Kongmali, K. Apiwattanakul, P. Jitvisate, M. Kangrang, N. Lithanatudom, P. Rimjaem, S. Saisut, J. Thongbai, C. JACoW Publishing Geneva, Switzerland 2673-5490 978-3-95450-227-1 10.18429/JACoW-IPAC2022-WEPOTK036 English 2146-2149 Contribution to a conference proceedings 2022 2022-07 https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK036 https://jacow.org/ipac2022/papers/wepotk036.pdf At present, one of diseases that kills many people worldwide is cancer. The FLASH radiotherapy (RT) is a promising cancer treatment under study. It involves the fast delivery of RT at much higher dose rates than those currently used in clinical practice. The very short time of exposure leads to the destruction of the cancer cells, while the nearby normal cells are less damaged as compared with conventional RT. This work focuses on study of FLASH-RT experiment using electron beams produced from the accelerator system at the PBP-CMU Electron Linac Laboratory. The structure and properties of our electron pulses with microbunches in picosecond time scale and macropulses in microsecond time scale match well to FLASH-RT requirement. To optimize the condition for experiment, the electron beam simulations are performed by varying energy, charge and bunch length. The 25 MeV electrons energy before hitting the window for 50 and 100 pC bunch length have a bunch length of 1.16 and 1.97 ps. The transverse rms beam sizes of 50 pC and 100 pC bunch charges have the differences between ASTRA and GEANT4 from 7.90 % to 34.0 %. The optimized electron beam properties from this study will be used as the guideline for further simulation and experiment preparation.