Energetic Vacuum Deposition

Niobium loses its superconductivity when the magnetic field at its surface reaches a critical value. In the RF frequency regime, this could well be the H sh. Following recent developments of RF superconductivity (SRF), the solid niobium based technology is reaching its ultimate goal: limitation only by the intrinsic critical magnetic field of niobium material. Within a decade, the technology will likely be fully mature within the particle accelerator field.

Due to the nature of the niobium material, the cost of such an accelerator remains quite expensive. While the solid niobium technology is being perfected, the next generation of research on SRF needs to be focused on the reduction of costs for the niobium based applications and on the exploration of new materials with further potential.

Thin film niobium coatings on copper cavity structures have been explored and used for decades. If the performance can be improved to approach that of solid niobium, it could provide a sizable cost reduction for SRF-based particle accelerators.

Energetic vacuum deposition features both high vacuum and high deposition energy, which are the keys to obtain a high quality thin film. To achieve energetic deposition of niobium, an electron cyclotron resonance (ECR) was employed to create a niobium plasma. The energy of the niobium ions was controlled by a bias voltage to obtain the best film quality. A prototype of a single-cell coating system is presently being developed at JLab.

Cathodic arc deposition is another method that also features high vacuum and higher deposition energy. JLab has formed a collaboration with Alameda Applied Science Corporation to investigate the thin films made by such a process.

An illustration of approximate deposition energy is shown in above figure. Different materials will have different energy ranges.

Content by genfa@jlab.org
updated November 6, 2004