Recent improvements of the LPSC charge breeder

Angot, J.; Thuillier, T.; Tarvainen, O.; Baylac, M.; Jacob, J.; Lamy, T.; Migliore, Myriam; Solé, Patrick

doi:10.1063/1.5053347

“…Thus, the actual τ CB is defined ambiguously, which makes it difficult to compare charge breeding times measured with different charge breeders and operational parameters. Table I summarizes reported performances from the SPIRAL1 (GANIL, France) [2], CARIBU (ANL, USA) [3,11], and LPSC (France) [12] charge breeders. Large variations can be seen especially in the reported τ CB .…”

Section: Introductionmentioning

confidence: 99%

Charge breeding time investigations of electron cyclotron resonance charge breeders

Angot

¹

,

Tarvainen

²

,

Thuillier

³

et al. 2018

Phys. Rev. Accel. Beams

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…The 1+→N+ test bench [4] at LPSC Grenoble is dedicated to the development and characterization of the Phoenix CB-ECRIS. The 1+ beam line is used for generating, characterizing and injecting the 1+ ion beam into the CB-ECRIS and the N+ beam line for analysing the extracted multicharged beams.…”

Section: Experimental Methodsmentioning

confidence: 99%

Measurement of ionization, charge exchange and ion confinement times in charge breeder ECR ion sources with short pulse 1+ injection of metal ions

Luntinen

¹

,

Angot

²

,

Tarvainen

³

et al. 2022

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

The Consecutive Transients (CT) method is used for estimating the characteristic times of ionization, charge exchange and confinement within the plasma of a Charge Breeder Electron Cyclotron Resonance Ion Source (CB-ECRIS). The method reveals differences in the characteristic times between different source configurations, with K9+ charge breeding efficiencies of 8.9 % and 20.4 %, and allows qualitative explanation of the improved breeding efficiency. The increase in K9+ efficiency is accompanied by a decrease in ionization time for low charge states, a decrease of charge exchange time for high charge states, and an overall decrease of the ion confinement time, which increases non-linearly with the charge state. The charge exchange time exhibits a minimum near charge state K8+, indicating low neutral density near the plasma core. The CT-method yields a distribution of possible ne and (Ee) corresponding to the spatial distribution of different charge state ions. The results hint at a non-uniform plasma electron density and energy distribution as well as a nested-layer distribution for the ion populations — hot and dense plasma with high charge state ions near the plasma core.

show abstract

“…The charge breeder was assembled with a hexapole providing a 0.8 T radial magnetic field strength at plasma chamber wall, on the poles. An additional soft iron plug was mounted under vacuum to increase the axial magnetic field strength at injection [33]. The plasma electrode aperture diameter was 8 mm.…”

Section: Methodsmentioning

confidence: 99%

“…Table 2 summarizes the measured charge breeding efficiencies of charge states between K + and K 12+ . For reference, the best efficiency measured for K with He as a support gas was 11.7 % for K 10+ in the previous test bench configuration [33], i.e. the data were taken in conditions relevant for the charge breeding process.…”

Section: Methodsmentioning

confidence: 99%

Method for estimating charge breeder ECR ion source plasma parameters with short pulse 1+ injection of metal ions

Angot

¹

,

Luntinen

²

,

Kalvas

³

et al. 2020

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

A new method for determining plasma parameters from beam current transients resulting from short pulse 1+ injection of metal ions into a charge breeder electron cyclotron resonance ion source has been developed. The proposed method relies on few assumptions, and yields local values for the ionisation times 1 / n e σ v q → q + 1 inz , charge exchange times 1 / n 0 σ v q → q − 1 cx , the ion confinement times τ q , as well as estimates for the minimum plasma energy contents n e E e and the plasma triple products n e E e τ q . The method is based on fitting the current balance equation on the extracted beam currents of high charge state ions, and using the fitting coefficients to determine the postdictions for the plasma parameters via an optimisation routine. The method has been applied for the charge breeding of injected K+ ions in helium plasma. It is shown that the confinement times of K q+ charge states range from 2. 6 − 0.4 + 0.8 ms to 16. 4 − 6.8 + 18.3 ms increasing with the charge state. The ionisation and charge exchange times for the high charge state ions are 2. 6 − 0.5 + 0.5 ms–12. 6 − 3.2 + 2.6 ms and 3. 7 − 1.6 + 5.0 ms–357. 7 − 242.4 + 406.7 ms, respectively. The plasma energy content is found to be 2 . 5 − 1.8 + 4.3 × 1 0 15 eV cm−3.

show abstract

Recent improvements of the LPSC charge breeder

Cited by 10 publications

References 11 publications

Charge breeding time investigations of electron cyclotron resonance charge breeders

Charge breeding time investigations of electron cyclotron resonance charge breeders

Measurement of ionization, charge exchange and ion confinement times in charge breeder ECR ion sources with short pulse 1+ injection of metal ions

Method for estimating charge breeder ECR ion source plasma parameters with short pulse 1+ injection of metal ions

Contact Info

Product

Resources

About