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The Observed Properties of Liquid Helium
at the Saturated Vapor Pressure

Chapter 20. Displacement Length and Vortex Core Parameter

The displacement and healing lengths and vortex core parameter of helium II are discussed in the appendix to a review article by Barenghi, Donnelly and Vinen 1. We give their spline fit and recommended values to the displacement length and recommended values of the core parameter a.

Table 20.1. Knots and coefficients for the displacement length in helium II as a function of log₁₀(1-T/T). The displacement length is given by 10^-8 times 10^S where S is the value returned by the spline. The core parameter is 0.45 times the displacement length

Knots	Coefficients
K( 1) = -8.00	C( 1) = 5.565787
K( 2) = -8.00	C( 2) = 4.059918
K( 3) = -8.00	C( 3) = 2.634489
K( 4) = -8.00	C( 4) = 0.7202562
K( 5) = -1.55	C( 5) = 0.5258717
K( 6) = -0.700	C( 6) = 0.3207715
K( 7) = -0.530	C( 7) = 0.3264315
K( 8) = 0
K( 9) = 0
K(10) = 0
K(11) = 0

Table 20.2. Table of recommended values of the displacement length of helium II.

T90 (K)	(cm)
1.30	3.072E-8
1.35	3.183E-8
1.40	3.303E-8
1.45	3.432E-8
1.50	3.568E-8
1.55	3.710E-8
1.60	3.855E-8
1.65	4.010E-8
1.70	4.181E-8
1.75	4.386E-8
1.80	4.649E-8
1.85	4.998E-8
1.90	5.478E-8
1.95	6.171E-8
2.00	7.247E-8
2.02	7.862E-8
2.04	8.647E-8
2.06	9.682E-8
2.08	1.111E-7
2.10	1.320E-7
2.12	1.654E-7
2.14	2.281E-7
2.16	4.040E-7
2.162	4.426E-7
2.164	4.912E-7
2.166	5.546E-7
2.168	6.416E-7
2.170	7.701E-7
2.172	9.837E-7
2.174	1.432E-6
2.176	3.373E-6
2.1761	3.691E-6
2.1762	4.095E-6
2.1763	4.630E-6
2.1764	5.377E-6
2.1765	6.517E-6
2.1766	8.536E-6
2.1767	1.350E-5

C. F. Barenghi, R. J. Donnelly, and W. F. Vinen, “Friction on Quantized Vortices in Helium II. A Review,” J. Low Temp. Phys. 52, 189-247 (1983).