摘要:

A 2.45 GHz compact National Institute of Radiological Sciences electron cyclotron resonance (NIRS-ECR) ion source has been developed for heavy ion medical accelerator in Chiba at NIRS. A new ECR source is expected to produceC2+ions of more than 160 e&mgr;A for the high-energy heavy-ion cancer treatment. An ECR-type ion source is adopted because of its excellent characteristics of long lifetime and easy operation. The compact ECR ion source is 15 cm in diameter, 20 cm in length, and about 20 kg in weight. A set of permanent magnets was adopted to generate both the axial mirror and the radial sextupole fields. Several gas materials, He,CO2,CH4,N2,and Ne, have been tested. The present performance forC2+ions, however, is 15 e&mgr;A and far below the medical requirements. The estimated vacuum in the plasma chamber is around5.0×10−5 Torr.A much better vacuum pressure is desired to produceC2+ions of more than 100 e&mgr;A. The ECR plasma, however, cannot be kept stable under such a high vacuum pressure. As another method to get the stable plasma, the different microwave injection was tested with a microwave antenna. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148637

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Different ion sources are used at GSI to match the requirements for specific tasks at the accelerator. At the standard injector a Penning ionization gauge ion source is used (design ionU10+,m/q<24,1 emA). Further development of this source is mainly aiming at an increase of the extractable currents and an increase of the lifetime of the source. The new injector produces the beam by means of an electron cyclotron resonance source (Caprice-type). Here the design ion isU28+,m/q<8.5,5 e&mgr;A. Clearly, the oven technology is our main development goal. In addition we are trying to improve the extraction flexibility by a moveable accel–decel system. For our high current project ion sources are required which are capable to deliver a beam of several mA even for heavy ions. Design ion here isU4+,m/q<65,15 emA. For that application two different types of ion source are used: the multicusp ion sources “cold or hot reflex discharge ion source” and “multicusp ion source” for gaseous ions and the MEVVA source for metal beams. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148638

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Current nuclear structure studies demand a wide range of heavy negative ion beams for tandem acceleration. Some of the wanted isotopes have low natural abundances and many have low or negative electron affinities. For these, gas injection or the use of hydrides, oxides, or fluorides is required to achieve usable intensities. The chemical properties of the target materials, and of the additive gases used to form molecular ions, often have detrimental effects on ion source performance and life. These effects include insulator breakdown, ionizer poisoning, and the erosion or deposition of material on critical electrodes. Methods of controlling sputter source conditions are being studied on the Wright Nuclear Structure Laboratory ion source test bench with the object of extending source life, increasing target efficiency, and achieving consistent negative ion outputs. Results are reported for several heavy ions including tellurium, neodymium, and ytterbium. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148711

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Advanced injector systems for proton synchrotrons and accelerator-based boron neutron capture therapy systems are being developed at the Lawrence Berkeley National Laboratory. Multicusp ion sources, particularly those driven by radio frequency, have been tested for these applications. The use of a radio frequency induction discharge provides clean, reliable, and long-life source operation. It has been demonstrated that the multicusp ion source can provide good-quality positive hydrogen ion beams with a monatomic ion fraction higher than 90&percent;. The extractable ion current densities from this type of source can meet the injector requirements for both proton synchrotron and accelerator-based boron neutron capture therapy projects. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148712

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This proceeding considers excitation of ion and electron oscillations in a plasma formed by the beam of fast positive ions. Linear and nonlinear stages of the oscillations developing, and the influence of these oscillations on the beam transportation properties are described. Also briefly described are some techniques for the stabilization of instabilities of electron and ion oscillations in compensated ion beams. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148748

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The space charge is one important force acting on the charged particle beam, when a beam is extracted from the particle source. Analytical solutions describing the beam properties are available for only a few special cases. Computational methods are therefore required for the optimization of extraction systems. These optimization methods are described and examples are shown. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148612

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The space-charge compensated state of drifting dc beams ofHe+ions of 10 keV ion energy and 0.14 and 1.5 mA current was determined with an electron beam probe, a rf resonance probe, the analysis of residual gas ion energies, and emittance measurement. The results are compatible with a basic model describing a two-dimensional multiplicity of possible self-consistent radial density distributions of beam ions, residual gas ions, and compensating electrons. The effects of electron drainage and beam current oscillations on space-charge compensation are pointed out. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148650

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The heating and confinement of electrons in an electron-cyclotron-resonance ion source (ECRIS) plasma is described: the single particle motion in a magnetic beach is presented, showing the role of the rf wave magnetic field in the electron losses. This effect can be approximately modeled by a Fokker–Planck quasilinear equation in velocity space. This modeling is discussed and numerical results are presented. The behavior of the wave close to resonance is analyzed, taking into account the thermal motion of the electrons. The role of the different design parameters (including rf frequency) is shown and the major ingredients for the design of an efficient ECRIS for multiply charged ions production are summarized. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148588

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A negative-ion source extraction model has been formulated and implemented that explicitly considers the motion of positive ions and the volume generation of negative ions. It is found that (1) for high-beam currents, the beam current is limited by a transverse space-charge limit, meaning that an increase in negative-ion density at the extraction sheath will result in a lower-beam current (this result is universally observed at high-beam current); (2) there is a saddle point with a potential barrier preventing most volume-produced negative ions from being extracted [the combination of (1) and (2) indicates that most of the negative ions being created do not find their way into the beam]; (3) the introduction of cesium may cause an increase in the transverse space-charge limit; (4) cesium also results in an increase in the fraction of volume-produced negative ions that are extracted; (5) cesium may also result in reduction of extracted electrons by producing a less negative bias on the plasma electrode with respect to the plasma, thus allowing the transverse space-charge limit budget to be taken up virtually totally by the ions. [The combination of (3)–(5) represents the way an actual increase in the beam current can be achieved]; (6) a strong ion time scale sheath instability due to violation of the Bohm criteria produces an anomalous ion temperature, which increases with the beam current, as routinely seen in measurements; and (7) the introduction of cesium may result in a reduction in this instability. These insights may lead to improvements in volume negative-ion sources.

ISSN:0034-6748    

DOI:10.1063/1.1148749

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A newly proposed type of multicharged ion source has several potential advantages over existing types and a number of useful applications. The basic principle is that multiphoton absorption in an intense uniform laser focus can give multiple charge states of high purity (Ref.1). Thus, charge state separation downstream is simplified or made unnecessary. Another advantage is that large currents (hundreds of amperes) can be extracted. This type of source could be used for heavy-ion fusion drivers (see Ref.1) or storage rings. There are also industrial application such as materials processing. We describe conceptual design studies for several specific cases. For example, we discuss extraction and focusing of a 4.1 MV, 144 A beam ofXe16+ions from an expanding plasma created by an intense laser. The maximum duration of the beam pulse is determined by the total charge in the plasma, while the practical pulse length is determined by the range of plasma radii over which good beam optics can be achieved. The initially diverging beam can be refocused to a small radius or made parallel by a combination of electrostatic and solenoid focusing. Our design studies are carried out first with an envelope code to determine the proper focusing parameters and then with a self-consistent particle code to optimize the beam quality. We present results from both codes and discuss several applications of this type of ion source.©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148872

出版商:AIP    

年代:1998

数据来源: AIP