ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Ac measurements of an effective critical velocity v scof superfluid 4He flow through a rectangular aperture 5 Μm × 0.3 Μm in a foil 0.2 Μm thick were made between 0.35 and 2.15 K. These measurements involved oscillatory flow in two different ranges of frequency, 70–118 Hz and 1818–1899 Hz. At temperatures T above 1.7 K, v sc(T) measured in the two frequency ranges coincided, decreasing with increasing T. Above 1.9 K, downward curvature toward V sc = 0 at T λoccurred in proportion to (ϱ s )/(T)0.83. At temperatures below 1.7 K, differences appeared between the critical velocity behaviors in the two frequency ranges. As temperature decreased, V sc(T) at the lower frequencies continued to rise in a nearly linear fashion, while at the higher frequencies V sc(T) tended to level off. At the same time, a pronounced increase in noise and metastability in the supercritical region was seen at the higher frequencies. Possible explanations for this divergence of behavior are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00120850
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