Decker, F.-J. Bane, K.L.F. Colocho, W.S. Lutman, A.A. Sheppard, J.C. JACoW Geneva, Switzerland 978-3-95450-179-3 10.18429/JACoW-FEL2017-TUP023 English 288-291 TUP023 ion photon wakefield experiment gun Contribution to a conference proceedings 2018 2018-02 https://doi.org/10.18429/JACoW-FEL2017-TUP023 http://jacow.org/fel2017/papers/tup023.pdf To get two electron bunches with a separation of up to 1 microsecond at the Linac Coherent Light Source (LCLS) is important for LCLS-II developments. Two lasing bunches up to 220 ns have been demonstrated. Many issues have to be solved to get that separation increased by a factor of 5. The typical design and setup for one single bunch has to be questioned for many devices: RF pulse widths have to be widened, BPMs diagnostic can see only one bunch or a vector average, feedbacks have to be doubled up, the main Linac RF needs to run probably un-SLEDed, and special considerations have to be done for the Gun and L1X RF.