[en] We present work in progress on the development of a new technique for measurements of μs lifetimes of metastable excited states of He like ions. The key element in this new technique is an electrostatic storage device for ions with keV energies

[en] We have developed a very simple and compact fully electrostatic ion storage device. It consists of only three electrodes: two conical and one central cylindrical. This simple setup works as two focusing electrostatic mirrors forming a resonator-like structure and thereby confining the ions. We present the design and show the first test results demonstrating an ion-storage lifetime in the 100 ms-range at modest vacuum conditions. Storage lifetimes in the order of minutes are foreseen when UHV conditions are introduced

[en] An ongoing discussion revolves around the question of what effect hydrogenation has oncarbon backbone fragmentation in polycyclic aromatic hydrocarbons (PAHs). In order to shedmore light on this issue, we have measured absolute single carbon loss cross sections incollisions between native or hydrogenated pyrene cations (C₁₆H⁺_10+m, m = 0, 6, 16) and He as functions of center-of-massenergies down to 20 eV. Classical molecular dynamics (MD) simulations give further insightinto energy transfer processes and also yield m-dependent threshold energies for prompt(femtoseconds) carbon knockout. Such fast, non-statistical fragmentation processesdominate CH_x-loss for native pyrene (m = 0), while much slowerstatistical fragmentation processes contribute significantly to single-carbon loss for thehydrogenated molecules (m =6 and m =16). The latter is shown by measurements of large CH_x-loss crosssections far below the MD knockout thresholds for C₁₆H⁺₁₆ and C₁₆H⁺₂₆. Graphical abstract: .

[en] Kinematic and Thomas capture mechanisms are studied in fast (MeV) electron-transfer collisions between fast protons or He²⁺ ions and neutral helium.

[en] We have measured the dependence on the molecular orientation of the cross section for two-electron transfer from hydrogen molecules to fast (1.2 and 2.0 MeV kinetic energy) He''2''+ ions. A very strong angular dependence is found, where the maximum and minimum cross sections differ by more than a factor of three. Further the angular dependencies are markedly different for the two different projectile energies. The variations are explained as resulting from the interference of two waves describing projectiles neutralized in the proximity of either of the two target protons. The molecular axis orientation determines the phase difference of these two waves and thereby affects the cross section.

[en] An assembly consisting of a stack of three microchannel plates (MCPs) and a phosphor screen anode has been operated over the temperature range from 300 to 12 K. We report on measurements at 6.4 kHz (using an alpha source) and with dark counts only (15 Hz). Without any particle source, the MCP bias current decreased by a factor of 2.1x10³ when the temperature was lowered from 300 to 12 K. Using the alpha source, and a photomultiplier tube (PMT) to monitor the phosphor screen anode, we first observed an increase in the decay time of the phosphor from 12 to 45 μs when the temperature was decreased from 300 to 100 K while the decay time then decreased and reached a value of 5 μs at 12 K. The pulse height distribution from the PMT was measured between 300 and 12 K and shows a spectrum typical for a MCP phosphor setup at 300 K and 12 K but is strongly degraded for intermediate temperatures. We conclude that the present MCP-phosphor detector assembly is well suited for position-sensitive particle counting operation at temperatures down to at least 12 K even for count rates beyond 6 kHz. This result is crucial and an important part of ongoing developments of new instrumentation for investigations of, e.g., interactions involving complex molecular ions with internal quantum state control

[en] In preparation for the upcoming DESIREE (Double Electrostatic Ion-Ring Experiment) facility in Stockholm, electrostatic storage and particle detection has been tested in a cryogenic environment. For vacuum in the range of 10^-10 mbar lifetimes in excess of 10 seconds have been measured for keV beams of Ar⁺ and He⁺.

[en] A warm electron beam ion source (EBIS) for the production of multiply charged ions for injection into the heavy-ion storage ring ASTRID (Arhus STorage RIng Denmark) at the Institute of Physics and Astronomy, University of Aarhus, has now become operational. The aim is to produce moderately charged ions in amounts which match the requirements of ASTRID. For elements lighter than oxygen, ions of all charge states can be produced with sufficient intensity for injection. The same is true for heavier ions with charge states up to ∼15

[en] We have measured the spontaneous neutral particle emission from beams of copper cluster anions (Cu"−_N, N = 3 − 6) stored in an electrostatic storage ring. These experiments have show that multiple structural isomers may be present in the beam. (paper)

[en] We report on the commissioning of an electrostatic ion storage ring of small dimensions, the so-called Mini-Ring. We demonstrate its capability to store ion beam for up to tens of milliseconds.