Preliminary Design of a Systematic Gain Calibration Tool Using MATLAB

By Samuel Fanfan

This paper presents a project done in collaboration with Brookhaven National Lab for the application of Radio Frequency Beam Position Monitors (BPM). These Radio Frequency Beam Position Monitors are to be used in the particle accelerator facility (NSLS-II) post construction. The purpose of the RF BPM is to detect transverse beam position with sub-micron resolution and stability for normal operation conditions. The most crucial parameter of the BPM to accurately measure the position is for the gains of the four channels to be matched. Traditional calibration schemes comprise of manually adjusting a signal generator coupled to the RF BPM unit under test and recording the receiver signal strength for various power level settings. A MATLAB “RF BPM Cal Tool” has been developed to automate the process. The tool controls the signal generator and communicates with the BPM unit, both over TCP/IP, and was developed utilizing the MathWorks Instrument Control Toolbox. Remote control of the signal generator is executed using the VISA-TCP protocol in conjunction with SCPI commands. Communication with the BPM is established using the ModBus-TCP protocol and the raw data is read and handled by the Cal Tool. A created graphical user interface implements the aforementioned functionality. A final post-processing step is implemented in the GUI and exports the calculated systematic gain coefficients to a user-specified filed to be used for further verification. Testing of the tool proved successful, although a ModBus-TCP Slave program was used to simulate the yet-to-be-completed BPM unit under test. Further testing will be required once the final hardware is completed.

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