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Abstract: Superconducting RF (SRF) cavities are key components of modern linear particle accelerators. The National Superconducting Cyclotron Laboratory (NSCL) is building a 3MeV/u re-accelerator (ReA3) using SRF cavities. Lightly loaded SRF cavities have very small bandwidths (high Q) making them very sensitive to mechanical perturbations whether external or self-induced. Additionally, some cavity types exhibit mechanical responses to perturbations that lead to high-order non-stationary transfer functions resulting in very complex control problems. A control system that can adapt to the changing perturbing conditions and transfer functions of these systems would be ideal. This paper describes the application of a control technique known as “Active Disturbance Rejection Control” (ARDC) to this problem. [Copyright &y& Elsevier]

Abstract: The authors report on 6 years of tests with systems used to harvest pulpwood from the SRF poplar stands in the Pacific Northwest USA. Four systems are described and analyzed. All can produce in excess of 400 green tonnes per day and return delivered cost varying from $15–30 per green tonne. Transportation is a major item: depending on distance, it may represent 30–70% of total delivered cost. Two opposing strategies proved the most cost-effective. System 1—felling and bunching, forwarding and delimbing/debarking/chipping—is simplest and easiest to implement. System 4—the central yard option—is more complex and has higher stump-to-truck costs, but these are more than offset by substantial savings on transportation. [Copyright &y& Elsevier]