At PSI, there is a growing interest in superconducting magnets build with Hight Temperature Superconductors (HTS) technology. The need to characterize these magnets during dynamic operation is becoming increasingly important. Although HTS magnets allow for large operational margins, they might exhibit poor field quality and/or excessive AC losses, depending on the practical design.
To assess field quality (i.e., field harmonics), the most suitable measurement technique is the rotating coil method. However, the measurement systems currently available at PSI are designed and implemented for magnets operating under steady-state conditions. As a result, the entire computational burden is shifted to post-processing. Moreover, data streaming during coil signal acquisition is time-limited (typically 5 s). This significantly simplifies the control software, as there is no need for sophisticated design patterns to manage the continuous reading and storage of large data volumes, which could otherwise create a bottleneck in the acquisition speed.
To meet the requirements of field quality measurements during dynamic magnet operation, a portion of the computational workload must be moved to real-time signal processing. This includes the numerical integration of the coils voltage signals once they have been converted into the digital domain. This approach preserves measurement accuracy while reducing the required data transmission rate, owing to the downsampling inherent in the integration process.
Typical measurement setups for AC losses in HTS magnets involve the use of expensive lock-in amplifiers. With appropriate hardware and clever signal processing, these instruments can be replaced by the same hardware used for real-time rotating coil measurements.
Within the framework of implementing real-time processing of rotating coil signals and the potential reuse of hardware for AC loss measurements, the objective of this work is to design, test, and commission the numerical integration of measurement coil signals on an NI FPGA board. The main tasks associated with the internship are:
- Get familiar with NI FPGA reconfigurable modules
- Design and develop NI LabVIew FPGA code that meets measurement requirements
- Commission the FPGA application during field quality measurements of actual magnets
- Integrate the new HW and SW in the existing Rotating Coil measurement control application