Beam and installation improvements of the NIO1 ion source.

The NIO1 (Negative Ion Optimization phase 1) source can provide continuous beam operation, which is convenient for systematic parameter and equipment studies. Even in the pure volume production regime, the source yield was found to depend on conditioning procedures. Magnetic configuration tests continued adding magnets to the existing setup; the filter field component Bx has been progressively extended to span the -12 to 5 mT range, and as a trend, source performances improved with |Bx|. The progress of camera beam diagnostics and of the quality of the volume-produced H- beam is also shown. The status, off-line results, and reliability of a first NIO1 cesium oven are discussed; other upgrades in preparation (cavity ring down spectrometer, the end calorimeter, and conceptual tests of the energy recovery system) are also listed.

Development and installation of a radio frequency quadrupole cooler test.

A Radio Frequency Quadrupole Cooler (RFQC) prototype was adapted for insertion into a high uniformity magnetic field, with Bz up to 0.2 T, to improve radial confinement. While the RFQC purpose is to reduce (by gas collisions) the energy spread and emittance of a beam of radioactive nuclei, to finely select ion mass in nuclear physics, the prototype is tested in a setup including a stable ion source, a pepper pot emittance meter, and two Faraday cups; this makes a precise characterization of the RFQC feasible. The ion extraction was studied in detail by simulations, both to match it to the emittance meter granularity and to verify the effect of the typical nonuniformity of the longitudinal electric field Ez inside the RFQC; an average motion description (including friction force from gas collisions) was used, introducing the ballistic and diffusive regimes. With a preliminary optimization of the electrode shape, buffer gas pressure pg, and radio frequency voltage, the ion beam can be extracted with a significant cooling margin.

Integration of RFQ beam coolers and solenoidal magnetic fields.

Electromagnetic traps are a flexible and powerful method of controlling particle beams, possibly of exotic nuclei, with cooling (of energy spread and transverse oscillations) provided by collisions with light gases as in the Radio Frequency Quadrupole Cooler (RFQC). A RFQC prototype can be placed inside the existing Eltrap solenoid, capable of providing a magnetic flux density component B(z) up to 0.2 T, where z is the solenoid axis. Confinement in the transverse plane is provided both by B(z) and the rf voltage V(rf) (up to 1 kV at few MHz). Transport is provided by a static electric field E(z) (order of 100 V/m), while gas collisions (say He at 1 Pa, to be maintained by differential pumping) provide cooling or heating depending on V(rf). The beamline design and the major parameters V(rf), B(z) (which affect the beam transmission optimization) are here reported, with a brief description of the experimental setup.

Plasma-beam traps and radiofrequency quadrupole beam coolers.

Two linear trap devices for particle beam manipulation (including emittance reduction, cooling, control of instabilities, dust dynamics, and non-neutral plasmas) are here presented, namely, a radiofrequency quadrupole (RFQ) beam cooler and a compact Penning trap with a dust injector. Both beam dynamics studies by means of dedicated codes including the interaction of the ions with a buffer gas (up to 3 Pa pressure), and the electromagnetic design of the RFQ beam cooler are reported. The compact multipurpose Penning trap is aimed to the study of multispecies charged particle samples, primarily electron beams interacting with a background gas and/or a micrometric dust contaminant. Using a 0.9 T solenoid and an electrode stack where both static and RF electric fields can be applied, both beam transport and confinement operations will be available. The design of the apparatus is presented.

Scaling properties and intermittency of two-dimensional turbulence in pure electron plasmas.

When the cold nonrelativistic guiding center approximation is valid, the transverse dynamics of highly magnetized electron plasma columns confined in Penning-Malmberg traps is analogous to that of an incompressible, inviscid, two-dimensional (2D) fluid whose vorticity corresponds, up to a constant of proportionality, to the axially averaged electron plasma density. In this work intermittency phenomena in the freely decaying 2D electron plasma turbulence are investigated through scaling properties of the probability density functions and flatness of spatial vorticity increments, computed by analyzing the results of experiments performed in the Penning-Malmberg trap ELTRAP. It is shown that the intermittency properties of the turbulence strongly depends on the initial conditions and the relation of these results to the dynamics of the system is discussed.

Electrostatic diagnostics of nanosecond pulsed electron beams in a Malmberg-Penning trap.

A fast electrostatic diagnostic and analysis scheme on nanosecond pulsed beams in the keV energy range has been developed in the Malmberg-Penning trap ELTRAP. Low-noise electronics has been used for the detection of small induced current signals on the trap electrodes. A discrete wavelet-based procedure has been implemented for data postprocessing. The development of an effective electrostatic diagnostics together with proper data analysis techniques is of general interest in view of deducing the beam properties through comparison of the postprocessed data with the theoretically computed signal shape, which contains beam radius, length, and average density as fit parameters.

First Penning trap mass measurements beyond the proton drip line.

The masses of six neutron-deficient rare holmium and thulium isotopes close to the proton drip line were determined with the SHIPTRAP Penning trap mass spectrometer. For the first time the masses of the proton-unbound isotopes 144,145Ho and 147,148Tm were directly measured. The proton separation energies were derived from the measured mass values and compared to predictions from mass formulas. The new values of the proton separation energies are used to determine the location of the proton drip line for holmium and thulium more accurately.