Abstract
A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs) and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode (TEM01*) in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the method and numerical results with reasonable parameters are both presented. It is shown that the temporal resolution can reach up to ∼100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.Received 16 January 2017DOI:https://doi.org/10.1103/PhysRevAccelBeams.20.050702Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam diagnosticsPhysical SystemsFree-electron lasersAccelerators & Beams
Highlights
Ultrashort electron beams with few femtosecond and sub-fs bunch length, have been generated and applied in various fields, such as beam injection studies in laserplasma wakefield accelerator (LWFA) [1] and producing ultrashort X-ray pulses in free-electron lasers (FELs) [2]
A novel scheme using high-power laser as a circular deflector with time-independent as-level resolution is proposed for the longitudinal diagnostics of fs and sub-fs electron beam
The scheme takes advantages of the interactions of the electron beam with a laser operating in doughnut mode in a helical undulator to generate uniform circular kicks in the transverse dimensions
Summary
Ultrashort electron beams with few femtosecond (fs) and sub-fs bunch length, have been generated and applied in various fields, such as beam injection studies in laserplasma wakefield accelerator (LWFA) [1] and producing ultrashort X-ray pulses in free-electron lasers (FELs) [2]. Since the oscillation period of the energy distribution is related to the laser wavelength, the temporal profile can be determined from the modulation Another scheme of optical streaking is the combination of a transverse mode laser and a rf deflecting cavity [16]. It should be noted that in the both schemes above, the temporal resolution depends on the longitudinal coordinate along the beam due to the sinusoidal modulation from the laser, which may have implications for retrieval of complex temporal profiles It is proposed in LWFA recently to utilize the interaction between the electron and the back of the driver laser in plasma to retrieve the beam’s current profile [17,18]
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