The Uranium Bomb, the Calutron, and the Space-Charge Problem

Abstract

A voice sbouted out into tbe night from the second floor of a dormitory in Oak Ridge, Tennessee. It was 6 August 1945. That day, President Harry S Truman bad announced to the world that the US had dropped a new weapon, a uranium bomb, on the city of Hiroshima, Japan. For years, tbose of us on the bomb project were cautioned not to say the word uranium, but now it was okay. There were code words and code letters for tbe things we worked with, and eacb of our new designs received a new name. The teletype messages tbat went back and forth between tbe radiation laboratory in Berkeley, California, and the Y-12 plant in Oak Ridge were total gihherish. The purpose of our effort was to separate "P," or ^^' ' U from "Q," or ^^^U. Tbose were easy to remember hecause P stood for precious and Q stood for qrap.Afew days later, another word burst on the scene with the issuance of the Smyth Report, the official government account of the history of the bomh project.' That word was "calutron." Now that the device had achieved its objective, Ernest Lawrence wished to give recognition to the University of California by using the name calutron for the apparatus developed to separate P from Q. He had made an arrangement with report author Henry Smyth that the name he included, but never divulged the deal until the war was won.The calutron's separation method was based on electromagnetic mass spectrometry. (See box 1 on page 46 for a tutorial.) All critical material was transported in beams of positive ions on wbich electric and magnetic fields could act. The needed quantity of material demanded very intense beams witb a bigh density of electric charge. But the positive beam itself should create so-called space-charge fields whose repulsive forces would alter ion trajectories and prevent the desired isotopic separation by mass from occurring. At least in 1940, any thinking physicist knew that. Cornell UniversityThe calutron story starts around 1940 at Cornell University. Fellow student A. Theodore Forrester and I were finishing our graduate work under the direction of Lloyd P. Smith, who had obtained a contract to separate a quantity of lithium-6 for use in an experimental study of a new cancer therapy. Knowing about the space-charge problem and

Unconventional ideas for ionization cooling of muons

“…This has reduced the longitudinal emittance from 1540 microns [32] to 890 microns [33]. The hydrogen in the channel neutralizes space charge and permits short bunch lengths [34][35][36]. Operating RF cavities in magnetic fields can lead to breakdown [37,38].…”

Mass Spectrophotometry: An Advanced Technique in Biomedical Sciences

“…Ernest O Lawrence then developed sector mass spectrometers that are known as "calutrons". They were basically utilized for separating the isotopes of uranium [27].…”

Gas Phase Formation, Structure and Reactivity of Gold Cluster Ions

“…Preparative mass spectrometry, whereby a species is ionised, mass selected and collected as a bulk sample for subsequent use, has a history dating back to the use of calutrons during World War II for separation and isolation of 235 U [333]. The low-energy collisions of ions with surfaces have been comprehensively reviewed and, depending on the conditions used, can be exploited for the deposition of massselected clusters onto surfaces [334].…”