Capturing the Light:
Advanced NSLS Detectors Boost Precision, Speed of Data Collection
As the capabilities of synchrotron facilities around the world continue to rapidly grow in number and complexity, a group of researchers at Brookhaven’s National Synchrotron Light Source (NSLS) and the Instrumentation Division are helping experimenters on site and world-wide implement new and more efficient ways to “see” their results.
There are three major components to a synchrotron experiment: an intense beam of infrared, ultraviolet, or x-ray light in the form of photons at varying energies;“optics,” an arrangement of mirrors and lenses used to focus and aim the light at the sample being studied; and a system of detectors used to determine how the light interacts with the sample. All three elements are equally important, yet the development of advanced detectors — used to collect data for a broad spectrum of experiments ranging from environmental studies to protein characterization — has not kept pace with the rest of the field, said NSLS physicist Pete Siddons.
“We’ve been building these synchrotrons around the world for 30 years, and each consecutive one is more powerful,” said Siddons, who leads the NSLS Experimental Systems Detectors Section. “But, with a couple of exceptions, the detectors have remained the same. Increasing the power of the accelerator doesn’t give an increase in the number of photons detected at the beamlines. And when you let those photons go, you’re limiting the depth at which you can study a certain phenomenon.”
In an ideal world, every experiment would have a customized detector, Siddons said. His group, made of a half dozen full-time staff and postdoctorate researchers, strives to meet that ambitious goal with a little help from some scientific neighbors.
Meet Peter Siddons
It was 1968, and halfway through a degree in electrical engineering from the University of Bristol in the United Kingdom, Pete Siddons “did what everyone else was doing in the late 60s and early 70s.” He dropped out. More...
“What saves the day is our strong collaboration with Brookhaven’s Instrumentation Division,” Siddons said. “That allows us access to great technology, which is applied to everything from nuclear and particle physics to medical imaging and synchrotron experiments.”
One recent example of the successful work from this collaboration is an x-ray fluorescence microprobe system that will be about 1,000 times faster than previous methods.
X-ray fluorescence is a powerful technique often used in the environmental and geological sciences for measuring trace element concentrations in a sample. Typically, a very tiny x-ray spot is focused on a sample, which ionizes electrons from the material’s atoms. These excited atoms relax, filling the vacancies, and in doing so, emit x-rays at energies characteristic of specific elements. However, scientists can only determine the elements present in the portion of the sample that’s exposed to the x-ray spot. To get an idea of the entire sample’s chemical composition, the spot must be manually moved from one location to another — a process that can take many hours to produce low-resolution maps of just a few thousand pixels. Working with Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO), the BNL team developed a method that allows researchers to scan the scheme continuously along a line. This “on-the-fly” scanning method, which has been tested at the NSLS, also incorporates many small detectors (32 in the test run)into one device, and advanced data analysis techniques that can handle the increased processing speed and map the x-ray energies in real time. Led by physicist Chris Ryan, scientists at CSIRO developed software and hardware to unfold the signals from chemical elements at up to 100 million events per second.