Soft x-ray high-harmonic generation in an anti-resonant hollow core fiber driven by a 3
μ
m ultrafast laser
D. Morrill, W. Hettel, D. Carlson, B. Shearer, C. Klein, J. Thurston, G. Golba, R. Larsen, G. Seifert, J. Uhrich, D. Lesko, T. N. NGuyen, Gunnar Arisholm, J. Knight, S. Diddams, M. Murnane, H. Kapteyn, M. Hemmer