Speaker
Maxwell LaBerge
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.2005.pdf
LPA Electron Bunch Spatial Reconstruction Through CTR Imaging
M. LaBerge1,2, O. Zarini2, A. Hannasch1,2, R. Zgadzaj1,2, J. Couperus2, A. Köhler2,
A. Debus2, A. Lumpkin3, A. Irman2, M. C. Downer1,2
1
University of Texas at Austin, Austin, USA
2
Helmholtz-Zentrum Dresden Rossendorf, Rossendorf, Deutschland
3
Fermi National Accelerator Laboratory, Batavia, USA
Due to their tiny accelerating cavities, laser-plasma accelerators (LPAs) can produce
extremely low-emittance e-beams, but to date the smallest transverse LPA e-beam sizes have
been characterized only indirectly inside the LPA by betatron x-ray spectroscopy. Here we
report observations of visible coherent transition radiation (CTR) imaged from a foil placed
immediately (<1mm) outside a ~300 MeV, 300 pC bubble-regime LPA. We use a double
foil: the first reflects the drive laser pulse; the front edge of the second foil (0.5-1mm
downstream) rejects emission from the first foil, while its back surface emits CTR from
transmitted LPA e-bunches. We observe radially polarized annular distributions with a
strong central minimum at many different wavelengths, which allows us to characterize the
beam shape. The size and radial distribution of the CTR images, which we observe in
conjunction with CTR and electron spectra, vary significantly and reproducibly as we
translate the double foil over a ~1mm range along the e-beam propagation axis. We will
present CTR data in conjunction with an e-beam 3D reconstruction model.
