A miniatured built-in surface ionization oven for the compact microwave ion source

At Peking University (PKU), a compact 2.45 GHz microwave ion source was developed to obtain high-intensity Li+ beam. To improve the generation efficiency of Li+ ions, we developed a built-in lithium oven named surface ionization oven (SIO), which consists of a heating oven for lithium vapor production and a surface ionizer for the ionization of lithium neutrals. Consequently, the surface ionization and electron cyclotron resonance heating (ECRH) principles are combined within the compact microwave ion source. In this work, the structure and materials of the SIO are investigated systemically to lower thermal risk and increase ionization efficiency. The oven is heated by resistance heating. To minimize the heat loss, polished stainless steel shields are used to surround the oven. The surface ionizer is installed at the exit of the nozzle of the heating oven. It consists of six rhenium wires with the diameter of 0.25 mm inside the ionizer tube. Limited space near the microwave window, the dimension of SIO is ⊘ 13.5 mm × 40 mm. This source has been tested with only heating oven and SIO. With only heating oven, which means the absence of surface ionization, and a 200 eμA pulsed Li+ ion beam was stably extracted from this ion source. When the surface ionizer and the heating oven work together, a pulsed Li+ ion beam of 800 eμA is obtained, which increased by about 300%. The experiment proved that surface ionization could dramatically increase the discharge efficiency of lithium plasma in ECRIS.

[1]  Wenbin Wu,et al.  A global model of 2.45 GHz ECR ion sources for high intensity H+, H2+ and H3+ beams , 2020 .

[2]  Wenbin Wu,et al.  Design of a compact magnets system for a hybrid 2.45 GHz microwave 7Li3+ ion source , 2020 .

[3]  G. Ceccio,et al.  Optimization of laser-target parameters for the production of stable lithium beam. , 2020, The Review of scientific instruments.

[4]  Wenbin Wu,et al.  The preliminary test of multi-charged ions generation with a 2.45 GHz microwave-driven ion source. , 2020, The Review of scientific instruments.

[5]  V. Toivanen,et al.  Lead evaporation instabilities and failure mechanisms of the micro oven at the GTS-LHC ECR ion source at CERN. , 2020, The Review of scientific instruments.

[6]  Wenbin Wu,et al.  Preliminary design of a hybrid ion source for 7 Li 3+ generation , 2018 .

[7]  F. Carra,et al.  Numerical study of the thermal performance of the CERN Linac3 ion source miniature oven , 2018, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.

[8]  G. Anda,et al.  Development of a high current 60 keV neutral lithium beam injector for beam emission spectroscopy measurements on fusion experiments. , 2018, The Review of scientific instruments.

[9]  M. Hasuo,et al.  Spectroscopic measurement of the degree of ionization in a helium electron cyclotron resonance discharge in a simple cusp field , 2017 .

[10]  M. Kidera,et al.  Operational test of micro-oven for 48Ca beam. , 2014, The Review of scientific instruments.

[11]  J. Wilson,et al.  Development of a kinematically focused neutron source with the p(7Li,n)7Be inverse reaction , 2014 .

[12]  Jin-Young Jung,et al.  Development and testing of a lithium ion source and injector , 2012 .

[13]  V. Esaulov,et al.  Li + -ion neutralization on metal surfaces and thin films , 2011 .

[14]  N. Angert.  ION SOURCES , 2010 .

[15]  H. Kawano.  Effective work functions for ionic and electronic emissions from mono- and polycrystalline surfaces , 2008 .

[16]  C. Lyneis,et al.  High intensity metal ion beam production with ECR ion sources , 2001 .

[17]  F. Stienkemeier,et al.  Langmuir–Taylor surface ionization of alkali (Li, Na, K) and alkaline earth (Ca, Sr, Ba) atoms attached to helium droplets , 2000 .

[18]  J. Ärje,et al.  Metal ions from the volatile compounds method for the production of metal ion beams , 1998 .

[19]  W. Yokota,et al.  METALLIC ION GENERATION FROM CERAMIC RODS BY ECR ION SOURCE AND THERMODYNAMIC FEATURE OF VAPORIZATION , 1997 .

[20]  D. Fick,et al.  Determination of the work functions of Pt(111) and Ir(111) beyond 1100 K surface temperature , 1995 .

[21]  R. Ernst,et al.  An ECR source for Li3+ ions , 1990 .

[22]  R. Ernst,et al.  THE KARLSRUHE ECR ION SOURCES , 1989 .

[23]  Giacinto Scoles,et al.  Atomic and Molecular Beam Methods , 1988 .

[24]  H. Kawano,et al.  A new and simple method to determine the temperature coefficient of effective work function for thermal positive ion production on a clean polycrystalline metal surface , 1985 .

[25]  C. B. Alcock,et al.  Vapour Pressure Equations for the Metallic Elements: 298–2500K , 1984 .

[26]  D. Clark,et al.  Recent Developments in High Charge State Heavy Ion Beams at the LBL 88-Inch Cyclotron , 1979, IEEE Transactions on Nuclear Science.

[27]  R. Haug,et al.  A Lithium Ion Source Using the Surface Ionization Process , 1970 .

[28]  A. Persky.  Positive Surface Ionization of Na, NaCl, NaBr, NaI, and LiCl on Rhenium and on Oxygenated Rhenium Surfaces , 1969 .

[29]  S. K. Allison,et al.  Lithium Ion Sources , 1961 .

[30]  J. Giordmaine,et al.  Molecular Beam Formation by Long Parallel Tubes , 1960 .

[31]  Irving Langmuir,et al.  Currents Limited by Space Charge between Coaxial Cylinders , 1923 .