摘要:

The electron beam ion source, CRYSIS, produces highly charged ions for injection into the heavy ion storage ring—CRYRING at MSL, as well as low energy atomic physics experiments and the Stockholm–Mainz Penning trap recently installed at MSL. CRYSIS has produced ions up to Ar18+and136Xe52+. Pulsed beams of Ar13+ions 60 &mgr;s in duration have been injected into CRYRING via an RFQ and ions of charge up to136Xe44+have been used in atomic physics experiments with pulse duration 10–250 ms. A vacuum separation of the cryostat and ionization volumes has been made. Temperature control and measurement of internal electrodes have increased the gas injection efficiency and reduced the memory effect associated with a cryogenic EBIS. External ion injection has been added as an alternative to neutral gas injection for introducing the species to be ionized to high charge states. Monitoring of the radio frequency noise signal with a spectrum analyzer has aided in the propagation of quiet, high current (450 mA) dc electron beams. These quiet electron beams have been used to produce extracted ion pulses of higher intensities than in previous operation.

ISSN:0034-6748    

DOI:10.1063/1.1144865

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We would like to present the initial results and description of the superconducting electron cyclotron resonance ion source (SCECR) operating in the high‐Bmode—a new high magnetic field, low‐frequency mode of operation. First, we describe the operating characteristics of this mode, which include very high mirror confinement in all directions, yet having a minimum field low enough for electron cyclotron resonance heating of 6.4 GHz. The source performance for oxygen, neon, argon, krypton, and xenon is presented and comparisons are made with several existing high‐performance ECR sources. In this high‐Bmode the SCECR matches or exceeds the performance of all existing ECR sources. These results perhaps invalidate the classical frequency squared source performance scaling law, and suggest the new possibility of high‐performance, low‐frequency (and hence low cost) sources as will be discussed.  

ISSN:0034-6748    

DOI:10.1063/1.1144866

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The use of ion sources in induction linacs for heavy ion fusion is fundamentally different from their use in the rf linac‐storage rings approach. Induction linacs require very high current, short pulse extraction usually with large apertures which are dictated by the injector design. One is faced with the problem of extracting beams in a pulsed fashion while maintaining high beam quality during the pulse (low emittance). Four types of sources have been studied for this application. The vacuum arc and the rf cusp field source are the plasma‐types and the porous plug and hot alumino–silicate surface source are the thermal types. The hot alumino–silicate potassium source has proved to be the best candidate for the next generation of scaled experiments. The porous plug for potassium is somewhat more difficult to use. The vacuum arc suffers from noise and lifetime problems and the rf cusp field source is difficult to use with very short pulses. Operational experience with all of these types of sources is presented.

ISSN:0034-6748    

DOI:10.1063/1.1144867

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

We have constructed a rf plasma sputter‐type heavy negative ion source, which can deliver high current negative ion beams such as Cu−of 12.1 mA, Si−of 3.8 mA, and B−2of 1 mA in dc operation mode. In our source, the estimated negative ion production probability of Cu was much more than the value obtained by the conventional negative ionization probability equation with an exponential dependence on velocity. We measured heavy negative ion production probabilities by Xe+sputtering on various cesiated metals. The probabilities were strongly affected by the cesiated surface condition which was determined by a flux of neutral cesium supply to the surface and a target surface temperature. The measured maximum probabilities at the optimal conditions were considerably high, and they were about 10% or more for Cu, C, Si, Ge, and W targets and about 1% for Ta and Mo targets. The probability for very low velocity particles such as sputtered heavy metal atoms might be affected by a surface ionization process with a high local surface temperature.

ISSN:0034-6748    

DOI:10.1063/1.1145233

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Production characteristics of Li−from powdery LiH immersed in argon and hydrogen discharges were investigated. The surface of the LiH powder was covered with a Mo mesh and a negative bias potential was applied to the mesh to bombard LiH powder with plasma ions. The amount of Li−current produced at the surface of the LiH powder was an increasing function of the bombarding ion energy. The decomposition of LiH by the ion bombardment accompanied the production of hydrogen gas, and the H−current was also extracted from the ion source plasma. The addition of Cs into a discharge showed little enhancement of Li−production.

ISSN:0034-6748    

DOI:10.1063/1.1144868

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

After 30 years of research, development, and qualification work of radio‐frequency ion thrusters (RIT), the RIT 10 engine has now been tested successfully in space onboard the European Retrievable Carrier (EURECA). RIT 10 produces a thrust of 10 mN and is designed for north–south stationkeeping of geosynchronous satellites. Besides, the European Space Agency (ESA/ESTEC) plans to implement ion propulsion in their technological satellite ARTEMIS, where ion thrusters shall be used operationally for north–south stationkeeping. In parallel, development and tests of a scaled‐up 50 mN engine RIT 15 have been continued successfully with xenon and krypton as propellants. A large ion engine with a 35 cm ionizer diameter, the RIT 35, has been developed for primary propulsion of interplanetary probes aiming at a thrust level in the 250 mN range. A laboratory prototype has been subjected to extensive testing and performance mapping. Recently, this work has been continued in European cooperation due to a redirection of contracts. The ion source diameter has been reduced to 26 cm but the performance should be kept using a British high perveance grid at the German rf‐ion source.

ISSN:0034-6748    

DOI:10.1063/1.1144869

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

The current trends of research and development work in ion‐beam microlithography are examined with particular emphasis on the choice of ion sources and the beam parameters. The common approach with duoplasmatron‐type ion sources for projection ion‐beam lithography is revisited, and the suitability of H−beams is examined. The beam brightness and energy spread, which constitute the figure of merit of a beam, appear to be better in the case of H−beams. From a surface plasma source type discharge operating under stable condition, H−beams with an emission current density of ∼1–5 A/cm2and a normalized brightness of ∼7×1012A/(m rad)2can be extracted. Several key issues of an ion‐projection lithography device, such as the ion source parameters, beam optics, and thermal load are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1144870

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A compact 5‐cm‐diam multipolar electron cyclotron resonance (ECR) ion source is characterized. The source is experimentally studied with no grids using argon gas with 50–250 W of 2.45‐GHz microwave input power. Using a microcoaxial probe it was confirmed that the exciting electromagnetic fields within the resonant cavity were indeed TE111, as expected from the critical cavity dimensions. Double Langmuir probe measurements indicate high densities of about (4–5)×1011/cm3near the source, and 5 cm downstream from the source output the densities become very uniform with a value of about 5×1010/cm3over a 10‐cm diameter. Electron energy distribution functions (EEDF) were measured using a single Langmuir probe. Average electron energies were seen to be about 8–10 eV with an energy distribution function falling between a Maxwellian and a Druyvesteyn distribution. Ion energy distribution functions (IEDF) were measured with a multigrid energy analyzer. It was seen that the distribution functions were narrow and peaked [with a full width half maximum (FWHM) of about 5 eV] except under certain conditions. Above 200‐W input power, and also below about 0.5 mTorr there is significant broadening of the ion distribution function. It is speculated that the former may be caused by gas heating, and the latter may be caused by the presence of Ar+2ions. With its high current densities (≳10 mA/cm2) and low average ion energies (<40 eV), it is expected that this ion/plasma source will be very useful in many etching and deposition applications.

ISSN:0034-6748    

DOI:10.1063/1.1144871

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

Recently, electron cyclotron resonance (ECR) discharges have been successfully applied to numerous ion source applications. These range from accelerator to etching and thin film deposition applications, and have strong potential for application in several commercial/industrial processes. Thus, new design requirements related to process automation and control are now imposed on plasma source design. Internal cavity tuning methods for excitation and impedance matching and ECR discharge control are presented. These impedance matching methods utilize a variable cavity end plate and an adjustable coupling probe to provide the two independent adjustments required to match the discharge loaded cavity applicator. Both end feed and side feed coupling create a well matched plasma source but the end feed excitation produces the most efficient (∼220–230 eV/ion) and most uniform (1&sgr;=2.5%) discharge. Control of internal tuning can serve not only to match discharge impedance, but with the proper control can also avoid hysteresis and multiple steady states and jumps in plasma source outputs. Adjusting the internal cavity tuning to always produce a slight mismatch helps insure a stable and repeatable discharge operation.

ISSN:0034-6748    

DOI:10.1063/1.1144872

出版商:AIP    

年代:1994

数据来源: AIP

摘要:

A microwave ion source equipped with two linear antennae set parallel to the wall of the source chamber has been designed and built. A homogeneous plasma of Ar was produced in an aluminum chamber of 22 cm long, 9 cm wide, and 6 cm deep. Beam forming grids produced a rectangular beam of 17 cm by 3 cm. The current density of the extracted Ar+beam was 0.16 mA/cm2at the center of the extraction area when the input power to the magnetrons was 360 W. The energy distribution function of the extracted ions was measured with an electrostatic analyzer. The measured energy distribution showed a presence of high energy ions in the extracted beam.

ISSN:0034-6748    

DOI:10.1063/1.1144873

出版商:AIP    

年代:1994

数据来源: AIP