The International Union of Pure and Applied Chemistry (IUPAC) has officially credited Lawrence Livermore scientists and international collaborators with the discovery of elements 115, 117, and 118. Livermore teamed with the Joint Institute for Nuclear Research in Dubna, Russia (JINR) in 2003, and again in 2006, to discover elements 113, 115, and 118. The Livermore–JINR team then worked with researchers from the Research Institute for Advanced Reactors (Dimitrovgrad, Russia), Oak Ridge National Laboratory, Vanderbilt University, and the University of Nevada at Las Vegas to discover element 117 in 2010.
Elements beyond atomic number 104 are referred to as superheavy elements. Not found in nature, superheavy elements have been created in a laboratory by accelerating beams of nuclei and shooting them at the heaviest possible target nuclei. The fusion of two nuclei occasionally produces a superheavy element that generally exists for only a short time. The discovery of heavier elements brings researchers closer to the “island of stability,” a term that refers to the possible existence of a region beyond the current periodic table where new superheavy elements with special numbers of neutrons and protons would exhibit increased stability.
Altogether, the Livermore–JINR team has reported the discovery of 6 new elements (113, 114, 115, 116, 117, and 118—the heaviest element to date.) IUPAC officially credited a Japanese collaboration with the discovery of element 113, although the Livermore–JINR team had submitted a paper on the discovery of elements 113 and 115 at about the same time as the Japanese group. Dawn Shaughnessy, Lawrence Livermore’s principal investigator for the Heavy Element Group, says, “It is a wonderful gift to the entire team that we are recognized for our efforts in accomplishing these highly difficult experiments and for the years of work it takes to successfully create a new chemical element.”
Contact: Dawn Shaughnessy (925) 422-9574 (firstname.lastname@example.org).
With support from the National Nuclear Security Administration’s nonproliferation and counterterrorism offices, Livermore scientists have created new, powerful mathematical tools to detect, analyze, and assess unknown objects containing fissionable material for a wide range of applications, including safeguards, border security, arms control, and counterterrorism. The research appears in the November 4, 2015, edition of the journal Nuclear Science and Engineering and was featured on the issue’s cover.
Special nuclear materials (SNM)—highly enriched uranium and plutonium-239—are unique among radioactive materials in that they create self-perpetuating fission chain reactions and in turn emit bursts of many neutrons and gamma rays. The novel Livermore-developed detection and analysis methods are designed to exploit the burst-timing pattern of neutrons and gamma rays emitted by these fission chains. Project leader and Laboratory scientist Les Nakae says, “We have been developing new detection systems that can count neutrons and gamma rays on nanosecond timescales. This counting capability can isolate individual fission events within a fission chain and requires a new theory to fully exploit and interpret the data.”
Livermore nuclear engineer Jerome Verbeke helped develop a new Monte Carlo code to exactly reproduce the finite statistic realization of probabilities for specific fission chain signatures. The code can rapidly generate characteristics of SNM sources and serves as a check for theoretical solutions. Using this theory, the team accurately predicted measurements from real systems with SNM in the form of time-correlated neutrons and gamma rays. The theory also has potential applications in scientific areas beyond nuclear physics, including the study of how disease spreads.
Contact: Les Nakae (925) 422-4861 (email@example.com).
A new set of calibration techniques developed in part by Livermore scientists has improved the sensitivity of the Large Underground Xenon (LUX) experiment—the most sensitive dark matter detector in the world. LUX, located at the Sanford Underground Research Facility in Black Hills, South Dakota, is designed to detect low-mass weakly interacting massive particles (WIMPs), which are among the leading candidates for dark matter. The recent improvements have increased LUX’s sensitivity to these elusive particles by more than two orders of magnitude. The research is described in a paper that was submitted to the journal Physical Review Letters and posted to arXiv on December 11, 2015.
The research team’s recent work re-examines data collected during LUX’s first experimental run in 2013, and helps rule out the possibility of dark matter detections at low-mass ranges previously reported possible with other experiments. “The first analysis of the LUX data was published in 2014,” says Livermore principal investigator and physicist Adam Bernstein. “Since then we have expanded our knowledge of the detector response through a combination of low-energy nuclear recoil measurements, low-energy electron recoil measurements, and an improved understanding of our background in the low-energy recoil regime where dark matter interactions are likely to appear.”
One calibration technique used neutrons as stand-ins for dark matter particles in experiments. Bouncing neutrons off xenon atoms allows scientists to quantify how the LUX detector responds to the recoil process. LUX scientists have also calibrated the detector’s response to the deposition of small amounts of energy from struck atomic electrons. As a result of their work, researchers can search with higher confidence for particles that were previously thought undetectable by LUX. The LUX experiment began its latest search for dark matter in late 2014 and is expected to run until July 2016.
Contact: Adam Bernstein (925) 422-5918 (firstname.lastname@example.org).