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: [A08] Linear Accelerators
57-912 - CEBAF Injector Achieved World's Best Beam Quality for Three Simultaneous Beams with a Wide Range of Bunch Charges

Reza Kazimi, Kevin Beard, Jay Benesch, Arne Freyberger, Joseph Michael Grames, Tommy Hiatt, Andrew Hutton, Geoffrey Arthur Krafft, Lia Merminga, Matthew Poelker, Michael Spata, Micheal Tiefenback, Byung Chel Yunn, Yuhong Zhang (Jefferson Lab, Newport News, Virginia)

The CEBAF accelerator simultaneously provides three 499 MHz interleaved continuous electron beams spanning 5 decades in beam intensity (a few nA to 200 uA) to three experimental halls. The typical three-user physics program became more challenging when a new experiment, G0, was approved for more than six times higher bunch charge than is routine. The G0 experiment requires up to 8 million electrons per bunch (at a reduced repetition rate of 31 MHz) while the lowest current hall operates at 100 electrons per bunch simultaneously. This means a bunch destined to one hall may experience significant space charge forces while the next bunch, for another hall, is well below the space charge limit. This disparity in beam intensity is to be attained while maintaining best ever values in the beam quality, including final relative energy spread (<2.5x10-5 rms) and transverse emittance (<1 mm-mrad norm. rms). The difficulties related to space charge emerge in the 10m long, 100 keV section of the CEBAF injector during initial beam production and acceleration. A series of changes were introduced in the CEBAF injector to meet the new requirements, including changes in the injector setup, adding new magnets, replacing lasers used for the photocathode and modifying typical laser parameters, stabilizing RF systems, and changes to standard operating procedures. In this paper, we will discuss all these modifications in some detail including the excellent agreement between the experimental results and detailed simulations. We will also present some of our operational results.

This work is supported by the U. S. Department of Energy under contract DE-AC05-84ER40150
Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
58-946 - Computation of the Longitudinal Space Charge Effect in Photoinjectors

Cecile Limborg-Deprey (SLAC/SSRL, Menlo Park, California), Zhirong Huang, James Welch, Juhao Wu (SLAC, Menlo Park, California), Paul Emma (SLAC/ARDA, Menlo Park, California)

The LCLS Photoinjector produces a 100A, 10 ps long electron bunch which is later compressed down to 100 fs to produce the peak current required for producing SASE radiation. SASE saturation will be reached in the LCLS only if the emittance and uncorrelated energy spread remain respectively below 1.2 mm.mrad and 5.10-4. This high beam quality will not be met if the Longitudinal Space Charge (LSC) instability develops in the injector and gets amplified in the compressors. The Longitudinal Space Charge instability originates in the injector beamline, from an initial modulation of the current density. Numerical computations, performed with Multiparticle Space Charge tracking codes, showing the evolution of the longitudinal phase space along the LCLS Photoinjector beamline, are presented. Those results are compared with an analytical model for various regimes of energy and acceleration. This study justifies the necessity to insert a "laser heater" in the LCLS Photoinjector beamline to warm up the beam and thus prevent the amplification of the LSC instability in the compressors. Numerical calculations of the 'laser heater' performances are presented.

This work was supported by US Department of Energy, contract No. DE-AC03-76SF00515

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
59-987 - Test Results of Injector Based on Resonance System with Evanescent Oscillations

Sergey Perezhogin, Mykola Ivanovich Ayzatskiy, Efrem Zakharovich Biller, Kateryna Kramarenko, Volodymyr Kushnir, Viktor Mytrochenko, Valentin Zhiglo (NSC/KIPT, Kharkov)

Report presents results of tune-up and tests of the compact electron S ? band injector consisting of the low-voltage diode electron gun and the bunching system based on the resonant system with the evanescent oscillation. In the considered bunching system electrical field increased from beam entrance to an exit of the buncher. The injector designed for bunching of electron beam with initial energy of 25 keV and pulse current of 300 mA and accelerating it to the energy of 1 MeV.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
60-1024 - S-band Electron Linac with Variation of Beam Energy Over a Wide Range

Viktor Mytrochenko, Mykola Ivanovich Ayzatskiy, Efrem Zakharovich Biller, Victor Boriskin, Anatoly Nikolayevich Dovbnya, Igor Khodak, Volodymyr Kushnir, Sergey Perezhogin, Yuriy D. Tur, Vyacheslav Uvarov, Valentin Zhiglo (NSC/KIPT, Kharkov)

The new S-band electron linac has been designed at NSC KIPT. The main feature of the linac is variation of beam energy in a range from 25 to 100 MeV. The linac consists of the injector based on evanescent oscillations and the two four-meter long piecewise homogeneous accelerating sections. Each section is supplied with RF power from the KIU-12AM klystron. To vary a mean energy of the beam, bunches are accelerated in different phases about the wave crest in the second accelerating section. The report presents layout of the linac, its present status and simulation results of self-consistent particle dynamics in the linac.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
61-1036 - Triple-spoke Cavities in FZJ

Evgeny Zaplatin, Werner Braeutigam, Rudolf Maier, Rolf Stassen, Raimund Tölle (FZJ/IKP, Jülich), Michael Pap, Manfred Skrobucha (FZJ, Julich)

We report the situation with superconducting triple-spoke cavity activities at the research center FZJ in Juelich. The Nb prototype of the 700 MHz, beta=0.2 cavity is already in fabrication and should be tested this year. This work has been initiated for the European Spallation Source project. In the frames of the new European project of High Intensity Pulsed Proton Injector the 352 MHz, beta=0.48 cavity is under developments. This cavity should be designed, built and tested in the Lab within next few years.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
62-1114 - A 40MeV Electron Source with a Photocathode for X-ray Generation through Laser-compton Scattering

Fumio Sakai (SHI, Tokyo)

.3 keV femtosecond X-ray generation through laser-Compton scattering with 14MeV electron source and a TW Ti:sapphire laser was achieved. In order to increase the X-ray energy up to 15 keV for some applications, e.g. protein crystallography, we modified the system to increase electron energy. Electron beams emitted from a S-band RF photocathode are accelerated up to 40MeV with two 1.5m standing-wave linacs. The beams are bended at 90 degree using an achromatic bending system, then focused with a triplet quadrupole-magnet to be interacted with laser pulses. The characteristics of electron beams, emittance, energy and energy dispersion, will be described.

The New Energy and Industrial technology Development Organization (NEDO) in Japan

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
63-1126 - RF Design of the MAFF IH-RFQ Power Resonator

Matteo Pasini (LMU, Garching), Thomas Sieber (CERN, Geneva), Dietrich Habs, Oliver Kester (LMU, München)

The low energy part of the LINAC of the MAFF facility will be an IH-RFQ cavity with 101.28 MHz resonance frequency. The RF design of the cavity has been completed, including design calculations and model measurements. The RFQ is designed to deliver ions of A/q = 6.5 up to 300 keV/u to be injected into the following LINAC. The structure chosen was an IH type of resonator since it was demontrated to have a better shunt impedance. The required voltage between the electrodes is 70kV and the operation mode is pulsed with a duty cycle of 10%. The structure will be made out from bulk copper in order to improve the shunt impedance and hence to allow not direct cooling on the electrodes. The optimizazion of the several parameters of the structure, and the technique for tuning the voltage distribution are presented in this paper. Measurements with a short model will be shown as well.

Work supported by the DFG

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
64-1136 - Improvements of SPring-8 Linac towards Top-up Operation

Shinsuke Suzuki, Takao Asaka, Hideki Dewa, Hirofumi Hanaki, Toshiaki Kobayashi, Takemasa Masuda, Akihiko Mizuno, Tsutomu Taniuchi, Hiromitsu Tomizawa, Kenichi Yanagida (JASRI/SPring-8, Hyogo)

The top-up operation of the SPring-8 storage ring will start in May, 2004. In order to realize alternative injection into the booster synchrotron in the top-up operation and the NewSUBARU, an AC bending magnet replaced the DC bending magnet in the beam transport line to the booster synchrotron. This magnet operates at 1 Hz with a trapezoid current pattern. The 1-GeV electron beam goes at the bottom of the current pattern to the NewSUBARU or at the top of the pattern to the booster synchrotron. In order to obtain the higher reliability of the linac for the top-up operation, reinforcement of the beam monitor systems, further improvement of RF phase stability and upgrade of the control system were required. BPM?s has been newly installed in energy dispersion sections, and beam transport feedback control is in development. The phase variation in the RF system was reduced by the regulation of the gas pressure in the waveguide of the klystrons drive system. We re-engineered the VME systems to maximize availability of the linac operation considering its reliability, usability, expandability and flexibility.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
65-1143 - Laser Temporal Pulse Shaping Experiment For SPARC Photoinjector

Carlo Vicario, Andrea Ghigo (INFN/LNF, Frascati (Roma)), Simone Cialdi (INFN-Milano, Milano), Massimo Petrarca (INFN-Roma, Roma), Ilario Boscolo (Universita' degli Studi di Milano, MILANO)

Laser for driving high brightness photoinjector have to produce UV square pulse which is predicted to be the optimum profile for emittance compensation in advanced photoinjectors. The longitudinal laser pulse distribution, according to numerical simulations for the SPARC photoinjector, must be square with rise and fall time shorter than 1 ps and flat top variable up to 10 ps FWHM. In this paper we report the results of pulse shaping obtained using an acousto-optic (AO) programmable dispersive filter (DAZZLER). The DAZZLER was used to perform spectral amplitude and phase modulation of the incoming 100 fs Ti:Sapphire pulses. Because of the finite length of the crystal the maximum duration of the shaped pulse is 6 ps. To overcome this limitation we used a configuration in which the laser pulses passed twice through the AO filter. A dispersive glass section was also used to lengthen the pulse with a single pass in the DAZZLER. In this paper we report the experimental setup, hardware description and time and frequency domain measurements.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
66-1147 - Design Studies of a high Current Deuteron RFQ

Chuan Zhang, Alwin Schempp (IAP, Frankfurt-am-Main), Jia-er Chen, Jia-Xun Fang, Zhiyu Guo (PKU/IHIP, Beijing)

A 201.5MHz, 50mA deuteron RFQ is proposed for the new neutron source project at Peking University, China. Considering minimum beam losses, the limited RF power and the demands of safety maintenance, design studies have been performed with the ParmteqM and Microwave Studio codes to optimize the structure design. Results of a conceptual design with a compact structure and high transmission efficiency is presented.

Mr. C.Zhang is supported by Gottlieb Daimler- und Karl Benz-Stiftung & GSI, Germany

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
67-1285 - First Results of Pulsed Superconducting Half-wave Resonators

Rolf Stassen, Ralf Eichhorn, Rudolf Maier, Gebhard Schug, Raimund Tölle, Evgeny Zaplatin (FZJ/IKP, Jülich), F.M. Esser, Bernhard Laatsch (FZJ, Julich)

A pulsed linac for the cooler synchrotron COSY was projected based on superconductive half-wave resonators (HWRs). The concept of single phased resonators is a great challenge related to the requirement of accelerating protons and deuterons up to a similar energy. A cryomodule, which houses four cavities was designed in Cooperation with FZJ-ZAT, taking into account the restricted space and the special requirements of a linear accelerator. Two prototypes of the 160MHz Half-Wave Resonators (HWRs) were built at different companies. The fabrication differs slightly concerning the top and bottom parts of the cavity as well as the welding of the inner and outer conductor. First results of warm and cold measurements will be presented. The behaviour of the adjustable 4kW main coupler as well as the mechanical tuner can be tested together with the HWR in a new vertical test-cryostat.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
68-1313 - Achievements of the High Current Beam Performance of the GSI Unilac

Winfried Barth, Ludwig Dahl, Joerg Glatz, Lars Groening, Simone Georgia Richter, Stephan Yaramishev (GSI, Darmstadt)

The present GSI-accelerator complex is foreseen to serve for the future synchrotron SIS100 as an injector for up to 1012 U28+ particles/sec. The High Current Injector of the Unilac was successfully commissioned five years ago. An increase of more than two orders of magnitude in particle number for the heaviest elements in the SIS had to be gained. Since that time many different ion species were accelerated in routine operation. In 2001 a physics experiment used 2×109 Uranium ions per spill. In order to meet this request the MEVVA ion source provided for the first time in routine operation a high intense Uranium beam. The main purpose for the machine development program during the last two years was the enhancement of the intensity for Uranium beams. Different hardware measures and a huge investigation program in all Unilac-sections resulted in an increase of the uranium intensity by a factor of 7. The paper will focus on the measurements of beam quality, as beam emittance and bunch structure for Megawatt-Uranium beams. Additionally the proposed medium- and long-term hardware measures will be described, which should gain in the required uranium intensity to fill the SIS up to the space charge limit.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
69-1317 - Analysis and Synthesis of Perturbations aimed at TRASCO RFQ Tuning

Antonio Palmieri, Andrea Pisent (INFN/LNL, Legnaro, Padova), Guiseppe Lamanna (INFN-Bari, Bari)

TRASCO RFQ requires a longitudinal electric field variation not exceeding the ±1% with respect to the design configuration. Therefore, the implementation of a suitable tuning procedure for such a structure requires a proper modelling of the RFQ, especially with regard to the effects of perturbations on fields and frequency spectrum configuration. In this article we present a model of the RFQ, based on normal mode analysis, in which it is possible, from the knowledge of frequency perturbations, to determine the associated field perturbation in the cavity (analysis problem). Then, starting from the actual knowledge of the field in each quadrant, the problem of determining the local frequency perturbation will be envisaged (synthesis problem).



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
70-1319 - Study of a High-current 176 MHz RFQ as a Deuteron Injector for the SPES Project

Marco Marchetto, Michele Comunian, Antonio Palmieri, Andrea Pisent (INFN/LNL, Legnaro, Padova)

The SPES project, aimed at the construction of a RIB facility at LNL, is initially based on the use of a primary proton beam, but it foresees a future development based on the usage of deuterons and light ions. In this article we report about the preliminary study of a 176 MHz RFQ to be used as an injector for such kind of beams. The structure explored foresees a ?four ladder? symmetric resonator, built in brazed copper. In particular beam dynamics, electrodynamics design and preliminary thermo-structural analysis of the cavity is presented.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
71-1338 - Status of the HITRAP Decelerator Linac at GSI

Charles Agbehonou Kitegi, Ulrich Ratzinger, Alwin Schempp (IAP, Frankfurt-am-Main), Thomas Beier, Ludwig Dahl, Christophor Kozhuharov, Wolfgang Quint, Markus Steck (GSI, Darmstadt), Sergey Minaev (ITEP, Moscow)

Within the European Network HITRAP (heavy Ion trap) trapped and cooled higly charged ions up to U92+ will become avilable for a variety of attractive experiments in atomic physics. Heavy ions are produced, accelerated and stripped in the GSI accelerator complex and are stored in the ESR down to 4 MeV/u. To be captured in HITRAP, ions have to be decelerated to energies below 6 keV/u. The decelerator proposed to achieve these energies is a combination of an IH Drift tube cavity operating in the H11(0) mode and a RFQ. The operating frequency is 108.408MHz . The A/q range of the linac is up to 3. A very efficient deceleration by up to 11 MV along the 2.7 m long IH cavity with a rf power of 200kw is achieved by applying the KONUS beam dynamics. The deceleration from 500 A.keV down 6A.keV is provided by a 1.8 m long 4-rod RFQ.The beam dynamics as well as the cavity design of that linac will be described.The decelerator linac will be installed in the reinjection beam line and is being developed in collaboration between GSI and the Frankfurt University .

supported by GSI

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
72-1472 - A PARMELA Model of the CEBAF Injector valid over a wide range of parameters

Yuhong Zhang, Kevin Beard, Jay Benesch, Yu-Chiu Chao, Arne Freyberger, Joseph Michael Grames, Reza Kazimi, Geoffrey Arthur Krafft, Rui Li, Lia Merminga, Matthew Poelker, Micheal Tiefenback, Byung Chel Yunn (Jefferson Lab, Newport News, Virginia)

A pre-existing PARMELA model of the CEBAF injector has been recently verified using machine survey data and also extended to 60 MeV region. The initial distribution and temperature of an electron bunch are determined by the photocathode laser spot size and emittance measurements. The improved injector model has been used for extensive computer simulations of the simultaneous delivery of the Hall A beam required for a hypernuclear experiment, and the Hall C beam, required for a parity experiment. The Hall C beam requires a factor of 6 higher bunch charge than the Hall A beam, with significantly increased space charge effects, while the Hall A beam has an exceedingly stringent energy spread requirement of 2.5x10-5 rms. Measurements of the beam properties of both beams at several energies (100 keV, 500 keV, 5 MeV, 60 MeV) and several values of the bunch charge were performed using the standard quad-wire scanner technique. Comparisons of simulated particle transmission rate, longitudinal beam size, transverse emittance and twiss parameters, and energy spread against experimental data yield reasonably good agreement. The model is being used for searching for optimal setting of the CEBAF injector.

Work supported by the U.S. Dept of Energy under Contract No. DE-AC05-84ER40150.

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
73-1499 - Dark Current Reduction System for SPring-8 Linac

Toshiaki Kobayashi, Takao Asaka, Hirofumi Hanaki, Masazumi Shoji, Shinsuke Suzuki, Kazuhiro Tamura (JASRI/SPring-8, Hyogo)

The SPring-8 linac accelerates dark currents generated by its injector part up to 1 GeV. These dark currents are injected with main beam into the SPring-8 storage ring and then spoil the purity of the stored beam. The dark currents are mainly composed of a grid emission current from a thermionic gun and field emission currents from rf accelerating structures. A beam deflector for kicking only the grid emission by a pulsed electric field was developed and installed in the SPring-8 linac. We observed that the beam deflector greatly reduced the grid emission current accelerated up to 1 GeV. The measured purity of the stored single-bunched beam was about 5x10^-6 when the deflector operated, which was almost 1/100 of the purity without filtering by the deflector. However, the deflector, which is installed before the prebucher, cannot reduced the field emission currents from the buncher cavities and the first acccelerating structure. These dark currents take considerable proportion of the total dark currents observed at the end of the linac. We are trying to spin off the field emission currents by weak magnetic fields across the accelerating structure generated by several coils.



Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
74-1547 - First Commissioning Experiments at DARHT-II

Carl Ekdahl (LANL, Los Alamos, New Mexico)

The second axis of the Dual Axis Radiographic Hydro-Test (DARHT) facility will provide up to four short(< 150 ns) radiation pulses for flash radiography of high-explosive driven implosion experiments[1]. The DARHT-II linear induction accelerator (LIA) will produce a 2-kA,18-MeV,2-micro-s electron beam. A fast kicker will cleave four short pulses out of the beam, which will focused onto a tantalum target for conversion to bremsstrahlung pulses for radiography. The first tests of the second axis accelerator were designed to demonstrate the technology, and to meet the modest performance requirements for closing out the DARHT-II construction project. These experiments demonstrated that we could indeed produce a 1.2 kA beam with pulse length 0.5-1.2 s and accelerate it to 12.5 MeV. These de-rated parameters were chosen to minimize risk of damage in these first experiments with this novel accelerator. The beam was stable to the BBU instability for these parameters. In fact, we had to reduce the magnetic guide field by a factor of 5 before any evidence of BBU was observed. We will discuss the results of these experiments and their implications, as well as our plans for continuing with DARHT-II commissioning.

United States Department of Energy

Type of presentation requested: Poster

Classification: [A08] Linear Accelerators
75-165 - New Developments of a Laser Ion Source for Ion Synchrotrons

Sergei Kondrashev, Alexander Balabaev, Konstantin Konukov, Boris Sharkov, Alexander Shumshurov (ITEP, Moscow), Olivier Camut, James Chamings, Hartmut Kugler, Richard Scrivens (CERN, Geneva), Andrei Charushin, Konstantin Makarov, Yuri Satov, Yuri Smakovskii (SRC RF TRINITI, Moscow region)

Laser Ion Sources (LIS) are well suited to filling synchrotron rings with highly charged ions of almost any element in a single turn injection mode. We report the first measurements of the LIS output parameters for Pb27+ ions generated by the new 100 J/1 Hz Master Oscillator - Power Amplifier CO2-laser system. A new LIS has been designed, built and tested at CERN, as an ion source for ITEP-TWAC accelerator/accumulator facility, and as a possible future source for an upgrade of the Large Hadron Collider (LHC) injector chain. The use of the LIS based on 100 J/1 Hz CO2-laser together with the new ion LINAC, as injector for ITEP-TWAC project is discussed.


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