He was born in Leiden in 1921 and studied there under Kramers (yes, this Hendrik Anthony one who worked with Bohr on the interactions of electromagnetic waves with matter). He figured out how to deal with singularities in quantum scattering problems; Kramers would say that this insight was important in the development of renormalization.
Later, he would move to Utrecht (for the whole career) and do research on statistical physics in general and stochastic processes in particular. For example, the book you see (and you may buy) on the left side has collected 10 thousand citations. Wow.
Van Kampen was also an uncle of Gerard 't Hooft. He encouraged his nephew to study in Utrecht.
How did I learn about him? Well, it was in the quantum wars. In a weird corner of the Internet where I was sent, a crackpot has attacked Van Kampen's essay
The Scandal of Quantum Mechanics (first page preview, second after a free registration, The American Journal in Physics 2008, 15 cits)where he argues that quantum mechanics is fully consistent, well-defined, complete, and the real scandal is that there are still writers (authors of articles, essays, popular books, and even textbooks) who keep on obscuring this point more than 80 years later. He points out that it's wrong to adjust the reality to your ideas; scientists should do it the other way around. Quantum mechanics may be counter-intuitive but it works perfectly. The only special thing occurring during the measurement is the disappearance of interference due to the presence of many microstates, i.e. decoherence.
(The second page of the paper above is short and only contains references. You may register a free account on Deepdyve – a commercial website offering science articles for discounted prices – by logging in via Facebook – you may preview one article a day for five minutes for free.)
The word "scandal" may be counted among the more dramatic descriptions of the activity of anti-quantum zealots. If you want to hear my guess – and it's just a guess – why Van Kampen was among those who get more irritated by the anti-quantum junk than others, I think that it's because he was exposed to the anti-quantum delusions through his nephew which had to be a disappointing and annoying experience. The more one gets exposed to this pseudoscientific anti-quantum movement, the more irritated one may get when he sees it again.
Van Kampen was an uncle of a famous fellow but his own uncle was also famous: Frits Zernike earned the 1953 Nobel prize in physics. The evidence suggests that it is a dynasty where exceptional skills are inherited by nephews.
RIP, Mr Van Kampen.