Measurement of ultra-short electron bunch duration by coherent radiation analysis in laser plasma catode

We have performed measurement of electron bunch duration from laser plasma acceleration. Spectrum analysis of the transition radiation from the electron bunch was selected for measurements, using an IR (infrared) bolometer with different filters first. The bunch is estimated to be 30 fs in PIC simulation, but measured duration was 2 ps by the result of bunch elongation at 340 mm downstream from the plasma edge due to broadness of energy spectrum. And then measurement by In-Sb polychromator aiming shot-by-shot measurement is also done. But the signal of transition radiation cannot be detected by X-ray background signal even if shielding by Pb. So we have done optimisation of X-ray shielding and position of detector.