Heavy-ion-induced electronic desorption of gas from metals.

During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dE_{e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

Generation of Soft X-Ray/VUV Photons with a Hybrid/Bias Micropole Undulator on the LLNL Linac.

The recently introduced class of micropole undulators, i.e., undulators with submilli-meter periods, promises a wide variety of useful applications in x-ray science and technology. One of the most important of these could turn out to be the efficient generation of highly coherent soft x rays on economical low-energy storage rings or linacs. Over the last year and a half, an intensive experimental effort has been in progress at the Lawrence Livermore National Laboratory (LLNL) to characterize the radiation emitted on a linac by a novel hybrid/bias micropole undulator fabricated at the Stanford Synchrotron Radiation Laboratory. In this initial report, the properties of this new 706-µm-period insertion device and its generation of 66-eV soft x rays on the LLNL linac are described. Although in the present experiment power levels of a fraction of a picowatt at linac currents of several tens of picoamperes were generated, this was in agreement with theoretical predictions. Operation of our prototype device on a higher energy machine at currents of several milliamperes could consequently be expected to produce milliwatt levels of soft x-ray output, making it an x-ray source potentially competitive with bending magnets on high-energy storage rings.