BNL’s Sivertz recreates cosmic radiation

BNL’s Sivertz recreates cosmic radiation

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Like a pit orchestra hidden beneath the stage during a musical, a collection of often unheralded people work for years to make it possible for astronauts to dazzle the world with their journeys further from home than anyone has ever gone.

A physicist at the NASA Space Radiation Laboratory, Michael Sivertz is one of the researchers working behind the scenes to help make those majestic launches that carry astronauts deep into space safer.

Along with other physicists, biologists, and a host of others, Sivertz helps run, maintain and prepare the equipment NASA built in 2003 to test the effects of cosmic radiation on everything from different systems in the human body to the electronics that make space flight possible.

While he doesn’t test the cells themselves, Sivertz helps create and understand the kinds of radiation that enable other scientists to see how these DNA-altering and cell-altering ions might affect people who spend prolonged periods in space. He studies mitigation efforts that include shielding.

“When a proton goes through your DNA, it dislodges an occasional base pair,” Sivertz said. That’s like knocking a piece out of a jigsaw puzzle. The human body then looks for a part that fits in the empty space. “The repair happens trivially.”

When an ion of iron, however, goes through DNA, “it’s like a bomb going off. It quite frequently breaks both legs of DNA, and much damage is done. There is no simple recipe for putting those pieces of DNA back together in a foolproof way. That’s what makes space radiation so different,” he said. Sivertz’s role, he explained, is to develop the instrumentation that makes tests of cellular reactions to different kinds of radiation possible.

Peter Guida, a biologist at BNL who provides a similar expertise at using the NSRL, appreciates his colleague’s work. Sivertz “was chosen in particular because of his background, expertise and work ethic to become part of the NSRL program,” said Guida, who has known Sivertz for more than a decade. “That’s proven to be an extremely wise choice.”

Sivertz is working to understand the beam, its energy, its fragmentation, the way it loses energy and its stopping range — how far it goes through a material before it stops. He recently conducted a series of measurements to study the scattering cross section and charge-changing cross section for a variety of ions, including oxygen, carbon, and helium 3 and helium 4, which are isotopes of helium. “BNL is one of the only places in the world that can accelerate helium ions to produce an ion beam,” he said, while NSRL is the only facility designed to simulate the entire cosmic ray spectrum.

Sivertz also helps make it possible for scientists to test the effect of radiation on electronic devices. “As the characteristic size of electronic devices has shrunk, they have approached the size of cells, and their activation energies are similar to that of cells,” he explained. “Models for electronic behavior are sharing understanding with models for cellular behavior.”

Sivertz recognizes the need to understand how the environment in space might affect expensive systems. “If you’re going to send up a $1 billion satellite, you want to make sure some $5 memory chip doesn’t bring it down when it gets hit” by radiation, he said.

About a quarter of the time, Sivertz gets to pursue his own research, which includes a more precise understanding of the nature of the beams he’s directing toward test samples. Ion beams delivered at NSRL begin as a pure beam. As that beam moves through the air and equipment along the way, some of those ions hit atoms in the air, scatter or break into fragments, he described. For some experiments, researchers need to know exactly what happens to the beam and how it changes.

He is also working with people on helping to build better proton therapy treatment for cancer. Proton therapy may be more targeted toward tumors because the protons move at a slower speed, causing them to distribute all their energy at the site of a tumor rather than in healthy layers of tissue before and after the tumor.

Like members of a pit orchestra, Sivertz and Guida both play the same instrument: the guitar. Guida said Sivertz keeps his nylon-stringed guitar near the beam line, to strum some classical strains during the unusual moments when the beam line isn’t functioning.

In addition to being a talented scientist, Guida said, Sivertz is “a pretty good guitar player.”