Session 8: Low and Intermediate Energy Accelerators and Sources spc coordinator: K. Blasche, gsi, Darmstadt




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Type of presentation requested: Poster

Classification: [T12] Beam Injection/Extraction and Transport
95-1174 - High Current Ion Beams at Frankfurt University

Martin Droba, Oliver Meusel, Ulrich Ratzinger, Klaus Volk (IAP, Frankfurt-am-Main)

A new building for the physics faculty at the Goethe-University in Frankfurt is under construction including an experimental hall. The Institute of Applied Physics IAP has started development of a high current ion beam facility consisting of a high voltage terminal(150 kV,I_beam < 300 mA,H-,p,Bi+), a 10 MV linear rf accelerator and a high current storage ring for 150 keV beams. The 150 kV terminal equipment is already ordered while the subsequent units are in the design stage. The storage ring will use a stellarator-like magnetic configuration to allow for a high degree of space charge compensation by electrons. The facility will allow high current beam investigations as well as experiments in fields of plasma, nuclear and atomic physics.



Type of presentation requested: Poster

Classification: [T12] Beam Injection/Extraction and Transport
96-1189 - A Comparison of High Current Ion Beam Matching from an Ion Source to a RFQ by Electrostatic and by Magnetic Lenses

Reinard Becker, Robert Jameson (IAP, Frankfurt-am-Main), Toshiyuki Hattori, Masahiro Okamura (RIKEN, Saitama), Kazuo Yamamoto (RIKEN/RARF/BPEL, Saitama), N Hayashizaki, H Kashiwagi (RLNR, Tokyo)

In order to improve the ?direct? injection scheme of the Riken Nd-YAK-laser driven ion source into a RFQ rf-accelerator, several basic methods have been investigated and compared, in order to transform the initially divergent ion beam into a convergent one, needed for matching the high current (100 mA C6+) ion beam at an energy of 100 keV to a RFQ. From the point of power supplies and break down characteristics, the simplest solution is a decelerating electrostatic lens, with the decelerating electrode operated on ion source potential. Due to the strong divergence of the ions beam after acceleration, this lens will be filled to an aperture, which causes strong aberrations. Therefore, we also investigated to use an accelerating potential on the lens electrode. This reduces significantly the filling of the lens and the emittance growth is only a factor of 3, as compared to the decelerating lens with a factor of 30! Finally we have been looking also into a magnetic matching system, which can match the ion beam to the RFQ with virtually no emittance growth.



Type of presentation requested: Poster

Classification: [T12] Beam Injection/Extraction and Transport
97-1206 - Improvement of a Field Gradient Corrector in Cyclotrons for Matching of Extracted Beams to a Beam Transport System

Mitsuhiro Fukuda, Takashi Agematsu, Kazuo Arakawa, Ikuo Ishibori, Satoshi Kurashima, Nobumasa Miyawaki, Yoshiteru Nakamura, Takayuki Nara, Susumu Okumura, Kenichi Yoshida (JAERI/ARTC, Gunma-ken)

We have developed a field gradient corrector, installed in the extraction region of a cyclotron, equipped with a pair of active coils to improve the matching of the extracted beam to a beam transfer line. Well-matched beam transport is required for production of a heavy-ion microbeam with a spot size of one micrometer in diameter by using a beam focusing system with a quadruplet of quadrupole lenses, in combination with a series of slits, which is being developed at the JAERI AVF cyclotron facility. Originally there was a discrepancy between the axis of the extracted beam and the beam transfer line, resulting from misalignment of magnets. Instead of installing more steering magnets on the beamline, due to insufficient space, the capability of beam bending has been given to a usual passive gradient corrector by mounting a pair of coils in the beam passing gap. The coils lower the field in the beam passing region to act as a steerer. In order to keep sufficient beam-focusing force, the iron piece shape of the gradient corrector has been optimized to increase the field gradient in the gap, changing with excitation currents of the coils.



Type of presentation requested: Poster

Classification: [T12] Beam Injection/Extraction and Transport
98-1303 - Progress in Ideal High-intensity Unbunched Beams in Alternating Gradient Focusing Systems

Ronak Bhatt, Chiping Chen, Enrique Henestroza, Jing Zhou (MIT/PSFC, Cambridge, Massachusetts)

A persistent challenge in high-intensity accelerator design is the optimization of matching conditions between a beam injector and a focusing system in order to minimize non-laminar flows, envelope oscillations, emittance growth, and halo production. It has been shown [*] that the fluid motion of a thin space-charge dominated beam propagating through a linear magnetic focusing channel consisting of any combination of uniform or periodic solenoidal fields and alternating gradient quadrupole fields can be solved by a general class of corkscrewing elliptic beam equilibria. The present work extends this discussion to asymmetric PPM focusing and derives conditions under which a uniform density elliptical beam can be matched to such a focusing channel by considering the fluid equilibrium in the paraxial limit. Methods of constructing such a beam are also discussed, with particular attention devoted to analytic electrode design for Pierce-type gun diodes of elliptical cross-section. Several applications are discussed, including heavy-ion fusion and a high-efficiency ribbon beam microwave amplifier for accelerator applications.

This work was performed under the auspices of the U.S Department of Energy and the Air Force Office of Scientific Research

* C. Chen, R. Pakter, R. Davidson, "Ideal Matching of Heavy Ion Beams," Nucl. Inst. And Methods, A 464 (2001) p. 518-523



Type of presentation requested: Poster

Classification: [T12] Beam Injection/Extraction and Transport
99-1335 - Upgrade of the Kiloampere Electron Gun with Secondary Emission

Sergiy Cherenshchykov (NSC/KIPT, Kharkov)

The Secondary Emission Magnetron Injection Gun (SEMIG) is a novel universal electron source with a cold cathode. It may be used for charge particle accelerators in injectors and power electron vacuum devices (RF and pulse).The SEMIG may have higher current density and lifetime much longer (up to 100,000 hours) than conventional thermionic guns. High power SEMIG with voltage up 1000 kV and current nearly 1 kA was calculated designed and manufactured. The gun was tested microsecond operating modes. The cathode testing permitted to obtain beam pulse with amplitude up to 1.2 kA at voltage of 400 kV in magnetic field of 0.3 T. There were obtained beam traces on the copper plate. Traces had the form of rings with diameter of 125 mm and width of 5 mm. The secondary emission nature of the beam current up to 1.2 kA was established. The identification was held basing on considered features of the exciting and on the maintenance of the secondary emission current. The large amount of criterion gives the high validity of the identification.



Type of presentation requested: Poster

Classification: [T12] Beam Injection/Extraction and Transport


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