Characterisation of Bright X-Ray Beams by Powder Diffraction Gavin Cheung Supervisor: Prof. Simon Hooker 17 TH ADVANCED ACCELERATOR CONCEPTS WORKSHOP WG7 – RADIATION AAC2016

Application of Brilliant X-Ray Beams Structural biology Materials science Radiotherapy Phase contrast imaging X-ray absorption spectroscopy, etc… 1.Bilderback, D. H., Elleaume, P. & Weckert, E. J. Phys. B At. Mol. Opt. Phys. 38, S773–S797 (2005). 2.Albert, F. et al. Plasma Phys. Control. Fusion 56, (2014).

Application of Brilliant X-Ray Beams Structural biology Materials science Radiotherapy Phase contrast imaging X-ray absorption spectroscopy, etc… Compact source: wakefield accelerators 1.Bilderback, D. H., Elleaume, P. & Weckert, E. J. Phys. B At. Mol. Opt. Phys. 38, S773–S797 (2005). 2.Albert, F. et al. Plasma Phys. Control. Fusion 56, (2014).

Radiation from a Wakefield 1.(Figure) Jinchuan Ju. Electron acceleration and betatron radiation driven by laser wakefield inside dielectric capillary tubes. Université Paris Sud - Paris XI, 2013.

Radiation from a Wakefield 1.(Figure) Jinchuan Ju. Electron acceleration and betatron radiation driven by laser wakefield inside dielectric capillary tubes. Université Paris Sud - Paris XI, 2013.

Measuring Betatron Radiation Techniques: Penumbral imaging (source size) Direct detection (divergence) Ross filter pairs (energy spectrum) Single crystal diffraction (energy spectrum) 1.(Top figure) Kneip, S. et al. Phys. Rev. Spec. Top. - Accel. Beams 15, (2012). 2.(Middle figure) Corde, S. et al. Phys. Rev. Lett. 107, (2011). 3.(Bottom figure) Albert, F. et al. Betatron x-ray production in mixed gases. 8779, 87791Q (2013).

Measuring Betatron Radiation Techniques: Penumbral imaging (source size) Direct detection (divergence) Ross filter pairs (energy spectrum) Single crystal diffraction (energy spectrum) Problems with current techniques: Often requires averaging Assumes a spectral shape Destructive measurement

XCERP Diffraction XCERP Diffraction: X-ray Characterisation by Energy Resolved Powder Diffraction

XCERP Diffraction Non-destructive, single-shot characterisation Retrieval of angular and energy resolved spectrum Single photon method + powder diffraction – Similar to SPEDX technique 1 1.Higginbotham, A. et al. Single photon energy dispersive x-ray diffraction. Rev. Sci. Instrum. 85, (2014).

Why Count Photons? Broadband source → overlapping Debye-Scherrer rings

Why Count Photons? Broadband source → overlapping Debye-Scherrer rings Single photon → pixel count relates to energy

Why Count Photons? Broadband source → overlapping Debye-Scherrer rings Single photon → pixel count relates to energy {111} {220} X-Ray CCD r

Retrieval of Energy Spectrum Dependencies of spectrum of detected photons: – Spectrum of beam incident on powder – Characteristics of powder – Geometry of experiment diffract ???

Dependencies of spectrum of detected photons: – Spectrum of beam incident on powder – Characteristics of powder – Geometry of experiment Calculate Retrieval of Energy Spectrum retrieve

Example: Synchrotron-like spectrum

Example: Retrieval of arbitrary spectrum Does not require assumption of spectral shape

Effect of Divergence

Retrieval of Divergence Can calculate theoretical distribution of radial position & perform least squares minimisation Requires shape of angular distribution to be assumed

Complete Spectral Characterisation Angularly integrated spectrum Energy dependence on distribution of incident angles Angularly resolved spectrum?

Assumed Angularly-Dependent Spectrum

Retrieved Angularly-Dependent Spectrum

Moving Forward with XCERP Implement arbitrary experimental geometries in code Do we need to assume shape of angular distribution? Experimental demonstration of XCERP using betatron radiation from LWFA Experimental demonstration of XCERP using other bright X-ray sources

Overview of Technique Characterise bright X-ray sources – Single shot retrieval – Non-destructive technique – Retrieve angularly-resolved energy spectra Paper accepted on PRAB Thanks for listening!

-End of slides-