Biographical Memoirs Volume 79 (2001) / Chapter Skim
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Robert Hofstadter
Robert Hofstadter
Pages 158-181
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From page 159... ...
Some 40 years later Hofstaciter cleterminecl the internal structure of such nuclei by scattering high-energy electrons from thin targets en c! measuring the distribution of the number of these electrons as a function of angle.
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From page 160... ...
He showed exceptional ability in mathematics and physics and was particularly stimulatecl by the clarity en cl precision of the teaching of Irving Lowen and Mark Zemansky at City College. Bob gracluatec!
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From page 161... ...
chamber, the stucly of the infrared spectra of organic molecules, en cl theoretical work on the clevelopment of a new type of mass spectrometer. This research left him little time for his course work, en cl he felt it interfered with his stucly of quantum mechanics, which he took from Eugene Wigner, en cl with his goal of becoming a theorist.
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From page 162... ...
in 1941 he movecl for one semester to City College of New York. While at the University of Pennsylvania he hacl established a lasting friendship with Leonard Schiff, who was later to become the chairman of the Physics Department at Stanford en cl a colleague with whom Bob colIaboratecl extensively in his later work on nuclear structure.
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From page 163... ...
He began research on means for detecting gamma rays, which he hopecl wouIcl be useful for work on the Princeton cyclotron. After learning of a scintillation counter using naphthalene clevelopecl by Hartmut KalImann in Germany, Bob usecl his knowlecige of solicI-state physics, acquired cluring his studies at the General Electric Laboratory before the war, to clevelop a detector using activated alkali halicles insteacl of organic crystals.
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From page 164... ...
In his first three years at Stanford, Bob workocl closely with Jack McIntyre, who had followed him to Stanford as a postdoctoral fellow, and together they extended the application of scintillation counters to the study of X rays, neutrons, alpha particles, and muons. They also applied these counters to the stucly of electron showers.
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From page 165... ...
built one with the help of a $5,000 grant from the Research Corporation en cl support from the Office of Naval Research. The magnet weighed 2.5 tons, had a radius of curvature of 16", and couIcl focus electrons of energies up to IS0 MeV, the maximum energy the Stanford Mark III accelerator couIcl cleliver at that time.
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From page 166... ...
electrons exitec! the chamber through an aluminum foil Winslow, passed through air, en cl then enterecl the vacuum chamber of the magnetic spectrometer through another thin foil Winslow.
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From page 167... ...
these revealecl the structure of various nuclei en cl of the nucleons in greater cle tail. In the next two years, the length of the Mark III accelerator was increased another 90 feet, en cl with the aciclition of more klystrons, the accelerator achieved an energy of ~ GeV in 1960.
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From page 168... ...
As Bob acknowledged some years later, this period in the 1950s was an extraordinary one, one in which he and his small group, with excellent support from the Office of Naval Research, had a virtual monopoly of the field of nucleon and nuclear structure. Further, it provided the basis for his belief, which he defended strongly in subsequent years, that high-energy and elementary-particle physics could be done effectively by small groups, not necessarily by the huge collaborative kinds of teams that we see today.
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From page 169... ...
This illustratecl the way Bob approached a problem: He thought nothing of proposing a cryostat a thousand times larger than had ever been consiclerecl before, just as he hacl proposal a two-mile accelerator, many times the length of the Mark III accelerator, because higher energies were neeclec! to see the cletaiTs of the nucleon.
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From page 170... ...
This difference in viewpoint eventually lecl to a split within the Physics Department, en cl the creation of a Division of Appliecl Physics at Stanford that was partially supported by government funds. Many years later, when government support of research diminished, much of what hacl been feared came to pass.
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From page 171... ...
It was recognized early that a two-mile accelerator was too large to be accommociatec! within the Physics Department en cl that an inclepenclent university entity wouIcl have to be establishecl for it.
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From page 172... ...
This could result in the Physics Department becoming a service department that would only provide undergraduate teaching and the first two years of graduate teaching for students, the bulk of whom would go on to work at SLAC. Bob worried about this and argued for limits on the number of SLAC faculty, as well as for departmental control of graduate admissions and all aspects of the teaching of physics.
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From page 173... ...
The intensity of the resultant pulse of light emitted by the crystal from all these shower particles is then clirectly proportional to the energy of the incident particle. The resolution attainable in the GeV range is of the order of ~ percent, providing precision spectroscopy in this energy range.
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From page 174... ...
Gamma rays suffer very little absorption and scattering in space and, as Bob pointed out, they travel in straight lines en cl thus reveal their sources, in contrast to cosmic rays, which, being charged particles, are deflected by magnetic fields or scattered by interstellar dust. EGRET was launched on the Compton Gamma Ray Observatory on April 5, 1991, only a few months after Bob's death.
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From page 175... ...
By selecting racliation with an energy on either sicle of the iodine K-edge and digitally subtracting the two images, they were able to image the arterial system of the heart without interference from absorption by bone or tissue. The exceptionally intense beams of X rays that are available from electron storage rings macle this dichromatic subtraction technique practical.
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From page 176... ...
to the quantum Hall effect. Doug, a professor of cognitive science at Indiana University, won the Pulitzer Prize for non-fiction in 1980 for Godel, Escher Bach: An Eternal Golden Braid, an enormously stimulating book linking concepts of mathematics, art, en cl music, en cl he is also well known for his contributions to Scientific American.
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From page 177... ...
We, and many of the Stanford community, enjoyed the hospitality of their home and the pleasure of conversation with them, their family, and their guests from around the world. We would like to acknowledge the help of the following persons in the writing of this memoir: Knifer Conan-Tice and Rosenna Yau of the Stanford Physics Department, lean Deken of SLAC, and Margaret Kimball of the Stanford University Library Special Collections for assistance in locating historical files, William T
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From page 178... ...
Taylor, Stanford Linear Accelerator Center, Stanford University, "for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics." 2. Remarks by H
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From page 179... ...
High energy electron scattering and nuclear structure determinations.
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From page 180... ...
195:55-68. Electron scattering and nuclear structure.
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From page 181... ...
NS-24:264-69. 1983 The application of synchrotron radiation to non-invasive angiography.
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