Ugo Fano Died
On
20 Feb. 2001 the News site
of PhysicsWeb (Institute of Physics Publishing) reported
the passing of Ugo Fano of the University of Chicago together with the passing
of Leonard Mandel of the University of Rochester, a pioneer in the field of
quantum optics. Fano, who made numerous contributions to the theory of atomic
and radiation physics, died on February 13 at the age of 88.
A web page in memorial to Ugo
Fano at the University of Chicago summarizes his work as follows:
Fano dedicated much of his work to achieving a better understanding of the
dynamics of atoms and molecules and the way they interact with light, electrons
and each other. His influence in physics is reflected in the number of phenomena
that bear his name: the "Beutler-Fano Profile," the "Fano-Lichten Mechanism,"
the "Fano Effect," and the "Fano-Factor."
. . .
His publications regarding the interaction of radiation with matter are related
to biological radiation effects, which form the basis for many diagnostic and
therapeutic applications in clinical settings.
In relation to the the latter paragraph cited above, we are also reminded ourselves of another theory that is called by his name: the "Fano theorem." Though not being precisely correct, this theorem is a good approximation and is widely applied to "homogeneous" cavity ionization chambers used in radiation dosimetry [1].
In the memorial web page Mitio Inokuti, a physicist at Argonne National
Laboratory in Illinois, tells about the reminiscences of Fano. The Argonne
physicist noted that Fano began his career working with one of the 20th
century's greatest physicists, Enrico Fermi, at the University of Rome from 1934
to 1936. Inokuti has just finished editing a special volume of the journal
Physics Essays that is dedicated to Fano's work.
- W. C. Roesch and F. H. Attix, "Basic concepts pf dosimetry," in "Radiation
Dosimetry" ed. F. H. Attix and W. R. Roesch (Academic Press, New York, 1968).
24 Feb 01
Further reading added later
Paul Kuroda of Pre-Fermi Reactors
Professor
Emeritus Paul K. Kuroda died at his home in Las Vegas, Nevada on
16 April 2001. He was born Kazuo Kuroda on 1 April 1917 in Fukuoka Prefecture, Japan, and became a United States Citizen in 1955. While at the University of Arkansas he was the author or coauthor of almost 400 publications. Among his many achievements, he is best known for the prediction, in 1956, of the existence of pre-Fermi (i.e., naturally occurring) nuclear reactors (confirmed in 1972) and the inference, in 1960, that the almost extinct isotope Pu-244 with a half-life of 82 million years had been present in the early solar system (confirmed in his laboratory in 1965). Professor Kuroda received the American Chemical Society Nuclear Applications in Chemistry Award (1978) and many other awards [1].
When she was young, Dr. Kazuko Megumi, formerly a colleague of mine at Research Institute for Advanced Science and Technology, Osaka Prefecture University, studied for a year under Professor Kuroda. On the two occasions of his visit to Japan he kindly came to the Institute to give us a talk. I remember that he showed the flag of the Rising Sun in the final slide of his second talk (at
least). Though having the citizenship of U. S. A., he was proud of having been
born in Japan. Dr. Megumi says that Professor Kuroda used to strut along with
large steps, discussed with colleagues and students by smoking elegantly and
goggling his big eyes, and was always enthusiastic about research.
- Summarized from the obituary written by William A. Myers, the
University of Arkansas, and distributed to its members by the Japan Society of
Nuclear and Radiochemical Science.
Related sites
21 Apr 01
Cosmic-Ray Intensity Versus Sunspot Number
Cosmic
rays are energetic particles that travel through space. Those in the
solar system are divided into two groups: solar cosmic rays originating at the
sun and galactic cosmic rays impinging on the solar system from interstellar
space. The intensity measured on earth of galactic cosmic rays with energies
below 10 GeV/nucleon is known to vary during the 11-year sunspot cycle, roughly in inverse correlation with the sunspot number. This effect is considered due to reduced diffusion and enhanced energy loss in the solar wind at times of
enhanced sunspot number [1].
Edward Cliver at the Air Force Research Laboratory in Massachusetts and Alan
Ling at Redex Incorporated in Massachusetts have discovered a partial lag of
cosmic ray intensity from this cycle [2, 3]. They have compared numbers of sunspots and measurements of galactic cosmic rays dating back to 1951, and have noticed that the cosmic ray curve lagged behind the rise in the number of sunspots by about a year during alternate solar cycles. The researchers interpret that the alternating pattern is due to the combined effects of the reversal of the Sun's magnetic field every 11 years and coronal mass ejections (CMEs). Details are as follows [3]:
Cosmic rays preferentially approach the Sun from the direction of its poles
when the magnetic field lines are pointing out of the Northern hemisphere. When the magnetic field flips, cosmic rays tend to approach equatorial regions of the Sun. CMEs have a trend to occur close to the Sun's equator early in the
solar cycle, and later migrate towards the poles. When cosmic rays impinge on
the solar poles early in an 11-year cycle, they do not encounter CMEs. When
they approach the equator at this time of the solar cycle, however, cosmic rays
do meet CMEs, and the interaction of cosmic rays with the strong magnetic
fields of CMEs affects the intensity of cosmic rays on Earth.
- J. V. Hollweg, "Cosmic rays: Solar System effects," in R. G. Lerner and G.
L. Trigg, ed., "Encyclopedia of Physics" (Addison-Wesley, London, 1981).
- E. W. Cliver and A. G. Ling, "22 year
patterns in the relationship of sunspot number and tilt angle to cosmic-ray
intensity," Astrophys. J. Vol. 551, pp. L189-192 (2001).
- "Lagging behind the
solar cycle," PhysicsWeb, 26 Apr. (2001).
28 Apr 01
Refraction of a Particle Beam at a Boundary
A
28.5-GeV electron beam can bore through several millimeters of steel.
However, Thomas Katsouleas of the University of Southern California in Los
Angeles and colleagues have shown that they can make this beam bounce off an
interface that is one million times less dense than air, similar to the
refraction of light at a boundary. To demonstrate this phenomenon they
performed simulation and experiment at the Stanford Linear Accelerator Center
in the U. S. [1, 2].
The team considers that the use of this phenomenon would replace magnetic
kickers in particle accelerators by fast optical kickers or produce compact
magnet-less storage rings in which beams are guided by plasma fiber optics.
The mechanism of the particle beam refraction is as follows [1, 2]: When a beam of
energetic electrons travels through a plasma, the collective space charge
force of the head of the beam expels plasma electrons. The plasma ions in the
beam path are more massive and remain, constituting a positively charged
channel through which the latter part of the beam travels. The ions provide a
net force that focuses the beam [3, 4]. When the beam comes close to the plasma boundary, the ion channel becomes asymmetric, producing a deflecting force in addition to the focusing force. This formation of an asymmetric plasma lens [5] gives rise to the bending of the beam path at the interface.
- P. Muggli, S. Lee, T. Katsouleas, R. Assmann, F.-J. Decker, M. J. Hogan,
R. Iverson, P. Raimondi, R. H. Siemann, D. Walz, B. Blue, C. E. Clayton, E.
Dodd, R. A. Fonseca, R. Hemker, C. Joshi, K. A. Marsh, W. B. Mori and S. Wang,
Nature 411, 43 (2001).
- PhysicsWeb, 2 May
(2001).
- J. J. Su, T. Katsouleas, and J. M. Dawson, Phys. Rev. A 41, 3321 (1990).
- D. Whittum, A. Sessler, and J. M. Dawson, Phys. Rev. Lett. 64, 2511 (1990).
- P. Chen, Part. Accel. 20, 171 (1987).
5 May 01
Two Japanese "Radiation Shielders"
The
June 2001 issue of RSICC
Newsletter, published by Radiation Safety
Information Computational Center, Oak Ridge National Laboratory, reported that
Dr. Shun-ichi Tanaka, the Deputy Director General of Japan Atomic Energy
Research Institute, had been awarded the Distinguished Research Service Award
from the Japanese Ministry of Education, Culture, Sports, Science, and
Technology on April 18, 2001. The award was for his outstanding contributions
on the development of shielding methods for gamma rays and neutrons, which are widely applied to the design of nuclear, medical and industrial facilities.
The same issue of the newsletter also carried a report on the recent
life of Dr. Tomonori Hyodo, a long time "shielder." Betty Maskewitz, former
Director of RSICC, recently heard from Dr. Hyodo himself that he had retired
from Kyoto University in March 1986 and had been president of a small junior
college for technical training for industry from 1986 to March 1990. Now he
lives with his wife Toshiko and elder son's family in Manazuru-machi, Kanagawa
Prefecture, Japan.
20 Jun 01; the stories have been adapted from RSICC Newsletter
No. 436.
John Hubbell Got Another Award
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John Hubbell giving a talk at Osaka Prefecture University, 1995.
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According
to the July 2001 issue of RSICC Newsletter, John H. Hubbell received
the 2001 Distinguished Scientific Achievement Award at the 46th Annual Meeting
of the Health Physics Society in Cleveland, Ohio, on June 12, 2001. John
joined the staff of the National Bureau of Standards (now known as NIST) in
1950 and spent his professional career there, directing the NBS/NIST X-Ray and
Ionizing Radiation Data Center from 1963 to 1981. His collection and critical
evaluation of experimental and theoretical photon cross section data resulted
in the development of tables of attenuation and energy-absorption
coefficients, as well as related quantities such as atomic form factors,
incoherent scattering functions, atomic photoeffect, and pair and triplet
production cross sections.
John's most widely known work is National Standard Reference Data Series
Report 29: Photon Cross Sections, Attenuation Coefficients, and Energy
Absorption Coefficients from 10 keV to 100 GeV. John has published extensively
during his career. One of the pieces of work in which he still takes great
pride is the first analytical solution to the Rectangular Source problem, now
called the Hubbell Rectangular Source Integral, published in the NBS Journal
of Research in 1960. John technically retired from NIST in 1988, but continues
to actively contribute to the organization as a Radiation Physics Consultant.
John is a Fellow of both the Health Physics Society (HPS) and the American
Nuclear Society (ANS). His awards include the Faculty Medal from the Technical
University of Prague, the Paul C. Aebersold Award from the Society of Nuclear
Medicine, the ANS Radiation Industry Award, the ANS Professional Excellence
Award, the University of Michigan Dept. of Nuclear Engineering Outstanding
Alumnus Award, and a Doctor Honoris Causa from the University of Cordoba,
Argentina, Faculty of Mathematics, Astronomy and Physics.
In April 19995, we had an honor of listening to John's talk at RIAST, Osaka
Prefecture University. The title of his talk was "Forty-five years (1950-1995)
with x-ray interactions and applications."
20 Jun 01; the news of the award and John's personal data have been adapted from RSICC Newsletter No. 437.
The Accuracy of Carbon Dating Questioned
For
dating organic remains such as wood, parchment and bones, radioactive
carbon-14 with the half-life of 5730 years is used. Carbon-14 is continuously
being created in the Earth's atmosphere, as cosmic rays bombard nitrogen gas.
The radioactive carbon then combines with oxygen to form carbon dioxide and
enters living organisms. The concentration of carbon-14 in the living organism
reaches equilibrium with its concentration in the atmosphere. When the
organism dies, it stops acquiring new carbon-14, and the content of carbon-14
begins to decrease according to the radioactive decay law. Thus we can
determine the age of organic samples by measuring the specific activity
(radioactivity per unit mass) of their carbon-14 content.1,2
The major assumption of this method is the relatively constant production of
carbon-14 by cosmic rays over the last 50,000 years or so. However, an
enormous peak discovered in the amount of carbon-14 in the atmosphere as a
function of calendar age casts doubt on this technique.3,4
The physicist Warren Beck of the University of Arizona, U. S. A., and his
colleagues tested slices of a half-meter long stalagmite that grew between
45,000 and 11,000 years ago in a cave in the Bahamas. Stalagmites are calcium
carbonate deposits left behind when carbon dioxide evaporates out of cave
seepage water. They found that carbon-14 concentrations were twice their
modern level during that period. Current records of the levels of carbon-14 in
the atmosphere only cover the last 16,000 years, and this discovery extends
those records by about 30,000 years.3
Beck's team concludes: The major features of the new record observed cannot be produced with solar or terrestrial magnetic field modulation alone but also
require substantial fluctuations in the carbon cycle.4
- P. Barnes-Svarney et al. ed., "The New York Publick Library Science Desk
Reference," (Macmillan, New York, 1995).
- K. S. Krane, "Introductory Nuclear Physics," (John Wiley & Sons, New York,
1987).
- "Carbon clock could show
the wrong time," PhysicsWeb News (2001).
- J. W. Beck, D. A. Richards, R. L. Edwards, B. W. Silverman, P. L. Smart,
D. J. Donahue, S. Hererra-Osterheld, G. S. Burr, L. Calsoyas, A. J. T. Jull and
D. Biddulph, "Extremely large variations of atmospheric
14C concentration during the last
glacial period," Science, Vol. 292, pp. 2453-2458 (2001); Published online 11
May 2001 (10.1126/science1056649).
22 Jul 01
The Wrong Discovery of Element 118
In
1999 scientists at Lawrence Berkeley National Laboratory (LBL) in
California, U. S. A., found evidence for the super-heavy element 118 in the
bombardment of lead-208 with 449-MeV krypton-86
ions [1]. Follow-up experiments
at LBL and elsewhere, i.e., the Institute for Heavy Ion Research (GSI) in
Germany, the GANIL Heavy-Ion Research Laboratory in France, and the
Institute of Physical and Chemical Research (RIKEN) in Japan, all failed to
confirm the results. The LBL scientists re-analyzed their data and concluded
that the original evidence had been spurious. In an article submitted to
Physical Review Letters, they retracted their claim for the discovery
of the element [2, 3, 4].
LBL Director Charles Shank said [2], "Science is self-corrective. If you get the
facts wrong, your experiment is not reproducible. In this case, not only did
subsequent experiments fail to reproduce the data, but also a much more
thorough analysis of the 1999 data failed to confirm the events. There are
many lessons here, and the lab will extract all the value it can from this
event." He added, "In retracting the paper, the experimenters are taking
responsibility to clear the record. The path forward is to learn from the
mistakes and to strengthen the resolve to find the answers that nature still
hides from us."
Kenneth Gregorich, a member of the Berkeley team, has little idea what caused
the false results. "One of the possibilities is an analysis problem," he says.
"The problem we have now is that none of the possibilities look very likely."
Sigurd Hofmann, a nuclear physicist at GSI, praises the Berkeley team's
candor, and, along with the rest of the heavy-ion community, hopes a fuller
accounting will reveal what went wrong. Dieter Ackermann, also of GSI, says [5],
"The problem now for me is that I need an explanation."
"The Mystery of Element 117" was the title of the science fiction written by
M. Smith [6] in 1949; the mystery of element 118 became a reality.
- V. Ninov, K. E. Gregorich, W. Loveland, A. Ghiorso, D. C. Hoffman, D. M.
Lee, H. Nitsche, W. J. Swiatecki, U. W. Kirbach, C. A. Laue, J. L. Adams, J. B.
Patin, D. A. Shaughnessy, D. A. Strellis, and P. A. Wilk1, "Observation of
Superheavy Nuclei Produced in the Reaction of
86Kr with
208Pb,"
Phys.
Rev. Lett. Vol. 83, No. 6, pp. 1104-1107 (1999).
- "Results of Element 118 Experiment Retracted," Berkeley
Lab Research News, 27 July 2001.
- P. Schewe, J. Riordon and B. Stein "Element 118 has been erased from the
periodic table," Physics News
Update, No. 550, August 1, 2001.
- "Element 118 disappears two years after it was discovered," PhysicsWeb News, August 1, 2001.
- C. Seife, "Berkeley crew unbags element 118," Science Vol. 293, No. 5531, p.
777 (2001).
- See p. 118 of C. A. Pickover, "Surfing through Hyperspace" (Oxford
University Press, Oxford, 1999).
14 Aug 01
Ion Beams Crystallized
In
ion beams used for high-energy experiment, collisions between ions cause
heating, thus reducing the energy and intensity of the beams. Collisions would
be suppressed by arranging ions neatly like atoms in a crystal. This was
achieved for stationary ions, but it is more difficult in a circulating beam.
Ulrich Schramm and colleagues at the University of Munich have created the first "crystalline" ion beam free from collisions.
They demonstrated the crystallization of laser-cooled
Mg+ beams circulating in
the radio frequency quadrupole storage ring PALLAS at a velocity of 2,800 m
s−1. This velocity corresponds to a beam energy of 1 eV. They observed a sudden collapse of the transverse beam size and the low longitudinal velocity spread, which clearly indicated the phase transition to the crystalline state. The continuous ring-shaped crystalline beam showed exceptional stability, surviving for more than 3,000 revolutions without
cooling [1].
Schramm is cited2 to have said, "The
technique could be used for a wide range of experiments. Crystalline ion beams could aid inertial confinement fusion, while precise experiments with relativistic beams could test special relativity."
- T. Schätz, U. Schramm and D. Habs, "Crystalline ion beams." Nature Vol. 412, pp. 717-720 (2001).
- "Ion strings make
brilliant beams." PhysicsWeb News, Aug. 15, (2001).
7 Sep 01
A Possible Reason for the Survival of High-Energy Rays?
Gamma
rays with very high energies are supposed to be emitted from a
galaxy-like object called a blazer. Astrophysicists expect most of these rays
to be removed by collisions with intervening microwave photons in space.
However, such rays have been detected on earth. Similarly, high-energy
subatomic particles from galaxies are predicted almost to disappear above a
certain energy because of collisions with photons. No such cut-off has however
been found experimentally. Richard Lieu of the University of Alabama proposed a possible reason for the survival of these high-energy gamma rays and subatomic particles [1, 2].
Many physicists agree that space and time are not smooth but quantized at the
very short intervals called the Planck distance and the Planck time, though the
idea has not yet been proved. If space-time is quantized, i.e., grainy, the
positions of particles cannot be determined more accurately than the grain
size. Namely, there is an intrinsic uncertainty equal to the Planck distance.
Similarly, there is an uncertainty in time equal to the Planck time.
According to Einstein's special theory of relativity, events involving
fast-moving objects relative to our laboratory frame S look different to an
observer at the center-of-mass frame S' of the objects. Lieu argues that the
Lorentz transformation of uncertainties in space and time from S to S' causes
much larger uncertainties in S' and that this is possibly the reason for the
survival of high-energy cosmic and gamma rays.
The intrinsic uncertainties in a system are transformed to the other system,
and are found to be larger than the intrinsic uncertainties that should be
found directly in the latter system. This is paradoxical. Is Lieu's argument
based on the sound application of the Lorentz transformation?
- R. Lieu,
"The effect of Planck scale space time fluctuations on Lorentz invariance at extreme speeds,"
Astrophysical Journal Letters, in press (2002).
- P. Ball, "Time
gives rays a break: Jumps in space-time might explain the curious survival of
energetic particles," Nature Physics Update, 6 March (2002).
12 Mar 02
The Worst Solution for the Problem of Element 118
In
1999, physicists at Lawrence Berkeley National Laboratory (LBNL) in
California announced that they had discovered elements 118 by smashing lead
and krypton nuclei together. Follow-up experiments at LBL and elsewhere all
failed to confirm the results. Re-analyzing their data, the LBL scientists
concluded that the original evidence had been spurious, and informally
retracted the discovery last July. However, the true reason for their
error was unknown at that time [1, 2].
All 15 authors of the original discovery paper except Victor Ninov published a
formal retraction of their claim in the 15-July issue of Physical Review
Letters [2]. Ninov, who had been in charge of the data analysis of the experiment, was fired in May from the laboratory. The conclusion was the worst one that the data had been fabricated. It was reported that two experiments performed at the Institute for Heavy Ion Research (GSI) in Darmstadt, Germany, for which Ninov had also worked for data analysis, also showed signs of scientific fraud. Luckily for the GSI team, the good data were enough to prove the existence of elements 110 and 112 [3, 4].
- "The wrong discovery of element 118," Radiation Physics News (14 aug 01).
- P. Schewe, J. Riordon and B. Stein, "Element 118 retraction,"
Physics News Update
No. 597 (9 Jul 2002).
- R. Dalton, "California lab fires physicist over retracted finding,"
Nature Vol. 418, p. 261 (2002).
- C. Seife, "Heavy-element fizzle laid to falsified data,"
Science Vol. 297, No. 5580, Issue of 19 Jul, pp. 313-315 (2002).
23 Jul 02
Sheldon Datz (1927-2001): His Passing Gave a Worry to Collision
Physicists
Sheldon
Datz, who contributed to the introduction of a new field of research,
molecular-beam studies of chemical dynamics, died on 15 August 2001 in Oak
Ridge, Tennessee. An obituary of him was published in the November 2002 issue
of Physics Today [1].
In 1998, Datz received the American Physical Society's Davisson-Germer Prize
in Atomic Physics. In 2000, he received the Enrico Fermi Award with Sidney
Drell and Herbert York. Datz also was a fellow of the American Association for
the Advancement of Science.
I saw Datz on the occasion of International Conference on Atomic Collisions in
Solids held in Hamilton, Canada, in 1979, and was fascinated by his
large-minded character.
In the last paragraph of the obituary, Martinez and his coauthors write:
Those of us who worry how the loss of this giant scientist will affect the
progress of collision physics should recall a saying of Sheldon's. . . . he
would say, with gestures for emphasis, "Not to worry." That will be difficult
for many of us to do.
- J. Martinez, H. Krause and B. Bederson, Physics Today, Vol. 55, No. 11,
p. 88 (2002); See also E. H. Taylor, "Datz's early work clarified," ibid.
Vol. 56, No. 1, p.70 (2003).
5 Nov 02; modified 2 Mar 2003
High-Power Terahertz Radiation
Electromagnetic
radiation of frequencies in the region of one terahertz (1 THz
= 1012 Hz) is considered useful for
scientific and technological applications including the imaging of biological
and other materials and manipulating quantum state in semiconductors. However, most sources developed have been unable to generate terahertz beams with high power.
Recently the team of Gwyn Williams from the Jefferson Laboratory and
colleagues at the Brookhaven and Lawrence Berkeley National Laboratories in
the US produced a high-power broadband THz radiation from subpicosecond
electron bunches in an accelerator at the Jefferson Laboratory in Virginia.
The average power was 20 W, several orders of magnitude higher than any
existing source (Ref. 1; for news and reviews, see Refs. 2 and 3).
The electron bunches were transversely accelerated by a strong magnetic field
to produce a 500-fs pulse (1 fs = 10−15 s) of electromagnetic radiation with a peak power of roughly
106 W. When electron
bunches are generated at the maximum rate of 37 MHz, the average power reaches about 20 W.
The scientists of the team suppose that their source would make it possible to
image the distribution of specific proteins or water in tissue, or buried
metal layers in semiconductors. It would also allow one full-field, real
time capture of such images, i.e., terahertz movies.
- G.L. Carr et al., "High-power terahertz radiation from relativistic
electrons," Nature, Vol. 420, pp. 153-156 (2002).
- M. Sherwin, "Terahertz power," Nature (News and views column) Vol. 420, pp.
131-133 (2002).
- B. Dume, "Power from terahertz beams," PhysicsWeb November 14 (2002).
26 Nov 02
Japanese Nuclear Bomb Document Returns to RIKEN
A
23-page document about a Japanese nuclear bomb plan was returned to the
Institute of Physical and Chemical Research (RIKEN) outside Tokyo. At the
close of World War II the document was secretly entrusted to a research
assistant Kazuo Kuroda, who worked on the project with Yoshio Nishina of
Klein-Nishina formula for Compton scattering. Kuroda immigrated to USA in
1949, eventually became a professor at the University of Arkansas and died in
April 2001 (see "Paul Kuroda of Pre-Fermi Reactors" on this
page). RIKEN personnel asked his widow to return the document, and it came back after 57 years, during which it was believed to have been destroyed. [Adapted from the "News Notes" column of Physics Today, Vol. 55, No. 11, 31 (2002)]
25 Dec 02
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