Design Of Calorimeter For Beam Detection Of HUST RF Negative Ion Source

To carry out the research on the key technology of powerful RF driven negative ions source used for neutral beam injection(NBI) for magnetic confinement fusion(MCF) reactor, HUST has been developing an experimental facility since 2011 under the support of the Ministry of Science and Technology(MOST) of China. In the first phase, a RF driver has been built which produces the plasma required for yielding the negative ions. The next goal is to develop a full negative ion source by adding cesium system and extraction system on the basis of the first phase. This paper designed a calorimeter for negative ion beam measurement of the source, to effectively detect the beam parameters such as the beam profile, power distribution and beam density distribution, which is an important part of the RF negative ion source to ensure the source can reach relevant parameters, and to lay the foundation of beam detection for the future RF negative ion source with larger extraction area and higher intensity.Through the simulation analysis of various type of calorimeter structure, this paper chose a nearly adiabatic calorimeter, not only can it ensure the accuracy and resolution of beam detection, but also meet the requirements of fast repetition, long pulse beam measurement. Designed Calorimeter chose the separate small copper block as a beam collector, copper blocks attached to the water cooling plate by the use of tiny copper column, this structure can avoid the heat exchange between the collectors and to ensure the spatial resolution of beam measurement; The tiny copper column is used to conduct the heat from collector to the water cooling plate, not only can it cool down the collector in a relatively short period of time after completing a measurement, but also won't cause large error of measurement; So that the collector can effectively recovery temperature and implement the next measurement. This paper has analyzed the water cooling part, part to ensure the water will cool the calorimeter temperature down in the limited time internal, thus ensuring the calorimeter can run stably for a long time to complete the measurement of fast repetition beam pulse. This paper has completed the design of the data acquisition system and control system of the calorimeter, studied the calorimeter data processing method, and written the program to calculate the beam parameters such as beam width and divergence according to the measurement data from the calorimeter. Developed a small simulation test device, the heat blower simulation experiments and electron beam irradiation experiment verified the feasibility and reliability of the calorimeter.