High pressure piston-cylinder apparatus at low temperature

High pressure piston-cylinder apparatus at low temperature G. Fujii and H. Nagano In order to study the galvano-magnetic effect of metals and semi-conductors under conditions of high pressure and low temperature, we have built a high pressure apparatus operating at liquid helium temperature. It is a direct piston displacement type, ~ and its basic form consists of a piston-cylinder cell, compression and tension components, and a high pressure off system. For the tension component, a long stainless steel pipe of 70 cm in length, and for the compression component a stainless steel rod were used, respectively. At one end of the tension component, there is an oil cylinder and at the other end two flanges. To facilitate easy changing of the sample the high pressure piston-cylinder cell is set between these flanges. Figure 1 shows a schematic plan of this apparatus. A pressure of up to 300 kg cm -2 (29 420 N m -2) is attained by the high pressure oil hand pump at room temperature and this pressure is transmitted through the fine stainless capillary tube of 0.083 in i d, 0.25 in o d, to the oil cylinder. High pressure in the oil cylinder acts on a compression component and also compresses the high pressure piston to increase the pressure inside the cell. The compression and tension components are made from stainless steel (SUS-27) due to its low thermal conductivity, ductility at the low temperature, and high yield strength. For the high pressure piston and cylinder, we used beryllium-copper alloys (Be 1-82%). As it is a non-magnetic material, we were able to measure the magnetic properties of the sample up to 27 k0e (2 047 A m-1 ) using a superconducting magnet. Beryllium-copper alloy is heat treated for 2½ hours at 310-+5 C and its R e hardness is 42. Figure 2 shows the high pressure piston cylinder cell. The sample chamber had been constructed from the pyropillite disc (8* x 2), the talc disc (8* x 2), the silver chloride disc, and the beryllium-copper disc stacked in sequence. The electrical lead wires could be freely extracted from between piston and cylinder clearance. Compared to the anvil-type cell, 2 the pressure attainable with this piston cylinder cell is lower but is suited to the measurement of fairly large samples. The sample, a single crystal of ytterbium or tellerium, is placed horizontally in a preformed cavity in a silver chloride disc. The arranged piston-cylinder cell is loosely compressed at room temperature, so that the silver chloride powder perfectly contains the sample, and is then cooled to liquid helium temperature. In this way, the experiment could be carried out without damage to the sample. In this apparatus, we measured the pressure dependence of the electrical resistance, transverse magneto-resistance,

The authors are with the Institute for Solid State Physics, University of Tokyo, Roppongi, Minato-ku, Tokyo, Japan. Received 27 August 1970. 142

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Figure 2. High pressure piston-cylinder cell CRYOGENICS . APRIL 1971

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and the Hall coefficient of single crystals of Yb and Te up to 17 kbar (1 700 MN m -2) between liquid helium temperature and 2 K by a d c method. In the case of Yb, the electrical resistance and the Hall coefficient increased with increasing pressure, while in the case of Te, the electrical resistance and the Hall coefficient

decreased. The transverse magneto-resistance decreased quadratically with magnetic field up to 27 kOe (2 047 A m -1 ), in both Yb and Te. With increasing pressure, the charge carrier density decreased in Yb but in the case of Te, it increased. The factor Np/No at 10 kbar was 0.6 in Yb and 2.2 in Te (Figure 3). 3 Our pressure scale was determined directly from the load/area ratio and the frictional effect was not considered. In order to determine the more accurate pressure scale, we should have to consider other methods, such as checking the pressure from the pressure dependence of the superconducting transition temperatures. 4

REFERENCES 1. SWENSON, C. A., and BEECROFT, R. I. J Appl Phys 30, 793 (1959) 2. CHESTER, P. F., and JONES, G. O. Phil Mag44, 1281 (1953) 3. FUJII, G., SHIMOMURA, O., MINOMURA, S., TANUMA, S., and NAGANO, H. (forthcoming) 4. SWENSON, C. A. Solid State Physics (SEITZ, F., and TURNBULL, D. (ed)) Vol 11, 41 (Academic Press, New York, 1960)

Measurement of the heat transport by conductivity of superfluid helium in 4 rn long pipes of 1-10 mm diameter C. H. Passow, G. Aupelt, R. Berg6tz, A. Heneka, W. Herz, H. Paetzold, L. Schaphals, and M. J. Spiegel The heat conduction in five different 4 m long pipes of a diameter of 1, 3, 5, and 10 mm was measured. The helium was at rest, that is, there was no mass transport in the pipes. The heat source was distributed along the pipe so that we achieved a heat flux of more than 1 W cm-2 at the end of the pipe. This is a highervalue than other authors measured in pipes of larger diameter. 1,2 Moreover the technical stability of the cooling system was verified. The experimental results were compared with theoretical calculations based on the two fluid model. It turns but that heat conduction in technical systems can be calculated sufficiently exactly with the two fluid model. The permissible heat flux in the helium seemed to be limited only by the possible temperature gradient. 3

Experimental set-up A vacuum tank was situated in a large cryostat filled with about 250 1 helium. Because of the large volume of the The authors are with Kernforschungszentrum Karlsruhe, Institut f o r Experimentelle Kernphysik, Karlsruhe, Germany. CHP is at present at the School of Electrical Engineering, Purdue University, Lafayette, Indiana, USA. Received 26 October 1970.

CRYOGENICS

. A P R I L 1971

helium reservoir temperature and pressure were stable even at high heat supply. Inside the vacuum tank five spiral pipes were installed. Table 1 gives the dimensions Of the pipes. A resistance wire which fed in heat was wound round the pipes to get a continuous heat distribution along the length of the pipe. To reduce the heat radiation, aluminium foil was wound round the pipes and the resistance filament. The two ends of the pipes were connected to the helium bath.

Temperature measurements The temperature was measured in the middle of the pipes and in addition at three other positions along pipe no 4 which was 5 mm diameter. We used calibrated germanium resistors as well as carbon resistors for temperature measurements. The most difficult problem was to get reasonable heat contact between the resistors and the pipes. Some resistors were pasted while others were fixed by winding thin wire around the resistors and the pipe. In addition we calibrated the resistors during the experiment by measuring the vapour pressure of the helium bath. The calibrations were done at high vacuum (10 -6 torr [1 torr = 133 N m - 2 ] ) as well as at low pressure (1 torr) in 143