Tandem accelerators

During its last full year of operation the performance of the EN-Tandem-Accelerator was exceptionally smooth and reliable. Because of rather low voltage stresses - almost all users demanded less than 3 MV - no severe machine failures occurred. The spiral-inclined Ti-acceleration tube still is in excellent condition after more than 48000 hours of operation. Operation of the MP-Tandem suffered from various defects, most of them related to the charging system. Aging effects of plastic minor design errors caused several near-breakages of the chains which were, however, detected in time. Two dramatic failures of turbo-pumps occurred in the ion-source and tube-vacuum systems. Routine operation of the high-intensity sputter source in the pulsed mode for TSR-injections was started with 12C, 16O and 7Li beams. The cathode power-supply was improved and a pulse-current monitor has been built for continuous monitoring of source performance. The former 3 UH negative heavy ion injector of the MP is presently being converted into a positive proton accelerator for PIXE-μ-beam experiments. The terminal ion source equipment is in an advanced state of production, the penning ion source has been tested and is ready for installation. (orig.)