Nozawa, I. Gohdo, M. Kan, K. Kondoh, T. Yang, J. Yoshida, Y. JACoW Geneva, Switzerland 978-3-95450-177-9 10.18429/JACoW-IBIC2016-TUPG64 English 499-501 TUPG64 electron radiation linac gun detector Contribution to a conference proceedings 2017 2017-02 http://dx.doi.org/10.18429/JACoW-IBIC2016-TUPG64 http://jacow.org/ibic2016/papers/tupg64.pdf Generation and diagnosis of ultrashort electron bunches are one of the main topics of accelerator physics and applications in related scientific fields. In this study, ultrashort electron bunches with bunch lengths of femtoseconds and bunch charges of picocoulombs were generated from a laser photocathode RF gun linac and an achromatic arc-type bunch compressor. Observing coherent transition radiation (CTR) emitted from the electron bunches using a Michelson interferometer, the interferograms of CTR were measured experimentally. The bunch lengths were diagnosed by performing a model-based analysis of the interferograms of CTR.