Abstract
The subject of this thesis is the theoretical and experimental study of matter at low temperatures, and the development of techniques to reach and measure these temperatures. A copper nuclear demagnetization cryostat was developed in order to reach low temperatures. This system distinguishes itself from other cryostats by its compact construction. The lowest temperature recorded by a pulsed Pt-NMR thermometer was 115 {mu}K. This system was used to search for superfluidity in solid {sup 4}He. Due to the large zero-point motion of the atoms, 4He remains liquid down to zero temperature; a pressure of 25.3 bar is needed to force the atoms in a lattice. Even in solid state, the {sup 4}He atoms remain very mobile, changing lattice sites at a frequency of approximately 10{sup 7} Hz. It is possible that solid {sup 4}He contains vacancies at zero temperature. These zero point vacancies are expected to behave like a gas of bosons, and should Bose-condense at some temperature. From experiments the upper limit to the vacancy concentration is set of 4{center_dot}10-5. (author). 217 refs.; 46 figs.; 2 tabs.
Citation Formats
Haar, P.G. van de.
A compact copper nuclear demagnetization cryostat and a search for superfluidity in solid {sup 4}He.
Netherlands: N. p.,
1991.
Web.
Haar, P.G. van de.
A compact copper nuclear demagnetization cryostat and a search for superfluidity in solid {sup 4}He.
Netherlands.
Haar, P.G. van de.
1991.
"A compact copper nuclear demagnetization cryostat and a search for superfluidity in solid {sup 4}He."
Netherlands.
@misc{etde_10111276,
title = {A compact copper nuclear demagnetization cryostat and a search for superfluidity in solid {sup 4}He}
author = {Haar, P.G. van de}
abstractNote = {The subject of this thesis is the theoretical and experimental study of matter at low temperatures, and the development of techniques to reach and measure these temperatures. A copper nuclear demagnetization cryostat was developed in order to reach low temperatures. This system distinguishes itself from other cryostats by its compact construction. The lowest temperature recorded by a pulsed Pt-NMR thermometer was 115 {mu}K. This system was used to search for superfluidity in solid {sup 4}He. Due to the large zero-point motion of the atoms, 4He remains liquid down to zero temperature; a pressure of 25.3 bar is needed to force the atoms in a lattice. Even in solid state, the {sup 4}He atoms remain very mobile, changing lattice sites at a frequency of approximately 10{sup 7} Hz. It is possible that solid {sup 4}He contains vacancies at zero temperature. These zero point vacancies are expected to behave like a gas of bosons, and should Bose-condense at some temperature. From experiments the upper limit to the vacancy concentration is set of 4{center_dot}10-5. (author). 217 refs.; 46 figs.; 2 tabs.}
place = {Netherlands}
year = {1991}
month = {Oct}
}
title = {A compact copper nuclear demagnetization cryostat and a search for superfluidity in solid {sup 4}He}
author = {Haar, P.G. van de}
abstractNote = {The subject of this thesis is the theoretical and experimental study of matter at low temperatures, and the development of techniques to reach and measure these temperatures. A copper nuclear demagnetization cryostat was developed in order to reach low temperatures. This system distinguishes itself from other cryostats by its compact construction. The lowest temperature recorded by a pulsed Pt-NMR thermometer was 115 {mu}K. This system was used to search for superfluidity in solid {sup 4}He. Due to the large zero-point motion of the atoms, 4He remains liquid down to zero temperature; a pressure of 25.3 bar is needed to force the atoms in a lattice. Even in solid state, the {sup 4}He atoms remain very mobile, changing lattice sites at a frequency of approximately 10{sup 7} Hz. It is possible that solid {sup 4}He contains vacancies at zero temperature. These zero point vacancies are expected to behave like a gas of bosons, and should Bose-condense at some temperature. From experiments the upper limit to the vacancy concentration is set of 4{center_dot}10-5. (author). 217 refs.; 46 figs.; 2 tabs.}
place = {Netherlands}
year = {1991}
month = {Oct}
}