The phrase "a breakthrough when a" is not complete and lacks clarity, but it is grammatically correct and can be used in written English if followed by additional context.
You can use it when discussing a significant advancement or discovery that occurs at a specific moment or under certain conditions.
Example: "The researchers experienced a breakthrough when a new method of analysis was introduced."
Alternatives: "an advancement when a" or "a discovery when a".
There was a breakthrough when a Greek-Orthodox surgeon was elected to the Ankara parliament in 1935, and the parliament elected in 1950 was unusually diverse with three Greeks, three Armenians and four Jews; but these were exceptions.
British plans for a nuclear renaissance centred on a nuclear reactor in Somerset achieved a breakthrough when a nine-month European Union state aid investigation ended with a call for Brussels to approve the project.
Last Friday, they made a breakthrough when a donor was found to help initiate employment tribunal proceedings – but their campaign for payment of seven weeks' unpaid wages and holiday money totalling £40,000 has illustrated the vulnerability of millions of workers in a low-wage economy.
United toiled against stubborn visitors but found a breakthrough when a loose ball ran to Mark Bradley whose low cross was converted by Wes Thomas amid offside claims.
She made a breakthrough when Exxon, a longtime client, asked for a credit line, according to "Fool's Gold".
In 1962, Grove had a breakthrough, when the Supreme Judicial Court of Massachusetts, on a four-to-three vote, reversed a trial-court judgment against the book.
There had been a hint of a breakthrough when Ivanovic flicked on a Yuri Zhirkov corner kick but Alex misconnected and scuffed the ball over the bar from close quarters in the 34th minute.
Both Pepsi and Coke are hoping for a breakthrough when they introduce beverages that use a natural, low-calorie sweetener derived from the stevia plant.
And I think the more guys that we have, I think it will make it easier for maybe that next level that maybe can make a breakthrough when there's a lot more guys around to win a major".
