G. Shirkov

Production of low energy, high intensity metal ion beams by means of a laser ion source

The ECLISSE (ECR coupled to Laser Ion Source for charge State Enhancement) project started in 1999 with the aim to obtain an intense beam of highly charged ions (pulsed mode) by means of the coupling between a laser ion source (LIS) and an electron cyclotron resonance (ECR) ion source. The major points to be investigated appeared to be the coupling efficiency between the ion beam produced by the LIS and the ECR plasma, as well as the possibility to enhance the available charge state by an ECRIS with respect to the standard methods which are used to produce ion beams from solid samples (e.g., evaporation, sputtering). The calculations have confirmed that this concept may be effective, provided that the ion energy from the LIS is lower than a few hundred eV. The main features of the calculations will be shown, along with the results obtained in the off-line test facility at laser power densities below 1011 W/cm2.

Preliminary tests for the electron cyclotron resonance ion source coupled to a laser ion source for charge state enhancement experiment

At the Laboratori Nazionali del Sud we have designed a hybrid ion source, consisting of a laser ion source as first stage, which gives intense currents of electrons and of multiply charged ions, followed by an electron cyclotron resonance (ECR) ion source as a second stage, which should act as a charge state multiplier. The ECR ion source coupled to a laser ion source for charge state enhancement (ECLISSE) experiment has been funded by INFN and preliminary experiments have been carried out at IPPLM in Warsaw, in order to confirm the beneficial effects of the axial magnetic field of the ECR ion source on the extraction of the ions from the LIS, as foreseen by calculations. The description of the ECLISSE experiment and of the results of the preliminary tests will be reported.

The electron cyclotron resonance coupled to laser ion source for charge state enhancement experiment: Production of high intensity ion beams by means of a hybrid ion source

The experiment concerning the ECLISSE method (ECR ion source coupled to a laser ion source for charge state enhancement) has been carried out by coupling a laser ion source (LIS) to the superconducting electron cyclotron resonance source (SERSE) electron cyclotron resonance (ECR) ion source with the goal to obtain intense beams of highly charged ions (cw or pulsed mode) from metal samples, especially from refractory elements. The coupling efficiency of the ion beam produced by the LIS with the ECR plasma was remarkable and the measured beam intensities were quite high. The maximum charge states, obtained with a good reproducibility, were 38+ for Ta and 41+ for Au. The highest current was obtained for 25+ and 28+ for Ta and Au ions, respectively, and it was in both cases of the order of some tens of microampere, i.e., higher than the current obtained from SERSE with other methods (i.e., evaporation and sputtering). The ion beam stability and reproducibility were both acceptable. The possibility to get a fu...

Multilayer Scintillator Responses for Mo Observatory of Neutrino Experiment Studied Using a Prototype Detector MOON-1

An ensemble of multilayer scintillators is discussed as an option of the high-sensitivity detector MOON (Mo Observatory of Neutrinos) for spectroscopic measurements of neutrinoless double beta decays. A prototype detector MOON-1, which consists of 6-layer plastic scintillator plates, was built to study the photon responses of the MOON-type detector. The photon responses, i.e., the number of scintillation photons collected and the energy resolution, which are key elements for high-sensitivity experiments, are found to be 1835 � 30 photoelectrons for 976 keV electrons and � ¼ 2:9 � 0:1% (� E=E ¼ 6:8 � 0:3% in FWHM) at the Q�� � 3 MeV region, respectively. The multilayer plastic scintillator structure with high energy resolution as well as a good signal for the background suppression of � –� rays is crucial for the MOON-type detector to achieve inverted-hierarchy neutrino-mass sensitivity. It will also be useful for medical and other rare-decay experiments as well.

Influence of the biased electrode on the plasma potential in ECRIS

Dedicated experiments have been carried out at the Frankfurt 14 GHz electron cyclotron resonance ion source (ECRIS) by using a special double biased-electrode assembly, which consists of a conventional disk electrode and a separately biased ring electrode installed in front of it. In this assembly, the ring can be used to modulate the fluxes to the disk and allows a detailed study of the role of secondary electron fluxes in ECRIS operation. It was found that these fluxes contribute more than 50% to the total disk currents. However, blocking them did not result in a drop in the extracted ion currents. Instead, it was observed that, under certain operational conditions, the injection of secondary electrons results in a decrease in the extracted currents by up to 20%. Parallel to the double disk measurements, Langmuir probe measurements have been performed close to the position of Bmax. From the probe characteristics, plasma potentials were determined to be about +30 V at the conditions of the experiment. Ap...

Time resolved experiments at the Frankfurt 14 GHz electron cyclotron resonance ion source

Time resolved measurements of the extracted ion currents at the Frankfurt 14 GHz electron cyclotron resonance ion source (ECRIS) are reported. These measurements were performed to provide more detailed information on the “biased disk effect” in an ECRIS. From a first series of measurements with pulsed biased disk voltage it was concluded that the “biased disk effect” is mainly due to improvements of the extraction conditions and the enhanced transport of highly charged ions into the extraction area. In this article we present new measurements with an improved setup allowing for a faster pulsing of the biased disk voltage. We also present data for the injection of neutral particles from laser ablated plasmas and Bremsstrahlung spectra for different dc biased disk voltages. All results from these measurements support our previous conclusion.

Fundamental processes determining the highly charged ion production in ECR ion sources

Abstract The ion confinement and loss conditions in the open magnetic traps have been analyzed in this article. In ECRIS the ions are confined in the negative potential well. The ions with higher charged states have the longer lifetimes and the less probability of escaping from the negative potential well. The mean charged ion state in the trap is higher than in the output ion beam. The general methods to increase the multiply charged ion extraction from the ECRIS are determined. The usage of the ion cooling mode to increase charged ion states in the plasma is substantiated. The large output pulse of multiply charged ions in the rf pulse mode is explained. The numerical simulation of the ion cooling and rf pulse processes for the MINIMAFIOS type ECRIS has been carried out. The simultaneous applications of ion cooling and pulse regime is proposed for pulse injection of highly charged ions in heavy ion accelerators and storage rings.

Plasma diagnostics at electron cyclotron resonance ion sources by injection of laser ablated fluxes of metal atoms

Short pulses of neutral particles generated by laser ablation of metal targets have been injected into the Frankfurt 14 GHz electron cyclotron resonance (ECR) ion source. Rise/fall times of pulses of highly charged ions of Cd and Mg were registered as a function of microwave power and gas pressure. From a comparison of the measured data to numerical simulations, values of the electron density and the temperature in the ECR plasma were estimated to be about 0.75×1012 cm−3 and a few keV. The effective electron temperature increases with increasing microwave power and decreases with increasing gas pressure. The electron density is only a weak function of the microwave power, but increases significantly with the gas pressure. In the Ar/O2 gas-mixing mode of operation, an improved confinement of lowly charged ions was observed.

Particle-in-cell code library for numerical simulation of the ECR source plasma

The code library is aimed for the three-dimensional simulation of the electron cyclotron resonance (ECR) plasma and ion production in an ECR ion source. The particle-in-cell method allows studying the detailed characteristics of plasma, taking into account distribution functions of particles real self and external fields, particle–particle interactions, and others.

Multicomponent consideration of electron fraction of electron-cyclotron resonance source plasma

The development of a model of electron and ion accumulation and production in the electron-cyclotron resonance (ECR) ion source is presented. Any kind of experimental or analytical electron distribution function can be approximated with a series of Maxwellian distributions with different temperatures and partial weights. A main positive plasma potential with negative potential dip is introduced into consideration. The first test of a new model and code with recent experimental data of the RIKEN 18 GHz ECR source has shown some new opportunities for investigators to study the ECR ion sources.