From The Laboratory for Laser Energetics (LLE) At The University of Rochester: “How does radiation travel through dense plasma?”

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From The Laboratory for Laser Energetics (LLE)

at

The University of Rochester

11.17.22
Lindsey Valich
lvalich@ur.rochester.edu

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Image of plasma bursting from the sun. Plasma—a hot soup of atoms with free moving electrons and ions—is the most abundant form of matter in the universe, found throughout our solar system in the sun and other planetary bodies. A new study from University of Rochester researchers provides experimental data about how radiation travels through dense plasmas, which will help scientists to better understand planetary science and fusion energy. Credit: NASA.

First-of-its-kind experimental evidence defies conventional theories about how plasmas emit or absorb radiation.

Most people are familiar with solids, liquids, and gases as three states of matter. However, a fourth state of matter, called plasmas, is the most abundant form of matter in the universe, found throughout our solar system in the sun and other planetary bodies. Because dense plasma—a hot soup of atoms with free-moving electrons and ions—typically only forms under extreme pressure and temperatures, scientists are still working to comprehend the fundamentals of this state of matter. Understanding how atoms react under extreme pressure conditions—a field known as high-energy-density physics (HEDP)—gives scientists valuable insights into the fields of planetary science, astrophysics, and fusion energy.

One important question in the field of HEDP is how plasmas emit or absorb radiation. Current models depicting radiation transport in dense plasmas are heavily based on theory rather than experimental evidence.

In a new paper published in Nature Communications [below], researchers at the University of Rochester Laboratory for Laser Energetics (LLE) [below] used LLE’s OMEGA laser [above] to study how radiation travels through dense plasma. The research, led by Suxing Hu, a distinguished scientist and group leader of the High-Energy-Density Physics Theory Group at the LLE and an associate professor of mechanical engineering, and Philip Nilson, a senior scientist in the LLE’s Laser-Plasma Interaction group, provides first-of-its-kind experimental data about the behavior of atoms at extreme conditions. The data will be used to improve plasma models, which allow scientists to better understand the evolution of stars and may aid in the realization of controlled nuclear fusion as an alternative energy source.

“Experiments using laser-driven implosions on OMEGA have created extreme matter at pressures several billion times the atmospheric pressure at Earth’s surface for us to probe how atoms and molecules behave at such extreme conditions,” Hu says. “These conditions correspond to the conditions inside the so-called envelope of white dwarf stars as well as inertial fusion targets.”

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(left to right) Philip Nilson, a senior scientist in the LLE’s Laser-Plasma Interaction group; graduate student Alex Chin; Suxing Hu, a distinguished scientist and group leader of the High Energy Density Physics Theory group at the LLE and an associate professor of mechanical engineering; and graduate student David Bishel (inset) contributed to the research to better understand how plasmas emit or absorb radiation. The research will be used to improve models of plasma. Credit: Eugene Kowaluk/University of Rochester.

Using x-ray spectroscopy

The researchers used x-ray spectroscopy to measure how radiation is transported through plasmas. X-ray spectroscopy involves aiming a beam of radiation in the form of x-rays at a plasma made of atoms—in this case, copper atoms—under extreme pressure and heat. The researchers used the OMEGA laser both to create the plasma and to create the x-rays aimed at the plasma.

When the plasma is bombarded with x-rays, the electrons in the atoms “jump” from one energy level to another by either emitting or absorbing photons of light. A detector measures these changes, revealing the physical processes that are occurring inside the plasma, similar to taking an x-ray diagnostic of a broken bone.

A break from conventional theory

The researchers’ experimental measurements indicate that, when radiation travels through a dense plasma, the changes in atomic energy levels do not follow conventional quantum mechanics theories often used in plasma physics models—so-called “continuum-lowering” models. The researchers instead found that the measurements they observed in their experiments can be best explained using a self-consistent approach based on density-functional theory (DFT). DFT offers a quantum mechanical description of the bonds between atoms and molecules in complex systems. The DFT method was first described in the 1960s and was the subject of the 1998 Nobel Prize in Chemistry.

“This work reveals fundamental steps for rewriting current textbook descriptions of how radiation generation and transport occurs in dense plasmas,” Hu says. “According to our experiments, using a self-consistent DFT approach more accurately describes the transport of radiation in a dense plasma.”
Says Nilson, “Our approach could provide a reliable way for simulating radiation generation and transport in dense plasmas encountered in stars and inertial fusion targets. The experimental scheme reported here, based on a laser-driven implosion, can be readily extended to a wide range of materials, opening the way for far-reaching investigations of extreme atomic physics at tremendous pressures.”

Researchers from Prism Computational Sciences and Sandia National Laboratories and additional researchers from the LLE, including physics graduate students David Bishel and Alex Chin, also contributed to this project.

Science paper:
Nature Communications
See the science paper for instructive material with images.

See the full article here .

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The Laboratory for Laser Energetics (LLE)

The Laboratory for Laser Energetics (LLE) is a scientific research facility which is part of the University of Rochester’s south campus, located in Brighton, New York. The lab was established in 1970 and its operations since then have been funded jointly; mainly by the United States Department of Energy, the University of Rochester and the New York State government. The Laser Lab was commissioned to serve as a center for investigations of high-energy physics, specifically those involving the interaction of extremely intense laser radiation with matter. Many types of scientific experiments are performed at the facility with a strong emphasis on inertial confinement, direct drive, laser-induced fusion, fundamental plasma physics and astrophysics using OMEGA. In June 1995, OMEGA became the world’s highest-energy ultraviolet laser. The lab shares its building with the Center for Optoelectronics and Imaging and the Center for Optics Manufacturing. The Robert L. Sproull Center for Ultra High Intensity Laser Research was opened in 2005 and houses the OMEGA EP laser, which was completed in May 2008.

The laboratory is unique in conducting big science on a university campus. More than 180 Ph.D.s have been awarded for research done at the LLE. During summer months the lab sponsors a program for high school students which involves local-area high school juniors in the research being done at the laboratory. Most of the projects are done on current research that is led by senior scientists at the lab.

The LLE was founded on the University of Rochester’s campus in 1970, by Dr. Moshe Lubin. Working with outside companies such as Kodak the team built Delta, a four beam laser system in 1972. Construction started on the current LLE site in 1976. The facility opened a six beam laser system in 1978 and followed with a 24 beam system two years later. In 2018, Donna Strickland and Gérard Mourou shared a Nobel prize for work they had undertaken in 1985 while at LLE. They invented a method to amplify laser pulses by “chirping” for which they would share the 2018 Nobel Prize in Physics. This method disperses a short, broadband pulse of laser light into a temporally longer spectrum of wavelengths. The system amplifies the laser at each wavelength and then reconstitutes the beam into one color. Chirp pulsed amplification became instrumental in building the National Ignition Facility at the DOE’s Lawrence Livermore National Laboratory and the Omega EP system. In 1995, the omega laser system was increased to 60 beams, and in 2008 the Omega extended performance system was opened.

The Guardian and Scientific American provided simplified summaries of the work of Strickland and Mourou: it “paved the way for the shortest, most intense laser beams ever created”. “The ultrabrief, ultrasharp beams can be used to make extremely precise cuts so their technique is now used in laser machining and enables doctors to perform millions of corrective” laser eye surgeries.

University of Rochester campus

The University of Rochester is a private research university in Rochester, New York. The university grants undergraduate and graduate degrees, including doctoral and professional degrees.

The University of Rochester enrolls approximately 6,800 undergraduates and 5,000 graduate students. Its 158 buildings house over 200 academic majors. According to the National Science Foundation, Rochester spent $370 million on research and development in 2018, ranking it 68th in the nation. The university is the 7th largest employer in the Finger lakes region of New York.

The College of Arts, Sciences, and Engineering is home to departments and divisions of note. The Institute of Optics was founded in 1929 through a grant from Eastman Kodak and Bausch and Lomb as the first educational program in the US devoted exclusively to optics and awards approximately half of all optics degrees nationwide and is widely regarded as the premier optics program in the nation and among the best in the world.

The Departments of Political Science and Economics have made a significant and consistent impact on positivist social science since the 1960s and historically rank in the top 5 in their fields. The Department of Chemistry is noted for its contributions to synthetic organic chemistry, including the first lab based synthesis of morphine. The Rossell Hope Robbins Library serves as the university’s resource for Old and Middle English texts and expertise. The university is also home to Rochester’s Laboratory for Laser Energetics, a Department of Energy supported national laboratory.

University of Rochester Laboratory for Laser Energetics.

The University of Rochester’s Eastman School of Music ranks first among undergraduate music schools in the U.S. The Sibley Music Library at Eastman is the largest academic music library in North America and holds the third largest collection in the United States.

In its history university alumni and faculty have earned 13 Nobel Prizes; 13 Pulitzer Prizes; 45 Grammy Awards; 20 Guggenheim Awards; 5 National Academy of Sciences; 4 National Academy of Engineering; 3 Rhodes Scholarships; 3 National Academy of Inventors; and 1 National Academy of Inventors Hall of Fame.

History

Early history

The University of Rochester traces its origins to The First Baptist Church of Hamilton (New York) which was founded in 1796. The church established the Baptist Education Society of the State of New York later renamed the Hamilton Literary and Theological Institution in 1817. This institution gave birth to both Colgate University and the University of Rochester. Its function was to train clergy in the Baptist tradition. When it aspired to grant higher degrees it created a collegiate division separate from the theological division.

The collegiate division was granted a charter by the State of New York in 1846 after which its name was changed to Madison University. John Wilder and the Baptist Education Society urged that the new university be moved to Rochester, New York. However, legal action prevented the move. In response, dissenting faculty, students, and trustees defected and departed for Rochester, where they sought a new charter for a new university.

Madison University was eventually renamed as Colgate University.

Founding

Asahel C. Kendrick- professor of Greek- was among the faculty that departed Madison University for Rochester. Kendrick served as acting president while a national search was conducted. He reprised this role until 1853 when Martin Brewer Anderson of the Newton Theological Seminary in Massachusetts was selected to fill the inaugural posting.

The University of Rochester’s new charter was awarded by the Regents of the State of New York on January 31, 1850. The charter stipulated that the university have $100,000 in endowment within five years upon which the charter would be reaffirmed. An initial gift of $10,000 was pledged by John Wilder which helped catalyze significant gifts from individuals and institutions.

Classes began that November with approximately 60 students enrolled including 28 transfers from Madison. From 1850 to 1862 the university was housed in the old United States Hotel in downtown Rochester on Buffalo Street near Elizabeth Street- today West Main Street near the I-490 overpass. On a February 1851 visit Ralph Waldo Emerson said of the university:

“They had bought a hotel, once a railroad terminus depot, for $8,500, turned the dining room into a chapel by putting up a pulpit on one side, made the barroom into a Pythologian Society’s Hall, & the chambers into Recitation rooms, Libraries, & professors’ apartments, all for $700 a year. They had brought an omnibus load of professors down from Madison bag and baggage… called in a painter and sent him up the ladder to paint the title “University of Rochester” on the wall, and they had runners on the road to catch students. And they are confident of graduating a class of ten by the time green peas are ripe.”

For the next 10 years the college expanded its scope and secured its future through an expanding endowment; student body; and faculty. In parallel a gift of 8 acres of farmland from local businessman and Congressman Azariah Boody secured the first campus of the university upon which Anderson Hall was constructed and dedicated in 1862. Over the next sixty years this Prince Street Campus grew by a further 17 acres and was developed to include fraternities’ houses; dormitories; and academic buildings including Anderson Hall; Sibley Library; Eastman and Carnegie Laboratories the Memorial Art Gallery and Cutler Union.

Twentieth century

Coeducation

The first female students were admitted in 1900- the result of an effort led by Susan B. Anthony and Helen Barrett Montgomery. During the 1890s a number of women took classes and labs at the university as “visitors” but were not officially enrolled nor were their records included in the college register. President David Jayne Hill allowed the first woman- Helen E. Wilkinson- to enroll as a normal student although she was not allowed to matriculate or to pursue a degree. Thirty-three women enrolled among the first class in 1900 and Ella S. Wilcoxen was the first to receive a degree in 1901. The first female member of the faculty was Elizabeth Denio who retired as Professor Emeritus in 1917. Male students moved to River Campus upon its completion in 1930 while the female students remained on the Prince Street campus until 1955.

Expansion

Major growth occurred under the leadership of Benjamin Rush Rhees over his 1900-1935 tenure. During this period George Eastman became a major donor giving more than $50 million to the university during his life. Under the patronage of Eastman, the Eastman School of Music was created in 1921. In 1925 at the behest of the General Education Board and with significant support for John D. Rockefeller George Eastman and Henry A. Strong’s family medical and dental schools were created. The university award its first Ph.D that same year.

During World War II University of Rochester was one of 131 colleges and universities nationally that took part in the V-12 Navy College Training Program which offered students a path to a Navy commission. In 1942, the university was invited to join the Association of American Universities as an affiliate member and it was made a full member by 1944. Between 1946 and 1947 in infamous uranium experiments researchers at the university injected uranium-234 and uranium-235 into six people to study how much uranium their kidneys could tolerate before becoming damaged.

In 1955 the separate colleges for men and women were merged into The College on the River Campus. In 1958 three new schools were created in engineering; business administration and education. The Graduate School of Management was named after William E. Simon- former Secretary of the Treasury in 1986. He committed significant funds to the school because of his belief in the school’s free market philosophy and grounding in economic analysis.

Financial decline and name change controversy

Following the princely gifts given throughout his life George Eastman left the entirety of his estate to the university after his death by suicide. The total of these gifts surpassed $100 million before inflation and as such Rochester enjoyed a privileged position amongst the most well endowed universities. During the expansion years between 1936 and 1976 the University of Rochester’s financial position ranked third, near Harvard University’s endowment and the University of Texas System’s Permanent University Fund. Due to a decline in the value of large investments and a lack of portfolio diversity the university’s place dropped to the top 25 by the end of the 1980s. At the same time the preeminence of the city of Rochester’s major employers began to decline.

In response the University commissioned a study to determine if the name of the institution should be changed to “Eastman University” or “Eastman Rochester University”. The study concluded a name change could be beneficial because the use of a place name in the title led respondents to incorrectly believe it was a public university, and because the name “Rochester” connoted a “cold and distant outpost.” Reports of the latter conclusion led to controversy and criticism in the Rochester community. Ultimately, the name “University of Rochester” was retained.

Renaissance Plan
In 1995 University of Rochester president Thomas H. Jackson announced the launch of a “Renaissance Plan” for The College that reduced enrollment from 4,500 to 3,600 creating a more selective admissions process. The plan also revised the undergraduate curriculum significantly creating the current system with only one required course and only a few distribution requirements known as clusters. Part of this plan called for the end of graduate doctoral studies in chemical engineering; comparative literature; linguistics; and mathematics the last of which was met by national outcry. The plan was largely scrapped and mathematics exists as a graduate course of study to this day.

Twenty-first century

Meliora Challenge

Shortly after taking office university president Joel Seligman commenced the private phase of the “Meliora Challenge”- a $1.2 billion capital campaign- in 2005. The campaign reached its goal in 2015- a year before the campaign was slated to conclude. In 2016, the university announced the Meliora Challenge had exceeded its goal and surpassed $1.36 billion. These funds were allocated to support over 100 new endowed faculty positions and nearly 400 new scholarships.

The Mangelsdorf Years

On December 17, 2018 the University of Rochester announced that Sarah C. Mangelsdorf would succeed Richard Feldman as President of the University. Her term started in July 2019 with a formal inauguration following in October during Meliora Weekend. Mangelsdorf is the first woman to serve as President of the University and the first person with a degree in psychology to be appointed to Rochester’s highest office.

In 2019 students from China mobilized by the Chinese Students and Scholars Association (CSSA) defaced murals in the University’s access tunnels which had expressed support for the 2019 Hong Kong Protests, condemned the oppression of the Uighurs, and advocated for Taiwanese independence. The act was widely seen as a continuation of overseas censorship of Chinese issues. In response a large group of students recreated the original murals. There have also been calls for Chinese government run CSSA to be banned from campus.

Research

Rochester is a member of the Association of American Universities and is classified among “R1: Doctoral Universities – Very High Research Activity”.

Rochester had a research expenditure of $370 million in 2018.

In 2008 Rochester ranked 44th nationally in research spending but this ranking has declined gradually to 68 in 2018.

Some of the major research centers include the Laboratory for Laser Energetics, a laser-based nuclear fusion facility, and the extensive research facilities at the University of Rochester Medical Center.

Recently the university has also engaged in a series of new initiatives to expand its programs in biomedical engineering and optics including the construction of the new $37 million Robert B. Goergen Hall for Biomedical Engineering and Optics on the River Campus.

Other new research initiatives include a cancer stem cell program and a Clinical and Translational Sciences Institute. UR also has the ninth highest technology revenue among U.S. higher education institutions with $46 million being paid for commercial rights to university technology and research in 2009. Notable patents include Zoloft and Gardasil. WeBWorK, a web-based system for checking homework and providing immediate feedback for students was developed by University of Rochester professors Gage and Pizer. The system is now in use at over 800 universities and colleges as well as several secondary and primary schools. Rochester scientists work in diverse areas. For example, physicists developed a technique for etching metal surfaces such as platinum; titanium; and brass with powerful lasers enabling self-cleaning surfaces that repel water droplets and will not rust if tilted at a 4 degree angle; and medical researchers are exploring how brains rid themselves of toxic waste during sleep.