Radiation Physics News Archive 2001-2002
Tatsuo Tabata


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.

  1. 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.

  1. 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.

  1. J. V. Hollweg, "Cosmic rays: Solar System effects," in R. G. Lerner and G. L. Trigg, ed., "Encyclopedia of Physics" (Addison-Wesley, London, 1981).
  2. 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).
  3. "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.

  1. 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).
  2. PhysicsWeb, 2 May (2001).
  3. J. J. Su, T. Katsouleas, and J. M. Dawson, Phys. Rev. A 41, 3321 (1990).
  4. D. Whittum, A. Sessler, and J. M. Dawson, Phys. Rev. Lett. 64, 2511 (1990).
  5. 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

John Hubbell
John Hubbell giving a talk at Osaka Prefecture University, 1995.

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

  1. P. Barnes-Svarney et al. ed., "The New York Publick Library Science Desk Reference," (Macmillan, New York, 1995).
  2. K. S. Krane, "Introductory Nuclear Physics," (John Wiley & Sons, New York, 1987).
  3. "Carbon clock could show the wrong time," PhysicsWeb News (2001).
  4. 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.

  1. 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).
  2. "Results of Element 118 Experiment Retracted," Berkeley Lab Research News, 27 July 2001.
  3. P. Schewe, J. Riordon and B. Stein "Element 118 has been erased from the periodic table," Physics News Update, No. 550, August 1, 2001.
  4. "Element 118 disappears two years after it was discovered," PhysicsWeb News, August 1, 2001.
  5. C. Seife, "Berkeley crew unbags element 118," Science Vol. 293, No. 5531, p. 777 (2001).
  6. 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."

  1. T. Schätz, U. Schramm and D. Habs, "Crystalline ion beams." Nature Vol. 412, pp. 717-720 (2001).
  2. "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?

  1. R. Lieu, "The effect of Planck scale space time fluctuations on Lorentz invariance at extreme speeds," Astrophysical Journal Letters, in press (2002).
  2. 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].

  1. "The wrong discovery of element 118," Radiation Physics News (14 aug 01).
  2. P. Schewe, J. Riordon and B. Stein, "Element 118 retraction," Physics News Update No. 597 (9 Jul 2002).
  3. R. Dalton, "California lab fires physicist over retracted finding," Nature Vol. 418, p. 261 (2002).
  4. 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.

  1. 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.

  1. G.L. Carr et al., "High-power terahertz radiation from relativistic electrons," Nature, Vol. 420, pp. 153-156 (2002).
  2. M. Sherwin, "Terahertz power," Nature (News and views column) Vol. 420, pp. 131-133 (2002).
  3. 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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