R. Geller

Electron Cyclotron Resonance Multiply Charged Ion Sources

We describe three ion sources working in our laboratory that deliver multiply charged ion beams. All of them are E.C.R. ion sources and are characterized by the fact that the electrons are emitted by the plasma itself and are accelerated to the adequate energy through electron cyclotron resonance (E.C.R.). They can work without interruption during several months in a quasi-continuous regime. (Duty cycle: <.5). Their charge state distributions (C.S.D.) depend on the size and the characteristics of the plasma. For the smallest source the performances are comparable to those of P.I.G. sources. For the biggest source, the C.S.D. tend towards those obtained by EBIS-type sources. Experimental results and guiding ideas concerning these three ion sources are reviewed.

The upgrading of the multiply charged heavy-ion source minimafios

The basic principles and performance of the Minimafios 10 GHz electron cyclotron resonance ion source (ECRIS) are reviewed. The source can operate either pulsed, with a pulse width of >50 ms, or ew, with 1011 fully stripped light ions per second and much higher amounts of lower charge state ions. The source has excellent reliability and reproducibility. It has good emittance and energy dispersion. The way of operation and adjustment of the source is very simple since it depends only on two parameters: gas feed and rf power injected. ECRIS is well suited for injection into heavy ion accelerators and for atomic physics. Thus more and better sources are desired. But the upgrading is not simple. In this paper, we show the experimental results when the electron cyclotron resonance is shifted from 10 to 16.6 GHz. This new source mainly aimed to small duty cycle acceleration (θ < 0.15) exhibits remarkable improvements in beam intensities and even more interesting results in the production of higher charged ions. A comparative study of the performances at 10 and 16.6 GHz is given.

Source d'ions lourds multicharges caprice 10 GHz pour tous les elements metalliques et Gazeux

Abstract A new compact multiply charged E.C.R. ion source completely enclosed by an iron return yoke is described. A new coaxial 10 GHz microwave accessibility is operating. This allows a very compact two stages source in an entirely removable vacuum chamber and a very easy increasing possibility of the axial magnetic field value. Then two different working modes are possible. A classical mode ( ω ce = ω rf , 100% cw, rf power 300 W, coils supply 20 kW) gives same performance than all the other reliable larger 10 GHz sources. A second mode (100% cw, rf power 600 W, coils supply 33 kW) operates with an additional resonant surface ω ce = 2 ω rf and increases by a factor 3 or 4 all currents on high charge states. Total extraction current is multiplied by a factor of 4 just as it would do by using a classical 20 GHz source by increase in density. This new resonant surface is unfortunately stopped in its radial part by the wall of the vacuum chamber due to a too low 10 GHz sextupole (0,4 T). Presently a better sextupole (0,8 T) is being built in order to work with both whole resonant surfaces inside the plasma chamber and perhaps so to improve charge states distribution by rising the plasma life time. On the other hand both the removable vacuum chamber and the coaxial rf feeder are well fitted to produce all metallic ions in long run and high intensity by working without any insulator inside the plasma chamber and by a good cleaning possibility. One shows cw spectra of 10 metallic elements from Al to Au and one can observe an exponential decrease for Ca, Ag and Au. This remark indicates a possible easy way to yield high charge states of all metals. One can expect to regulate all the easiest elements like Al, Si, Fe, Ni, Mo, Ta and W for 100 h. For example a good (within 1%) regulation of a 15 μA 56 26 Fe 7+ for 10 h is partly shown.

Source d'ions lourds caprice 10 GHz 2ωce

Abstract By using a new 0.8 T sextupole, the second step of metamorphosis of the ECR magnetic structure of the CAPRICE source is achieved. This ECR source was described in detail in a previous publication [2]. The 2 ω ce surface is now extended everywhere in the second stage except the extraction part. Thus, a strong flux of deconfined plasma is available at the extraction area and therefore high currents of high charge state ions are extracted. Optimum rf power is increased by a factor of 3 with respect to the single ω ce profile and currents of high charge state ions are increased by a factor of 10. The optimum performance for all gases and all solid elements is shown. The third step of the metamorphosis is planned for next year to achieve and work with two complete ECR surfaces. Future developments are also expected.

MINIMAFIOS — Nouvelle source d'ions fournissant des faisceaux d'ions lourds fortement multicharges

Abstract MINIMAFOOS is an ECRIS type source delivering multiply charged ion beam like MICROMAFIOS [1,2,7] but where the first and second stages are compound in a unique microwave cavity. There the microwaves create the cold plasma and heat the electrons, the plasma being confined by the min. B magnetic well in which the cavity is imemersed.

Minimafios, source d'ions pulsee fournissant des faisceaux d'ions completement epluches

Resumen The multiply charged ECR ion source MINIMAFIOS enables to operate in the pulsed regime with low repetition rates and in the cw regime. In both cases, the source can deliver 1011 N7+ ions per second. Under these conditions MINIMAFIOS can be utilized as an injector for synchrotrons as well as for continously working accelerators.

Nouvelle source d'ions multicharges a hautes performances

Abstract A new high performance multiply charged ion source is described. It is based on three magnetic bottles in series and containing electron cyclotron resonances. Results are given for CO 2 as test gas. Roughly ≈10 14 ions/s of C 5+ and O 6+ are extracted.

A High Intensity E.C.R. Stripped Ion Source

An ion source based on E.C.R. heating in a magnetic bottle works in our Laboratory since 1964. The characteristics of the plasma are: n = 1012 cm-3; w-> 1 keV ; W+ ~10 eV ; p > 10-5 torr. The microwave power P < 2 1KW at 10 GHz is coupled to the electrons either by a standing wave or a propagating wave. Our preliminary results with a 16 nA beam gave N+ = 44 %; N2+ = 36 % ; N3+ = 14 % ; N4+ = 4 % ; N5+ + N6++ N7+= 2 %. However due to the presence of H+2 the rate of N6+ and N7+ could not be measured correctly.

Source d'ions multicharges MINIMAFIOS: Nouvelles caracteristiques

Abstract New experimental characteristics and results of MINIMAFIOS are given. This multiply charged ECR ion source is now working on a 20 kV high voltage with only one microwave power generator feeding injector and stripper stage. Its performances have been improved while its maintainance and tuning problems have been simplified. Mltiply charged gaseous ion yields are given verses microwave power.

Project of a new type of neutral injector based on negative deuterons

Abstract We describe a new approach to D − injectors based on double charge exchange. The characteristics of a conceptual injector line are given and compared to other systems. The importance of the magnetic field is emphasized. A new type of D − injector immersed in a magnetic field is proposed.