Extracted beam

Fig. 1.10. The fully electrostatic high-brightness positron beam developed by the Brandeis group. The positron Soa gun is located near B. The beam is deflected at C using a cylindrical mirror analyser and focussed onto a remoderator in chamber D. The extracted beam is then focussed and remoderated at the lower left of D. The double brightness-enhanced beam is then transported into the target chamber, E. Reprinted from Nucl. Instrum. Methods B143, Charlton, Review of Positron Physics, 11-20, copyright 1998, with permission from Elsevier Science.

An apparatus to perform a laser-stimulated 3D-3P transition in muonic helium ions (at the Single Burst Extraction Beam of the Brookhaven National Laboratory Alternating Gradient Synchrotron) is presented together with some results. 

The first on-line studies were performed by the present author and co-workers [7,8] on the intense circulating beam of the heavy ion cyclotron U-300 at JfNR, Dubna. Extracted beams were then not available. To realize experiments inside the cyclotron chamber was not easy because of controversial technical requirements. The schematics of the setup [9,10] shown in Fig. 1.3 resulted from several trial-and-error attempts. 

With a flow rate of the carrier gas of about 20 L min-1, this technique of chemical identification is still a record as to its rapidness of a few tenths of a second, and to the almost quantitative chemical yield. Later on [17], a setup based on similar principals was mounted on an extracted beam of U-300 cyclotron, which greatly enabled the experiments about 40 more atoms of Rf were isolated and detected. 

Fig. 1.4 Thermochromatographic identification of element 104 as ekaHf [18]. Extracted beam of the JINR cyclotron U-300.

Fig. 1.5 Chemical identification of element 106, now seaborgium [20] extracted beam of JINR U-300. The combined hatched histogram shows s.f. events from three separate runs. The white histogram shows fission events detected in an experiment with the inert carrier gas only. The thermochromatogram of simultaneously produced 176W was traced through y-radiation.

Most of the irradiations for medical radioisotope production at cyclotrons are done using extracted beams. There is more versatility in working with the extracted beam than with the internal beam. Through controlled defocusing and wobbling, it is possible to decrease the... 

Size, energy spread, and emittance of the extracted beam... 

The cell used for our studies of hydrodynamically extracted beams is smaller than that used in the diffusive regime beam studies, making it possible to achieve = 1... 

In estimating the velocity spread of an extracted beam, we assume an energy spread 8E, not considering details of the distribution which strongly depend on the particular ion source. The dimensionless parameter j8 = t)/ c is used for the velocity. For its dependence on the acceleration voltage U and the atomic mass m, it is sufficient to take the nonrelativistic expression... 

Applications fall into four broad categories human resource development, irradiations, extracted beam work and testing. 

Overall this project has been moving ahead on all fronts during the past year with major contributions from a large collaboration. It appears that all systems will be ready by December, 1990. We expect to run during the next AGS slow extracted beam period, now scheduled for March, 1991. 

Ion implanters delivering higher beam currents have also been developed during the last 10 years. The ion sources are either of a Freeman or the bucket type CHORDIS [89. 90). Both types exist in versions for gaseous elements, as oven versions for elements with higher vapor pressure, and as sputter versions for metallic elements. In Freeman sources a chlorination technique is often used to produce a ga.seous compound from the solid feed material. The mass spectrum Is then much more complex, because the chlorine compounds are present in the extracted beam prior to mass separation. 

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