Electron Cyclotron Resonance Ion Trap Research Articles

High-precision x-ray spectroscopy in few-electron ions

The experimental and spectrum analysis procedures that led to about 15 new, high-precision, relative x-ray line energy measurements are presented. The measured lines may be used as x-ray reference lines in the 2.4–3.1 keV range. Applications also include tests of the atomic theory, and in particular of quantum electrodynamics and of relativistic many-body theory calculations. The lines originate from 2- to 4-electron ions of sulfur (Z=16), chlorine (Z=17) and argon (Z=18). The precision reached for their energy ranges from a few parts per million (ppm) to about 50 ppm. This places the new measurements among the most precise performed in mid-Z highly charged ions (Z is the nuclear charge number). The elements of the experimental setup are described: the ion source (an electron cyclotron resonance ion trap), the spectrometer (a single, spherically bent crystal spectrometer), as well as the spectrum acquisition camera (low-noise, high-efficiency CCD). The spectrum analysis procedure, which is based on a full simulation of the spectrometer response function, is also presented.

Precision studies on strong interaction in pionic hydrogen

The goal of the research program of the Pionic Hydrogen Collaboration at the Paul Scherrer Institute is a precise determination of the shift and width of the pionic hydrogen ground state induced by strong interaction. A crystal spectrometer is used to measure the X-ray transitions to the ground state in order to extract the strong interaction shift and width with a precision of ∼0.2% and ∼1% respectively. The improvement in the precision of the width will amount to almost an order of magnitude compared to the most precise former experiment. The isospin-dependent pion-nucleon scattering lengths can be determined from the shift and width. The high intensity pion beam available at PSI, a cyclotron trap and a high resolution crystal spectrometer provide optimal experimental conditions. For determining the resolution function of the crystal spectrometer the Bragg crystals are characterized using the high intensity X-rays from He-like ions produced in an electron cyclotron resonance ion trap. Measurements of X-ray de-excitation in muonic hydrogen - an exotic atom without strong interaction - were performed to study the effect of Doppler broadening due to Coulomb transition within the electromagnetic cascade which is an important systematic effect in pionic hydrogen and has to be understood in detail. This will allow the determination of the strong interaction width with unsurpassed accuracy, thus resulting in a precise value of the isovector pion-nucleon scattering length. The present status of the experiment and the preliminary results on the strong interaction shift and width are presented.

He-like argon, chlorine and sulfur spectra measurement from an Electron Cyclotron Resonance Ion Trap

We present a new measurement on X-ray spectroscopy of multicharged argon, chlorine and sulfur obtained with the Electron Cyclotron Resonance Ion Trap installed at the Paul Scherrer Institut (Villigen, Switzerland). For this purpose, we used a crystal spectrometer with a spherically bent crystal having an energy resolution of about 0.4 eV. High intensity Kα X-ray spectra were obtained from ions with one 1s hole ranging from almost neutral to heliumlike charge states. In particular we observed the 1s2s 3S1 → 1s2 1S0 M1 and 1s2p 3P2 → 1s2 1S0 M2 transitions in He-like argon, chlorine and sulfur with unprecedented statistics and resolution. The preliminary analysis presented here describes a new technique to measure precisely energy differences between transitions using a Johann-type Bragg spectrometer. A recent characterization of the spectrometer will allow for a drastic reduction of the systematic errors.

Highly charged ions in exotic atoms research at PSI

During their de-excitation, exotic atoms formed in low pressure gases reach a state of high or even complete ionization. X-rays emitted from higher n-states of electron-free atoms have well defined energies with the error originating only from the error in the mass values of the constituent particles. They served as a basis for a new determination of the pion mass as well as for a high precision measurement of the pionic hydrogen ground state shift. The response function of the Bragg spectrometer has been determined with X-rays from completely ionized pionic carbon and with a dedicated electron cyclotron resonance ion trap (ECRIT). A further extension of the ECRIT method implemented in the experiment allows a direct calibration of exotic atom transitions as well as a precise determination of the energy of fluorescence lines.

ECRIS as ion source and charge breeder

We will recall the main characteristics of ECR ion sources and their very good property of ionization efficiency. We will start with a review of on line use of ECR ion sources for production of mono or multicharged radioactive ions, and then we will specially focus our attention on charge breeding process for multicharged ion production. Initially developed for the PIAFE project from ISN Grenoble, the ECR charge breeder shows that the beam injection of a primary beam inside an ECR ion source is a very general process for beam production. We will review the latest results obtained on the ISN Grenoble test bench for the production of CW or pulsed metallic ion beams with the so called ‘1 +/ n +’ method. New results are given for CW operation where the efficiency is particularly optimized for application to multicharged radioactive ion production (for example, 3.5% for Zn 1+→Zn 9+, 4.2% for Pb 3+→Pb 24+, 5% for Rb 1+→Rb 15+). Different ion sources have been used to study the variation of the efficiency as a function of the energy of the 1 + primary beam. Charge-state distributions are especially measured for Pb and Rb ions. A new mode of operation, the Electron Cyclotron Resonance Ion Trap (ECRIT) breeder/buncher, which permits the trapping and the bunching of the n + ion beam is demonstrated and experimentally verified. This new method shows that it is possible to modify the time structure of the injected beam, just by trapping the ions inside the plasma and reextracting them by using the ‘afterglow pulsed mode’. We will finish by the presentation of the first result obtained with the first especially dedicated ECR booster developed at the ISN and called PHOENIX.

Electron cyclotron resonance ion trap: A hybrid magnetic system with very high mirror ratio for highly charged ion production and trapping

In the Paul Scherrer Institute [PSI Switzerland] an experimental program was started to measure the ground state shift and width of pionic hydrogen. To calibrate the crystal spectrometer x-ray transitions in hydrogen-like heavy ions (e.g., Ar17+), produced by electron cyclotron resonance (ECR) ion sources, are necessary. In PSI a superconducting cyclotron trap magnet, originally developed for particle physics experiments, will be transformed into an ECR ion trap (ECRIT). The SC magnet can deliver more than 4 T magnetic fields with a mirror ratio of 2. A careful calculation showed this mirror ratio can be increased upto 10 and the trap can operate with frequencies between 5 and 20 GHz. To form a closed resonance zone an open structure NdFeB hexapole will be applied. The first tests will be performed at 6.4 GHz. Later higher frequencies and the two-frequency heating (6.4+10, 6.4+14.5, or 10+14.5 GHz) are planned to be applied to get enough quantity of H-like heavy ions. The ECRIT will operate at ground potential while a simple 90° beamline (at negative potential) will help the fine tuning of the plasma for very high charge states.

Electron cyclotron resonance charge breeder (invited)

Initially developed for radioactive ion beam production, the electron cyclotron resource (ECR) charge breeder shows that the beam injection of a primary beam inside an ECR ion source is a very general process for beam production. In this article we will review the latest results obtained on the ISN Grenoble test bench for the production of clockwise (CW) or pulsed metallic ion beams with the so-called “1+/n+” method. New results are given for CW operation where the efficiency is particularly optimized for application to multicharged radioactive ion production (for example, 3.5% for Zn1+→Zn9+, 4.2% for Pb1+→Pb24+, 5% for Rb1+→Rb15+). Different ion sources have been used to study the variation of the efficiency as a function of the energy of the 1+ primary beam. Charge state distributions are especially measured for Pb and Rb ions. A new mode of operation, the electron cyclotron resonance ion trap breeder/buncher, which permits the trapping and the bunching of the n+ ion beam is demonstrated and experimentally verified. The injection of a 400 nAeRb1+ ion beam leads to a 11.5 μAe peak current of the Rb15+ ion beam extracted during the first ms. The temporal evolution of the cumulated particle transformation and trapping efficiency is measured in the case of Rb15+. This new method shows that it is possible to modify the time structure of the injected beam, just by trapping the ions inside the plasma and re-extracting them by using the “afterglow pulsed mode.” It will also be shown that it is possible to produce “multi-charged metallic ions” by using a primary source for the dissociation of a complex molecule and then by injecting the low charge state beam inside the multicharged electron cyclotron resonance ion source. A preliminary example will be presented for the production of U26+ by injection of U3+ obtained from dissociation of UF6 gas.

ECRIT: An Electron Cyclotron Resonance Ion Trap for Stable and Radioactive Ions Injectors, Accumulators and Targets

ECRIT: An Electron Cyclotron Resonance Ion Trap for Stable and Radioactive Ions Injectors, Accumulators and Targets

Electron cyclotron resonance ion trap, a multicharged ion breeder/buncher

The basic mode of operation of an electron cyclotron resonance ion source is recalled, particularly when using such a device as an ion charge breeder for the production of radioactive ion beams suitable for acceleration (1+→n+conversion). A new mode of operation, Electron Cyclotron Resonance Ion Trap (ECRIT), permitting to trap and bunch the n+ ion beams is demonstrated. The principle of the ECRIT mode is explained. The charge breeder/buncher system is experimentally verified by the injection of a 400 nA Rb 1+ ion beam leading to a 11.5 μA peak current of the Rb 15+ ion beam extracted during the first ms. The temporal evolution of the cumulated particle transformation efficiency is measured in the case of Rb 15+ and shows a 2.2% efficiency during the first 20 ms of the ECRIT extraction. The interest of the ECRIT mode is finally shown when used for the production of high-energy radioactive ion beams.