Niobium is a soft, grey, ductile transition metal with atomic number 41. A majority of niobium is currently mined in Brazil, and its primary commercial use is as an alloy to improve strength, heat resistance and ductility in steel. Many different metals and alloys become superconducting if they get cold enough, but niobium has the highest transition temperature of any element. Niobium is also a nice material to build resonant structures out of, and can sustain high currents needed for accelerators. Niowave takes advantage of niobium’s superconducting properties to fabricate our highly efficient superconducting accelerators. High purity niobium has a value roughly equal to silver on a per pound basis. Niowave has invested significantly to build up the largest high-purity niobium stockpile in North America.
Niowave has over ten years of experience in custom fabrication of normal conducting and superconducting radio frequency cavities. We have built cavities for Brookhaven National Lab, Jefferson Lab, Los Alamos National Lab, Fermilab, CERN and others. Cavities range in frequency from 28 MHz up to 9 GHz. Niowave has experience building cavities of various shapes as well, including: elliptical cell, spoke, half wave, quarter wave, and crabbing cavities. With our stock of niobium, we are able to provide quick turnaround in fabrication by cutting out delays of material acquisition.
In superconducting accelerators, focusing of high-energy beams can be achieved by incorporating superconducting magnets into the module design. Especially for superconducting electron guns, a strong magnet near the exit of the gun is important to preserve the quality of the beam. Niowave builds superconducting magnets for accelerators, with in-house expertise in magnet design, winding of superconducting coils, and testing of the magnet assemblies before delivery.
The residual resistivity ratio (RRR) is an electrical measurement of the purity of niobium. The higher the RRR value, the higher the purity (and the thermal conductivity) of the material. Superconducting accelerators made with pure niobium can reach higher field levels, as the heat from the radio-frequency currents is better coupled to the helium bath. Niowave provides testing of niobium to determine the RRR value of bulk niobium, with just a small sample. Niowave is the only company in North America to offer this service, and we can report results within weeks of receipt of samples.
Niobium becomes superconducting at temperatures below 9.26 K. Liquid helium at atmospheric pressure boils at 4.2 K, making it a good refrigerant for superconducting accelerators. Niowave operates liquid-helium based cryocoolers with capacities of up to 115 W to cool our high-power electron accelerators. With our partners in the cryogenics industry we have also tested conduction-cooled cryocoolers up to 5 W at 4 K and integrated these systems with accelerator cryomodules. These low-cost industrial cryogenics systems are critical infrastructure for our superconducting accelerators. They are available for purchase for accelerators or other applications requiring significant cryogenic cooling capacity.