Plasma instabilities of a charge breeder ECRIS

Tarvainen, O.; Angot, J.; Izotov, I. V.; Skalyga, V. A.; Koivisto, H.; Thuillier, T.; Kalvas, Taneli; Lamy, T.

doi:10.1088/1361-6595/aa8975

Cited by 13 publications

(13 citation statements)

References 32 publications

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“…For example, with the LPSC charge breeder, a 50% decrease of the O 6þ beam current has been induced by a continuous injection of 1 μA of Cs þ ions [9]. Experiments have also demonstrated that, for particular magnetic configurations, the accumulation of injected Cs in the plasma can trigger kinetic instabilities which cause the charge breeding efficiency to collapse [10].…”

Section: Introductionmentioning

confidence: 99%

Charge breeding time investigations of electron cyclotron resonance charge breeders

Angot

Tarvainen

Thuillier

et al. 2018

Phys. Rev. Accel. Beams

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To qualify electron cyclotron resonance charge breeders, the method that is traditionally used to evaluate the charge breeding time consists in generating a rising edge of the injected beam current and measuring the time in which the extracted multicharged ion beam reaches 90% of its final current. It is demonstrated in the present paper that charge breeding times can be more accurately measured by injecting short pulses of 1 þ ions and recording the time resolved responses of Nþ ions. This method is used to probe the effect of the 1 þ ion accumulation in the plasma known to disturb the buffer gas plasma equilibrium and is a step further in understanding the large discrepancies reported in charge breeding times. The experiments are conducted injecting a 85 Rb þ ion beam into the Laboratoire de Physique Subatomique et de Cosmologie (LPSC) charge breeder operated with helium as a buffer gas. The time needed for the extraction of 90% of the multicharged ions in short pulse mode is found slightly shorter (9%) than the charge breeding time measured with the traditional method. The charge breeding efficiency is identical with both methods. The pulse width and amplitude of the 1þ injection pulses have been varied to study their influence on the Nþ response and temporal parameters are proposed to qualify the time response. The short pulse method can be used to study the influence of the ion source tuning parameters on the charge breeding temporal characteristics. For example, it is shown here that an increase of the minimum magnetic field strength of the LPSC charge breeder in the range 0.432-0.444 T improves the multicharged ion confinement in the electron cyclotron resonance plasma, and so increases the charge breeding efficiency. The short pulse method is also used to estimate the charge breeding efficiencies of radioactive Rb isotopes taking into account their half-lives and charge states. The neutron-rich heavy isotopes have short half-lives, which makes the charge state distributions shift to lower charge states and the estimated charge breeding efficiencies of high charge states being close to three times less in comparison to the stable ions.

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Section: Introductionmentioning

confidence: 99%

Charge breeding time investigations of electron cyclotron resonance charge breeders

Angot

Tarvainen

Thuillier

et al. 2018

Phys. Rev. Accel. Beams

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“…plasma potential inferred from the energy spread of the extracted ion beams and the ion current transient collected by the biased disk provides further evidence for the origin of increased impurity background of the extracted beams in the unstable operating regime, being especially relevant for charge breeder ECR ion sources. 9 The electron burst collected by the biased disk can be used for estimating the order of magnitude of the total electron losses, both absolute and the fraction of the confined electrons. It is assumed that the electron density in the 100-130 cm 3 volume enclosed by the ECR zone (estimated for the range of B min /B ECR of 0.75-0.80) is 10 11 -10 12 cm −3 , which translates to the total negative charge of 1.6-21 μC, i.e., on the order of 10 μC.…”

Section: Discussionmentioning

confidence: 99%

The biased disc of an electron cyclotron resonance ion source as a probe of instability-induced electron and ion losses

Tarvainen

Kronholm

Kalvas

et al. 2019

Review of Scientific Instruments

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“…In order to improve the CB operation in these two facilities, the LPSC continues the R&D on the PHOENIX charge breeder. In the context of beam production for physics, the reduction of the radioactive beams contamination is crucial, and is one of the main limitation for the use of ECR charge breeders, some recent work has shown that plasma instabilities may drastically increase this contamination [3]. Concerning the PHOENIX charge breeder, simulations have shown that the magnetic structure has some deficiencies that may affect the performances.…”

Section: Contextmentioning

confidence: 99%