MacArthur, J.P. Duris, J.P. Huang, Z. Marinelli, A. JACoW Geneva, Switzerland 978-3-95450-182-3 10.18429/JACoW-IPAC2017-WEPAB118 English 2848-2850 WEPAB118 Contribution to a conference proceedings 2017 2017-05 http://dx.doi.org/10.18429/JACoW-IPAC2017-WEPAB118 http://jacow.org/ipac2017/papers/wepab118.pdf The desire to resolve sub-femtosecond electron dynamics has pushed FEL facilities to shorter pulse lengths. However, current short-pulse schemes provide low pulse energy and a gain-length limited lower bound on the pulse duration. The X-ray Laser-Enhanced Attosecond Pulses (XLEAP) project at SLAC is designed implement an Enhanced Self Amplified Spontaneous Emission (ESASE) scheme, which produces sub-fs current spikes by modulating and compressing the electron beam. We show through a series of Genesis simulations that the current spike is capable of producing sub-fs pulses with a peak power well above 100 GW. Space-charge induced beam chirp can decrease pulse lengths below 400 as, and multi-stage schemes can increase peak x-ray powers to around 1 TW.