摘要:

The potential for the production of intense negative‐ion‐yields by means of laser target interaction has been reported already in an earlier publication. In a recent study we have performed experiments with a wide variety of different target materials and by changing the laser wave length too. Calculations, by applying the Saha‐equation, indicate that the extremely dense laser plasma is very favorable for the generation of negative ions. The results achieved will be discussed in detail. It turned out that the extraction of the negative ions is an important parameter as well. Tests and measurements done will be presented.

ISSN:0094-243X    

DOI:10.1063/1.44756

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The main physical processes allowing negative ion production by surface sputtering for further acceleration in tandem acceleration are briefly reviewed. The sputtering yield and the probability of negative ion ejection are discussed. The properties of negative ion beams for an efficient acceleration in tandem accelerators are also discussed, with an emphasis on space charge problems. The main features and performances of the heavy negative ion injector of the Bucharest tandem accelerator are given.

ISSN:0094-243X    

DOI:10.1063/1.44757

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Several variants of sources for nuclear polarized negative ion production have been proposed and tested. The simple adaptation of a high intensity polarized proton source for nuclear polarized H−production has been examined. A pulsed current of H−up to 0.15 mA has been obtained. For the examination of H−production in the collision of H atoms with exited alkali atoms, the conversion of a low energy atomic beam from an RF dissociator into negative ion flow by using cesium vapor target with discharge has been tested. The formation of H−ions by simultaneous operation of the RF dissociator and a discharge in the cesium target has been observed. Finally, the polarization of nuclei in molecules by collisions with electron polarized (optically pumped) alkali atoms, nuclear polarization in molecules, induced by chemical reaction in cyclic molecules, and the possibility of using this for ion sources are discussed.

ISSN:0094-243X    

DOI:10.1063/1.44758

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A high resolution mass spectrometer is being developed for the sensitive detection of the isotope carbon‐14 (14C). This system, a variant of Accelerator Mass Spectroscopy, uses a cyclotron to give high mass resolution. The development program for this system is described. In particular, the development of a gas phase volume production ion source for generation of C−ions will be detailed. Preliminary results obtained with several precursor gases will be shown. In addition, an extraction system to separate the ions from the electrons has been conceptually designed. Finally, applications of the mass spectrometer system will be discussed.

ISSN:0094-243X    

DOI:10.1063/1.44760

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Polarized protons have been available for acceleration in the AGS for the high energy physics program since 1984. The polarized H−source, PONI‐1, has routinely supplied a 0.4 Hz, 400 &mgr;sec pulse having a nominal intensity of 40 &mgr;A. Polarization is ∼80% out of the ion source. After PONI‐1 became operational, a program was initiated to develop a more intense source based on a cold ground state atomic beam source, followed by ionization of the polarized H° beam by D−charge exchange. Various phases of this work have been fully reported elsewhere, and only a summary is given here.

ISSN:0094-243X    

DOI:10.1063/1.44761

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An effort is underway at the Tandem Van de Graaff Facility (TVDG) at Brookhaven National Laboratory to improve the performance of the negative heavy ion sources used during the Heavy Ion Physics program. The primary focus of this effort is to increase the pulsed beam current available for injection into the MP7 accelerator by improving ion source intensity, emmitance, and reliability. Development efforts are focused upon two commercially available sputter sources: 1) The General Index Model 860, 2) The Peabody Scientific PSX‐120.

ISSN:0094-243X    

DOI:10.1063/1.44762

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A 6 cm diameter, 6 cm long multicusp ion source was used to test the extraction characteristics of both the surface‐produced and volume‐produced Li−ion beams. The ion source was equipped with a Li oven, a Cs oven, and a heat shield to increase the recirculation of alkali metals. A preliminary test with a low arc power discharge showed that the amount of Li−current extracted from a Li plasma can be doubled by the addition of Cs into the discharge. Merits and demerits of using a volume production Li−source for plasma diagnostic applications are discussed by comparing the performance with that of a surface conversion Li−source.

ISSN:0094-243X    

DOI:10.1063/1.44763

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An RF plasma sputter‐type heavy negative ion source with mA‐class ion currents in DC‐mode has been developed. A dense plasma of 1011cm−3order was generated in the xenon gas pressure range of 10−5–10−4Torr (10−2Pa), whose low gas pressure discharge is essential to extract produced negative ions without loss (electron detachment). A cesiated sputtering target surface (42 mm in diameter) was negatively biased by several hundreds volts against the plasma. The extracted total negative ion currents of 12.5 mA for a copper target and 4.2 mA for a graphite target were obtained.

ISSN:0094-243X    

DOI:10.1063/1.44764

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A number of laser, spectroscopic, and probe diagnostic techniques has been used to study inductively coupled radio frequency discharges used as H−ion sources. Time‐resolved detection of Balmer‐alpha emission has been used to study the excited state hydrogen atoms. Vacuum ultraviolet laser absorption spectroscopy and 2+1 multiphoton laser‐induced fluorescence have been used to measure the ground state atomic hydrogen populations. Langmuir probe measurements which are synchronized with the exciting rf radiation have also been made. The Balmer‐alpha emission exhibits a modulation in its intensity at a frequency of twice the exciting rf radiation. On the other hand, the laser absorption measurements show that the density of ground state hydrogen atoms does not vary significantly with the phase of the exciting rf. At the same time, the probe measurements indicate that the plasma density and the temperature of the thermalized electrons are also invariant with respect to the rf phase. These results are qualitatively explained.

ISSN:0094-243X    

DOI:10.1063/1.44765

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The photodetachment technique developed for measuring negative ion density and temperature has been used to study the difference between hydrogen and deuterium operation of the hybrid source. It was found that the negative ion temperature scales linearly with the electron temperature in both hydrogen and deuterium, but is higher in hydrogen than in deuterium for the same electron temperature. This dependence is affected by the volume of the source chamber. Recent progress in the photodetachment diagnostics of negative ions is reported. The presence of a capacitive component was observed in the photodetachment signal recorded using conventional, conductive probes. Capacitive probes have been constructed and tested. A bare probe at floating potential leads to workable signals. Experiments proving that the capacitive signal is proportional to the negative ion density are described.

ISSN:0094-243X    

DOI:10.1063/1.44766

出版商:AIP    

年代:1992

数据来源: AIP