J. Varju

A cryogenic electrostatic trap for long-time storage of keV ion beams

We report on the realization and operation of a fast ion beam trap of the linear electrostatic type employing liquid helium cooling to reach extremely low blackbody radiation temperature and residual gas density and, hence, long storage times of more than 5 min which are unprecedented for keV ion beams. Inside a beam pipe that can be cooled to temperatures <15 K, with 1.8 K reached in some locations, an ion beam pulse can be stored at kinetic energies of 2-20 keV between two electrostatic mirrors. Along with an overview of the cryogenic trap design, we present a measurement of the residual gas density inside the trap resulting in only 2 x 10(3) cm(-3), which for a room temperature environment corresponds to a pressure in the 10(-14) mbar range. The device, called the cryogenic trap for fast ion beams, is now being used to investigate molecules and clusters at low temperatures, but has also served as a design prototype for the cryogenic heavy-ion storage ring currently under construction at the Max-Planck Institute for Nuclear Physics.

Temperature dependence of binary and ternary recombination of H3+ ions with electrons

We study binary and the recently discovered process of ternary He-assisted recombination of

Recombination of H+3 ions in the afterglow of a He–Ar–H2 plasma

\text{H}_{3}{}^{+}

Status of the COMPASS tokamak and characterization of the first H-mode

ions with electrons in a low-temperature afterglow plasma. The experiments are carried out over a broad range of pressures and temperatures of an afterglow plasma in a helium buffer gas. Binary and He-assisted ternary recombination are observed and the corresponding recombination rate coefficients are extracted for temperatures from 77 to 330 K. We describe the observed ternary recombination as a two-step mechanism: first, a rotationally excited long-lived neutral molecule

Energy-sensitive imaging detector applied to the dissociative recombination of D2H+

\text{H}_{3}{}^{\ensuremath{\ast}}

Experimental study of para- and ortho-H3+ recombination

is formed in electron-

Application of NIR – CRDS for state selective study of recombination of para and ortho H3+ ions with electrons in low temperature plasma

\text{H}_{3}{}^{+}

Measurements of EEDF in recombination dominated afterglow plasma

collisions. Second, the

Recombination of KrD+ and KrH+ ions in afterglow plasma

\text{H}_{3}{}^{\ensuremath{\ast}}

Electron energy distribution function in the divertor region of the COMPASS tokamak during neutral beam injection heating

molecule collides with a helium atom that leads to the formation of a very long-lived Rydberg state with high orbital momentum. We present calculations of the lifetimes of