A High Resolution Single-Shot Longitudinal Profile Diagnostic Using Electro-Optic Transposition

Electro-Optic Transposition (EOT) is the basis for an improved longitudinal bunch profile diagnostic we are developing in ASTeC as part of the CLIC UK research program. The scheme consists of transposing the Coulomb field profile of an electron bunch into the intensity envelope of an optical pulse via the mixing processes that occur between a CW laser probe and Coulomb field in an electro-optic material. This transposed optical pulse can then be amplified and characterised using robust laser techniques ' in this case chirped pulse optical parametric amplification and frequency resolved optical gating, allowing the Coulomb field to be recovered. EOT is an improvement over existing techniques in terms of the achievable resolution which is limited by the EO material response itself, reduced complexity of the laser system required since nanosecond rather than femtosecond lasers are used, and insensitivity of the system to bunch-laser arrival time jitter due to using a nanosecond long probe. We present results showing the retrieval of a THz pulse (Coulomb field stand-in) which confirms the principle behind the EOT system.