Hsieh, C.-Y. Chen, S.-H. Lin, M.W. JACoW Publishing Geneva, Switzerland 978-3-95450-184-7 10.18429/JACoW-IPAC2018-THPML018 English 4690-4692 THPML018 Contribution to a conference proceedings 2018 2018-06 https://doi.org/10.18429/JACoW-IPAC2018-THPML018 http://jacow.org/ipac2018/papers/thpml018.pdf Laser wakefield accelerator (LWFA) can be achieved in a scheme in which a sub-terawatt (TW) laser pulse is introduced into a thin, high-density target*. As a result, the self-focusing and the self-modulation can greatly enhance the peak intensity of the laser pulse capable of exciting a nonlinear plasma wave to accelerate electrons. A particle-in-cell model was developed to study the sub-TW LWFA, in which a 0.6-TW laser pulse is injected into a hydrogen gas cell with a flat-top density profile. In addition to using 800-nm laser pulses, laser pulses of 1030 nm were used in simulations as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems**. Process of the electron injection is complicated in such a high-density plasma; however, the simulation results show that the appropriate injection and acceleration of electrons can be achieved by optimizing the length of the gas cell. When a 340-micrometer long gas cell is introduced, energetic electrons (> 1 MeV) are produced with a relatively low emittance of 3.5 pi-mm-mrad and a total charge of 0.32 nC accordingly.