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Conference on Precision Measurements with Slow Neutrons

[Slide 1: Conference poster]

Ladies and gentlemen, colleagues and distinguished guests: good morning.

It is my distinct pleasure to welcome you, today, to NIST, the National Institute of Standards and Technology, to participate in this International Conference on Precision Measurements with Slow Neutrons, the sixth conference in this series to be convened since the first was held at the Institut Laue-Langevin (ILL) in Grenoble, France in 1977, and the second conference in the series to be convened at NIST (the first NIST conference having been held in 1986).

I am delighted that you could attend.

[Slide 2: NIST collage: AML, NCNR, JILA, CARB]

As many of you may know, NIST, is the national metrology institute of the United States, and in this capacity the Institute pursues a vigorous portfolio of critical, state-of-the-art scientific and technical programs unified through, among other attributes, the theme of precision metrology. As such, NIST operates many unique and specialized facilities that permit our staff to advance NIST's scientific program. Chief among these facilities is the newly completed Advanced Measurement Laboratory (AML), which provides world's most sophisticated scientific laboratory in terms of its environmental control for providing the measurements and standards needed to support advances in 21st-century science, technology, and industry.

In addition to the AML, NIST operates other world-class scientific laboratories, one of with which you all are all undoubtedly familiar: the NIST Center for Neutron Research (NCNR) - a facility unique in the United States that provides thermal and cold neutron beams and the affiliated scientific instrumentation needed for advanced neutron measurement capabilities in neutron condensed-matter physics, materials science and engineering, analytical and nuclear chemistry, and, of course, for the reason for which you are here today, in fundamental neutron physics.

[Slide 3: Radium standards and certificates]
As many of you are no doubt aware, NIST enjoys a fairly rich history in nuclear science and technology, which began soon after the inception of NIST's predecessor organization, the National Bureau of Standards (NBS, founded in 1901). The Bureau established and then maintained an active program in nuclear science, that incorporates elements of both basic research and the development of applied technologies, and which dates back to 1913, a mere 12 years after the Bureau's birth. It was at that time that NBS acquired its first standard radiation source: a radium-226 standard designated "Secondary Radium Standard No. 6," which contained 20.28 mg of radium obtained from pitchblende. This source was used for performing basic radiometric calibrations, and, in fact, still resides at NIST today; although, I might add, in an inactive status due to its fragility.

Vugraph Notes:

  • The images you see before you depict two of NIST's early radium standards prepared in 1937 (along with the primary radium standard of Germany (far right)). Like the first source, Secondary Radium Standard No. 6, these sources consist of tiny glass ampoules that contain milligram quantities of radium as anhydrous radium-226 chloride salt. Also depicted are the calibration certificates issued by the International Commission on Radium Standards for the Bureau's original "Secondary Radium Standard No. 6" and the Bureau's second source: Radium Standard XIV (far left). You'll note that the certifying authorities on the first certificate are scientists of such notable stature as Madame Marie Curie, Earnest Rutherford, and Steffan Meyer, who headed the Institute for Radium Research in Vienna where the sources were fabricated; while the second certificate bears the signature of Marie's daughter Irène Joliot-Curie, after taking over her mother's position on the Commission following Madame Curie's death.

[Slide 4: Taylor, Mann, Curtis ....]
Over the decades, work at the Bureau/NIST in nuclear and radiation physics progressed steadily and included contributions in atomic and nuclear physics by Leon F. Curtis, Ugo Fano and Edward Condon (who, incidentally, became the Bureau's fourth Director), radiation physics and metrology by Wilfrid Basil Mann, and in radiation metrology and dosimetry by Lauriston S. Taylor, who's Bureau of Standards Handbook 15, entitled X-Ray Protection (1931), established this country's first guidelines for radiation protection, and ultimately led to current U.S. Nuclear Regulatory Commission regulations for radiation protection (10 CFR 21).

Vugraph Notes:

  • In this image you see photographs of some of the important contributors to NBS/NIST programs in nuclear and radiation physics.
  • Wilfrid Basil Mann became one of the most influential radionuclide metrologists in the world during his 30-year tenure at the Bureau, where he undertook microcalorimetric experiments to intercompare national radiometric standards. Mann came to the National Bureau of Standards as the head of the Radioactivity Section, after having served at the British Embassy in Washington, D.C. He retired from NBS in 1980. The photo depicts a young Mann working at the Berkeley cyclotron in 1937.
  • Leon F. Curtis came to the Bureau in 1926, following an appointment as a National Research Fellow at the Cavendish Laboratory at Cambridge. Curtis was made Chief of the Radioactivity Section in 1940 and Chief of the Neutron Measurements Section in 1949. During his career, he was engaged in studies of radioactivity, beta-particle spectra, photography of alpha-particle tracks and the development of Geiger counters. He published a book entitled Introduction to Neutron Physics in 1959, and retired from NBS in 1961.
  • Lauriston Taylor was a pioneer in the measurement of radiation. He helped create the International Commission on Radiation Protection (ICRP) approx 1928, and served as its Secretary. He also served as Chairman, to the ICRU: the International Commission on Radiation Units and Measurements, and became first President of the NCRP: National Council on Radiation Protection and Measurements. Taylor built the Bureau's first free-air ion chamber, and pioneered many developments in radiation metrology: he is credited with building the World's first portable survey meter. In the photo Taylor stands in front of the 1.4 MeV x-ray generator (1958), pointing to radiation protection guidelines that he developed, which became the basis for present-day guidelines.
  • Edward Uhler Condon and Ugo Fano, both internationally known theoretical physicists who made contributions in many areas of physics. Condon became the fourth Director of the NBS in 1945

[Slide 5: Parity]

Over the years, physicists assigned to the Bureau have helped answer some of the most fundamental questions in physics, in particular, those dealing with the fundamental symmetries of space and time. In the now-famous landmark experiment performed at the Bureau in 1956 led by C.-S. Wu of Columbia University, modern physics was revolutionized by the demonstration that parity symmetry was indeed violated by the weak interaction, as predicted by T.D. Lee and C.N. Yang, who, as you all know, were awarded the 1957 Nobel Prize in Physics for their prediction of this effect. This work was performed at the Bureau because of its impeccable reputation for low-temperature physics. I invite you to view the apparatus used to demonstrate the "downfall of parity," along with many other interesting scientific artifacts, in the NIST museum.

Vugraph Notes:

  • Chien-Shiung Wu of Columbia University, in collaboration with and Ernest Ambler, Raymond Hayward, Dale Hoppes and Ralph Hudson of the NBS, performed the definitive experiment that led to the 1957 Nobel Prize in Physics being awarded to Tsung Dao Lee and Chen Ning Yang.
  • Ambler, Hoppes and Hayward observe as Ralph Hudson places the outer Dewar flask over the Co-60 sample in preparation for positioning the sample between the poles of the magnet used for cooling the sample.

Interestingly, it was this important scientific discovery, the non-conservation of parity, that helped usher in the relatively nascent field of fundamental neutron physics by breathing new life into the seminal experiments aimed at measuring the electric dipole moment of the neutron (Smith, Purcell and Ramsey, 1957 at ORNL). Other seminal studies proceeded at the Chalk River Nuclear Laboratory in Canada (by Clark and Robson), and at Argonne National Laboratory (by Telegidy, Ringo, Kron) who performed the first measurements using polarized neutrons to quantify the beta-decay coefficients of the free neutron. And, of course, major advances in the field were realized in the early seventies and subsequently, after the 60 MW neutron source at the ILL (Institut Laue-Langevin) came on line (1970) providing high-intensity neutron beams to exceptional experimentalists from all over the world.

[Slide 6: Neutron Physics]

Vugraph Notes:

  • NBSR being prepared for initial operation
  • Panoramic view of the NCNR guide-hall floor, with the fundamental neutron physics end-station shown in the foreground
  • Family of neutron interferometers used at the Neutron Interferometer and Optic Facility (NIOF)
  • Preparations being made for the production and magnetic trapping of ultracold neutrons

From the world's first demonstrations of the production of ultracold neutrons (UCN) by the groups at Dubna and Munich (1971, roughly simultaneously) to the first use of the neutron's wavelike nature to demonstrate interfrometry by Bonse and Rauch at Vienna (1974), to the first demonstration of the magnetic trapping of (very) cold neutrons in 1989 at the ILL by Anton and Paul (Wolfgang Paul, Nobel Prize in Physics 1989 for Electromagnetic Traps for Charged and Neutral Particles), new scientific discoveries revealed by you who are working in fundamental neutron physics continue to play an important role in revealing new physics and shaping our understanding of the physical universe at its most fundamental level.

Indeed programs and facilities in neutron physics world-wide support directions specifically called-out in the U.S. Department of Energy / National Science Foundation, Nuclear Science Advisory Committee long-range plan: Opportunities in Nuclear Science. As you know, for example, measurements of the free neutron lifetime currently underway at NIST and elsewhere play a crucial role in the development and testing of the Standard Model and in understanding the physics governing nuclear beta decay and the electroweak interaction, while other experimental tests of parity-violating neutron interaction processes provide important information regarding hadronic structure.

As you will hear of over the course of the next three days, the Institute's intramural research program in fundamental neutron physics has enjoyed a number of recent successes of which we are quite proud - some of these programs are represented in the present slide. From improvements in the magnetic trapping of ultracold neutrons, to the search for time-reversal-symmetry violation in neutron beta decay; from precision measurements of the lifetime of an unbound neutron, to the accurate determination of the neutron fluence-rate, to the investigation of neutron optical properties using neutron interferometry, I am confident that you will agree with me when I say that NIST is indeed privileged to have here working both for us and with us some of the world's leading experts in experimental neutron physics. I say "with us" because I specifically want to acknowledge the international scientific collaborations in neutron physics in which NIST scientists are presently engaged, both at home and abroad, that allows NIST to participate fully in this international community of profound stature.

Whether it's experimental studies in basic nuclear physics, the operation of one of the world's premier facilities for neutron condensed-matter research, or the development of the world's most precise atomic clocks, NIST will absolutely continue its scientific leadership well into the future through the strong support of our rich scientific programs. In this regard, I encourage, indeed welcome, you to take advantage of all that NIST has to offer: its people and its facilities, by inviting you to come to NIST to pursue your work in neutron physics.

As we look to the future, I see wonderful and valuable results continuing to emerge from the field of fundamental neutron physics. This can only be bolstered by the advent of new facilities like the Munich reactor, just now coming on-line, and the forthcoming commissioning of the Spallation Neutron Source (SNS) presently being constructed at Oak Ridge National Laboratory.

Honored guests, as we now attend to the business of this conference on precision measurements with slow neutrons, you will see from our agenda that you will be treated to a wonderful array scientific topics to be presented by the world's leaders in neutron physics. I again welcome you to NIST, and invite you to enjoy our hospitality and the cultural richness of the greater Washington D.C. metropolitan area as you share with your colleagues your extraordinary scientific discoveries.

Thank you.

Created October 14, 2009, Updated October 22, 2016