Study On Thermal Conduct Perfoemance And Temperature Control Of Silicon ARM At Liquid Hydrogen Temperatures

The uniformity and consistency of the fuel target pellet are stronglydemanded for inertial confinement fusion reaction. The roughness of theinner surface of DT ice layer should be strictly controlled. To fabricatequalified target pellets and properly reserve them, stable cryogenicenvironment around liquid hydrogen temperature must be assured. Besides,an imaging diagnostic system is implemented to characterize and monitor theDT ice layer during the fabrication of the target pellet, which required steadytemperatures with oscillation within1mK. The target pellet is located at thecenter of a specially-designed hohlraum, which is placed at the ends of twosilicon cooling arms. Based on all the information above, a cryogenic systemat liquid hydrogen temperature is introduced in this paper. The silicon coolingarm is the investigation object, and researches on realizing temperaturecontrol with oscillation within1mK on it and the performance of the thermalconductivity of the arm are carried out.A construction-simplified silicon slice is used to substitute for thecooling arm as the subject investigated. An experimental system is designedand built up to conduct experiments on temperature control and thermalconductivity performance. Components like vacuum vessel, sample holder,clamps etc. are designed and manufactured. Thermal shields and multilayerheat insulation materials are fabricated for thermal protection. Propercryocooler and vacuum unit are selected and connected with other parts ofthe system. Furthermore, a data acquisition system based on LabVIEW is applied to automatically collect and store the data from temperature controller,temperature monitor and other instruments.Plenty of temperature measurements are required in our system, so anumber of temperature sensors were purchased. Since only a few of thesensors come with calibration tables, we need to calibrate the ones with nocalibration data before the experiments. Therefore, we designed anothersample holder where temperature sensors can conveniently be placed forcalibration. Calibration experiments are carried out. Through theseexperiments, we not only successfully calibrated all the sensors needed fortemperature measurements, but also had a more comprehensiveunderstanding on the characteristics of various types of temperature sensorsand their applicable temperature zone.Before conducting experiments on silicon slice, experiments ontemperature control performance on the sample holder were carried out, sothat we could analyze and improve the temperature control performance ofthe system itself. In this part, the subject investigated is the sample holderthat holds the silicon slice. The factors we studied that might influence theperformance of temperature control include the excitation for the sensors,control methods, the heat capacity of the sample holder and a secondary coldshield. Through a number of contrast experiments, this paper compared thecontribution of each factor to the suppression of temperature oscillation, andcame out with an optimized configuration to achieve best temperaturestability.Investigation on the thermal conductivity performance of silicon arm isthe most important part of the research. To better understand thecharacteristics of the thermal conduct performance of the silicon arm athydrogen temperatures, both practical and simulating experiments wereconducted. Furthermore, we also explored a new way for temperaturemeasurements and control, namely, to integrate the temperature sensors andheater into the silicon arm. This measure is expected to provide temperature measurements with higher accuracy and better control performance.