Large Undulator Neodymium Permanent Magnets
China MPCO MAGNETICS has some customers, who request permanent magnets for undulator, like N50M neodymium arc magnets in large sizes, with cutted sides, Nickel coating, working temperature 80 ℃. Customers usually send us drawings with enough information. A few of them require spread of magnetization less than 0.5%.
As for the spread of magnetization of large neodymium magnets, it can only be tested when the magnets are finished. The size is very large and we do not have magnets with similar size in stock, so we are not able to estimate the value. But we can assure that the magnets will be produced with China’s highest technology and standard.
China MPCO MAGNETICS can supply large neodymium magnets used in undulator, as per current production status, delivery time for 300pcs is about 50-60 working days. Recently, Nd raw material price is rising rapidly and tends to increase continuely, price validity is only 2-7days.
What is “spread of magnetization”?
Some people may don’t know spread of magnetization, may think it as the consistency of Br value or surface gauss value or the magnetization angle error. It is the spread of the component of magnetization vector (it’s module is Br/(mu0)) along the direction of the thickness edge, averaged over the magnet volume. It usually can be measured by two methods. One is to measure the field far (about 1 m) from the magnet and then to calculate its total dipol magnetic moment. Typically it can be fixed to the hall probes at some positions and use a guide detail to install each testing magnet in the same position. Another one also measures the interesting component of the total dipole magnetic moment vector by inserting the magnet into the special solenoidal coil and integrating the voltage on coil over time.
For some customers, the surface field is not good specification in their case, as the neodymium permanent magnet is large, and magnetization may be different in different points of it.