Novel Single Shot EO based 3D Bunch Charge Distribution Monitor with Femto-second Bunch Resolution

Friday 4 Sept 2009, 11:30 → 12:30 Europe/Rome

Franco Tazzioli Room (Bldg. 2) (Laboratori Nazionali di Frascati, Via Enrico Fermi 40, Frascati)

ABSTRACT

High-brightness electron bunches are required with low slice emittance and bunch length of 30 fs (FWHM) in a targeting lasing part for XFEL/SPring-8. To obtain maximum brightness, it is very important to measure 3D bunch charge distribution (BCD) in real time. In order to measure the temporal distribution of several-tens-femtosecond bunches, the measurement with an RF deflector is the most reliable method at present and it is planning to install in XFEL/SPring-8. It is, however, a destructive measurement and cannot be used in operation for SASE (Self-Amplified Spontaneous Emission) generation. Therefore, another measurement system without destruction of the electron bunches is also required for a beam tuning to generate stable SASE radiation as a user facility. In EO-based bunch duration measurements, the temporal resolution is limited to 120 fs (FWHM) at present because ZnTe and GaP, which are widely used EO crystals, have the absorption at 5 THz and 11 THz, respectively. In order to achieve 30-fs temporal resolution, EO material should be transparent up to 30 THz. One candidate for such a material is DAST crystal, which is an organic EO material. Because the DAST crystal is used as the broadband THz source (more than 20 THz), it is also expected to be effective for the ultrashort bunch duration measurements. In this seminar, I report the developing status of the broadband probe laser pulse and the optical components for its transportation.