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The Center for Bright Beams, A National Science Foundation Science and Technology Center

Development of sub-nm emittance diagnostics in accelerators

Fuhao Ji, Jorge Giner Navarro, Pietro Musumeci, Daniel Durham, Andrew Minor, Daniele Filippetto

The low emittance measurement system at HiRES. More in Caption.

A diagram showing on the left three blue rectangles representing lenses. A horizontal plane comes off to the right from the lenses and cuts through two black disks. The first disk represents a knife-edge and has a flame-like tongue shooting up from the center where the plan cuts through it. The second disk represents a detector and has a flam coming off to the right from a line running perpendicular to the plane.

Schematic of the low emittance measurement system at HiRES, in which a knife-edge is inserted gradually into the beam along the horizontal and vertical direction near its waist and a detector located downstream records the resulting beam image for each step.

The ability to measure small emittance (volume occupied by the beam in position-momentum phase space) is essential to the development of bright electron beams. CBB researchers and affiliates developed a technique to measure record low (sub-nm) emittances in accelerators using a nano-fabricated knife edge and novel phase space reconstruction algorithms. The reconstruction of the full transverse phase space of bright electron beams is obtained from the precise scan of the beam profile using a nano-fabricated knife-edge in the vicinity of the beam waist. The knife-edge diagnostics allows for a better control of phase space parameters for sub-um beams and, in particular, it has been applied to ultrafast electron diffraction and microscopy experiments. The algorithm has been experimentally demonstrated at the High Repetition-rate Electron Scattering (HiRES) beamline, a recently developed Ultrafast Electron Diffraction and Microscopy instrument at the Lawrence Berkeley Lab.

The development of such precise diagnostics are associated to the characterization of extremely low emittance beams.