Who Put the 'L' in NanoSIMS 50L?
They say everyone wants to build a better mousetrap. But for Earth and Planets Laboratory (EPL) researchers, the device of their dreams is less about catching unwanted intruders and more about peering deep inside the planet or exploring outer space. Since its founding, generations of Carnegie scientists have pushed the limits of technology to improve our ability to understand our planet and its place in the Universe.
Last month, a paper from Carnegie's late Erik Hauri and two former EPL postdocs—Elizabeth Cottrell and Marion Le Voyer—examined how carbon acts under the high pressures and temperatures at which Earth's core formed. They found that carbon makes up a surprisingly small percentage of the core's overall composition.
As you can imagine, those kinds of pressures are hard to come by here on the Earth’s surface. Pressure is defined as force divided by area. Therefore the only way for scientists to achieve such high pressures using the force available in a lab is for the sample to be extremely small. Each sample was only a dozen or so micrometers wide, and the experiment required the ability to measure nanoscopic sections of that sample to determine carbon's compatibility with the silicate "mantle" and the metal "core."
But how do scientists measure the precise chemical content of something so tiny?
The answer is the Cameca NanoSIMS 50L, a special type of ion probe that uses a finely focused beam of ions to measure the chemical and isotopic composition of solid samples on very, very small scales.
What is the NanoSIMS?
NanoSIMS stands for Nanoscale Secondary Ion Mass Spectrometry. As its name suggests, the room-sized device, made by a company called CAMECA, is built to measure the chemical and isotopic composition of a sample to a spatial resolution of around 100 nanometers or 1/10th of a micrometer. To give you an idea of how small this is: a human red blood cell is about 7000 nanometers wide.
According to Carnegie cosmochemist Larry Nittler, the machine works by shooting a beam of ionized oxygen or cesium at a sample like a rock, meteorite, or, in the case of the carbon compatibility paper, a lab-made mini-planet. The ion hits the sample like a sandblaster, knocking newly ionized atoms loose into the mass spectrometer, which essentially sorts the charged atoms by their atomic weight. The machine then provides the researchers with the exact chemical composition of each ion-blasted section of the sample and can map the data to build an image.
The NanoSIMS hits the sample with a precise beam of ions, which knocks parts of the sample loose so it can be analyzed. Here is a simplified diagram of how the NanoSIMS 50L measures secondary ions, illustration courtesy of Eden Camp.
For Nittler, the NanoSIMS is an essential tool that he uses to peer into the early machinations of our galaxy by scanning meteorite samples for the unique isotopic signature of tiny pre-solar grains, which predate other solid material in the Solar System. These grains provide clues to how elements are synthesized in stars, how our galaxy evolved, and how our Solar System came to be.
"I would not be able to do the research I do without a NanoSIMS," explains Nittler, "A lot of my fundamental research is on these tiny grains in meteorites. The NanoSIMS is really the ideal tool to characterize them." He reflects, "I'm very, very happy that we have one."
Hauri Led the Way to the First NanoSIMS 50L
Erik Hauri sits in front of the NanoSIMS with colleague Alberto Saal, together they co-authored the paper in which they found evidence for water on the moon using ion microprobe technology.
There are at least 32 NanoSIMS 50Ls in labs around the world, but the Earth and Planets Laboratory got the very first one in 2006 under the leadership of the late Erik Hauri, who was a co-author on the carbon compatibility paper and to whom it is dedicated.
Hauri became a staff geochemist at the Department of Terrestrial Magnetism* in 1994, where he promptly began building one of the best ion microprobe laboratories in the world starting with the CAMECA IMS 6F in 1995 followed by the CAMECA NanoSIMS 50L in 2006. Hauri passed away in 2015 at the age of 52 after a field-transforming and tragically short career. Now, years later, his legacy lives on as papers continue to be published based on the data collected by the renowned master of ion microprobe technology.
As a geochemist, Hauri studied the movement of matter inside planets and how volatile compounds such as water originated on Earth and other planetary bodies. In fact, one of Hauri's most famous accomplishments is his discovery of water on the Moon, a feat he could not have accomplished without the help of his trusty NanoSIMS.
According to Nittler, who worked parallel to Erik Hauri in the ion microprobe lab for years, “Erik was a master of measuring volatile trace elements, like hydrogen and carbon, using SIMS as a tool. He really pushed the methodology. He could measure hydrogen in samples that basically don't have any hydrogen and do it accurately. He could find one atom in a million.”
When the original NanoSIMS came out in 2000, its potential to revolutionize geochemical and cosmochemical research with its sub-100-nanometer resolution was clear. But the premier model at the time, the NanoSIMS 50, didn't meet Hauri's high expectations.
The 'L' stands for 'larger.'
Thanks to the dedication of Erik Hauri, the Carnegie Institution for Science was the first organization to own a NanoSIMS 50L, pictured here.
Working with Larry Nittler as well as scientists at NASA’s Johnson Spaceflight Center, Hauri convinced CAMECA to optimize the design by making the magnet larger, a change that would provide increased capabilities and precision to the machine. CAMECA liked the idea, and in 2005, the NanoSIMS 50L was born. The 'L' stands for 'larger.'
In 2006, Carnegie became the world's first owner of a NanoSIMS 50L thanks to Hauri's dedication and innovation. This machine is now an essential feature in any top tier ion microprobe lab.
Nittler recalls, "Erik was really the driver, pushing on CAMECA and asking, 'What else can we improve." He continues, "I was blown away mostly by how good Erik was at this kind of thing. He knew how to talk to CAMECA and say, 'We need this' much better than I could. He was an amazing man, an incredibly nice man. He was brilliant and fantastic with collaborators, students, and postdocs. He was truly a pleasure to be around and co-manage a lab with."
In some ways, the carbon compatibility paper represents a full circle for Hauri's NanoSIMS vision. Nittler explains, "I was really excited to see this paper because this type of deep carbon experimental work is something we talked about for many, many years when we were originally writing the proposals to obtain the NanoSIMS. Erik was excited about its potential for doing this kind of measurement. So it's exhilarating to see it actually being done."
* In 2020, the Department of Terrestrial Magnetism merged with the Geophysical Laboratory to create the Earth and Planets Laboratory.