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: [A07] Electrostatic Accelerators
37-541 - Ring of FIRE

Carsten Peter Welsch (MPI-K, Heidelberg), Christian Glaessner, Kai-Uwe Kuehnel, Alwin Schempp (IAP, Frankfurt-am-Main), Reinhard Doerner, Horst Schmidt-Boecking (IKF, Frankfurt-am-Main)

A small electrostatic storage ring is the central machine of the Frankfurt Ion stoRage Experiments which will be build up at the new Stern-Gerlach-Center of Frankfurt university. With ion energies up to 50 keV it will allow new methods to analyze complex many-particle systems from atoms to very large bio molecules. The high luminosity of the beam allows measurements with many orders of magnitude better resolution compared to traditional measurements. It will be combined with existing experiments, like the reaction microscope COLTRIMS and the ECR ion source. In comparison to earlier designs, the ring lattice was modified in many details: Problems in earlier designs were related with e.g. the detection of light particles and highly charged ions with different charge states. Therefore, the deflectors were redesigned completely, allowing a more flexible positioning of the diagnostics. In this contribution the final design of the storage ring is presented and the layout of all elements given. First results from vacuum measurements in the recently assembled quarter ring section are summarized.



Type of presentation requested: Poster

Classification: [A07] Electrostatic Accelerators
38-1004 - Electrostatic Charging of an Insulated Spherical Target by Particle Beam

Boris Yurievich Bogdanovich, Valery Kapin, Alexander Nesterovich (MEPhI, Moscow)

In the paper [*], the accelerator complex for custom examinations had been discussed. The complex consists of RF electron linac and the direct-voltage proton accelerator. The 2-MeV electron beam used for the X-ray generation is also utilized for electrostatic charging of the high-voltage terminal of a proton accelerator. High-voltage terminal can be constructed as a large sphere to minimize peak electric field stress. In this report, the charging process of the spherical target by electron beam is studied. The particle motion is described by the classical Coulomb scattering in the field of the charged sphere. The effects of secondary emission and resistive divider are included as leakage currents. The differential equation for the time-derivative of the sphere charge is derived in a non-relativistic approach. The time-dependences for the charge accumulated on sphere and the energy of hitting electrons are obtained analytically. The final values of the sphere voltage and the energy of hitting electrons depend on total value of leakage current. The numerical model for studying relativistic effects is outlined. The simulations are performed under conditions of negligible leakage currents.

* P.Alferov et al., EPAC-98, pp.812-814.

Type of presentation requested: Poster

Classification: [A07] Electrostatic Accelerators
39-122 - A 5 MeV Electron Linac for Radiation Processing

Antonio Trifirò, Lucrezia Auditore, Renato Calogero Barnà, Domenico De Pasquale, Antonio Italiano, Marina Trimarchi (INFN - Gruppo Messina, S. Agata, Messina)

In recent years, radiation processing is rapidly growing in various field of industrial treatments and scientific research as a safe, reliable and economic technique. To match the requirements of several applications, a 5 MeV, 1 kW electron linac has been developed at the Dipartimento di Fisica (Università di Messina), in collaboration with the ENEA Accelerators Group (Frascati- Rome). This self- containing standing wave accelerator, driven by a 3 GHz, 2.5 MW Magnetron, has been designed, by means of the SUPERFISH and PARMELA codes, in such a way as to obtain an autofocusing structure, that will be used to develop a transportable system for 'in-situ' industrial radiography and X-ray digital tomography. For this accelerator, compact pulse forming circuits have been properly developed for the magnetron and the cathode, and pulse frequency can be varied ranging from 1 to 300 Hz, thus allowing the study of several applications of radiation processing. Main features of the accelerating structure, as well as beam spot dimensions, surface dose distribution and electron beam energy range will be described.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
40-223 - A High Current Deuteron Linac

Petro Olexandrovich Demchenko, Yevgeny Gussev, Mikola Shulika, Vladimir Sotnikov, Vladimir Voronko (NSC/KIPT, Kharkov)

On the basis of numeric simulation a deuteron linac accelerating channel has been calculated and the dynamics of a beam with average current of 1 mA and particle energy of 14 MeV has been investigated. The accelerated deuteron beam may be used both for radio isotope molybdenum 99 production, bombarding natural molybdenum targets, and for neutron generation by irradiation of a beryllium target. Beam acceleration and particle focusing are carried out the same RF electric field of 152.5 MHz frequency and 2% duty factor. The accelerating channel consists of three sections. The initial section is a radio frequency quadrupole of 4.7 m length and injection deuteron energy 100 keV and output energy of 2 MeV. Another two sections are the interdigital H cavities with alternating phase focusing. The lengths of these sections are 3.14 m and 3.8 m and output particle energies are 6.4 MeV and 14 MeV respectively. Magnet lenses, in particular quadrupole triplets, are applied only for beam matching between linac sections. An activation dose rate map for the linac has been computed in dependence on linear beam current losses along the channel, time activation and cooling time after the accelerator stop. The permissible deuteron beam losses for the given energy range were determined.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
41-224 - Beam Dynamics in 100 MeV S-Band Linac for CANDLE

Bagrat Grigoryan, Vasili Mkrtich Tsakanov (CANDLE, Yerevan)

The report presents the results of the beam dynamics study in 100 MeV S-band linear accelerator foreseen as an injector for the CANDLE light source. An impact of the excited longitudinal and transverse wake fields on the particle energy spread and the beam transverse emittance are given.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
42-338 - Photoelectron Gun for Formation a Systems of Bunches with Given Configuration

Marzik Petrosyan, Mikhaiel Akopov, Yurik Garibyan, Edouard Laziev, Robert Melikian, Yuri Nazaryan, Mesrop Oganesyan, Gevorg Petrosyan, Lyudvig Petrosyan, Vazgen Pogosyan, Gagik Tovmasyan (YerPhI, Yerevan)

The operation of a photoelectron gun is described and preliminary results of investigations of its parameters are presented. The photoelectron gun is intended for deriving single or double electron bunches with the following parameters: the energy of electrons up to 2 MeV; length of bunches 1-3 cm; controlled distance between bunches 5-20 cm; the current in the first bunch up to 1000 A and current in the second bunch up to 100 A. The similar configurations of electron bunches are necessary at investigations of new acceleration methods, in particular at acceleration of electrons using wake fields in plasma. The photoelectric gun is the accelerator of a direct action with a feed from a high-voltage impulse source of a microsecond range. The high-voltage source is a pulse transformer without of core located in a metal tank with gas under pressure up to 10 atm. The material for a photocathode is chosen an alloy of magnesium with a small content of zinc and aluminum. The zinc cathode is used also. For a photoemission of electrons the fourth harmonics of the Nd:YAG laser with energy in impulse 0.1 mJ is used.

ISTC (International Science & Technology Center). Project # 405

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
43-481 - Defocusing Factor in the Stepped RF Phase Structures

Nikita Vasyukhin, Yurij Senichev (FZJ/IKP, Jülich)

The super-conducting linear accelerators are based on stepped RF phase structures, when many cavities belonging to one family have identical geometry. The particles are sliding down or up relative to the RF wave in dependence of the ratio between the particles and the wave velocities. Thus, the particles are almost never in synchronism with the equivalent traveling wave, and the proper phasing of the RF cavities provides the longitudinal stability. However, in transverse plane the defocusing factor in such structures cannot be found using classical analytical formalism, and usually it is estimated numerically. In this paper we developed new theoretical approach to this problem.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
44-544 - Numerical simulations for the Frankfurt Funneling Experiment

Jan Thibus, Alwin Schempp (IAP, Frankfurt-am-Main)

High beam currents are necessary for heavy ion driven fusion (HIF) or XADS. To achieve these high beam currents several ion beams are combined at low energies to one beam using the funneling technique. In each stage a r.f. funneling deflector bunches two accelerated beam lines to a common beam axis. The Frankfurt Funneling Experiment is a scaled model of the first stage of a HIF driver consisting of a Two-Beam RFQ accelerator and a funneling deflector. Our two different deflectors have to be enhanced to reduce particle losses during the funneling process. This is done with our new developed 3D simulation software DEFGEN and DEFTRA. DEFGEN generates the structure matrix and the potential distribution matrix with a Laplace 3D-solver. DEFTRA simulates ion beam bunches through the r.f. deflector. The results of the simulations of the two existing deflectors and proposals of new deflector structures will be presented.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
45-563 - The Buncher Optimization for the Biperiodic Accelerator Structure with the High Frequency Focusing

Alexey Igorevich Fadin (MEPhI, Moscow)

The bunching part optimization results of an on-axis coupled biperiodic accelerating structure of electron linac with the high frequency focusing are presented. System is intended for operation in the continuous regime at working frequency of 2856 MHz and input power 5.5MW. The basic development challenge for similar installations on average input currents is the effective beam tracking through the structure. Some variants of the bunching sections distinguished by number of bunching cells were considered. The optimum capture ratio and an acceptable spectrum are provided by structure with five bunching cells. Optimization was carried out by means of dynamic simulation code PARMELA and a package of applied programs for the axial symmetric structures calculation SUPERFISH. Taking into account space charge limitation the maximum capture ratio is 55 %.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
46-573 - Delta-T Procedure for Superconducting Linear Accelerator

Alexander Bogdanov, Yurij Senichev (FZJ/IKP, Jülich)

Development of the tune-up procedure for a linear accelerator is the next important stage after the design is complete. Conventional delta-T procedure developed for tuning of a normal-conducting linear accelerator by Crandall allows setting up of accelerating field amplitude and phase in cavity with known phase velocity. However, application of the delta-T procedure to a superconducting linac meets some difficulties. In particular, the synchronous phase velocity in superconducting linac is determined by RF phase shift between cavities, but not by geometrical size of accelerating cells as in normal conducting linac. Additionally, in superconducting linac the smaller phase advance leads to an insensibility of particles at the cavity exit to the variation of the electric field inside the cavity. In the paper we consider the modified delta-T procedure adjusted for superconducting linac. Numerical simulations prove that by proposed technique both tasks of preservation of necessary stable region motion and providing the beam with required final energy can be successfully solved.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
47-574 - Separatrix Formalism Applied to Linacs Accelerating Particles with Different Charge to Mass Ratio

Alexander Bogdanov, Yurij Senichev (FZJ/IKP, Jülich)

We have developed separatrix formalism for superconducting linear accelerators. This method allows optimizing the quasi-synchronous velocity behavior along a linac. It gives a great advantage in acceleration of particles with different charge to mass ratio. In the article design optimization of structure supposed to accelerate different particles is presented. As an example for numerical simulation superconducting injector COSY is taken.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
48-581 - The CERN-SPL Chopper Concept and Final Layout

Fritz Caspers, Yves Cuvet, Jacques Genest, Mauro Paoluzzi (CERN, Geneva)

The fast chopper for the CERN SPL (Superconducting Proton Linac) consists of a double meander structure with a beta (v/c) value of 8 % printed on an alumina substrate for the deflecting plates. Each chopper unit is 50 cm long and housed in a quadrupole magnet surrounding the vacuum chamber. The deflecting plates are operated simultaneously in a dual mode, namely traveling wave mode for frequencies above about 10 MHz and as quasi electro-static deflectors below. The deflecting structures are water-cooled to handle heating from beam losses as well as from the deflecting signal. A detailed mechanical layout is presented including the tri-axial feeding and termination technique as well as a discussion of the drive amplifier



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
49-588 - Status of the Superconducting D+-CH-DTL Design for IFMIF

Andreas Christoph Sauer, Horst Deitinghoff, Horst Klein, Holger Liebermann, Oliver Meusel, Holger Podlech, Ulrich Ratzinger, Rudolf Tiede (IAP, Frankfurt-am-Main)

Within the IFMIF project (International Fusion Materials Irradiation Facility) a high current D+-linac operated in cw mode has to be developed. The acceleration of a 125 mA D+-beam from 0.1 MeV up to 40 MeV must be performed at an extremely low loss rate (0.1-0.2 microA/m). One optional layout of the acceleration facility consists of a high current ion source, low energy beam transport (LEBT), Radio-Frequency-Quadrupol (RFQ) followed by a superconducting H-type DTL. The matching of the beam between subsequent linac sections has to be carefully optimized to avoid an activation of the structures. Actual beam dynamics simulations for such a linac design including parameter errors of components are reported. Consequences for the LEBT- and RFQ-section are discussed.

Work supported by the EC, GSI and BMBF

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
50-710 - Design of the Low-beta, Quarter-wave Resonator and its Cryomodule for the SPIRAL 2 Project

Pierre-Emmanuel Bernaudin, Guillaume Devanz (CEA/DSM/DAPNIA, Gif-sur-Yvette), Pierre Bosland, Stéphane Chel (CEA/DSM, Gif-sur-Yvette)

The SPIRAL 2 project, to be built in GANIL, consists of a 40 MeV linear accelerator for 5 mA of deuterons and a target-source complex for the production of exotic isotopes. The accelerator is also optimised to accelerate q/A = 1/3 ion up to 14.4 MeV/u. The three stages of the linac are a RFQ (up to 0.75 MeV/A), a low beta (0.007) and a high beta (0.12) sections consisting of quarter-wave, 88 MHz superconducting resonators. This paper focuses on the low beta cavity and its cryomodule. The cavity nominal accelerating gradient is at least 6.5 MV/m in operation conditions. RF properties of the cavities are dealt with, as well as the mechanical ones: helium pressure effects, tunability, vibrations. The cryomodule is designed so as to save longitudinal space and therefore is partly assembled in clean room.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
51-713 - The Frankfurt Funneling Experiment

Holger Zimmermann, Ulrich Bartz, Norbert Mueller, Alwin Schempp, Jan Thibus (IAP, Frankfurt-am-Main)

The Frankfurt Funneling Experiment is a scaled model of the first funneling stage of a HIF driver to gather experiences in the funneling technique. It is a procedure to multiply beam currents at low energies in several stages. In each stage two beam lines are combined to a common beam line. The funneling technique is required for new proposed high current accelerator facilities like HIDIF. The main goal is to prevent emittance growth during the funneling process. Our experiment consists of two ion sources, a Two-Beam RFQ accelerator, two different funneling deflectors and a beam diagnostic equipment system. We have demonstrated the principle of funneling with both deflector types. But the measurements have shown a bad matching of the RFQ to the funneling deflector. Now with our new RFQ electrode design we achieve a special three dimensional matching to the deflector. The new results of our measurements and simulations will be presented.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
52-742 - Development of Finger Drift Tube Linacs

Kai-Uwe Kuehnel, Alwin Schempp (IAP, Frankfurt-am-Main), Carsten Peter Welsch (MPI-K, Heidelberg)

At higher particle energies the efficiency of RFQs decreases and DTL structures in combination with magnetic quadrupoles are used. One approach at IAP is the combination of RFQ and DTL. To compensate the defocusing effects of a DTL structure, the accelerating gaps of a spiral loaded cavity were equiped with small focusing fingers. These fingers arranged in a quadrupole symmetry provide an additional focusing field component. The beam dynamics of such a cavity has been studied with PARMTEQ. Simulations of the rf properties have been done using microwave studio. A prototype of a spiral loaded cavity with finger drift tubes has been built and low power measurement were made. Results of the calculations as well as low level and bead pertubation measurements are presented in this contribution.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
53-743 - Study of a Linac Booster for Proton Therapy in the 30-62 MeV Energy Range

Vittorio Vaccaro, Alessandro D'Elia (Naples University Federico II, Napoli), Tarcisio Clauser, Antonio Rainò (Bari University, Bari), Vincenzo Variale (INFN-Bari, Bari), Maria Rosaria Masullo (INFN-Napoli, Napoli), Carlo De Martinis, Dario Giove, Marco Mauri (INFN/LASA, Segrate (MI))

Recent results in accelerator physics have shown the feasibility of a coupling scheme between a cyclotron and a linac for proton acceleration. Cyclotrons with energies up to 30 MeV, mainly devoted to radioisotopes production, are available in a large number of medical centres. These two evidences have suggested the idea to study and design a linac booster able to increase the initial proton energy up to the values required for the treatment of tumors, like the ocular ones. The main challenge in such a project is related to meet the requirements arising from the beam dynamics with the constrains due both to the mechanical structures and tolerances and to the heat dissipation mechanism chosen in the design. In this paper we will review the rationale of the project and we will discuss the basic design of a compact 3 Ghz linac with a new approach to the cavities used in a SCL (Side Coupled Linac) structure

Istituto Nazionale di Fisica Nucleare

Università di Napoli "Federico II"

Università di Milano

Università di Bari



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
54-805 - High Intensity Linac Driver for the SPIRAL-2 Project : Design of Superconducting 88 MHz Quarter Wave Resonators (beta 0.12), Power Couplers and Cryomodules

Tomas Junquera, Jean-Luc Biarrotte, Sebastien Blivet, Sébastien Bousson, Guillaume Olry, Herve Saugnac (IPN, Orsay), Pascal Balleyguier (CEA/DAM, Bruyères-le-Châtel), Michel Fruneau, Yolanda Gomez-Martinez, Emmanuelle Vernay, Francis Vezzu (LPSC, Grenoble)

A Superconducting Linac Driver, delivering deuterons with energy up to 40 MeV (5 mA) and heavy ions with energy of 14.5 MeV/u (1 mA ), is proposed for the Spiral-2 radioactive beams facility. For the high energy section of the linac, a superconducting 88 MHz Quarter Wave Resonator (beta 0.12) has been designed and the optimisation of RF and mechanical performances will be presented. Based on the present state-of-art of the Superconducting RF technology, maximum electric surface field of 40 MV/m and magnetic surface field of 80 mT, have been adopted which should allow to reach an accelerating field of 7 MV/m (energy gain 3 MeV per resonator). A first complete prototype is under construction. The high intensity deuteron beam specifications have imposed the design of an original power coupler (maximum power 20 KW). The RF, mechanical, and thermal characteristics will be presented. The design of the cryomodule for this high energy section, integrating two QWR with its associated equipments (couplers, tuners, helium tanks), will be presented.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
55-808 - Calculation of Thermal Transient Conditions

Dmitry Alexandrovich Zavadtsev (Introscan, Moscow)

Industry electron linear accelerator is built on base of on-axis coupled biperiodic accelerating structure. Designed parameters are: accelerated electron energy is up to 10 MeV, average beam power is up to 10 kW, pulse length is (10-15) microsecond, accelerating section length is 1 m, peak RF generator power is 2.5 MW, average RF generator power is up to 25 kW. Time dependences of accelerating structure frequency at step-like changing of RF power loss, temperature and flow of the water have been got. The processes are not exponential. Effective time constant, estimated at 0.9 frequency level, is equal to 16 sec at RF power changing and 19 sec at water temperature changing. Effective time constant, estimated using derivative in control region, is equal to 11 sec at RF power changing and 21 sec at water temperature changing. Got numerical analysis results are intended for use in engineering of RF power supply system of industry accelerator at mentioned parameters.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
56-827 - Approaching to a Mono-modal Accelerating Cavity based on Photonic Band-gap Concepts

Maria Rosaria Masullo (INFN-Napoli, Napoli), Giorgio Keppel, Vincenzo Palmieri, Diego Tonini (INFN/LNL, Legnaro, Padova), Antonello Andreone, Emiliano Di Gennaro, Ferdinando Francomacaro, Gianrico Lamura, Vittorio Vaccaro (Naples University Federico II, Napoli)

One of the main problem of high intensity accelerators is the presence of high order modes (HOMs) which might degrade the beam quality. Accelerating cavities require HOMs suppression while keeping high quality factor (Q) fundamental mode. Both these requirements can be hardly met in closed metallic cavities. In low frequency cases and for particular geometries it is possible to partially suppress HOMs, but at high frequencies and for superconducting cavities configuration becomes cumbersome and technically unviable. We propose here a high Q cavity based on Photonic Band Gap (PBG) concepts, operating in the microwave region. The cavity consists of a two-dimensional lattice, where posts (dielectric, metallic or superconducting) are sandwiched by two conducting plates. This sandwich exhibits two kinds of frequency bands: 'pass-bands' and 'stop-bands'. It is possible to localize modes in an equivalent cavity obtained by removing posts. These modes are localized in the 'cavity'. In this way, one can obtain a quasi-mono-modal cavity: high Q fundamental mode and HOMs falling into the pass bands. We will present the study, the optimisation and the measurements of our metallic (Copper) PBG structure working in the 2-20 GHz range. The development of a different cryogenic set-up, necessary to characterise an all superconducting or an hybrid (dielectric/metallic) structure, is under way.

Istituto Nazionale di Fisica Nucleare

Università di Napoli "Federico II", Dipartimento di Scienze Fisiche

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