

Monochromatic X-ray • Bragg diffraction on a crystal n λ = 2 d sin θ 6/20/2016 SAXS and SANS facilities 24 Clement Blanchet

Monochromator • Before • Polychromatic • After • One wavelength + harmonics 6/20/2016 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 6/20/2016 SAXS and SANS facilities 26 Clement Blanchet

Focusing X-ray • Compound refractive lenses • X-ray mirrors 6/20/2016 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] 6/20/2016 SAXS and SANS facilities 28 Clement Blanchet

Focussing mirror – harmonics filter Monochromatic, focused x-ray beam 6/20/2016 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 6/20/2016 SAXS and SANS facilities 30 Clement Blanchet

Collimation neutrons • The collimator is used to obtain a parallel beam 6/20/2016 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 6/20/2016 SAXS and SANS facilities 33 Clement Blanchet

Hybrid slits • On the P12 beamline 6/20/2016 SAXS and SANS facilities 34 Clement Blanchet

Sample environment 6/20/2016 SAXS and SANS facilities 35 Clement Blanchet

Flight tube 6/20/2016 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 6/20/2016 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 6/20/2016 SAXS and SANS facilities 38 Clement Blanchet

Detectors 6/20/2016 SAXS and SANS facilities 39 Clement Blanchet

CCD detector 6/20/2016 SAXS and SANS facilities 40 Clement Blanchet

6/20/2016 SAXS and SANS facilities 41 Clement Blanchet

Single photon counting detector principle 6/20/2016 SAXS and SANS facilities 42 Clement Blanchet

Single photon counting detector Pilatus – High dynamic range – No background noise – (relatively) Fast framing  Ideal for SAXS 6/20/2016 SAXS and SANS facilities 43 Clement Blanchet

Neutron detection • He3 detector: n + 3 He → 3 H + 1 H + 0.764 MeV 6/20/2016 SAXS and SANS facilities 44 Clement Blanchet

Sample environment 6/20/2016 SAXS and SANS facilities 45 Clement Blanchet

Samples SAS applicable to many type of samples. Metal alloys Sufactants Tissues Polymers Nanomagnetic materials Bio-macromolecules in solution 6/20/2016 SAXS and SANS facilities 46 Clement Blanchet

Sample environment Heating stages Magnetic field system Rapid mixing device Sample changers Example ID02 (ESRF) multipurpose beamline 6/20/2016 SAXS and SANS facilities 47 Clement Blanchet

Sample environment • Bio-macromolecules in solution are weakly scattering sample. • For biological macromolecules in solution: – fragile – Preferably in vacuum – Thermostated 6/20/2016 SAXS and SANS facilities 48 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 6/20/2016 SAXS and SANS facilities Clement Blanchet 49

Solution SAXS 10 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 6/20/2016 SAXS and SANS facilities 50 Clement Blanchet

SAXS sample changer @EMBL Hamburg 6/20/2016 SAXS and SANS facilities 51 Clement Blanchet

SAXS sample changer 6/20/2016 SAXS and SANS facilities 52 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 6/20/2016 SAXS and SANS facilities 53 Clement Blanchet

Online size exclusion column 6/20/2016 SAXS and SANS facilities 54 Clement Blanchet

SEC + SAXS Defined buffer region 6/20/2016 SAXS and SANS facilities 55 Clement Blanchet

Experimental practice 6/20/2016 SAXS and SANS facilities 56 Clement Blanchet

Buffer subtraction 6/20/2016 SAXS and SANS facilities 57 Clement Blanchet

Buffer subtraction • Biological sample scatters very weakly, SAXS curves collected on the buffer should be carefully subtracted – Exactly matching buffer (dialysis, elution buffer) – Sample and buffer measured in the same cell 6/20/2016 SAXS and SANS facilities 58 Clement Blanchet

Monodispersity • SAS is very sensible to aggregation, the sample should be monodisperse 6/20/2016 SAXS and SANS facilities 59 Clement Blanchet

Monodispersity • Check the monodispersity of your sample before coming to the beamline. (native gel, dynamic light scattering, ultracentrifugation,…) • Use online chromatography 6/20/2016 SAXS and SANS facilities 60 Clement Blanchet

Inter-particle interactions 6/20/2016 SAXS and SANS facilities 61 Clement Blanchet