Low Temperature Heat Pulse Thermal Relaxation Calorimeter

1. Low Temperature Heat PulseThermal Relaxation Calorimeter ●Principle The specific heat of a substance is defined as the quantity of heat required to raise the temperature of a unit mass of the substance by a unit degree of temperature. The heat capacity is then obtained as ●Technique The calorimetry technique used here is known as the time constant or relaxation method. It consists of changing step-wise the power supplied to the sample. The variations of heater power and chip temperature are sketched below. Power and temperature during a transient Sample mounting schematic chip The heat capacity is calculated by C= ד(1/RTH) =ד (∆P/∆T0),where RTH=∆T0/∆P is the effective thermal resistance involving sample, chip and wire. ד=time constant which can be obtained from the result of thermal transient. ●Experimental chart Transfer liquid helium into Dewar Check the needle valves in 1 K pot and sorb Put the probe into Dewar Vacuum the OVC of Dewar Cooling the He3 pot down to 0.5 K Cut the specimen into propersize (2 mg) Start the measurement Mount sample Put in the active carbon and connect T-cell with probe Put in the exchange gas into IVC (helium gas ) Vacuum the IVC of probe Put the probe into tank Bake active carbon ●Result Field dependence of C/T vs T2 Calibration of copper with various magnetic fields Schematic diagram of the insert of the calorimeter