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The properties of the isotope He3 differ considerably from those of He4 at low temperatures because of quantum effects arising from the differences in their masses and in the statistics obeyed by the two molecules, At higher temperatares, where both substances behave classically, their properties become identical. Most of the previous work done on He3 has been in the liquid region in an attempt either to observe superfluid behavior or to establish the vapor-pressure curve as a primary temperature standard from 0.2° to 3.3°K. This study presents the P-V-T properties and C v for He3 in the temperature range from 4° to 20°K at pressures of up to 150 atm. These data and some of Keller’s data [1] have been fitted to a modified Strobridge equation and the derived thermodynamic properties S, H, and U have been obtained using this equation of state. In addition, using a quantum version of corresponding states, the P-V-T surface entropy and enthalpy have been predicted from 20° to 100°K. The correlation agrees well with the experimental results between 12° and 20°K. Combining the two regions, the properties of He3 have thus been determined from 1° to 100°K.

The nuclear magnetic resonance (NMR) properties of very high density 3He in metals are discussed in the context of the corresponding properties in relatively high density bulk 3He. In particular, the effects of 3He diffusion on the contribution of the 3He-3He dipolar interaction to the lineshape and to the spin-lattice relaxation parameter (T1) are described. It is shown that the temperature dependence of the lineshape and of T1 are independent sources of information about helium density and also about helium diffusivity. Moreover, T1 is shown to be a sensitive indicator of melting transitions in bulk 3He. Palladium tritide is presented as a model system for NMR studies of 3He in metals. Experimental NMR studies of this system reveal behaviour analogous to what has been observed for bulk helium. Evidence for a 3He phase transition near 250 K is provided by the temperature dependence of T1 Assuming this to be a melting transition, a density is obtained from the bulk helium EOS that is in good agreement with theory and with swelling measurements on related metal tritides. 3He NMR measurements have also provided information about the density distribution, helium diffusivity, and mean bubble size in palladium tritide.

The observation of free molecule drag coefficients below 2 for helium clusters of either isotope is taken to indicate quantum fluid inviscity of the helium microdroplets.

This paper reports on gas exchange research activities pursued at this laboratory, with the aim of increasing present knowledge on gas exchange and on the parameters which control it. Laboratory (wind tunnel) experiments as well as field work (with Rn-222 and He-3) are under way. — Two of the present authors (K.O.M. and D, F.) have previously presented [l] a theoretical treatment of the problem. Another, more detailed recent publication by Deacon [2] draws similar conclusions. The most important factor controlling gas exchange is wind speed; at low wind, however, surface cooling by evaporation is also to be considered.

We have found that the mobility of negative ions increases rapidly below Tc in both superfluid 3He phases. The ratio μ/μN of superfluid to normal mobility is larger in the B phase than in the A phase. A critical velocity consistent in magnitude with the Landau limit for pair breaking has also been observed. In the normal fluid we find a temperature independent mobility between 40 mK and Tc for all pressures between 0 and 28 bar. The increase of μN with increasing pressure is in agreement with the bubble model for the negative ion.

Information on the physics of superfluids and quantum solids is covered in the proceedings. Areas covered include: neutron scattering, ion motion and zero sound in liquid /sup 3/He; unusual quantum systems like spin-aligned hydrogen, /sup 6/He, superfluid solids, and liquid crystals; solid helium; quantum fluids and solids at low dimensionality; and properties of /sup 3/He-/sup 4/He mixtures. (GHT)

In 1966 a program was initiated at the NASA-Lewis Research Center to study the scattering of 600 MeV protons from light nuclei. Deuterium, Helium (3) and Helium (4) were chosen partly for experimental reasons, and partly because a systematic study of these nuclei might be most suitable for testing multiple scattering theories. Such theories require a good knowledge of the elementary interaction between the incident particle and the target nucleons, and the nuclear wavefunction (or equivalently Fermi momentum distribution). Therefore, we have supplemented existing nucleon-nucleon scattering data by measuring the p-p differential cross section and polarization, and we have determined the momentum distribution for the proton in the deuteron and in Helium (4) from (p,2p) measure-ments. In this contribution I will report our results of differential cross section and polarization in elastic p-p, p-d, p-3He, p-4He scatterings. The (p,2p) results will be presented by Perdrisat in a separate contribution to this conference. The experiments were performed at the proton synchrocyclotron of the NASA-Space Radiation Effects Laboratory in Virginia. Our team, in addition to W. K. Roberts, J. S. Vincent and myself consisted of M. Blecher, K. Gotow, P. C. Gugelot, C. F. Perdrisat, and L. W. Swenson of the Virginia Universities and J. R. Priest from Miami University.

In this lecture series, I will cover the following: 1. Atomic capture rate in hydrogen. 2. Molecular processes and molecular capture rate in liquid hydrogen. 3. Capture rate in He3. 4. Partial capture rate in nuclei. 5. Experimental partial capture rate.

We have studied the 6Li (p, p 3He) 3H, 7Li (p, pt) 4He and 12C (p, pd) 10B reactions at 156 MeV with kinematical conditions chosen so as to favour quasi-elastic scattering. The proton and the charged particle x were detected in coincidence; the angle and energy of the proton were fixed, and measurements were performed on particle x at several angles around the angle corresponding to q(recoil) = 0. The protons were analysed with a magnetic spectro- meter followed by a plastic scintillator telescope; the particles x were analysed in energy and identified by ΔE/Δx — E silicon solid state detector telescopes; identification was performed with an analogue Goulding identifier or with an on-line computer system.

Anderson and Johnson1 have measured the Kapitza resistance between liquid 3He and copper for the same copper surface in both the work-hardened and annealed states. Below 0.2°K the Kapitza resistance of work-hardened copper was found to be ten times smaller than that of annealed copper. This result probably explains the high Kapitza resistivities measured in dilution refrigerator heat exchangers compared to previous resistivity measurements on unannealed bulk copper.2 High-surface-area copper heat exchangers are generally sintered together at temperatures high enough to completely anneal copper.

The use of liquid He3 is proving to have many advantages over magnetic cooling for the convenient production of temperatures in the limited but useful range from about 1o to 0.3°K. This is especially so in the field of nuclear orientation, for in favorable cases (e.g., Ho, Tb, U, Np) considerable nuclear polarization—up to 85% in one case—can be obtained. It should be noted also that these nuclei are of special interest for study in such experiments, since they all possess very large permanent deformations. The apparatus described was designed for carrying out such experiments, in particular, for performing nuclear reactions with oriented nuclei. The first experiment that has been performed was to measure the (γ, n) cross section for aligned Ho165 nuclei in conjunction with a betatron [1]. Although certain features of the construction of the apparatus, especially the lower parts, are peculiar to this experiment and to nuclear orientation in general, the design is such as to make a wide variety of experiments possible by means of simple modifications. This is accomplished by making much of the lower part of the apparatus, i.e., the experimental space, demountable and therefore interchangeable, without altering at all the main cryogenic features of the apparatus.

In recent years the investigation of the interaction of hundreds MeV protons with complex nuclei accompanied with knocking out of lightest nuclei such as deuterons, tritium, helium and heavier ones has become one of the sources of new valuable information on the structure of complex nuclei, and mainly, on the structure peculiarities which are determined by intranuclear nucleon associations-clusters. Indeed, if such knocking out is considered as a result of direct interaction of incident protons with some nucleons of the nucleus, the reaction differential cross sections should be dependent on the parameters describing cluster behaviour and hence, it can be expected that such experiments can allow clarification of the certain features of the physical nature of cluster phenomena in nuclei.

The use of high-surface-area materials in dilution refrigerators has prompted several studies of the thermal resistance between such materials and dilute or concentrated 3He in 4He. Roubeau et al. t first reported anomalously high values for the Kapitza resistance of 20-μm-thick copper foil as compared with the Kapitza resistance of bulk copper. They proposed that this was a result of a thermal resistance between phonons and electrons. Wheatley et al.2 also saw this higher resistance when using 32-μm copper foil. We looked for this effect in sintered copper powders of 27, 20, and 2 μm diameter and also found high resistances.3 Our results were in semiquantitative agreement with Seiden’s calculations’ on the phonon-electron resistance.

In 1969 Doake and Gribbon,1 using the Cunsolo technique2 for measuring charged particle velocities, found a negative charge carrier with a much higher mobility than either the normal positive or negative carrier studied for the past fifteen years. They found that this new species, rather than producing vortex rings, reached a velocity apparently limited by roton creation. They were able to produce it below 1.05°K with large electric fields and a radioactive a source. We have studied a new species having similar characteristics and have found that a large family of negative charge carriers can be produced in liquid helium.3

This paper reports, for the first time, intense spectator peaks from the reaction D(3He,tp)p, which may result from quasi- elastic scattering (QES) accompanied by charge exchange (CE). Quasielastic scattering was first observed by Kuckes, Wilson and Cooper1, who found that large peaks (called spectator peaks) are observed in the p-p coincidence cross sections from the reaction D(p,2p)n when momentum is transferred only between the two protons, and the neutron (called the spectator particle) remains nearly at rest in the laboratory. QES from the proton in the deuteron has also been studied2-4 in the reactions D(d,dp)n, D(3He,3He p)n, and D(a,ap)n. In CEQES for D(3He,tp)p reaction (see Fig. la), the and neutron would transfer momentum and exchange charge, emerging as triton and proton, and the proton from the deuteron would remain nearly at rest. Alternatively, a direct knockout (KO) process (see Fig. lb) might also produce spectator peaks.

In this paper we report some,comparative results on the two-body photodisintegration of 3He and 4He niklei at a c.m. energy comparable with the first pion-nucleon isobar. We have measured the differential cross section at 90° in the c.m.s. for the reactions

Until the rare, light helium isotope, He3, became easily available in the early 1950’s the expression “temperatures below 1°K” was frequently used as a synonym for “cooling by adiabatic demagnetization.” There was some justification for this. It is true that even He4 permitted the attainment of temperatures somewhat below 1°K-the lowest seems to have been about 0.7°K-but this was rather the exception and a glance at the literature shows that the bulk of experiments using liquid He4 stopped near 1°K and work below this temperature relied almost entirely on the magnetic cooling method. He3 with its lower boiling point and higher vapor pressure has changed all this since quite a few He3 cryostats now operate down to 0.25°K. These cryostats are thus within the scope of this discussion. However, they will be treated rather briefly for the following reasons.

In a recent publication we presented the results of some measurements of the specific heat of liquid 3He/4He mixtures at saturated vapor pressure near the interesting junction of the lambda and phase-separation curves which occurs at a temperature T0 ≅ 0.87° Kand a 3He mole fraction x0 ≅ 0.67.1 The purpose of the present report is to indicate some of the possibilities for determining a variety of thermodynamic information about the junction region from the specific heat data.

Measurements of the viscosity of dilute solutions of 3He in 4He made by different groups show little agreement. Viscosities measured by Black et al.1and later by Fisk and Hall2 are quite different from those of Webeler and Allen3 and Bertinat et al.4 Webeler and Allen and Bertinat et al. used the torsional crystal method to measure lower viscosities, those of Bertinat et al. being an order of magnitude lower at low temperatures. The reason for this discrepancy is not known.

In the analysis of the photoproduction of pions from He3 and H3 presented earlier1 a pure S-state corresponding to the s 3 configuration was assumed for the ground states. As small admixtures of the mixed symmetric S‘-state and the S-state with T = 3/2 are found to play very important roles,2–6 it is worth studying the effects of these admixtures on the differential cross sections for the photoproduction of pions from these nuclei.