Magnetic response of clean NS proximity cylinders

We discuss recent investigations on the magnetic response of NS proximity c ylinders of niobium coated with a clean silver layer at 150 mu K < T < 9 K, which show strong induced superconductivity in N. The temperature dependen ce of the susceptibility in the diamagnetic regime is described successfull y by the quasiclassical Eilenberger theory including an elastic mean free p ath l as the only fit parameter. In the mesoscopic temperature regime the N S system shows the paramagnetic reentrant effect, superimposing on the full Meissner screening. The logarithmic slope of the reentrant paramagnetic su sceptibility chi(para)(T) proportional to exp(- L/xi(N)) is limited by the condition xi N = nL with xi N = (h) over bar upsilon(F)/2 pi k(B), the ther mal coherence length. In AgNb wires with perimeter L = 72 mu m, we observe the integer multiples mu m = 1,2,4 as T is reduced. (C) 2000 Elsevier Scien ce B.V. All rights reserved.