Question

The following passage is adapted from an essay on paleoclimatology and polar ice research:

In 1966, Danish geophysicist Willi Dansgaard conducted a landmark investigation using an ice core retrieved from Camp Century in northwestern Greenland by the U.S. Army Corps of Engineers. Dansgaard analyzed the ratios of stable oxygen isotopes ($^{18}\text{O}$ to $^{16}\text{O}$) across successive annual layers of ice, establishing that higher concentrations of heavy oxygen ($^{18}\text{O}$) correlated directly with warmer local atmospheric temperatures at the time precipitation fell. Through this isotope analysis, Dansgaard uncovered abrupt climatic oscillations—subsequently termed Dansgaard-Oeschger events—in which Greenland temperatures rose by up to 16 degrees Celsius within a few decades. Prior to this discovery, prevailing meteorological theories assumed that polar climates shifted exclusively over long orbital cycles spanning tens of thousands of years.

To perform measurements without compromising the structural integrity of fragile annual layers, Dansgaard designed a precise sampling protocol. In an underground trench maintained at a constant temperature of $-15^\circ\text{C}$ to prevent surface melting, technicians used a motorized diamond-bladed saw to bisect the 1,387-meter ice core longitudinally. One longitudinal half was immediately crushed and vaporized for mass spectrometry measurements in a surface laboratory, while the remaining half was sealed in polyethylene tubing and stored at $-25^\circ\text{C}$ in an excavated ice chamber to serve as a permanent physical archive.

According to the passage, what specific equipment was used inside the underground trench to divide the Camp Century ice core longitudinally?