beam-loading

Paper	Title	Other Keywords	Page
MOOCH02	First Full Beam Loading Operation with the CTF3 Linac	linac, gun, acceleration, instrumentation	39
	R. Corsini, H.-H. Braun, G. Carron, O. Forstner, G. Geschonke, E. Jensen, L. Rinolfi, D. Schulte, F. Tecker, L. Thorndahl CERN, Geneva M. Bernard, G. Bienvenu, T. Garvey, R. Roux LAL, Orsay A. Ferrari Uppsala University, Uppsala L. Groening GSI, Darmstadt R.F. Koontz, R.H. Miller, R.D. Ruth, A.D. Yeremian SLAC, Menlo Park, California T. Lefevre NU, Evanston
	The aim of the CLIC Study is to investigate the feasibility of a high luminosity, multi-TeV linear e+e- collider. CLIC is based on a two-beam method, in which a high current drive beam is decelerated to produce 30 GHz RF power needed for high-gradient acceleration of the main beam running parallel to it. To demonstrate the outstanding feasibility issues of the scheme a new CLIC Test Facility, CTF3, is being constructed at CERN by an international collaboration. In its final configuration CTF3 will consist of a 150 MeV drive beam linac followed by a 42 m long delay loop and an 84 m combiner ring. The installation will include a 30 GHz high power test stand, a representative CLIC module and a test decelerator. The first part of the linac was installed and commissioned with beam in 2003. The first issue addressed was the generation and acceleration of a high-current drive beam in the "full beam loading" condition where RF power is converted into beam power with an efficiency of more than 90%. The full beam loading operation was successfully demonstrated with the nominal beam current of 3.5 A. A variety of beam measurements have been performed, showing good agreement with expectations.
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MOPLT054	High Current Operation of Pre-bunching Cavities in the CTF3 Accelerator	coupling, simulation, klystron, gun	674
	R. Roux, G. Bienvenu LAL, Orsay E. Jensen CERN, Geneva
	In the framework of the CLIC studies for a 3 TeV centre of mass linear collider the CLIC Test Facility-3 accelerator (CTF3) is developed to validate the novel concept of CLIC drive beam generation. The front end of the CTF3 linac uses a 140 kV thermionic gun capable to deliver a beam with currents of up to 10 A during 1.5 microseconds. Theμtime structure of this beam is generated with two standing wave single-cell 3 GHz pre-buncher cavities. The high current demands special care in the design of the pre-bunchers to preserve beam quality and transmission. A particular concern was beamloading in the second pre-buncher. In this paper, the design and the conditioning of the pre-bunchers are reported but the main focus is on the commissioning with the electron beam, which showed unexpected results. Indeed, contrary to our expectations, the unbunched beam seems to induce a kind of beamloading in the first pre-buncher while the second one shows none.
MOPLT133	Beam Loading and Higher-band Longitudinal Wakes in High Phase Advance Traveling Wave Accelerator Structures for the GLC/NLC	impedance, simulation, higher-order-mode, linear-collider	848
	R.M. Jones, V.A. Dolgashev, Z. Li, T.O. Raubenheimer SLAC, Menlo Park, California
	A multi-bunch beam traversing traveling wave accelerator structures, each with a 5pi/6 phase advance is accelerated at a frequency that is synchronous with the fundamental mode frequency. As per design, the main interaction occurs at the working frequency of 11.424 GHz. However, modes with frequencies surrounding the dominant accelerating mode are also excited and these give rise to additional modal components to the wakefield. Here, we consider the additional modes in the context of X-band accelerator structures for the GLC/NLC (Global Linear Collider/Next Linear Collider). Finite element simulations, mode-matching and circuit models are employed in order to calculate the wakefield.
TUPKF009	RF Control of the Superconducting Linac for the BESSY FEL	injection, simulation, klystron, linac	973
	J. Knobloch, A. Neumann BESSY GmbH, Berlin
	In the BESSY-FEL superconducting linac, precise RF control of the cavities' voltage is imperative to maintain a bunch-to-bunch time jitter of less than 50 fs for synchronization in the HGHG section. The average beam loading is less than 1.5 kW/m and the cavity bandwidth is small so that high-gain RF feedback is required. Noise, in particular microphonic detuning, strongly impact the achievable level of control. Presented here are simulations of the cavity-feedback system, taking into account beam loading and noise sources such as measurement noise, microphonics and injection jitter. These simulations are used to estimate the resultant time and energy jitter of the bunches as they enter the HGHG section of the BESSY FEL.
TUPKF016	Dynamic Lorentz Force Detuning Studies in TESLA Cavities	linac, resonance, coupling, acceleration	994
	V. Ayvazyan, S. Simrock DESY, Hamburg
	Dynamic detuning of the superconducting rf cavities due to Lorentz force induced mechanical excitation is a critical concern since the magnitude can approach the cavity bandwidth and require significant additional rf power for field control. In this paper, the influence of high accelerating fields on the resonance frequency in superconducting TESLA cavities is discussed. Cavities at the TESLA Test Facility have been operated at the design operating gradient close to 25 MV/m. It is shown that Lorentz force detuning constant factors are different for different cavities, significant spread have been observed.
TUPKF034	Low Output-Impedance RF System for 2nd Harmonic Cavity in the ISIS Synchrotron	feedback, cathode, impedance, synchrotron	1036
	T. Oki, S. Fukumoto, Y. Irie, M. Muto, S. Takano, I. Yamane KEK, Ibaraki R.G. Bendall, I.S.K. Gardner, M.G. Glover, J. Hirst, D. Jenkins, A. Morris, S. Stoneham, J.W.G. Thomason, T. Western CCLRC/RAL/ISIS, Chilton, Didcot, Oxon J.C. Dooling, D. Horan, R. Kustom, M.E. Middendorf, G. Pile ANL, Argonne, Illinois
	In the ISIS facility based at Rutherford Appleton Laboratory (RAL) in the UK, second target station project was funded, which requires to increase the current intensity by 1.5-times (300 micro-A). Four 2nd harmonic RF cavities will be installed in the ISIS synchrotron in order to increase the trapping efficiency, and to mitigate the space charge detuning. A very low output-impedance RF system for the 2nd harmonic cavity has been developed by the collaboration between RAL, Argonne National Laboratory (US) and KEK (Japan). The system comprises the 240 kW triode as a final amplifier with plate-to-grid feedback path. The measured output-impedance was less than 30 ohms over the frequency range of 2.7 - 6.2 MHz, which agreed well with calculations. High power test was also performed under frequency swept mode at 50 Hz repetition. The operation was almost stable, and more than 12 kVpp was obtained as maximum. The voltage gain of the final amplifier was 25 - 30, which decreased gradually with frequency due to decreasing input-impedance of triode. The beam test is planned at ISIS in near future.
TUPLT072	Dual Harmonic Acceleration with Broadband MA Cavities in J-PARC RCS	impedance, emittance, simulation, acceleration	1318
	M. Yamamoto JAERI, Chiba-ken S. Anami, E. Ezura, K. Hara, Y. Hashimoto, C. Ohmori, A. Takagi, M. Yoshii KEK, Ibaraki M. Nomura, A. Schnase, F. Tamura JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
	In the J-PARC RCS rf system, since the fundamental rf acceleration voltage and the 2nd higher harmonic one are applied to each cavity, the impedance of hte cavity has a broadband characteristic. The Q-value of the cavity is chosen to make the higher harmonic beam loading effect as small as possible. The analysis of the amplifier and the beam loading effect on the dual harmonic rf system is described.
WEOACH01	High Field Gradient Cavity for J-PARC 3 GeV RCS	impedance, acceleration, synchrotron, injection	123
	C. Ohmori, S. Anami, E. Ezura, K. Hara, Y. Hashimoto, A. Takagi, M. Toda, M. Yoshii KEK, Ibaraki M. Nomura, A. Schnase, F. Tamura, M. Yamamoto JAERI/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
	A new type of rf cavity will be used for J-PARC project. To minimize the beam loading effects, the quality factor of the core stack is increased by a cut core configuration. High power test of the rf system has been performed. Temperature rise around the cut surface of the cores were observed. It is minimized by improving the cooling efficiency.
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WEYCH03	Low and Medium Beta Superconducting Cavities	linac, proton, ion, heavy-ion	142
	A. Facco INFN/LNL, Legnaro, Padova
	The use of low- and intermediate-beta superconducting cavities, once confined to low current heavy ion linacs, is steadily increasing in accelerators. The progress in this technology allowed a significant increase in cavity performance during the last 10 years; a large number of resonators, with different geometries, frequencies and gap numbers have been built for a large variety of applications and the development is still going on. The main boost is given by new projects of radioactive beam facilities and high power proton accelerators worldwide. While the advantages of SC resonators, compared with normal conducting structures, are rather well established in high-beta linacs, this is not always the case at low-beta. The choice of the optimum transition beam energy in a linac, where superconducting cavities should replace the room temperature ones, requires a careful evaluation that depends on the linac specifications.
	Video of talk
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WEPLT036	Energy Loss of a Single Bunch in the CERN SPS	impedance, single-bunch, kicker, pick-up	1909
	E.N. Shaposhnikova, T. Bohl, T.P.R. Linnecar, J. Tuckmantel CERN, Geneva A. Hofmann Honorary CERN Staff Member, Grand-Saconnex
	The dependence of energy loss on bunch length was determined experimentally for a single proton bunch in the SPS at 26 GeV/c. This was done from measurements of the synchronous phase as a function of intensity for different capture voltages. The results are compared with the expected dependence calculated from the resistive part of the SPS impedance below 1 GHz. Two impedance sources, the cavities of the 200 MHz RF system and the extraction kickers, give the main contributions to particle energy loss in very good agreement with experiment. The results obtained allow a better understanding of some mechanisms leading to capture loss of the high intensity LHC beam in the SPS.
WEPLT072	Preliminary Design of the RF Systems for the SPIRAL 2 SC Linac	linac, rfq, feedback, coupling	2017
	M. Di Giacomo, B. Ducoudret, J.F. Leyge GANIL, Caen J.F. Denis, M. Desmons, M. Luong, A. Mosnier CEA/DSM/DAPNIA, Gif-sur-Yvette
	In the SPIRAL 2 Linac, a 5 mA, CW , Deuteron beam is accelerated up to 40 MeV, through a normal conducting RFQ and 26 independent-phase SC quarter wave resonators, working at 88,05 MHz. Tube and solid state amplifiers derived from the standard FM transmitter modules are used while a new digital control system has been designed for the feed-back and feed-forward control system. The paper presents the power and low level systems for both the normal and superconducting cavities and results of simulations of the RF system in operating conditions.
WEPLT097	Beam Loading in the RF Deflector of the CTF3 Delay Loop	injection, emittance, linac, simulation	2077
	D. Alesini, F. Marcellini INFN/LNF, Frascati (Roma)
	In this paper we describe the impact of the beam loading in the RF deflectors on the transverse beam dynamics of the CTF3 Delay Loop. The general expression for the single passage wake field is obtained. A dedicated tracking code has been written to study the multi-bunch multi-turn effects on the transverse beam dynamics. A complete analysis for different machine parameters and injection errors is presented and discussed. The numerical simulations show that the beam emittance growth due to the wake field in the RF deflectors is small.
THPLT080	Simulation Study of the Beam Loading Effect in an RF Gun	gun, simulation, laser, emittance	2682
	K. Shinto, H. Hama, F. Hinode, A. Miyamoto, T. Tanaka LNS, Sendai
	Because of simple structure and apparatus, a thermionic rf gun has been considered to be employed in a new pre-injector for the future synchrotron radiation facility at Tohoku University. A 3-D beam simulation code for the rf gun using a Finite Difference Time Domain (FDTD) method to solve Maxwell's equations has been developed. In the rf gun, especially in case of the high beam current, electromagnetic fields induced by the electron beam are considered to affect beam characteristics such as beam emittance and energy spread. In the FDTD method, because the Maxwell?s equations are able to be solved including the term of current density of the charge, the electromagnetic fields produced by both the external rf power and the electron beam can be anticipated. Using the simulation code, beam loading effects on the characteristics of the electron beam extracted from the rf gun is investigated.
THPLT111	An Accelerator-based Thermal Neutron Source for BNCT Application	target, proton, electron, rfq	2745
	A. Makhankov, A. Gervash, R. Giniyatulin, I. Mazul, M. Rumyantsev NIIEFA, St. Petersburg J. Esposito, L.B. Tecchio INFN/LNL, Legnaro, Padova V. Khripunov RRC Kurchatov Institute, Moscow
	An accelerator-based thermal neutron source, aimed at the BNCT treatment of skin melanoma is in construction at the INFN-LNL in the framework of SPES project. The BNCT device exploit the intense proton beam provided by a 5 MeV, 30 mA RFQ that represent the first accelerating step of the SPES exotic nuclei production beam facility. Neutrons are generated by 9Be(p,n)9B nuclear reaction in a high power (150 kW) Beryllium target. The operational condition of the Beryllium converter is close to the condition of Be-armoured components in fusion reactors. The main difference consists in the necessity of limitation of structural materials amount used in the design in order to meet therapeutic irradiation requirements. Two possible design of neutron converter are developed: one with saddle block tiles brazed to CuCrZr tubes and another one with Be target made from solid Be block. Results of R&D works on the development of water cooled Be target for converter are presented, including data on selected materials, technological trials and mockups high heat flux testing.
THPLT124	Simulation Technique for Study of Transient Self-consistent Beam Dynamics in RF Linacs	simulation, linac, acceleration, impedance	2762
	V.V. Mytrochenko, A. Opanasenko NSC/KIPT, Kharkov
	The report describes a simulation technique for study of unsteady self-consistent dynamics of charged particles in resonant linacs. The technique allows simulating the linacs that consist of resonant cavities and traveling wave sections. The proposed approach is based on unsteady theories of excitation of resonant cavities and waveguides by a beam of charged particles and RF feeders. The theory of waveguide excitation is generalized to the case of spatially inhomogeneous traveling wave structures. The system of self-consistent differential equations for fields and motion of particles is integrated over time and space. The SUPERFISH code is used to evaluate characteristics of the axially symmetrical cavities and traveling wave sections. The PARMELA code is applied to simulate motion of the particles at each time step of the integration. In such a way the fields and beam characteristics in the axially symmetrical accelerating structures can be obtained for transient and steady state operation. Description of the algorithm and results of its validation are presented.
THPLT133	Simulation of RF Control of a Superconducting Linac for Relativistic Particles	linac, simulation, feedback, proton	2774
	M. Huening, P. Bauer, G.W. Foster Fermilab, Batavia, Illinois
	We present a code to simulate the rf field and field control in a superconducting linac for relativistic heavy particles. In such a linac the field stability is strongly influenced by the longitudinal beam dynamics. So the code has to simulate both the field and the beam dynamics with the resulting varying beam loading. Other effects included in the simulation are Microphonics and Lorentz force. The code can simulate both single cavity and vector sum control.