Investigation On The Key Technology For Portable Atom Gravimeter

With the realization of the laser cooling and trapping atoms technology, the atom interferometry gravimeter as a new type of gravimeter was invented 20 years ago. Its sensitivity is closed to, even exceed the traditional gravimeter. The atom gravimeter has lots of advantages. First, it can measure not only the relative gravity, but also the absolute gravity. Second, it has a short measurement period, high precision and a stable performance. Currently, atomic fountain gravimeter has a sensitivity of up to 0.03 μGal(?)Hz. The development of atom gravimeter is still on the way to make it portable, more compact and low cost. It has an extremely high theoretical accuracy, which is applicable in many prospects, such as in resource exploration, global gravity mapping, earthquake prediction, inertial navigation, etc.The thesis is focused on the scheme and the realization of the portable atomic gravimeter. The key technology in the scheme will be introduced in detail from three aspects, which is the gravimeter sensor, the laser system, and the control system. In the following we will present the relevant experiment processes, including the preparation of the cold atoms, the state and velocity selection by the microwave and optical Raman pulses, and a sequence of three Raman pulses. Then we give the results of the gravity measurements, which contain the sensitivity of the gravimeter and the measurement of tide and absolute gravity value. The initial analysis of the major noise elements has also been discussed. Finally, we also investigate the environmental adaptability of the portable atom gravimeter, providing a reference for the outdoor measurements in the next step.Currently, we have designed and developed a high-precision portable atom gravimeter. Based on this apparatus, the short-term sensitivity of the gravity measurements is up to 1×10-8g@200.s as the interference pulse interval T is equal to 60ms. The change of gravity with the tide is also measured. In addition, the local absolute gravity is measured with a precision of gabs= 9.793362m/s2. Finally, We study the environmental adaptability of the gravimeter, and find if the environmental temperature rises up 10℃ in a short time, the noise level of gravity measurements will increase three to five times of its original level, which brings a new system error. If the environmental temperature quickly goes back to its original level, the noise and systematic error could automatically restore to the original level. Now, the gravimeter has realized the high-precision measurements of gravity, and the environmental compatibility study can provide a basis for future outdoor measurements. The contents of this thesis have guiding significance for the miniaturization and mobility of the atom gravimeter. The main content of each chapter is as follows:In the first chapter, the background and development status of atom gravimeter is introduced. At first, we present the applications and development of gravity measurements, and then we describe the development of atom interferometry gravimeter, and finally describe the current situation and prospects of the development of mobile atom gravimeter.In the second chapter, the theoretical basis of cold atom gravimeter is described, including the preparation of cold atoms, stimulated Raman transitions, the phase shift of atom interferometer and noise analysis theory.In the third, fourth and fifth chapters, the three important parts of the portable atom gravimeter-gravimeter sensor, laser system and control system are described in detail respectively. At first, we discuss the overall design and the requirements of the experiment, then introduce the details of the physical devices and the implementation process, finally give some of the test results.In the sixth chapter, the main experimental procedures and results based on the portable atom gravimeter apparatus are described. The experimental process mainly includes the preparation of cold atoms, the state preparation and cold atoms interferometry process. The results mainly include the fringe, the sensitivity analysis, the absolute gravity measurements and noise analysis.In the seventh chapter, the study of the environmental adaptability of the portable atom gravimeter is described, and the performance of the environmental adaptability is evaluated preliminarily.In the eighth chapter, a conclusion is given which contains the main results of the gravity measurements, the estimate of environmental adaptability and the current problems. Finally we look into the future of the atom gravimeter.