An idea to better characterize nuclear physics and the extreme conditions of space explosions

Michigan researchers have helped look into a new one – a type of astrophysical nuclear explosion – without leaving Earth.

These stellar events help create the chemical elements of the universe, and the Spartans helped explore their nature with an intense isotope beam and a special experimental device with record sensitivity at the National Superconducting Cyclotron Laboratory, or NSCL. The team published its work on May 3 in the journal Physical review letters.

“We’ve been working on this project for about five years, so it’s very interesting to see this work come out,” said Christopher Wrede, a professor of physics at the Facility for Rare Isotop Beams, or FRIB, and at MSU. Physics and astronomy. Vrede, a lecturer at MSU / FRIB, led an international research project.

The NSCL has been the object of the National Science Foundation, which has served the scientific community for decades. FRIB, an institution for users of the U.S. Department of Energy’s Office of Science, was officially launched on May 2nd. Now FRIB will open a new era of experiments that enable researchers like Wrede to better test and test scientific theories that explain space.

For example, in their experiments at NSCL, researchers provided better calibration for what is known as “nuclear thermometers”. Experimental results have increased the accuracy of the calculations that scientists use to determine the internal temperature of new – plural of new. Through their results, the team confirmed that the inside of a new new one called the V838 Herculis was about 50,000 times hotter than the Sun’s surface.

“Ultimately, the information we learned from our experiments reduced the uncertainty in these calculations by two to four times,” Vrede said. “We were actually amazed at how close it was to the temperature we were expecting.”

This agreement helps strengthen the theories underlying new nuclear physics that say something. Our understanding of new lights has come a long way since people first observed them hundreds of years ago – a fact exemplified by the very name nova, which means “new”.

“A long time ago, when something in the sky appeared out of nowhere, you can imagine people thinking,‘ Wait a minute. What the hell is that? “Wred said.” It must be a star that never existed before. “

Since then, scientists have learned that they are not new new starsbut distant existing stars that become visible on Earth when they explode or cause explosions. Perhaps the most famous example of a “new star” is a supernova when an entire star explodes. In our galaxy, the Milky Way, this happens relatively rarely, once every hundred years or so.

However, the nuclear reactions that Vrede and his team are investigating are manifested in the so-called classic new ones that are more common in our space neighborhood. Scientists observe about a dozen in a typical year, often with the help of amateur astronomers. And because the star doesn’t explode completely in a classic new one, the same one can appear multiple times (although the typical time between appearances is about 10,000 years, Vrede said).

The classic new one is formed by two stars orbiting each other close enough that one star can pump nuclear fuel from another. If a siphon star borrows enough fuel, it could cause a vigorous series of nuclear explosions.

Understanding the nuclear processes of all stars helps researchers understand where elements of the universe come from, and those involving two stars are especially important in the Milky Way, Vrede said.

“About half of the stars we see in the sky are actually two-star systems, or binary star systems,” he said. “If we really want to understand how our galaxy works on the production of chemical elements, we can’t ignore them.”

Vrede studies a specific nuclear reaction in new units, which in nature includes versions or isotopes of phosphorus. Phosphorus inside the new one can eat the extra proton to create sulfur isotopes, but unfortunately, scientists cannot reproduce this reaction in stellar conditions on Earth. So Vrede and the team did the next best thing.

Instead, they started with chlorine isotopes that break down into sulfur isotopes. They then watched as sulfur isotopes spit out protons to turn into phosphorus. It is a reaction of interest in the opposite direction, allowing researchers to essentially synthesize an instantaneous reproduction of an action that they can rewind back to better understand the textbook of nature.

But there was another wrinkle. To achieve their goal, the team needed to conduct record-breaking measurements of the lowest-energy protons that came out of sulfur. To do this, researchers created a tool they called Gaseous Detector with Germanium Tagging, or GADGET.

“These protons have very low energy, and using conventional methods, the signal will be confused by the background,” Vrede said. GADGET took an unconventional approach – using a gas detector instead of solid silicon – to achieve the sensitivity needed to observe protons.

“In terms of sensitivity, it’s a world record,” Vrede said.

Proton detection data from the GADGET instrument. The readings from one detector site are shown in black, and the aggregate signal from the five sites is shown in pink. On both curves several peaks are evident above energies of about 800 keV or kiloelectronvolts. What GADGET has allowed researchers to discover is the important but tiny brightness at low energy of 260 keV (highlighted by a gray band). Prior to these measurements, the proton peak, so weak from this nuclear process, had never been detected below 400 keV. Credit: phys. Reverend Let.

Of course, tools and methods are only part of the equation. The team also needed talent to build the tool, conduct experiments and interpret the data. Vrede, in particular, gave a high postgraduate degree to the Spartan graduate student researcher Thomas Budner, the first author of the article to take part in each phase of the project.

Budner will earn his doctoral degree this summer from MSU’s graduate school in nuclear physics thanks in large part to this project, which he called random. When he first started graduate school in 2016, he didn’t know in whose lab he would work and for which project he would take.

“When I came to MSU, I really didn’t know what I wanted to work on. But it seemed like an exciting environment where people were working on a lot of different things with a lot of cool, advanced technology, ”Budner said. .

“I wrote Chris an email about this project and it put a lot of options for me. I could see all the stages of the process: creating a new detector, conducting a new experiment and analyzing the data, ”he said. “It had everything I wanted to try.”

Researchers from all over the world also joined the Spartans in this project. Team members come from institutions in France, Spain, China, Israel, Canada and South Korea. There was also an internal cohort of staff who joined from the University of Notre Dame in Indiana and the Oak Ridge National Laboratory in Tennessee.

MSU, however, has been the epicenter of experiments since the home for the NSCL, which provided the necessary beam of high-intensity chlorine isotopes. Now FRIB will continue the NSCL tradition, continuing to attract leading researchers from around the world to answer some of the biggest science questions through experiments that are impossible elsewhere.

And the Wrede team will be a part of that. He has already received permission to conduct a new experiment in FRIB with the new GADGET system for download.

“We have already updated the GADGET. We call it GADGET 2, ”Vrede said. “It’s a much more complex system and can measure protons even more sensitively.”