TRIUMF Scientists Develop Innovative Multi-layer Carbon Film

Carbon thin films are used in a variety of applications, including beam strippers, particle accelerator targets, X-ray and extreme UV filters, charge-changing targets, and in-line attenuators. Many of these applications require that the carbon thin films be without a supporting substrate. Traditional self-supporting carbon thin films can be produced using a variety of methods. However, conventional techniques have certain limitations, particularly in regards to high beam current applications which may damage fragile stripping or extraction foils. Films made only of amorphous carbon film dissipate generated heat efficiently, but are mechanically weak and have a short lifetime under intense particle beams. In contrast, diamond-like carbon (DLC) film is very strong and durable but provides less efficient heat dissipation.

TRIUMF scientists, Dr. Stefan Zeisler and Vinder Jaggi, have developed an innovative carbon thin film that addresses the shortcomings of current technologies. Their product comprises alternating layers of nano-crystalline DLC and amorphous carbon, combining the mechanical strength of DLC and the heat dissipation efficiency of amorphous carbon. As a result, this carbon film is ideal in beam strippers. Using TRIUMF facilities, including a 3-Joule laser ablation system and a thermal evaporation chamber, the highly skilled team at TRIUMF is able to fabricate high quality layers of amorphous and DLC carbon films.
		One configuration of alternating layers of amorphous carbon and diamond-like carbon.

A wide range of layer configurations is possible, depending on the combination of properties desired for the final product. While TRIUMF offers several standard dimensions, it is also able to accommodate custom orders of different specifications. One method to produce a carbon thin film of three layers, for example, involves a series of steps. The first is to prepare an appropriate substrate, typically a highly polished glass or sapphire substrate, before applying a layer of soluble parting or release agent. Next, the substrates are placed in a thermal evaporation chamber, where rods of graphite are evaporated. The evaporated carbon atoms are deposited on the release agent to form the first layer of amorphous carbon. Then, the substrate is transferred to another chamber, where an ablation laser is directed on a rotating graphite disc in order to vaporize the carbon atoms. These atoms are deposited on top of the amorphous carbon layer to form the nano-crystalline DLC layer. Finally, the substrate is returned to the evaporation chamber to have a second amorphous carbon layer deposited on the DLC layer. The composite carbon film is then annealed and removed from the substrate. The composite carbon films that are produced exhibit improved initial mechanical properties as well as improved lifetime, thereby reducing maintenance and operator exposure.

		Stefan and Vinder recently brought their innovative product to India at the Asian Particle Accelerator Conference 2007, held in Indore at the Raja Ramanna Centre for Advanced Technology. The conference was an opportunity for scientists and engineers from around the world to share their experiences in the particle accelerator field and discuss the latest developments and future direction for research. The multi-layer carbon films were showcased at the conference in an exhibit, which attracted a great deal of attention and numerous expressions of interest from potential customers. Samples of the product have been sent to several interested parties, including Michigan State University and Fermilab.•
A representative of the Indian government, Vinder Jaggi, and Dr. Stefan Zeisler promote multi-layer carbon films with diamond-like carbon at their booth at the Asian Particle Accelerator Conference.

Roshena Huang

For more information about Applied Technology at TRIUMF, please visit the Technology Transfer website at:
http://www.triumf.info/public/tech_transfer/tech_transfer_5.php


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