Question: Who was the director of the lab that designed bombs for the project that used mass spectrometers to separate isotopes of uranium?

<P0-S0> Wilhelm Walcher (7 July 1910 in Kaufbeuren – 9 November 2005 in Marburg) was a German experimental physicist. <P0-S1>  During World War II, he worked on the German nuclear energy project, also known as the Uranium Club; he worked on mass spectrometers for isotope separation. <P0-S2>  After the war, he was director of the Institute of Physics at the University of Marburg. <P0-S3>  He was a president of the German Physical Society and a vice president of the German Research Foundation. <P0-S4>  He helped found the Society for Heavy Ion Research and the German Electron Synchrotron DESY. <P0-S5>  He was also one of the 18 signatories of the Göttingen Manifest. <SEP> <P1-S0> The history of mass spectrometry has its roots in physical and chemical studies regarding the nature of matter. <P1-S1>  The study of gas discharges in the mid 19th century led to the discovery of anode and cathode rays, which turned out to be positive ions and electrons. Improved capabilities in the separation of these positive ions enabled the discovery of stable isotopes of the elements. <P1-S2>  The first such discovery was with the element neon, which was shown by mass spectrometry to have at least two stable isotopes: Ne (neon with 10 protons and 10 neutrons) and Ne (neon with 10 protons and 12 neutrons). <P1-S3>  Mass spectrometers were used in the Manhattan Project for the separation of isotopes of uranium necessary to create the atomic bomb. <SEP> <P2-S0> The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. <P2-S1>  It was led by the United States with the support of the United Kingdom and Canada. <P2-S2>  From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the U.S. Army Corps of Engineers. <P2-S3>  Nuclear physicist Robert Oppenheimer was the director of the Los Alamos Laboratory that designed the actual bombs. <P2-S4>  The Army component of the project was designated the Manhattan District; "Manhattan" gradually superseded the official codename, Development of Substitute Materials, for the entire project. <P2-S5>  Along the way, the project absorbed its earlier British counterpart, Tube Alloys. <P2-S6>  The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US $2 billion (about $ in 2016 dollars). <P2-S7>  Over 90% of the cost was for building factories and to produce fissile material, with less than 10% for development and production of the weapons. <P2-S8>  Research and production took place at more than 30 sites across the United States, the United Kingdom, and Canada. <SEP> <P3-S0> Mass-independent isotope fractionation or Non-mass-dependent fractionation (NMD), refers to any chemical or physical process that acts to separate isotopes, where the amount of separation does not scale in proportion with the difference in the masses of the isotopes. <P3-S1>  Most isotopic fractionations (including typical kinetic fractionations and equilibrium fractionations) are caused by the effects of the mass of an isotope on atomic or molecular velocities, diffusivities or bond strengths. <P3-S2>  Mass-independent fractionation processes are less common, occurring mainly in photochemical and spin-forbidden reactions. <P3-S3>  Observation of mass-independently fractionated materials can therefore be used to trace these types of reactions in nature and in laboratory experiments.