@article{TEXTUAL,
      recid = {11630},
      author = {Gordon, M. and van der Geer, S. B. and Maxson, J. and Kim,  Y.-K},
      title = {Point-to-point Coulomb effects in high brightness  photoelectron beam lines for ultrafast electron  diffraction},
      journal = {Physical Review Accelerators and Beams},
      address = {2021-08-24},
      number = {TEXTUAL},
      abstract = {In an effort to increase spatial and temporal resolution  of ultrafast electron diffraction and microscopy,  ultrahigh-brightness photocathodes are actively sought to  improve electron beam quality. Beam dynamics codes often  approximate the Coulomb interaction with mean-field space  charge, which is a good approximation in traditional beams.  However, point-to-point Coulomb effects, such as  disorder-induced heating (DIH) and the Boersch effect,  cannot be neglected in cold, dense beams produced by such  photocathodes. In this paper, we introduce two new  numerical methods to calculate the important effects of the  photocathode image charge when using a point-to-point  interaction model. Equipped with an accurate model of the  image charge, we calculate the effects of point-to-point  interactions on two high-brightness photoemission beam  lines for ultrafast diffraction. The first beam line uses a  200 keV gun, whereas the second uses a 5 meV gun, each  operating in the single-shot diffraction regime with  ${10}^{5}\text{ }\text{  }\mathrm{electrons}/\mathrm{pulse}$. For the beam lines  simulated in this paper, assuming a zero photoemission  temperature, it is shown that including stochastic Coulomb  effects increases the final emittance by over a factor of 2  and decreases the peak transverse phase space density by  over a factor of 3 as compared to mean-field simulations.  We then introduce a method to compute the energy released  by DIH using the pair correlation function and approximate  the contribution DIH has on the emittance, which may serve  as a reasonable estimate for the effects of DIH beyond the  cases studied in this work. This DIH energy was found to  scale very near the theoretical result for stationary  ultracold plasmas, and it accounts for over half of the  emittance growth above mean-field simulations.},
      url = {http://knowledge.uchicago.edu/record/11630},
}