Friday , April 16 2021

FIONA measures the mass number of two super heavy elements



A view of the instrumentation of FIONA. Credits: Marilyn Chung / Berkeley Lab

A team led by nuclear physicists from the Energy Department's Lawrence Berkeley National Laboratory (Berkeley Lab) reported the first direct measurements of the mass numbers of the nuclei of two super-fast elements: moscovium, item 115 and nihonium, item 113.


The results were obtained using a new tool, FIONA, in Berkeley Lab, designed to solve the nuclear and atomic properties of the heaviest elements. The results were published on November 28th. Physical Examination Letters magazine.

FIONA is an abbreviation for the definition of "Nuclide A", "A" representing a scientific symbol for the mass number of an element – the total number of protons and neutrons in an atomic nucleus. Protons are positively charged and the number of protons is also known as atomic number; Neutrons have a neutral charge. Superheavy elements are man-made and have a higher number of atoms than those found in naturally occurring elements.

Global rush for mass numbers

Since FIONA's first launch in 2018, FIONA has been working with scientists working for the first experimental work of FIONA. Cyclotron and Nuclear have made it a priority for the Science Division. which lasted five weeks.

Di It's exciting to see FIONA coming online, ğ said Barbara Jacak, Director of the Department of Nuclear Science. Because compressing the masses of super-heavy elements is extremely important, Çünkü he said. "So far, mass assignments were made with conditional evidence rather than direct measurement."

Jackie Gates, a scientist working in the Department of Nuclear Sciences at Berkeley Lab, who played a pioneering role in FIONA's conceptualization, construction and testing of FIONA and pioneered mass counting efforts by FIONA. have more interest. To make an experimental measurement of super heavy mass numbers. "

Gates added that global efforts have been made to measure the massive numbers of superpowers, with mass measurements of super-fast elements using teams from the Argonne National Laboratory and Japan's nuclear research program, using very few different approaches or tools.

FIONA is a new system that provides direct serial number measurements of super-fast elements in the 88-inch-Cyclotron of Berkeley Lab. Credits: Marilyn Chung / Berkeley Lab

Guy Savard, a senior scientist at the Argonne National Laboratory, designed, built and contributed many components for FIONA. He also assisted in the commissioning and first scientific campaign of FIONA.

Roderick Clark, a senior scientist at the Department of Nuclear Sciences of Berkeley Lab, said, "Everyone is coming together in this great race. They can open up all of the physics of these heavy and super-heavy specimens." and a deeper understanding of how they are connected with other elements.

Öl If we can measure the mass of one of these super-fast elements, you can nail the entire area, Clark Clark said.

A new chapter in heavy element research

The mass number and atomic number (or "Z") – a measure of the total number of atoms in the nucleus of an atom – depend on the accuracy of nuclear mass models of superfast elements. Therefore, in the case of a problem with the models, it is important to have a reliable way to measure these numbers by experiments. Ken Gregorich, a recently retired veteran of the Department of Nuclear Sciences of Berkeley Lab, worked closely with Gates to build and build FIONA.

For example, he said, superfast elements could show proton and neutron intensities not taken into account in unexpected nuclear shapes or models.

The Berkeley Lab made great contributions to the field of heavy element research: Lab scientists have played a role in the discovery of 16 elements in the periodic table, based on neptunium synthesis in 1940 and also provided hundreds of isotope definitions. . Isotopes are different element forms that share the same number of protons but have a different number of neutrons in their nuclei.

FIONA (see related article) is an add-on to the Berkeley Gas Separator (BGS). For decades, the BGS separated heavy elements from other charged particles that could act as unwanted "noise" in the experiments. FIONA is designed to capture and cool individual atoms, separate them according to mass and charge characteristics, and transmit them to a low-noise detector station, up to 20 milliseconds or 20,000 times a second.

Jackie Gates is on the left and Ken Gregorich is working on FIONA for the first time in 2017. Credits: Marilyn Chung / Berkeley Lab

& # 39; One atom per day & # 39;

"We can make, give or receive an atom one day," Gregorich said, adding that it is a super-weight element. In its first operation, FIONA was specifically assigned to capture individual moscovium atoms. "Our chances of capturing each atom are 14 percent," he added. Therefore, the researchers were hoping to measure a single moscovium mass number once a week.

Moskovium was discovered in Russia in 2015 by a joint US-Russian team, including scientists from the Lawrence Livermore National Laboratory, and in 2004, a team in Japan was thrown into the discovery of nihonium. Element names were officially approved in 2016.

Scientists in the 88-Shank Cyclotron to produce the Moskovium, together with a particle bundle produced from the rare isotope calcium-48, isotope of an element discovered by Berkeley Lab's Glenn T. Seaborg and others in 1962 bombed an american target. The required half grams were provided by the calcium-48 DOE Isotope Program.

There is a separate cycle signature for each atom captured and measured by FIONA – such as the bicycle turning forward by following a fixed point on the bicycle bicycle tire. The trajectory of this cycle behavior is associated with the atomic "mass-charge ratio", the timing and position of the energy signal measured in the detector, which informs the scientists of the mass number.

Ideally, the measurement includes several steps in the decay chain of the particle: the Moscovium has a half-life of 160 milliseconds, indicating that an atom has a 50% chance of decaying to another element known as the "daughter" element in each decay chain. millisecond. In a few steps in this decay chain, capturing the energy signature can verify which main atom this cascade begins.

Paul Fallon, a senior scientist at the Department of Nuclear Sciences at Berkeley Lab, Paul Fallon, who runs the department's low-energy program, said, "We've been trying to build the number of masses and protons here for years." Said. He noted that the sensitivity of the detector is constantly improving, as well as the ability to isolate each atom from other noise. "Now we have the first exact measurements."

Confirming the number of elements 113 and element 115

In the first scientific study of FIONA, researchers identified one moscovium atom and its related rotten girls and one nihonium atom and rotting girls. Measurements of atoms and decay chains verify the estimated mass numbers for both elements.

At the same time, the researchers confirmed a measure for the nihonium after a deconstruction of the nihilium before a Nexus atom reached NIONE, while the researchers were only trying to create and measure the properties of a moscovium atom.

Alma The success of this first measurement is incredibly exciting, Jenn said Jennifer Pore, a post-doctoral person involved in FIONA's commissioning experiments. "The unique capabilities of FIONA have created a new renaissance for super-fast element research in the 88-inch Cyclotron."

Gregorich encouraged the efforts of the 88-inch Cyclotron staff to maximize FIONA's testing period during their first five-week study, including mechanical, electrical, operations and control systems specialists.

He made special contributions from other BGS and FIONA group members, including Greg Pang, a former project scientist who participated in the construction and testing of FIONA; Jeff Kwarsick, Ph.D. the thesis is focused on FIONA results; and Nick Esker, a former graduate student with a PhD. It is concentrated on the mass separator technique incorporated by FIONA.

New measurements and & # 39; SHEDevil & # 39; plans for inclusion

Fallon said another scientific study was planned for FIONA over the next six months. At this time, nuclear physics researchers can perform a new round of measurement for moscovium and nihonium or for other super fast elements.

It is also planned to set up and test a new vehicle called "SHEDevil" (Super Heavy Element Detector for Low Statistical Overheats) which will help detect the gamma rays produced by the scientists and determine the shape of the super heavy atoms. These gamma rays will provide clues for the regulation of neutrons and protons in nuclei.


Explore more:
Measuring the mass number of the broom, man-made elements

Magazine reference:
Physical Examination Letters

Presented by:
Lawrence Berkeley National Laboratory


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