MMR's Variable Temperature Hall System (VTHS) allows the user to make automatic measurements of resistivity, mobility and carrier concentration of a wide range of samples using the Van der Pauw method over a temperature range from 70K to 730K. Sample mounting is simple and allows rapid interchange of samples. The VTHS Hall Measurement Controller, the H-50, is compatible with a variety of computers through an IEEE-488 (GPIA) or RS-232 interface. MMR's Benchtop Electromagnet and Programmable Power Supply complement the VTHS. The system uses the VTHS Dewar described below.
The VTHS Dewar is a low-profile Dewar designed to fit between the poles of a magnet to enable measurements to be made of the resistivity, Hall mobility and other properties of materials over a wide range of temperatures. Guarded triax leads provide electrical input to the sample via similarly guarded leads on a Kapton Harness to the sample on the cold stage. A Hall sensor immediately adjacent to the sample allows measurement of the magnetic field at the sample location.
In addition to the refrigerator and vacuum chamber, a temperature controller is needed, either manual or programmable; a source of dry nitrogen (99.998% purity); a filter dryer; and a vacuum pump capable of maintaining a vacuum <5 mTorr in the chamber. Other accessories that add to the convenience of operating the system are available from MMR.
MMR's Model M-25 Benchtop Permanent Magnet has been designed for use with MMR's Variable Temperature Hall System; the VTHS refrigerator and Dewar mount between the poles of the magnet. The magnet may also be used for a variety of other laboratory applications. It requires neither water- nor fan-cooling. It is a compact, efficient magnet standing only 7.5" high, and it occupies only 4" x 3" of bench space. It provides a vertical field of 5000 gauss between flat 2.5" x 3.0" pole pieces with a 0.75" gap. The size of the gap has been designed specifically for a good fit with the Hall Dewar System.
MMR's Model MK-50 Benchtop Electromagnet has been designed for use with MMR's Variable Temperature Hall System; the VTHS refrigerator and Dewar mount between the poles of the magnet. The magnet may also be used for a variety of other laboratory applications. It requires neither water- nor fan-cooling. It is a compact, efficient magnet standing only 7.5" high, and it occupies only 10" x 16" of bench space. It provides a vertical field of 5000 gauss with a 0.75" gap at 8 amps. The size of the gap can be easily adjusted.
The magnet is designed to be used with MMR's MPSK-50 Programmable Power Supply, and the VTHS-D Hall System Dewar, to provide rapid and simple determination of Hall mobilities of semiconductors over a wide range of sample temperatures from 70 K to 730 K.
MMR's Model M-150 Large Field Electromagnet is supplied with a 38 mm face diameter pole pair to provide the highest field versus current values. It provides a vertical field of 14000 gauss, operating with up to 40 amps of current. Higher current is possible but requires magnetic power supplies other than those provided by MMR Technologies. The size of the gap can be easily adjusted.
The magnet is designed to be used with MMR's MPS-150 Programmable Power Supplies, the C150 Chiller system, and the VTHS-D Hall System Dewar, to provide rapid and simple determination of Hall mobilities of semiconductors over a wide range of sample temperatures from 70 K to 730 K
MMR's Model MPSK-50 Programmable Power Supply is a 240 Watt, fully reversible power supply providing up to ±8 amps at up to ±30 volts. It is continuously controllable over both the current and voltage range window. The front panel liquid crystal display shows the voltage and current and any operating or error messages.
Easy to use, the only front panel controls are the reset button and display viewing angle adjustment. All controls are handled by a personal computer via an IEEE-488 (GPIB) or RS-232C interface, both interfaces are included in the MPSK-50.