Customer SolutionsDetection and Protection of Superconducting Accelerator Magnets with LabVIEW, PXI
Author(s):Ruben Carcagno, Fermilab National Accelerator Laboratory
Industry:Energy/Power, Research
Product:LabVIEW FPGA, PXI/CompactPCI
The Challenge:Updating a superconducting accelerator magnet test system to be more portable and scalable.
The Solution:Replacing the outdated system, composed of NIM and VME modules, with a single system based on National Instruments LabVIEW software and PXI hardware.
At Fermilab, we created our previous superconducting accelerator magnet test system at our Magnet Test Facility (MTF) from VME and NIM modules. We used this system for several years, and, though it was very reliable, the system lacked the scalability required for a new series of tests we were developing. But with National Instruments software and hardware, we were able to design a system to meet all of our requirements, including quench protection. Quench Protection Superconducting accelerator magnets generally need to be cooled significantly to reach the levels of conduction required for a superconductor. Quenching happens when a resistive point occurs in the magnet. A quench can be very dangerous for a superconducting magnet because the increased resistance begins to immediately dissipate the energy in the magnet as heat, creating extreme temperature gradients. It is imperative that we detect the quench quickly so we can take protective measures. These magnets are very expensive. If they survive a quench, they can reach even greater levels of conductivity when the process is repeated. We now can meet the entire MTF quench detection and protection standard using the National Instruments PXI-7831R reconfigurable multifunction I/O module. This capability provides for a smaller, more portable test system than was previously attainable. We also implemented several safety features to further protect the magnets under test. These safety features include a heartbeat from the NI PXI-7831R, normally closed logic, signal saturation protection, and the capability to accept an external trip. With these features, we can use external systems in conjunction with the test system to prevent damage to the magnet in the event of a power failure or unplugged cable. The PXI-7831R contains an FPGA that is reconfigurable using the NI LabVIEW FPGA Module. With the PXI-7831R, we can detect and protect against quench in the superconducting magnet. To quickly and easily program the PXI-7831R, we use the LabVIEW FPGA graphical user interface, which we can access from a standard Windows XP machine or from a Web browser through the Remote Panels feature in LabVIEW. This flexibility increases system usability and safety because the user does not have to be next to the magnet during testing. We use additional modules in the PXI chassis to log data to characterize the quench. Using the PXI backplane, the PXI-7831R triggers the NI PXI-6143 S Series multifunction data acquisition module to capture data during the quench. A LabVIEW application running on the PXI controller programs the NI PXI-6733 high-speed analog output module that controls the power supply. Because of the modularity of the PXI system, multiple systems can coexist independently in the same chassis for simultaneous testing of multiple units. Successful Applications We used and verified the new PXI-based system in two types of superconducting magnet test systems – a corrector coil measurement system (we tested this twice) as well as two vertical magnet test facilities (VMTFs). One of our corrector coil tests showed that three corrector coils exhibited no adverse effects due to coupling of the coils. The multiple system configuration worked well in the corrector coil tests, and the data loggers performed satisfactorily during the VMTF tests. The VMTF tests also incorporated quench propagation heaters and an energy extraction (dump) resistor to protect the magnet conductor. In all tests, the new PXI-based system performed admirably. Because the LabVIEW graphical programming environment is very easy to understand, programming the PXI-7831R and conducting system maintenance and upgrades are easier than if we used a lower-level programming language. We can include extra modules in the PXI chassis for testing multiple magnets simultaneously. The PXI-based system provides all the functionality of the previous VME- and NIM-based system with less hardware and more flexibility. For more information, contact: R.H. Carcagno Fermilab National Accelerator Laboratory Tel: (630) 840-3915 Fax: (630) 840 4343
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