U Penn QuarkNet Abstract
Hardware and electronics
D. Ells and N. Zavanelli worked on the assembly of the cosmic ray tower. This included the testing of the proportional drift tubes, making sure that their connections were intact, that the capacitor connections and the ones to the Xilinx Field Programmable Gate Array (FPGA) were functioning as intended. They worked on establishing the optimal voltage for two scintillator paddles, which were used to trigger the detector. The above work involved learning how to solder at the millimeter level, reading the counter instruments, and using an oscilloscope to identify possible cosmic rays. They had to make sure that connections, voltage levels to power sources were appropriately set, and that the high voltage sources for the drift tubes were safely connected and handled. They managed to fix many of the problems with the drift tubes, so that two sets of 16 tubes were functioning so that the detector could track cosmic ray paths in two dimensions.
Software and programming
M. Macerato was responsible for programming the firmware of the Xilinx FPGA, which converted the electrical signals from the drift tubes and provided data for computer analysis. In order to do this he had to learn Verilog, the programming system for the FPGA. Since this differs substantially from programming languages like Java and C++, it was a daunting task even for a talented young programmer like him. But through many frustrating trials, he managed to design a number of alternate versions of the program, each time he ran into obstacles in reading the drift tube signals. In the final version of the program, he designed a counter driven scope-like acquisition of data, based on the FPGA inputs from all the drift tubes for a fixed number of 10 ns clock periods, and had the board send this information to the Raspberry Pi computer for analysis.
D. Grabovsky tackled the computer programming tasks. This involved taking raw data from the FPGA, storing them, and, using a functional algorithm, translating the numbers into a set of cosmic ray tracks. Since there were a number of iterations of the Verilog program for the FPGA, he had to rewrite his program for the Raspberry Pi each time. He succeeded because of his thorough understanding of the Math and the programming requirements.
The students were disappointed that they did not have enough time to identify cosmic tracks and to analyze these, in spite of the clear signals obtained from the drift tubes, but they certainly left with a much clearer idea of how experiments work in a physics laboratory. They had a thorough introduction into the complex and cumulative nature of cosmic ray detection and analysis.