A brief history of high power RF proton linear accelerators Page: 1 of 12
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A Brief History of High Power RF Proton Linear Accelerators
John C. Browne
Los Alamos National LaboratoryIntroduction
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The first mention of linear acceleration was in a paper by G. Ising in 1924 (Ref 1) irrwlich
he postulated the acceleration of positive ions induced by spark discharges whicl ro~tuded
electric fields in gaps between a series of "drift tubes". Ising apparently was not able to
demonstrate his concept, most likely due to the limited state of electronic devices. Ising's
work was followed by a seminal paper by R. Wideroe (Ref 2) in 1928 in which he
demonstrated the first linear accelerator. Wideroe was able to accelerate sodium or
potassium ions to 50 keV of energy using drift tubes connected alternately to high
frequency waves and to ground. Nuclear physics during this period was interested in
accelerating protons, deuterons, electrons and alpha particles and not heavy ions like
sodium or potassium. To accelerate the light ions required much higher frequencies than
available at that time. So linear accelerators were not pursued heavily at that time.
Research continued during the 1930s but the development of high frequency RF tubes for
radar applications in World War 2 opened the potential for RF linear accelerators after the
war. The Berkeley laboratory of E. O. Lawrence under the leadership of Luis Alvarez
developed a new linear proton accelerator concept that utilized drift tubes that required a full
RF period to pass through as compared to the earlier concepts. This development resulted
in the historic Berkeley 32 MeV proton linear accelerator which incorporated the "Alvarez
drift tube" as the basic acceleration scheme using surplus 200 MHz radar components. This
development was key to the future directions for proton linacs (Ref 3).
The first attempt at a very high power linac was made at a branch of the Berkeley laboratory
at a former Navy base in Livermore, California. This Livermore RF accelerator was
designed in 1948 to produce a continuous wave (CW) beam of protons or deuterons with
the goal of producing plutonium by bombarding uranium. This was a challenging project
since only 12 MHz RF tubes were available that operated CW. The result was a vacuum
tank to hold the drift tubes that was 60 ft in diameter and 60 ft. long as shown in Figure 1.
Overcoming some major difficulties they were able to achieve CW currents of 50 mA up to
10 MeV and pulsed currents as high as 225 mA. Later generation accelerators at Livermore,
such as the A-48, were able to use smaller cavities as tube development improved; the A-48
achieved 75 mA of protons at 3.75 MeV and 30 MeV of deuterons at 7.5 MeV. This project
was abandoned in 1958.
These developments set the stage for the significant advances that were made starting in the
mid-1960s until the present time. The remainder of this paper will discuss those advances
and how they have lead to the present situation in which routine acceleration (production
plants) of proton beams up to 100s of milliamperes can be realistically considered.
The Los Alamos Meson Physics Facility (LAMPF) M A STE R
In the 1960s there was considerable interest in developing very high intensity beam of
pions for nuclear physics studies. These pion "factories" were proposed using both linacs
and cyclotrons. In 1967, the U.S. chose to build at Los Alamos National Laboratory an
800 MeV pulsed proton linac with an average current of 1 milliampere for pion and muon
research. This accelerator facility, called LAMPF for Los Alamos Meson Physics Facility,PROCESSED FROM BEST AVAILABLE C PY
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Browne, J. C. A brief history of high power RF proton linear accelerators, article, December 31, 1996; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc679270/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.