I'm a bit of a one-track mind recently, so my apologies if I keep on bringing up nuclear research and science in the Cold War era. Although, I want to focus a little on where scientific collaboration was heading at the tail end of things.
During a summit meeting between Richard Nixon and Leonid Brezhnev in July 1974, the USSR and US established what would become the basis of the Threshold Test Ban Treaty. This treaty, signed at a time when military planners in both nations were concerned about the testing of high-yield "first strike" weapons, designated that neither power could test any nuclear device with a yield exceeding a threshold of 150 kilotons of TNT. While the treaty allowed both sides to continue weapons development, this threshold effectively put a brake on miniaturization efforts for long range cruise missiles.
When the treaty was signed, provisions were included to share technical data - such as geological maps, rock densities, and water table depths. However, neither side could agree on how to directly verify if the treaty was being upheld - a sticking point that would dog both nations for over a decade.
Fast forward to 1987. With renewed engagement from the Soviet Union, scientific specialists and diplomatic representatives of the USSR and USA met in Geneva to discuss the problem of the verification once again. In an unorthodox suggestion, scientists from Arzamas-16 (known today as VNIIEF), Chelyabinsk-70 (VNIITF), Lawrence Livermore National Laboratory, and Los Alamos National Laboratory agreed to create a series of jointly-designed experiments to solve the issue of remotely evaluating the measurement of weapon yields. To insure that the experiments were conducted to the satisfaction of both sides, Soviet and American scientists received unprecedented access to each other's nuclear test sites - a test program known as the Joint Verification Experiment (JVE).
A few months later...
Official program for the first official Soviet visit to the Nevada Test Site, establishing the basis for the Touchstone Kearsarge test in mid-August 1988.
Staff from the Nevada Test Site raising the Soviet Flag, January 1988
Soviet and US flags fly atop a drill rig at the Nevada Test Site
To: Nevada From: Semipalatinsk
Soviet scientists observe the emplacement of diagnostic equipment for a typical subterranean nuclear test - January 1988.
Soviet and American scientists gather in front of the USSR's experimental trailer at the Nevada Test Site, less than a kilometer from ground zero, August 1988.
“I am certain that the main result of the Joint Verification Experiment was not the development of procedures and extent of nuclear test monitoring of the joint development of technical verification means, but the chance for interpersonal communications with the American nuclear physicists.”
Viktor N. Mikhailov, leader of the Soviet technical delegation to the JVE at the Nevada Test Site, August 17, 1988
Nevada Test Site Mission Control - August 17, 1988
Scientific delegation heads Igor Palenykh (at podium) and C. Paul Robertson at the Kearsarge post-shot press conference. The test proved successful, producing an experimentally verified yield of 140 kilotons. The experiments performed at the Nevada Test Site would be replicated in Semipalantinsk one month later.
I have a very distinct personal interest in this event. As part of the JVE, each nation sent over equipment and material that - prior to 1987 - had been closely guarded national secrets. One of the most crucial items was the exchange of geologic cores - rock samples extending hundreds of meters below the surface of each test site - each carefully prepared to precise treaty specifications.
Just a few months ago, tucked away in a transportable container, Los Alamos uncovered several pallets of geologic samples - each sealed in wax, wrapped in brown paper, and accompanied with exceptionally detailed geological field notes in Cyrillic.
I was asked to identify the source of these samples and provide my assessment on their historical significance. After some sleuthing, it was decisively determined that these samples came directly from the Semipalatinsk Test Site as part of this experiment, and efforts are underway to curate and preserve these artifacts as a lasting legacy of détente and collaboration in the waning days of the Cold War.