摘要:

This paper describes a special designed 8‐cm‐diam broad beam ion source. Special cusp magnetic fields are used to control the beam spot area by magnetic convergence, so that a focusing beam can be extracted from a simple two‐grid accelerator system without using dished grids. A beam current over 350 mA can be extracted from this source for argon gas, and the maximum of beam current density is over 20 mA/cm2at a location 40 cm downstream of the source. The highest energy of the extracted ions is about 10 keV and the maximum of sputter coating rate from high to low sputter yield of target material is 15 A˚/s for aluminum, 7.5 A˚/s for titanium and 2.5 A˚/s for graphite, respectively.

ISSN:0034-6748    

DOI:10.1063/1.1144966

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Experiments involving polarized beams and/or internal polarized targets are performed or proposed at many laboratories equipped with various type of accelerators and storage rings. Currently, the most powerful sources of polarized atoms and ions base on the atomic beam and the optical pumping methods. The present status of the polarized hydrogen source is discussed, with emphasis on the most recent improvements of the basic techniques allowing for the production of highly polarized, intense, dc or pulsed, positive or negative ion beams.

ISSN:0034-6748    

DOI:10.1063/1.1144967

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The progress of ion source research in China, including the main achievements, present status, suggestions, and problems are reviewed.

ISSN:0034-6748    

DOI:10.1063/1.1144968

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An optically pumped polarized H−source (OPPIS), which is based on the charge exchange between H+ions and electron‐spin polarized alkali atoms has been developed at KEK. Just by applying this scheme to a deuteron beam, it is difficult to obtain a highly vector polarized deuteron beam. To obtain highly vector polarized D−ions, we have developed a ‘‘dual optical pumping type’’ of polarized D−source. With this scheme, a 100% vector nuclear‐spin polarization for D−ions is possible in principle. In a preliminary experiment, a 60% vector nuclear‐spin polarized D−ion was obtained.

ISSN:0034-6748    

DOI:10.1063/1.1144969

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The Holifield Radioactive Ion Beam Facility now under construction at the Oak Ridge National Laboratory will use the 25‐MV tandem accelerator for the acceleration of radioactive ion beams to energies appropriate for research in nuclear physics; negative ion beams are, therefore, required for injection into the tandem accelerator. Because charge exchange is an efficient means for converting initially positive ion beams to negative ion beams, both positive and negative ion sources are viable options for use at the facility. The choice of the type of ion source will depend on the overall efficiency for generating the radioactive species of interest. Although direct‐extraction negative ion sources are clearly desirable, the ion formation efficiencies are often too low for practical consideration; for this situation, positive ion sources, in combination with charge exchange, are the logical choice. The high‐temperature version of the CERN‐ISOLDE positive ion source has been selected and a modified version of the source designed and fabricated for initial use at the facility because of its low emittance, relatively high ionization efficiencies and species versatility, and because it has been engineered for remote installation, removal and servicing as required for safe handling in a high‐radiation‐level ISOL facility. The source will be primarily used to generate ion beams from elements with intermediate to low ionization potentials. Prototype plasma‐sputter negative ion sources and negative surface‐ionization sources are under design consideration for generating radioactive ion beams from high‐electron‐affinity elements. The design features of these sources and expected efficiencies and beam qualities (emittances) will be described in this report.

ISSN:0034-6748    

DOI:10.1063/1.1144970

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The ion beams are produced by a cylindrical thermal contact‐ionization plasma source with an electrostatic lens system. The source plasma is produced at the inside surface of a 5‐mm‐diam 20‐mm‐long Re foil cylinder protected with a W cylinder. The surface is heated up to 3000 K by electron bombardment. The material to be ionized is fed to the surface through a guide pipe from a reservoir. Generation of all alkaline metal ions have been tested and a beam current of hundreds of &mgr;A is obtained. The efficiency for Li+production is 30%, while that for Cs+is nearly 100%. Alkaline earth ion beams, except Mg, are generated. A current of Ba+up to 200 &mgr;A is obtained, while a Tl+beam of over 200 &mgr;A is achieved. Halogen negative ion beams, except F−, of the order of 10 &mgr;A are also obtained when alkali halides are used. Attempts to extract Li−from the source are also being made.

ISSN:0034-6748    

DOI:10.1063/1.1144971

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

An rf driven ion source has been developed and tested at LBL for positive hydrogen ion production. Studies of this new source on ion species and current densities for a dc arc discharge are made in the 60‐kV PSI ion source test stand and the results compared with those obtained using the rf discharge. This source, using both discharge modes, will be installed in the PSI Cockcroft–Walton preinjector to increase the 870‐keV dc proton beam intensity from the present 8–10 mA operation to about 25 mA.

ISSN:0034-6748    

DOI:10.1063/1.1144972

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

In easily attainable high vacua (Pr≊20–0.2 &mgr;Torr), the efficiency (&bgr;+) for producing ions (M+) from diatomic molecules (MX) incident on a polycrystalline surface of W, Mo, or Re was measured as a function of surface temperature (T≊800–2300 K). Theoretical analysis of &bgr;+elucidated the temperature dependence of the effective work function (&fgr;+) for the ionization. Namely, (1) above ∼2000 K, each surface is kept virtually clean, having &fgr;+≊5.2, 4.9, and 5.4 eV for W, Mo, and Re, respectively. (2) At ∼1400–1200 K, the range of which depends uponPr, &fgr;+is increased up to ∼7 eV by adsorption of residual gas molecules (RGM), thereby yielding &bgr;+=1 for even Tl and the current density of ∼10 &mgr;A cm−2for the flux of 1014molecules cm−2 s−1. (3) Below ∼1200 K, however, &fgr;+is much decreased by coadsorption of MX and RGM. A theoretical diagram ofTvs &fgr;+is devised to predict the best condition for &bgr;+=1. The best condition (&fgr;+,T, andPr) to make &bgr;+as large as possible may readily be selected according to the diagram and the present data on &fgr;+.

ISSN:0034-6748    

DOI:10.1063/1.1144974

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The model HOLCROSS ion source is designed for the production of high‐current and brightness ion beams for application in ion implantation and particle accelerator injection. This ion source has been designed to deliver an ion beam up to a maximum of 30 mA at an energy of 30 keV and will serve as an injector to a radio frequency accelerator. This ion source is equipped with an additional cross‐type hollow cathode system placed between the auxiliary plasma generator and the extractor. A negative voltage is applied to the cathode so that dependent low pressure gas discharge (DGD) is observed. High homogeneity and emission density of the plasma (50 mA/cm2) in the extraction region and multiaperture extraction are advantages of this version. The voltage of the DGD has the value 300–1200 V depending on the auxiliary discharge current so the plasma chemical reactions in the extraction region may be controlled. A description of the source is given, together with some recent results.

ISSN:0034-6748    

DOI:10.1063/1.1145237

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Characteristics of the ion beam created when the CO2‐laser radiation heats the anode of a vacuum diode are investigated. The diode with a carbon plate anode and a high‐transparency grid cathode has been used. The gap and the applied voltage were equal to 5 cm and 40 kV accordingly. Laser power density on the anode was varied in the range of 107–108W/cm2by changing the focal spot size from 1 to 7 mm. It is shown that the specific regime without breakdown of the vacuum diode can be obtained by adjusting the laser power density and the focal‐spot size on the anode. The ion beam with a total current of 100 mA and a pulse duration of 30 mks was obtained in such a regime. The number of carbon clusters C+2and C+3constitutes about 60% of the total number of ions in the beam, which is equal to 1013per pulse. The maximum current density of the carbon cluster beam is equal to 3 mA/cm2, and the emittance of this beam is less than 10 cm mrad. On the basis of results obtained, a new method is proposed for production of intensive cluster and molecular ion beams with different elements and chemical compounds on the target.

ISSN:0034-6748    

DOI:10.1063/1.1144975

出版商:AIP    

年代:1994

数据来源: AIP