Proton imaging of an electrostatic field structure formed in laser-produced counter-streaming plasmas by Morita, T, Kugland, N, Wan, W, Crowston, R, Drake, R, Fiuza, F, Gregori, G, Huntington, C, Ishikawa, T, Koenig, M, Kuranz, C, Levy, M, Martinez, D, Meinecke, J, Miniati, F, Murphy, C, Pelka, A, Plechaty, C, Presura, R, Quirós, N, Remington, B, Reville, B, Ross, J, Ryutov, D, Sakawa, Y, Steele, L, Takabe, H, Yamaura, Y, Woolsey, N, Park, H