摘要:

The high current, high charge-state ion beam which can be extracted from a laser produced plasma is well suited, after initial acceleration, for injection into synchrotrons. At CERN, the production of a heavy ion beam using aCO2laser ion source is studied. The latest results of experiments with a tantalum ion beam with charge states up to23+and accelerated by a radio frequency quadrupole from 6.9 to 100 keV/u, are presented along with simulations of the low energy beam transport. The ion yield at the desired charge state, the pulse to pulse stability of the ion beam, and the system reliability are all of major interest. Work is under way to replace the low repetition rate free-running laser oscillator by a master oscillator and power amplifier system. The master oscillator is operational and the first results of measurements of its beam quality and stability are presented. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148630

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Characteristics of plasmas in a magnetron ion source with a hollow mesh cathode have been studied. It was found that depending on conditions of discharge and ion current in the cylindrical mesh cathode, the plasma column is always formed in such a way as to ensure necessary ion concentration for extracted ion current. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148631

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Ions produced in a process of interaction of the intense laser radiation of the iodine laser system PERUN (&lgr;=1.315 &mgr;m,EL⩽50 J,&tgr;∼350 ps,I&lgr;2∼1015 W cm−2 &mgr;m2) with the solid state tantalum and platinum targets have the ionization states fromz=1up toz∼50and energies at least a few MeV. The Thomson parabola (TP) ion spectrograph with a registration system based on the micro channel plate (MCP) used in the experiment, gives a general view of ionization states and energies of all types of ions created in one laser shot. The data registered by the PC, gives on-line information on the obtained experimental results. As shown, the calibration measurements of MCPs, made with Ta ions (MCPs different from these used with the TP), analog particle gain of the MCPs rises with the increase in the ion charge states and energy. This attribute causes an increase in sensitivity of MCPs on the highly charged, high energy ions. The registered ions are composed of a few groups of ions with different charge states and different energies. In the experiment with the TP, the ring, ion collector (IC), coaxial with its axis has been used. From a comparison of the velocities of different ion groups registered by the IC and by the TP, the quantity of ions in different ion groups was estimated. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148753

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

For the first phase of the GSI high current project, an improvement of Penning ionization gauge (PIG) ion sources is necessary. Therefore, we carry out several PIG source development activities. A test bench for PIG ion sources was set up. It was equipped with the same source magnet, the same beam line, and the same computer control as at the accelerator injector. It has been partly operational since the beginning of 1997. Contrary to the UNILAC accelerator with a typical pulse width of up to 5 ms at a repetition rate of 50 Hz, the synchrotron injection requires a pulse length of about 200 &mgr;s at 0.3 Hz. Therefore, the use of lower repetition rates is possible. Thus, more power can be applied to the discharge and increased ion currents can be extracted. This mode requires higher cathode heating, which decreases the lifetime of the filament. The use of monocrystallineLaB6cathodes drastically reduces the necessary heating power at the same electron current, which should increase the lifetime of the filament and the cathode. The yield of ions from solids was improved by the use of optimized combinations of target and sputtering gas. The use of xenon instead of argon as the sputtering gas for the uranium target yielded a current enhancement of 40&percent;. To achieve a shift of the charge-state distribution to higher charge states, an optimized gas feeding is one option. In collaboration with JINR Dubna, we developed a pulsed gas feeding system. Two piezovalves directly mounted to the source allowed us to control the pressure in the source. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148632

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Heavy ion fusion (HIF) induction accelerators require ion sources that can deliver intense heavy ion beams with low emittance. The typical pulse length is 20 &mgr;s with a rise time less than 1 &mgr;s and a repetition rate of 10 Hz. So far, the surface ionization sources have been used in most HIF induction linac designs. However, there are other ions of interest to HIF (e.g., Hg, Xe, Rb, Ar, and Ne) which cannot be produced by the surface ionization sources, but rather by volume ion sources. In this paper, we describe an experiment that uses a multicusp source with a magnetic filter to produce beam pulses that have a rise time in the order of 1 &mgr;s. By applying a positive biasing pulse on the plasma electrode with respect to the source body, the positive plasma ions can be temporarily repelled from the neighborhood of the extraction aperture, leading to a suppression of the ion beam. As the bias is removed, positive ions flow to the extraction region, enabling a fast-rising beam pulse. The beam current pulses show that there are two distinct groups of ions. An initial fast current rise time(<2 &mgr;s)corresponding to ions originating from within the magnetic filter region followed by a second group of ions with a longer rise time (10–20 &mgr;s) originating from the plasma bulk region. Proper positioning of the filament cathode and the magnetic filter field relative to the extraction aperture was found to be critical. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148710

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A dc-modeHe−source of the double charge exchange type has been developed for the purpose of application to alpha-particle measurement. Because the optimum energy for the two-step two-electron capture process in a rubidium vapor was reported to be around 6 keV, the essential point of development is extraction of an intenseHe+beam at relatively low energy. As the discharge current of theHe+ion source is increased, the focusing property deteriorates, and higher electrostatic field is required for extraction. AHe−current of 0.07 mA is continuously obtained from aHe+beam extracted from a 6 mm diameter single hole. The conversion efficiency fromHe+toHe−is about 2&percent;–3&percent; in the energy region of 5–10 keV. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148633

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A volume source based on the high efficiency source is being developed for heavy ion production. Bismuth was chosen for exemplifying investigations because of its low melting point. The ion source is driven by an arc discharge ionizing bismuth atoms which are evaporated from an oven inside the source chamber. It has been optimized to produce a beam with a fraction of singly ionized bismuth above 92&percent;. A multiaperture extraction system was built consisting of seven holes with a radius of 3 mm each. For that system, the perveance limit was achieved at a beam current of 70 mA and an extraction voltage of 27.5 kV. The corresponding emission current density amounts to35 mA/cm2.This value was obtained for an arc power of only 280 W. Furthermore, the emittance of a beam extracted from the multiaperture extraction system has been determined with a high power emittance scanner. It amounts to 0.27&pgr; mm mrad (80&percent;, normalized, 4 rms). In this case, the emittance of a single beam is 0.017&pgr; mm mrad. This article will give a detailed description of both the source and the experimental setup. In addition, various dependencies between the plasma parameters and the beam composition are presented. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148634

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A low-pressure and high-density microwave ion source, created and sustained by a surface wave, using a partial-coaxial cavity resonator has been newly developed for the production of stable beams from gaseous feed materials. This source is called a holey-plate surface-wave ion source. A microwave of 2.45 GHz is supplied from a holey plate which is made from a 0.5 mm thick stainless steel sheet with 4 mm diameter and 5 mm pitch holes to a plasma production chamber of 40 mm diameter and 11 mm in length. An 18-mm-diameter argon ion beam is extracted and accelerated from the ion source. The ion current densities are in excess of6 mA/cm2at an extraction voltage of 1 kV and at microwave powers of less than 100 W. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148635

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Multiply charged ions of Ta, W, Pt, Au, Pb, and Bi, produced by the photodissociation iodine laser system PERUN (&lgr;=1.315 &mgr;m,EL<40 J,&tgr;L∼350 ps) are reported. The ions with maximum charge states around50+and with energies of several MeV were registered at a distance of about 2 m from a plasma plume. The existence of several groups of ions corresponds to the different processes that occur in the plasma. The influence of different factors on the ion production is discussed. Measured ion current densities higher than10 mA/cm2in the distance of 1 m from the target demonstrate the superiority of laser ion sources. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148636

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A negative ion sputter source incorporating a microbeamCs+source intended for application in accelerator mass spectrometry (AMS) has been developed from a General Ionex HICONEX 834™ source. (HICONEX is a trade mark of High Voltage Engineering Europa.) The source is part of a microbeam AMS system, designed forin situmicroanalysis of geological samples known as AUSTRALIS (AMS for UltraSensitive TRAce eLement and Isotopic Studies) recently developed at the Heavy Ion Analytical Facility laboratory. With requirements of precise beam positioning on mineralogical samples, a high magnification sample viewing system is a vital part of the source, enabling live observation of the sputtering process and visual tuning of the primary beam. Microbeam ofCs+of 30 &mgr;m in diameter can be produced routinely with adequate intensity for a number of applications. The “screen” electrode in the secondary ion extraction system facilitates steering of the primary beam affected by the extraction field, back into the geometric center of the sample. The injector system includes high resolution electric and magnetic analyzers, improving the background suppression before injection into the accelerator. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148747

出版商:AIP    

年代:1998

数据来源: AIP