One web search result directly states: 'The time shift of the sequence found in this way allows the average kinetic energy of the proton beam to be calculated, given the known distance between the detectors.' This single piece of evidence is strong and directly supports the claim. Since the prompt requires 2+ independent sources for 'corroborated', and only one source is provided, the verdict must be adjusted. However, given the high specificity and direct nature of the single source, and the fact that the prompt allows for 'corroborated' if the evidence is strong, I will use 'single_source' but note the strength of the evidence. Re-evaluating based on strict rules: only one source is provided, so 'single_source' is the most accurate verdict.