IPAC2011 - List of Keywords (space-charge)

Paper	Title	Other Keywords	Page
MOODB01	Dynamics of the IFMIF Very High-intensity Beam	rfq, emittance, linac, cryomodule	53
	P.A.P. Nghiem, R.D. Duperrier, A. Mosnier, D. Uriot CEA/DSM/IRFU, France N. Chauvin, O. Delferrière, W. Simeoni CEA/IRFU, Gif-sur-Yvette, France M. Comunian INFN/LNL, Legnaro (PD), Italy C. Oliver CIEMAT, Madrid, Spain
	For the purpose of material studies for future nuclear fusion reactors, the IFMIF deuteron beams present a simultaneous combination of unprecedentedly high intensity (2x125 mA CW), power (2x5 MW) and space charge. Special considerations and new concepts have been developed in order to overcome these challenges. The global strategy for beam dynamics design in the 40 MeV IFMIF accelerators is presented, stressing on the control of micro-losses, and the possibility of on-line fine tuning. The obtained results are then analysed in terms of beam halo and emittance growth.
	Slides MOODB01 [3.807 MB]

MOPC132	Influences of the Inner-conductor on Microwave Characteristics in an L-band Relativistic Backward-wave Oscillator*	resonance, simulation, plasma, coupling	388
	X.J. Ge, L. Liu, B.L. Qian, J. Zhang, H.H. Zhong National University of Defense Technology, Changsha, Kaifu District, People's Republic of China
	Funding: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, People’s Republic of China. gexingjun230230@yahoo.com.cn* The influences of the inner-conductor on microwave characteristics in an L-band relativistic backward-wave oscillator (RBWO) are investigated theoretically and experimentally. The numerical results show that the resonance frequency decreases obviously with the increase in the inner-conductor radius. To verify the above conclusions, an L-band coaxial RBWO is investigated in detail with particle-in-cell (PIC) code. It is shown that the frequency is lowered from 1.63 GHz to 1.51 GHz when the inner-conductor radius increases from 0.5 cm to 2.5 cm. And the efficiency varies in the range of 35.4-27.7%. Furthermore, experiments are carried out at the Torch-01 accelerator. When the diode voltage is 887.6 kV and the current is 7.65 kA, the radiated microwave with frequency of 1.61 GHz, power of 2.13 GW and efficiency of 31.3% is generated. It is found that the frequency decreases from 1.64 GHz to 1.58 GHz when the inner-conductor radius increases from 0.5 cm to 1.5 cm. And the efficiency varies in the range of 31.3-29.8%.

MOPS002	Mitigation of Space Charge and Nonlinear Resonance Induced Beam Loss in SIS100	beam-losses, resonance, acceleration, simulation	589
	G. Franchetti GSI, Darmstadt, Germany
	The control of beam loss in SIS100 is essential for avoiding vacuum instability and guarantee the delivery of the foreseen beam intensity. On the other hand simulations show that the simultaneous presence of space charge and lattice resonances creates during 1 second cycle a progressive beam loss exceeding the limit of 5%. Until now the mechanism of periodic resonance crossing were suspected to be, in conjunction with pure dynamic aperture effects, at the base of the beam loss. In this proceeding we present the state of the art in the beam loss prediction and we prove that the periodic resonance crossing is the deteriorating mechanism, and show that the compensation of a relevant resonance intercepting the space charge tune spread sensibly mitigate the beam loss. A short discussion on beam loss during acceleration is addressed as well.

MOPS004	Mitigation of Beam Instability due to Space Charge Effects at 3 GeV RCS in J-PARC	impedance, kicker, bunching, injection	595
	Y. Shobuda, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y.H. Chin KEK, Ibaraki, Japan F. Tamura KEK/JAEA, Ibaraki-Ken, Japan
	In order to accomplish high intensity proton beams, it is important to identify the impedance source in accelerators. At 3 GeV rapid cycling synchrotron (RCS) in Japan Proton Research Complex (J-PARC), the kicker impedance is the most dominant among such impedance sources. Beam instability can be observed by correcting chromaticity during the acceleration. Growth rate due to the beam instability can be reduced by making peak current larger (bunching factor smaller). In other words, it is experimentally found that space charge effects mitigate the beam instability.

MOPS013	Transverse Low Frequency Broad-band Impedance Measurements in the CERN PS	impedance, proton, extraction, injection	622
	S. Aumon EPFL, Lausanne, Switzerland P. Freyermuth, S.S. Gilardoni, O. Hans, E. Métral, G. Rumolo CERN, Geneva, Switzerland
	The base-line scenario for the High-Luminosity LHC upgrade foresees an intensity increase delivered by the injectors. With its 53 years, the CERN PS would have to operate beyond the limit of its performances to match the future requirements. Beam instabilities driven by transverse impedance are an important issue for the operation of high intensity beams as for the high-brightness LHC beams. Measurements of transverse tune dependence with beam intensity were performed at injection kinetic energy 1.4~GeV and at LHC beam extraction momentum 26~GeV/c. This allows deducing the low frequency inductive broad-band impedance of the machine. Then an estimation of the real part of the impedance is made by the rise time measurement of a fast transverse instability believed to be a TMCI type. Those are the first step towards a global machine impedance characterization in order to push forward the performances of the accelerator.

MOPS014	Tune and Space Charge Studies for High-brightness and High-intensity Beams at CERN PS	resonance, emittance, injection, beam-losses	625
	S.S. Gilardoni, S. Aumon, J. Brenas, P. Freyermuth, A. Huschauer, R. Maillet, E. Matli, R.R. Steerenberg, B. Vandorpe CERN, Geneva, Switzerland E. Benedetto National Technical University of Athens, Zografou, Greece
	The current 1.4 GeV CERN PS injection energy limits the maximum intensity required by the future High-Luminosity LHC. The bare-machine large chromaticity combined with the non-linear space charge forces make high-brightness and high-intensity beams crossing betatron resonances along the injection flat bottom, inducing transverse emittance blow-up and beam losses. A scan of the working point plane {Qx,Qy} was done in order to identify beam destructive resonances, in the framework of a possible 2 GeV injection energy upgrade which would reduce the space charge effect on the tune. Experiments were carried out in order to review the maximum space charge tune shift for which no transverse emittance blow-up is observed. The results of measurements and simulations will be presented in this paper.

MOPS016	First Observations of Intensity-dependent Effects for Transversally Split Beams	resonance, extraction, booster, coupling	631
	S.S. Gilardoni, M. Giovannozzi CERN, Geneva, Switzerland
	During the commissioning of the CERN PS Multi-Turn Extraction (MTE) tests with different beam intensities were performed. The beam current before transverse splitting was varied and the properties of the five beamlets obtained by crossing the fourth-order horizontal resonance were studied. A clear dependence of the beamlets’ parameters on the total intensity was found, which is a first observation of intensity-dependent effects for such a peculiar beam type. The experimental results are presented and discussed in this paper.

MOPS018	Simulation and Measurement of Half Integer Resonance in Coasting Beams on the ISIS Ring	resonance, emittance, simulation, injection	637
	C.M. Warsop STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom D.J. Adams, B. Jones, B.G. Pine, H. V. Smith, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on an 800 MeV rapid cycling synchrotron (RCS), which provides 3·10¹³ protons per pulse at 50 Hz, corresponding to a beam power of 0.2 MW. In common with many lower energy, high intensity proton rings, a key loss mechanism on ISIS is half integer resonance under space charge. This paper summarises experimental and simulation work studying half integer resonance in a “2D” coasting beam in the ISIS ring: understanding this is an essential prerequisite for explaining the more complicated case of RCS operation. For coasting beam experiments, the ring is reconfigured to storage ring mode with RF off and main magnets powered on DC current only. A 70 MeV beam is injected, painted appropriately, and manipulated so as to approach resonance. Understanding how the resonant condition develops is central to explaining observations, so realistic simulations of resonance, including injection, ramping of intensity and tunes are being developed. Results from the ORBIT code are presented and compared with experimental and theoretical results. Finally, future plans are summarized.

MOPS019	High Intensity Longitudinal Dynamics Studies for Higher Energy Injection into the ISIS Synchrotron	injection, simulation, bunching, linac	640
	R.E. Williamson, D.J. Adams, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the world’s most productive pulsed neutron and muon source, at the Rutherford Appleton Laboratory in the UK. Operation is centred on a loss-limited 50 Hz proton synchrotron which accelerates 3·10¹³ protons per pulse from 70 MeV to 800 MeV, delivering a mean beam power of 0.2 MW. Present studies on ISIS upgrades are focussed on a new linac for higher energy injection into the existing ring, potentially increasing beam current through reduction in space charge and optimized injection. Studies assume injection of a chopped beam at 180 MeV and offer the possibility of beam powers in the 0.5 MW regime. A critical aspect of such an upgrade is the longitudinal dynamics, associated RF parameters, space charge levels and stringent requirements on beam loss. This paper outlines studies optimizing longitudinal parameters including key design requirements such as bunching factor and satisfying the Keil-Schnell-Boussard stability criterion throughout acceleration. Work developing and benchmarking the in-house longitudinal dynamics code used for these studies is also summarized.

MOPS023	An Analytical Lagrangian Model for Analyzing Temperature Effects in Intense Non-neutral Beams*	emittance, simulation, focusing, controls	646
	E.G. Souza, A. Endler, R. Pakter, F.B. Rizzato IF-UFRGS, Porto Alegre, Brazil
	High-intensity charged-particle beams are used in several areas of physics. We can mention as an illustration, high-energy colliders, particle accelerators and vacuum electron devices. In all cases quoted above, the beam lose particles in the acceleration process, between its production to its final destination. These ejected particles, generally, produce a surrounding structure around the beam core, called halo. This undesirable structure is seen in simulation as well as in actual linacs, and its formation has been one of the main sources of energy loss in the acceleration devices. For this reason, the need for an advance in understand the mechanism that produce the halo becomes necessary. In view of the whole problem, we contruct a 1D Lagrangian warm-fluid model for describe the behavior of inhomogeneous charged-particle beam in solenoidal focusing magnetic field. The equations of motion are derived for an adiabatic process with a state equation originated from the ideal gas law. In the end, the model is compared with self-consistent simulation and is used to explain emittance growth and jets of particle, even when the system is out of equilibrium.

MOPS024	Bunch Dynamics through Accelerator Column	TRIUMF, gun, electron, cathode	649
	R.A. Baartman TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	Funding: TRIUMF research is supported by the National Research Council of Canada. The differential equations for the bunched beam envelope through an axially symmetric DC accelerator are derived. In the case of no space charge, a particle's total energy is conserved, so the longitudinal evolution is simple: particles of same energy are a fixed time increment apart and this implies in first order that their separation is proportional to their speed. However, with space charge, the longitudinal force depends upon the bunch length, so we need equations that track this parameter. The full 6-dimensional and relativistically correct envelope equations are derived.

MOPS025	Studies of Emittance Measurement by Quadrupole Variation for the IFMIF-EVEDA High Space Charge Beam	emittance, quadrupole, simulation, beam-transport	652
	P.A.P. Nghiem, E. Counienc CEA/DSM/IRFU, France N. Chauvin CEA/IRFU, Gif-sur-Yvette, France C. Oliver CIEMAT, Madrid, Spain
	For the high-power (1 MW) beam of the IFMIF-EVEDA prototype accelerator, emittance measurements at nearly full power are only possible in a non-interceptive way. The method of quadrupole variation is explored here. Due to the high space charge regime, beam transport is strongly non-linear, and the classical matrix inversion is no more relevant. Inverse calculations using a multiparticle code is mandatory. In this paper, such emittance measurements are studied, aiming at checking its feasibility and evaluating its precision, taking into account the constraints of losses and quadrupole limitations.

MOPS027	Stability Charts for the IFMIF SRF-Linac	emittance, linac, resonance, SRF	658
	W. Simeoni, N. Chauvin CEA/IRFU, Gif-sur-Yvette, France A. Mosnier, P.A.P. Nghiem, D. Uriot CEA/DSM/IRFU, France
	Among the most recent projects, the IFMIF-EVEDA accelerators break the record of high intensity, leading to a multi-MW beam power at relatively low energy. The concern for such accelerated beams is the predominance of the self-field energy upon the beam energy. In these conditions, the space charge effect is at its maximum, which triggers different nonlinear mechanisms implying emittance growth, halo formation and sudden particle lost. In this proceeding we show the stability charts constructed for the IFMIF SRF-Linac, with which are identified the collective space charge resonances responsible of transverse-longitudinal emittance exchange and emittance growth.

MOPS029	Experiments with a Fast Chopper System for Intense Ion Beams	ion, electron, simulation, high-voltage	664
	H. Dinter, M. Droba, M. Lotz, O. Meusel, I. Müller, D. Noll, U. Ratzinger, K. Schulte, C. Wagner, C. Wiesner IAP, Frankfurt am Main, Germany
	Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.

MOPS034	Progress on Space Charge Compensation Study in Low Energy High Intense H⁺ Beam*	emittance, electron, injection, ion	676
	P.N. Lu, Z.Y. Guo, S.X. Peng, Z.X. Yuan, J. Zhao PKU/IHIP, Beijing, People's Republic of China H.T. Ren Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China
	This article lays emphasis on the relationship between the Space Charge Compensation (SCC) and the beam quality in different conditions. Ar and Kr are used to compensate a 35keV/90mA H⁺ beam with the gas pressure from 3.7×10^-4 Pa to 6×10^-3 Pa. Experiments are conducted in different compensation states with three approaches. With an energy spectrometer, we have got the energy spectra of Extra Compensation Gas Ions (ECGI). By a beam profile meter, the beam profiles are obtained when the injection of compensation gas is gradually rising. In the meantime, the beam emittance is measured under different compensation conditions. After measurements of the above data, the potential and the rest charge distributions in the beam are calculated by analyzing the ECGI energy spectra and beam profiles. All experiments performed aimed to seek out the best circumstance for SCC dominated low energy high intensity ion beams.together to calculate the potential distribution are calculated by analyzing the energy spectra and beam profiles. All experiments performed aimed to seeking for the best circumstances in SCC dominated low energy high intensity ion beams.

MOPS037	High Intensity Transient Beam Dynamic Study in Travelling Wave Electron Accelerators with Accounting of Beam Loading Effect	simulation, beam-loading, linac, electron	682
	S.M. Polozov, T.V. Bondarenko, E.S. Masunov, V.I. Rashchikov, A.V. Voronkov MEPhI, Moscow, Russia
	The beam loading effect is one of main problems limiting the beam current. The methods of beam dynamic simulation taking into account the beam loading effect were discussed previously. Simulation methods and the especial code version BEAMDULAD-BL was described in the paper. The beam loading effect was considered only for traveling wave linacs and for stationary beam only. Now it is important to study the beam dynamics of short current pulses, i.e. for transient process. We can consider only one beam bunch (or a packet of bunches) in a long external RF field pulse in stationary case. The beam radiation and wave fields can be calculated in the quasi-statically approximation. This approximation can not be used for transient mode. The methods of beam dynamics simulation will be discussed in this paper for transient mode. New code version BEAMDULAC-BLNS will be described. The simple test simulations will be carried out. A.V. Voronkov et al., "Beam Loading Effect of High Current Trawling Wave Accelerator Dynamic Study", Proc. of IPAC’10, Kyoto, Japan, TUPEA012, p. 1348 (2010).

MOPS043	Beam Performance in H⁻ Injector of LANSCE	emittance, simulation, beam-transport, ion-source	697
	Y.K. Batygin, C. Pillai, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	During beam development time in 2010 we performed a series of beam emittance and beam profile scans along 750-keV H⁻ beam transport and 800-MeV linac. The purpose of the measurements was to determine the effects of space charge, slow-wave intensity modulation or chopping, RF buncher fields, and vacuum conditions on beam performance. As previously reported, from our observation and analysis we concluded that the 750 keV H⁻ beam transport is space-charge uncompensated. This presentation will look at the relative importance of space-charge, chopping, and RF-buncher on the observed emittance growth for beam in the short and long pulse regime as well as the effects of beam line vacuum degradation on beam size and emittance at the end of the linac. Y. Batygin et al., “Space-charge effects in H⁻ Low-Energy Beam Transport of LANSCE,” to be published in Proc. of the 2011 Particle Accelerator Conference, March 28-April 1, 2011, New York, NY.

TUPC032	Beam Phase-Space Study for AREAL RF Photogun Linac	gun, emittance, electron, linac	1069
	B. Grigoryan, G.A. Amatuni, I.N. Margaryan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan CANDLE, Yerevan, Armenia
	In order to produce high brightness electron beams with sub-picosecond bunch duration, the creation of Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun is under consideration. For several experimental setup purposes the linac will operate in single and multibunch modes with final beam energy 5-20 MeV and the bunch charge 10 100 pC. The study of beam phase space evolution along the linac is performed to optimize the beam main characteristics: emittance, bunch length and energy spread. The dependence of longitudinal and transverse distribution of electrons in photocathode region on RF cavity performances is analyzed.

TUPC041	Self-consistent Time-dependent Quasi-3D Model of Multipactor in Dielectric-loaded Accelerating Structures	electron, vacuum, multipactoring, plasma	1090
	O.V. Sinitsyn, T.M. Antonsen, G.S. Nusinovich UMD, College Park, Maryland, USA
	Funding: This work is supported by the Office of High Energy Physics of the US Department of Energy. Multipactor (MP) manifests itself as a rapid growth of the number of secondary electrons emitted from a solid surface in the presence of the RF field under vacuum conditions. The secondary electrons appear as the result of surface impacts of energetic primary electrons accelerated by the RF field. MP occurs in various microwave and RF systems and usually severely degrades their performance. Therefore, theoretical and experimental studies of MP are of great interest to researchers working in related areas of physics and engineering. In this paper we study MP in dielectric-loaded accelerating (DLA) structures. We started our work with the development of a self-consistent time-dependent 2D model of MP in such structures. To benchmark that model, we compared its results with available experimental data. The comparison showed good agreement between theory and experiment for DLA structures of larger diameter, however for structures of smaller diameter a significant discrepancy was observed. Therefore, we decided to develop a new quasi-3D model of MP that would allow us to take into account the effects ignored in our 2D studies. Results of our 3D analysis are presented in this paper. O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., Phys. Plasmas, 16, 073102 (2009). ** O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., AIP Conf. Proc., 1299, 302 (2010).

TUPC055	Strongly Space Charge Dominated Beam Transport at 50 keV	solenoid, beam-transport, simulation, electron	1123
	D. Heiliger, W. Hillert, B. Neff ELSA, Bonn, Germany
	Funding: supported by DFG (SFB/TR16) A pulsed (100 nC in 1 us), low energetic beam of polarized electrons is routinely provided by an inverted source of polarized electrons at ELSA. The beam transport to the linear accelerator is strongly space charge dominated due to the beam energy of 50 keV. Thus, the actual beam current has an impact on the beam dynamics, and the optics of the transfer line to the linear accelerator must be optimized with respect to the chosen beam intensity. Numerical simulations of the beam transport demonstrate that an intensity upgrade from 100 mA to 200 mA is feasible. In order to successfully adjust the focussing strength of the magnets according to the final results of the simulation, dedicated beam diagnostics like wire scanners suitable for extreme-high vacuum applications are required.

TUPC064	Transverse Phase Space Tomography in TRIUMF Injection Beamline	emittance, TRIUMF, quadrupole, injection	1144
	Y.-N. Rao, R.A. Baartman TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	Funding: TRIUMF receives funding via a contribution agreement through the National Research Council of Canada. By tomography is meant the reconstruction of a 2-dimensional distribution from a number of 1-dimensional projections. In the case of transverse phase space, one records many profiles while varying a focusing device such as a quadrupole. Our aim was to investigate the two transverse phase space distributions in our 300keV H-minus beamline. We performed a series of measurements of beam profiles as a function of the voltage of an electrostatic quadrupole and used these along with the corresponding calculated transfer matrices in an iterative program based upon the Maximum Entropy algorithm, to find the phase space distributions. As well, we made measurements using an Allison-type emittance scanner to scan both planes. In this paper we present the details of these measurements, calculations, and we compare the two techniques.

TUPC098	Beam Profile Measurement using Flying Wire Monitors at the J-PARC Main Ring*	injection, simulation, proton, emittance	1239
	S. Igarashi, K. Ohmi, Y. Sato, M.J. Shirakata, M. Tejima, T. Toyama KEK, Ibaraki, Japan Y. Hashimoto, K. Satou J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	Transverse beam profiles have been measured using flying wire monitors at the main ring of the Japan Proton Accelerator Research Complex (J-PARC). The flying wire is a beam profile monitor using a thin carbon fiber as a target. The beam is scanned with the wire target at the maximum speed of 5 m/s. The secondary particles from the beam-wire scattering are detected using a scintillation counter as a function of the wire position. The measurement has revealed a characteristic temporal change of the beam profile during the injection period of 120 ms. A multiparticle tracking simulation program, SCTR, taking account of space charge effects has successfully reproduced the beam profiles.

TUPC109	Electron Bunch Slice Emittance Measurement with the Space Charge Effects*	solenoid, emittance, electron, simulation	1272
	C. Li, Y.-C. Du, W.-H. Huang, C.-X. Tang, L.X. Yan TUB, Beijing, People's Republic of China
	Funding: supported by the National Natural Science Foundation of China (Grant Nos. 10735050, 10805031, 10875070 and 10925523), and the National Basic Research Program of China (Grant No. 2007CB815102). Since slice transverse emittance of the electron beam is critical to a high-gain short-wavelength FEL, its characterization is very important. For space charge dominated electron beam, conventional emittance measurement techniques, such as solenoid scanning and quadruple scanning, without considering space charge forces lead to large errors of emittance evaluations. This essay introduces a modified solenoid-scan method of slice emittance measurement for space charge dominated beam, and simulations show that the new method brings the emittance evaluations much closer to actual values.

TUPC150	The Effect of Space-Charge on the Tomographic Measurement of Transverse Phase-Space in the EMMA Injection Line	quadrupole, injection, emittance, simulation	1380
	M.G. Ibison, M. Korostelev The University of Liverpool, Liverpool, United Kingdom K.M. Hock, D.J. Holder, B.D. Muratori, A. Wolski Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: STFC Phase-space tomography for particle beams depends upon detailed knowledge of the particle transport through specified sections of a beam line. In the simplest case, only the effects of magnets (such as quadrupoles) and drift spaces need to be taken into account; however, in certain parameter regimes (high charge density and low energy) space charge forces may play a significant role. The ALICE accelerator is the electron source for EMMA, a prototype ns-FFAG machine. Results are presented of investigations into these effects on phase-space tomography in the injection line between ALICE and EMMA. The application of suitable correction techniques* to the EMMA injection line tomography measurements in the presence of space-charge is also discussed. * D. Stratakis et al., Phys. Rev. ST Accel. Beams 9, 112801 (2006).

TUPO004	Generation of Attosecond Soft X-ray Pulses in a Longitudinal Space Charge Amplifier	undulator, electron, laser, radiation	1449
	M. Dohlus, E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	A longitudinal space charge amplifier (LSCA), operating in soft x-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond x-ray pulses. It is shown that a compact and cheap addition to the soft x-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long x-ray pulses with the peak power at 100 MW level and a contrast above 98%.

TUPO028	Emittance Compensation Scheme for the BERLinPro Injector	emittance, solenoid, linac, booster	1497
	A.V. Bondarenko, A.N. Matveenko HZB, Berlin, Germany
	Following funding approval late 2010, Helmholtz-Zentrum Berlin officially started Jan. 2011 the design and construction of the Berlin Energy Recovery Linac Project BERLinPro. The initial goal of this compact ERL is to develop the ERL accelerator physics and technology required to accelerate a high-current (100 mA) low emittance beam (1 mm•mrad normalized), as required for future ERL-based synchrotron light sources. Given the flexibility ERLs provides, a short bunch operation mode will also be investigated. The space charge is the main reason of emittance degradation in injector due to rather low injection energy (7 MeV). The implementation of emittance compensation scheme in the injector is necessary to achieve such low emittance. Since injector’s optics is axially non-symmetric, the 2D- emittance compensation scheme* is proposed to be used. Other sources of emittance growth are also discussed. * S.V. Miginsky, "Emittance compensation of elliptical beam", NIM A 603 (2009) 32.

TUPO033	Emittance Minimization by Courant-Snyder Parameter Scan in Merger Section at the Compact Energy Recovery Linear Accelerator.	emittance, betatron, SRF, dipole	1506
	J.G. Hwang Kyungpook National University, Daegu, Republic of Korea E.-S. Kim KNU, Deagu, Republic of Korea T. Miyajima KEK, Tsukuba, Japan
	The project of compact-Energy Recovery Linac(c-ERL) at Photon Factory in KEK is a test facility for the 5 GeV ERL, which is one of the candidates of next generation light source. It consists of injector system, merger section, main SRF section, return arc, long straight section and beam dump. The injector system produces beams with a low-energy of 5 MeV and low-emittance less than 1 mm-mrad. It causes the large emittance growth by space charge force in merger section, which consists of two rectangular type dipole magnets and one sector type magnet. Dispersion also causes the displacement of bunch sllice on horizontal plane. The displacement of bunch slice is laid on the kick angle induced by space charge force. Also, each slice has the orientation of the phase ellipse on horizontal phase space. Therefore, the emittance growth due to the displacement of bunch sllice induced by space charge force in the horizontal phase space can be minimized by matching the displacement to the orientation of the phase ellipse at the exit of merger. We present the results of the emittance minimization performed by mathcing of the angle of the phase ellipse by scan of CS (Courant-Snyder) parameter.

TUPS105	Beam Brightness Booster with Self-Stabilization of Electron-Proton Instability	ion, electron, brightness, proton	1789
	V.G. Dudnikov, C.M. Ankenbrandt Muons, Inc, Batavia, USA
	The brightness and intensity of a circulating proton beam now can be increased up to the space charge tune shift limit by means of charge exchange injection or by electron cooling but cannot be increased above this limit. Significantly higher brightness can be produced by means of charge exchange injection with space charge compensation. The brightness of the space charge compensated beam is limited at low level by an electron-proton (e-p) instability. Fortunately, the e-p instability can be self-stabilized at a high beam density. The “cesiation effect” significantly increases negative ion emission from gas discharges, and surface-plasma sources for intense high brightness negative ion beam production have been developed. These developments make it possible to produce stable “superintense” circulating beams with intensity and brightness far above the space charge limit. A beam brightness booster (BBB) for significant increases of accumulated beam brightness is discussed. Superintense beam production can be simplified by developing a nonlinear nearly-integrable focusing system with broad betatron tune spread and a broadband feedback system for e-p instability suppression. M. Reiser, “Theory and Design of Charged Particle Beam”, second edition, p. 565-570, Wiley-VCH, (2006).

WEPC003	Low-Beta Empirical Models used in Online Modeling and High Level Applications	cavity, solenoid, controls, simulation	2001
	Y.-C. Chao, G. Goh TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	Using empirically models for elements generated by simulations codes such as Astra in low-beta beamline to provide efficient and more accurate models for machine diagnostic and tuning is discussed. Experience of such application in the framework of XAL may also be presented.

WEPC101	Simulation of the Interaction of an Electron Beam with Ionized Residual Gas	ion, simulation, electron, emittance	2250
	G. Pöplau, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany A. Meseck HZB, Berlin, Germany
	Funding: Supported by BMBF under contract number 05K10HRC Light sources of the next generation such as ERLs require minimal beam losses as well as a stable beam position and emittance over the time. Instabilities caused by ion accumulation have to be avoided. In Rostock the tracking code MOEVE PIC Tracking has been developed for the simulation of space charge influenced beam dynamics, which is recently applied for simulations of the interaction beam - e-cloud. In this paper we apply MOEVE PIC Tracking for simulation of the interaction of the ionized residual gas with an electron bunch. We demonstrate numerical results with parameters planed for the ERL BERLinPro.

WEPC102	Recent Developments for Efficient 3D Space Charge Computations Based on Adaptive Multigrid Discretizations	simulation, brightness, injection, optics	2253
	G. Pöplau, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany M.J. de Loos TUE, Eindhoven, The Netherlands S.B. van der Geer Pulsar Physics, Eindhoven, The Netherlands
	Funding: Partly supported by BMBF under contract number 05K10HRC Efficient and accurate space-charge computations are essential for the design of high-brightness charged particle sources. Recently a new adaptive meshing strategy based on multigrid was implemented in GPT and the capabilities were demonstrated. This new meshing scheme uses the solution of an intermediate step in the multigrid algorithm itself to define optimal mesh line positions. In this paper we discuss further developments of this adaptive meshing strategy. We compare the new algorithm with the current meshing scheme of GPT, where the mesh line positions are based upon the projected charge density.

WEPC107	Development of a Steady State Simulation Code for Klystron Amplifiers	cavity, simulation, klystron, electromagnetic-fields	2265
	C. Marrelli CERN, Geneva, Switzerland M. Migliorati, A. Mostacci, L. Palumbo Rome University La Sapienza, Roma, Italy B. Spataro INFN/LNF, Frascati (Roma), Italy S.G. Tantawi SLAC, Menlo Park, California, USA
	The design of klystrons is based on the intensive utilization of simulation codes, which can evaluate the complete beam-cavities interaction in the case of large signals. In the present work, we present the development of a 2-D steady state simulation code that can self-consistently evaluate the effects of the electromagnetic field on the particles and of the particles back on the field. The algorithm is based on the iterative solution of the power balance equation in the RF structures and allows determining the amplitude and phase of the electromagnetic field starting from the cavity modes. Some applications of the code to a single cavity and a two cavity klystron are presented and compared with the results obtained from other codes. The effect of the space charge forces in the klystron drift tubes is also evaluated.

WEPS018	The Proposed CERN Proton-Synchrotron Upgrade Program	injection, emittance, cavity, electron	2520
	S.S. Gilardoni, S. Bart Pedersen, W. Bartmann, S. Bartolome, O.E. Berrig, C. Bertone, A. Blas, D. Bodart, J. Borburgh, R.J. Brown, A.C. Butterworth, M.C.L. Buzio, C. Carli, P. Chiggiato, H. Damerau, T. Dobers, R. Folch, R. Garoby, B. Goddard, M. Gourber-Pace, S. Hancock, M. Hourican, P. Le Roux, L.A. Lopez Hernandez, A. Masi, G. Metral, Y. Muttoni, E. Métral, M. Nonis, J. Pierlot, S. Pittet, C. Rossi, I. Ruehl, G. Rumolo, L. Sermeus, R.R. Steerenberg, M. Widorski CERN, Geneva, Switzerland
	In the framework of the High-Luminosity LHC project, the CERN Proton Synchrotron would require a major upgrade to match the future beam parameters requested as pre-injector of the collider. The different beam dynamics issues, from space-charge limitations to longitudinal instabilities are discussed, as well as the proposed technical solutions to overcome them, covering the increase of the injection energy to RF related improvements.

WEPS073	A Low Energy Cyclotron Injector for DAEdALUS Experiment	cyclotron, proton, extraction, cavity	2673
	L.A.C. Piazza, M.M. Maggiore INFN/LNL, Legnaro (PD), Italy L. Calabretta, D. Campo, D. Rifuggiato INFN/LNS, Catania, Italy A. Calanna CSFNSM, Catania, Italy
	Multi Megawatt accelerators are today requested for different use. In particular the experiment DAEdALUS, recently proposed by MIT scientist to search for CP violation in the neutrino sector, needs three accelerator with energy of about 800 MeV, average power of some MW and duty cycle of 20%. To reduce the cost of the accelerators a cyclotron complex consisting of an injector and of a booster ring cyclotron has been proposed. The main characteristics of the new kind of a separated sector cyclotron injector able to accelerate a H²⁺ molecule beam up to 50 MeV/n will be presented. Due to the low duty cycle, the peak current to be accelerated is 5 mA. The problem related to the injection of a H²⁺ beam, delivered by a compact ion source, and to the space charge effects will be discussed. The main parameters of the magnetic sectors, RF cavities, the isochronous magnetic field and the beam dynamics along the injection and extraction path and during the acceleration will be presented, too. J. Alonso et al., “A Novel Search for CP Violation in the Neutrino Sector: DAEdALUS”, June 2010. e-Print: arXiv:10⁰⁶.0260 ** L. Calabretta et al., ICCA, Lanzhou 2010; http://www. JACoW.org.

WEPS088	Space Charge Studies of a 1 GeV Isochronous Non-scaling FFAG Proton Driver	acceleration, lattice, simulation, emittance	2715
	S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	The production of very high power proton drivers in the 10 MW range is a considerable challenge to the accelerator community. Non-scaling FFAGs have gained interest in this field, as they may be able to provide smaller, cheaper accelerators than existing options. The recent development of an isochronous non-scaling FFAG is a promising advance, but must be shown to have stable beam dynamics in the presence of space charge. Simulations of this design including space charge are presented and the implications discussed.

WEPS101	Lattice Design of a RCS as Possible Alternative to the PS Booster Upgrade	lattice, quadrupole, injection, booster	2745
	M. Fitterer, M. Benedikt, H. Burkhardt, C. Carli, R. Garoby, B. Goddard, K. Hanke, H.O. Schönauer CERN, Geneva, Switzerland A.-S. Müller KIT, Karlsruhe, Germany
	In the framework of the LHC Injectors Upgrade (LIU) a new rapid cycling synchrotron as alternative to the PS Booster has been proposed. In this paper we present the lattice constraints and requirement as well as the current status of the RCS lattice design and beam dynamics studies.

WEPS104	Transverse Beam Dynamics for the ISIS Synchrotron with Higher Energy Injection	resonance, simulation, injection, synchrotron	2754
	B.G. Pine, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on an 800 MeV rapid cycling synchrotron, which provides 3·10¹³ protons per pulse at 50 Hz, corresponding to a beam power of 200 kW. Studies are underway to increase the energy of the ISIS linac from 70 to 180 MeV. This would reduce space charge in the synchrotron, and enable a larger current to be accumulated, possibly up to 0.5 MW. As part of the study, transverse beam dynamics have been re-examined on ISIS, building up models from incoherent space charge tune shift, through smooth focusing models with space charge to 2D alternating gradient lattice simulations. These later simulations, using the in-house space charge code Set, include harmonic perturbations to the focusing lattice, closed orbits and images. A clearer picture of the dynamics is emerging, where there may be important constraints on the highest intensities, including half integer resonance, image induced structure resonances and transverse instabilities.

WEPS106	Status of Injection Upgrade Studies for the ISIS Synchrotron	injection, simulation, linac, synchrotron	2760
	C.M. Warsop, D.J. Adams, D.J.S. Findlay, I.S.K. Gardner, S.J.S. Jago, B. Jones, R.J. Mathieson, S.J. Payne, B.G. Pine, A. Seville, H. V. Smith, J.W.G. Thomason, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom J. Pasternak Imperial College of Science and Technology, Department of Physics, London, United Kingdom C.R. Prior, G.H. Rees STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a high intensity proton accelerator, consisting of a 70 MeV linac and an 800 MeV rapid cycling synchrotron, which provides a beam power of 0.2 MW. Obsolescence issues are motivating plans to replace the ageing 70 MeV linac, and this paper summarises the status of studies looking at how a new, higher energy linac (~180 MeV) could be used to increase beam power in the existing synchrotron. Reduced space charge and optimized injection might allow beam powers in the 0.5 MW regime, thus providing a very cost effective upgrade. The key areas of study are: design of a practical injection straight and magnets; injection painting and dynamics; foil specifications; acceleration dynamics; transverse space charge; instabilities; RF beam loading; beam loss and activation; diagnostics and possible damping systems. Results from work on most of these topics suggest that beam powers of ~0.5 MW may well be possible, but a number of topics, particularly transverse stability, still look challenging. Conclusions so far are presented, as is progress on R&D on the main intensity limiting issues.

WEPZ021	Self-Consistent Dynamics of Electromagnetic Pulses and Wakefields in Laser-Plasma Interactions	laser, plasma, wakefield, simulation	2811
	A. Bonatto, R. Pakter, F.B. Rizzato IF-UFRGS, Porto Alegre, Brazil
	In the present work we study the stability of laser pulses propagating in a cold relativistic plasma, which can be of interest for particle acceleration schemes. After obtaining a Lagrangian density from the one-dimensional equations for the laser pulse envelope and the plasma electron density, we define a trial function and apply the variational approach in order to obtain an analytical model which allows us to calculate an effective potential for the pulse width. Using this procedure, we analyze the stability of narrow and large laser pulses and then compare its results with numerical solutions for the envelope and density equations.

THPC101	Fitting Formulas for Space-charge Dominated Free-electron Lasers	FEL, electron, undulator, simulation	3122
	G. Marcus, E. Hemsing, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	A simple power-fit formula for calculating the gain length of the fundamental Gaussian mode of a free-electron laser having strong space-charge effects in the 3D regime has been obtained. This tool allows for quick evaluation of the free-electron laser performance in the presence of diffraction, uncorrelated energy spread, and longitudinal space-charge effects. Here, we use it to evaluate the performance of high-gain FEL amplifiers considered candidates as high average power light sources. Results are compared with detailed numerical particle simulations using the free-electron laser code Genesis.

THPC135	Optimal Parameters of the Photocathode Gun Space Charge to Improve Beam Quality	laser, cathode, gun, electron	3203
	M.G. Fedurin, C. Swinson, V. Yakimenko BNL, Upton, Long Island, New York, USA
	Accelerator Test Facility at Brookhaven National Laboratory operates with 5 MeV photocathode gun and 70 MeV linac for different range of experiments with a few picoseconds and a few micrometers emittance electron bunch. Many conducted experiments require beam with good spatial resolution and short length as well. NdYaG laser pulse turns to the electron bunch in the gun with space charge affecting on the own bunch length and transverse profile. Optimal beam loading parameters of the space charge in the photocathode RF gun could be found and used to improve bunch length and emittance. Simple model and experimental results on the Accelerator Test Facility at Brookhaven national Laboratory will be described

THPS001	Experimental Studies of Beam Loss during Low Energy Operation with Electron Cooled Heavy Ions in the ESR	ion, emittance, bunching, resonance	3424
	P.A. Görgen, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany S. Appel, C. Dimopoulou, S.A. Litvinov, M. Steck GSI, Darmstadt, Germany
	At the ESR at GSI electron cooled heavy ion beams are decelerated to 4 MeV/u and extracted for the HITRAP experiment. We will report about cooling equilibrium measurements at 4 and 30 MeV/u for Ar¹⁸⁺ coasting beams. We compare the equilibrium beam parameters with results from beam dynamics simulations using the BETACOOL code and an analytic model of reduced complexity. The time slot in which HITRAP accepts beam is 2μs long. For optimum efficiency the beam has to be bunched to this length before extraction. The obtained bunch profiles are compared to longitudinal beam dynamics simulations. Our measurements show that at both energies bunching leads to severe beam loss. The estimated transverse space charge tune shifts during the rf bunching indicate that resonance crossing might be responsible for the observed the beam loss. The influence of the tune shift will be further evaluated through resonance measurements.

THPS034	Studies on Electron Cloud Dynamics for an Optimized Space Charge Lens Design	electron, plasma, ion, diagnostics	3493
	K. Schulte, M. Droba, B. Glaeser, S. Klaproth, O. Meusel, U. Ratzinger IAP, Frankfurt am Main, Germany
	Funding: Work supported by HIC for FAIR. Space charge lenses using a stable electron cloud for focusing low energy heavy ion beams are an alternative concept to conventional ion optics. Due to external fields electrons are confined inside the lens’ volume. In case of a homogeneously distributed electron cloud the linear electric space charge field enables beam focusing free of aberration. Since the mapping quality of the lens is related to the confinement, non-destructive diagnostics has been developed to determine the plasma parameters and to characterize the collective behavior of the confined nonneutral plasma. Moreover, a scaled up space charge lens was constructed for a detailed investigation of the nonneutral plasma properties as well as beam interactions with a stable confined electron cloud. Experimental results will be presented in comparison with numerical simulations.

THPS052	Studies on Transverse Painting for H⁻ Injection into the PSB	injection, emittance, linac, kicker	3544
	C. Bracco, C. Carli, T. Fowler, B. Goddard, G. Gräwer, J.-B. Lallement, M. Martini, M. Scholz, W.J.M. Weterings CERN, Geneva, Switzerland
	Linac4 will inject 160 MeV H− ions in to the CERN PS Booster (PSB). This will allow to reduce space charge effects and increase beam intensity but will require a substantial upgrade of the injection region, with the implementation of a charge-exchange multi-turn injection scheme. The PSB has to provide beam to several users with different requirements in terms of beam intensity and emittance. Four kicker magnets (KSW), which are already installed in the PSB lattice, will be used to accomplish painting in the horizontal phase space to match the injected beams to the required emittances. Double linear functions, with varying slopes for each user, have been defined for the KSW generators waveforms according to detailed beam dynamic studies for all target intensities and emittances. Effect of space charge, injection offsets, dispersion and betatron mismatch have been taken into account. Preliminary studies have been carried out to evaluate how to obtain the required vertical emittance and the option of a transverse painting, also in the vertical plane, is explored.

THPS058	Third Integer Resonance Slow Extraction Using RFKO at High Space Charge.	extraction, resonance, dipole, betatron	3559
	V.P. Nagaslaev, J.F. Amundson, J.A. Johnstone, C.S. Park, S.J. Werkema Fermilab, Batavia, USA
	A proposal to search for direct mu->e conversion at Fermilab requires slow, resonant extraction of an intense proton beam. Large space charge forces will present challenges, partly due to the substantial betatron tune spread. The main challenges will be maintaining a uniform spill shape and moderate losses at the septum. We propose to use "radio frequency knockout" (RFKO) for fine tuning the extraction. Strategies for the RFKO method will be discussed here in the context of the mu->e experiment. Feasibility of this method has been demonstrated using simulations.

Paper

Title

Other Keywords

Page

MOODB01

Dynamics of the IFMIF Very High-intensity Beam

rfq, emittance, linac, cryomodule

53

P.A.P. Nghiem, R.D. Duperrier, A. Mosnier, D. Uriot
CEA/DSM/IRFU, France
N. Chauvin, O. Delferrière, W. Simeoni
CEA/IRFU, Gif-sur-Yvette, France
M. Comunian
INFN/LNL, Legnaro (PD), Italy
C. Oliver
CIEMAT, Madrid, Spain

For the purpose of material studies for future nuclear fusion reactors, the IFMIF deuteron beams present a simultaneous combination of unprecedentedly high intensity (2x125 mA CW), power (2x5 MW) and space charge. Special considerations and new concepts have been developed in order to overcome these challenges. The global strategy for beam dynamics design in the 40 MeV IFMIF accelerators is presented, stressing on the control of micro-losses, and the possibility of on-line fine tuning. The obtained results are then analysed in terms of beam halo and emittance growth.

Slides MOODB01 [3.807 MB]

MOPC132

Influences of the Inner-conductor on Microwave Characteristics in an L-band Relativistic Backward-wave Oscillator*

resonance, simulation, plasma, coupling

388

X.J. Ge, L. Liu, B.L. Qian, J. Zhang, H.H. Zhong
National University of Defense Technology, Changsha, Kaifu District, People's Republic of China

Funding: College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, People’s Republic of China. *gexingjun230230@yahoo.com.cn
The influences of the inner-conductor on microwave characteristics in an L-band relativistic backward-wave oscillator (RBWO) are investigated theoretically and experimentally. The numerical results show that the resonance frequency decreases obviously with the increase in the inner-conductor radius. To verify the above conclusions, an L-band coaxial RBWO is investigated in detail with particle-in-cell (PIC) code. It is shown that the frequency is lowered from 1.63 GHz to 1.51 GHz when the inner-conductor radius increases from 0.5 cm to 2.5 cm. And the efficiency varies in the range of 35.4-27.7%. Furthermore, experiments are carried out at the Torch-01 accelerator. When the diode voltage is 887.6 kV and the current is 7.65 kA, the radiated microwave with frequency of 1.61 GHz, power of 2.13 GW and efficiency of 31.3% is generated. It is found that the frequency decreases from 1.64 GHz to 1.58 GHz when the inner-conductor radius increases from 0.5 cm to 1.5 cm. And the efficiency varies in the range of 31.3-29.8%.

MOPS002

Mitigation of Space Charge and Nonlinear Resonance Induced Beam Loss in SIS100

beam-losses, resonance, acceleration, simulation

589

G. Franchetti
GSI, Darmstadt, Germany

The control of beam loss in SIS100 is essential for avoiding vacuum instability and guarantee the delivery of the foreseen beam intensity. On the other hand simulations show that the simultaneous presence of space charge and lattice resonances creates during 1 second cycle a progressive beam loss exceeding the limit of 5%. Until now the mechanism of periodic resonance crossing were suspected to be, in conjunction with pure dynamic aperture effects, at the base of the beam loss. In this proceeding we present the state of the art in the beam loss prediction and we prove that the periodic resonance crossing is the deteriorating mechanism, and show that the compensation of a relevant resonance intercepting the space charge tune spread sensibly mitigate the beam loss. A short discussion on beam loss during acceleration is addressed as well.

MOPS004

Mitigation of Beam Instability due to Space Charge Effects at 3 GeV RCS in J-PARC

impedance, kicker, bunching, injection

595

Y. Shobuda, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y.H. Chin
KEK, Ibaraki, Japan
F. Tamura
KEK/JAEA, Ibaraki-Ken, Japan

In order to accomplish high intensity proton beams, it is important to identify the impedance source in accelerators. At 3 GeV rapid cycling synchrotron (RCS) in Japan Proton Research Complex (J-PARC), the kicker impedance is the most dominant among such impedance sources. Beam instability can be observed by correcting chromaticity during the acceleration. Growth rate due to the beam instability can be reduced by making peak current larger (bunching factor smaller). In other words, it is experimentally found that space charge effects mitigate the beam instability.

MOPS013

Transverse Low Frequency Broad-band Impedance Measurements in the CERN PS

impedance, proton, extraction, injection

622

S. Aumon
EPFL, Lausanne, Switzerland
P. Freyermuth, S.S. Gilardoni, O. Hans, E. Métral, G. Rumolo
CERN, Geneva, Switzerland

The base-line scenario for the High-Luminosity LHC upgrade foresees an intensity increase delivered by the injectors. With its 53 years, the CERN PS would have to operate beyond the limit of its performances to match the future requirements. Beam instabilities driven by transverse impedance are an important issue for the operation of high intensity beams as for the high-brightness LHC beams. Measurements of transverse tune dependence with beam intensity were performed at injection kinetic energy 1.4~GeV and at LHC beam extraction momentum 26~GeV/c. This allows deducing the low frequency inductive broad-band impedance of the machine. Then an estimation of the real part of the impedance is made by the rise time measurement of a fast transverse instability believed to be a TMCI type. Those are the first step towards a global machine impedance characterization in order to push forward the performances of the accelerator.

MOPS014

Tune and Space Charge Studies for High-brightness and High-intensity Beams at CERN PS

resonance, emittance, injection, beam-losses

625

S.S. Gilardoni, S. Aumon, J. Brenas, P. Freyermuth, A. Huschauer, R. Maillet, E. Matli, R.R. Steerenberg, B. Vandorpe
CERN, Geneva, Switzerland
E. Benedetto
National Technical University of Athens, Zografou, Greece

The current 1.4 GeV CERN PS injection energy limits the maximum intensity required by the future High-Luminosity LHC. The bare-machine large chromaticity combined with the non-linear space charge forces make high-brightness and high-intensity beams crossing betatron resonances along the injection flat bottom, inducing transverse emittance blow-up and beam losses. A scan of the working point plane {Qx,Qy} was done in order to identify beam destructive resonances, in the framework of a possible 2 GeV injection energy upgrade which would reduce the space charge effect on the tune. Experiments were carried out in order to review the maximum space charge tune shift for which no transverse emittance blow-up is observed. The results of measurements and simulations will be presented in this paper.

MOPS016

First Observations of Intensity-dependent Effects for Transversally Split Beams

resonance, extraction, booster, coupling

631

S.S. Gilardoni, M. Giovannozzi
CERN, Geneva, Switzerland

During the commissioning of the CERN PS Multi-Turn Extraction (MTE) tests with different beam intensities were performed. The beam current before transverse splitting was varied and the properties of the five beamlets obtained by crossing the fourth-order horizontal resonance were studied. A clear dependence of the beamlets’ parameters on the total intensity was found, which is a first observation of intensity-dependent effects for such a peculiar beam type. The experimental results are presented and discussed in this paper.

MOPS018

Simulation and Measurement of Half Integer Resonance in Coasting Beams on the ISIS Ring

resonance, emittance, simulation, injection

637

C.M. Warsop
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
D.J. Adams, B. Jones, B.G. Pine, H. V. Smith, R.E. Williamson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on an 800 MeV rapid cycling synchrotron (RCS), which provides 3·10¹³ protons per pulse at 50 Hz, corresponding to a beam power of 0.2 MW. In common with many lower energy, high intensity proton rings, a key loss mechanism on ISIS is half integer resonance under space charge. This paper summarises experimental and simulation work studying half integer resonance in a “2D” coasting beam in the ISIS ring: understanding this is an essential prerequisite for explaining the more complicated case of RCS operation. For coasting beam experiments, the ring is reconfigured to storage ring mode with RF off and main magnets powered on DC current only. A 70 MeV beam is injected, painted appropriately, and manipulated so as to approach resonance. Understanding how the resonant condition develops is central to explaining observations, so realistic simulations of resonance, including injection, ramping of intensity and tunes are being developed. Results from the ORBIT code are presented and compared with experimental and theoretical results. Finally, future plans are summarized.

MOPS019

High Intensity Longitudinal Dynamics Studies for Higher Energy Injection into the ISIS Synchrotron

injection, simulation, bunching, linac

640

R.E. Williamson, D.J. Adams, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the world’s most productive pulsed neutron and muon source, at the Rutherford Appleton Laboratory in the UK. Operation is centred on a loss-limited 50 Hz proton synchrotron which accelerates 3·10¹³ protons per pulse from 70 MeV to 800 MeV, delivering a mean beam power of 0.2 MW. Present studies on ISIS upgrades are focussed on a new linac for higher energy injection into the existing ring, potentially increasing beam current through reduction in space charge and optimized injection. Studies assume injection of a chopped beam at 180 MeV and offer the possibility of beam powers in the 0.5 MW regime. A critical aspect of such an upgrade is the longitudinal dynamics, associated RF parameters, space charge levels and stringent requirements on beam loss. This paper outlines studies optimizing longitudinal parameters including key design requirements such as bunching factor and satisfying the Keil-Schnell-Boussard stability criterion throughout acceleration. Work developing and benchmarking the in-house longitudinal dynamics code used for these studies is also summarized.

MOPS023

An Analytical Lagrangian Model for Analyzing Temperature Effects in Intense Non-neutral Beams*

emittance, simulation, focusing, controls

646

E.G. Souza, A. Endler, R. Pakter, F.B. Rizzato
IF-UFRGS, Porto Alegre, Brazil

High-intensity charged-particle beams are used in several areas of physics. We can mention as an illustration, high-energy colliders, particle accelerators and vacuum electron devices. In all cases quoted above, the beam lose particles in the acceleration process, between its production to its final destination. These ejected particles, generally, produce a surrounding structure around the beam core, called halo. This undesirable structure is seen in simulation as well as in actual linacs, and its formation has been one of the main sources of energy loss in the acceleration devices. For this reason, the need for an advance in understand the mechanism that produce the halo becomes necessary. In view of the whole problem, we contruct a 1D Lagrangian warm-fluid model for describe the behavior of inhomogeneous charged-particle beam in solenoidal focusing magnetic field. The equations of motion are derived for an adiabatic process with a state equation originated from the ideal gas law. In the end, the model is compared with self-consistent simulation and is used to explain emittance growth and jets of particle, even when the system is out of equilibrium.

MOPS024

Bunch Dynamics through Accelerator Column

TRIUMF, gun, electron, cathode

649

R.A. Baartman
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Funding: TRIUMF research is supported by the National Research Council of Canada.
The differential equations for the bunched beam envelope through an axially symmetric DC accelerator are derived. In the case of no space charge, a particle's total energy is conserved, so the longitudinal evolution is simple: particles of same energy are a fixed time increment apart and this implies in first order that their separation is proportional to their speed. However, with space charge, the longitudinal force depends upon the bunch length, so we need equations that track this parameter. The full 6-dimensional and relativistically correct envelope equations are derived.

MOPS025

Studies of Emittance Measurement by Quadrupole Variation for the IFMIF-EVEDA High Space Charge Beam

emittance, quadrupole, simulation, beam-transport

652

P.A.P. Nghiem, E. Counienc
CEA/DSM/IRFU, France
N. Chauvin
CEA/IRFU, Gif-sur-Yvette, France
C. Oliver
CIEMAT, Madrid, Spain

For the high-power (1 MW) beam of the IFMIF-EVEDA prototype accelerator, emittance measurements at nearly full power are only possible in a non-interceptive way. The method of quadrupole variation is explored here. Due to the high space charge regime, beam transport is strongly non-linear, and the classical matrix inversion is no more relevant. Inverse calculations using a multiparticle code is mandatory. In this paper, such emittance measurements are studied, aiming at checking its feasibility and evaluating its precision, taking into account the constraints of losses and quadrupole limitations.

MOPS027

Stability Charts for the IFMIF SRF-Linac

emittance, linac, resonance, SRF

658

W. Simeoni, N. Chauvin
CEA/IRFU, Gif-sur-Yvette, France
A. Mosnier, P.A.P. Nghiem, D. Uriot
CEA/DSM/IRFU, France

Among the most recent projects, the IFMIF-EVEDA accelerators break the record of high intensity, leading to a multi-MW beam power at relatively low energy. The concern for such accelerated beams is the predominance of the self-field energy upon the beam energy. In these conditions, the space charge effect is at its maximum, which triggers different nonlinear mechanisms implying emittance growth, halo formation and sudden particle lost. In this proceeding we show the stability charts constructed for the IFMIF SRF-Linac, with which are identified the collective space charge resonances responsible of transverse-longitudinal emittance exchange and emittance growth.

MOPS029

Experiments with a Fast Chopper System for Intense Ion Beams

ion, electron, simulation, high-voltage

664

H. Dinter, M. Droba, M. Lotz, O. Meusel, I. Müller, D. Noll, U. Ratzinger, K. Schulte, C. Wagner, C. Wiesner
IAP, Frankfurt am Main, Germany

Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.

MOPS034

Progress on Space Charge Compensation Study in Low Energy High Intense H⁺ Beam*

emittance, electron, injection, ion

676

P.N. Lu, Z.Y. Guo, S.X. Peng, Z.X. Yuan, J. Zhao
PKU/IHIP, Beijing, People's Republic of China
H.T. Ren
Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China

This article lays emphasis on the relationship between the Space Charge Compensation (SCC) and the beam quality in different conditions. Ar and Kr are used to compensate a 35keV/90mA H⁺ beam with the gas pressure from 3.7×10^-4 Pa to 6×10^-3 Pa. Experiments are conducted in different compensation states with three approaches. With an energy spectrometer, we have got the energy spectra of Extra Compensation Gas Ions (ECGI). By a beam profile meter, the beam profiles are obtained when the injection of compensation gas is gradually rising. In the meantime, the beam emittance is measured under different compensation conditions. After measurements of the above data, the potential and the rest charge distributions in the beam are calculated by analyzing the ECGI energy spectra and beam profiles. All experiments performed aimed to seek out the best circumstance for SCC dominated low energy high intensity ion beams.together to calculate the potential distribution are calculated by analyzing the energy spectra and beam profiles. All experiments performed aimed to seeking for the best circumstances in SCC dominated low energy high intensity ion beams.

MOPS037

High Intensity Transient Beam Dynamic Study in Travelling Wave Electron Accelerators with Accounting of Beam Loading Effect

simulation, beam-loading, linac, electron

682

S.M. Polozov, T.V. Bondarenko, E.S. Masunov, V.I. Rashchikov, A.V. Voronkov
MEPhI, Moscow, Russia

The beam loading effect is one of main problems limiting the beam current. The methods of beam dynamic simulation taking into account the beam loading effect were discussed previously. Simulation methods and the especial code version BEAMDULAD-BL was described in the paper*. The beam loading effect was considered only for traveling wave linacs and for stationary beam only. Now it is important to study the beam dynamics of short current pulses, i.e. for transient process. We can consider only one beam bunch (or a packet of bunches) in a long external RF field pulse in stationary case. The beam radiation and wave fields can be calculated in the quasi-statically approximation. This approximation can not be used for transient mode. The methods of beam dynamics simulation will be discussed in this paper for transient mode. New code version BEAMDULAC-BLNS will be described. The simple test simulations will be carried out.
* A.V. Voronkov et al., "Beam Loading Effect of High Current Trawling Wave Accelerator Dynamic Study", Proc. of IPAC’10, Kyoto, Japan, TUPEA012, p. 1348 (2010).

MOPS043

Beam Performance in H⁻ Injector of LANSCE

emittance, simulation, beam-transport, ion-source

697

Y.K. Batygin, C. Pillai, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

During beam development time in 2010 we performed a series of beam emittance and beam profile scans along 750-keV H⁻ beam transport and 800-MeV linac. The purpose of the measurements was to determine the effects of space charge, slow-wave intensity modulation or chopping, RF buncher fields, and vacuum conditions on beam performance. As previously reported*, from our observation and analysis we concluded that the 750 keV H⁻ beam transport is space-charge uncompensated. This presentation will look at the relative importance of space-charge, chopping, and RF-buncher on the observed emittance growth for beam in the short and long pulse regime as well as the effects of beam line vacuum degradation on beam size and emittance at the end of the linac.
* Y. Batygin et al., “Space-charge effects in H⁻ Low-Energy Beam Transport of LANSCE,” to be published in Proc. of the 2011 Particle Accelerator Conference, March 28-April 1, 2011, New York, NY.

TUPC032

Beam Phase-Space Study for AREAL RF Photogun Linac

gun, emittance, electron, linac

1069

B. Grigoryan, G.A. Amatuni, I.N. Margaryan, A.V. Tsakanian, V.M. Tsakanov, A. Vardanyan
CANDLE, Yerevan, Armenia

In order to produce high brightness electron beams with sub-picosecond bunch duration, the creation of Advanced Research Electron Accelerator Laboratory (AREAL) at CANDLE based on photocathode RF gun is under consideration. For several experimental setup purposes the linac will operate in single and multibunch modes with final beam energy 5-20 MeV and the bunch charge 10 100 pC. The study of beam phase space evolution along the linac is performed to optimize the beam main characteristics: emittance, bunch length and energy spread. The dependence of longitudinal and transverse distribution of electrons in photocathode region on RF cavity performances is analyzed.

TUPC041

Self-consistent Time-dependent Quasi-3D Model of Multipactor in Dielectric-loaded Accelerating Structures

electron, vacuum, multipactoring, plasma

1090

O.V. Sinitsyn, T.M. Antonsen, G.S. Nusinovich
UMD, College Park, Maryland, USA

Funding: This work is supported by the Office of High Energy Physics of the US Department of Energy.
Multipactor (MP) manifests itself as a rapid growth of the number of secondary electrons emitted from a solid surface in the presence of the RF field under vacuum conditions. The secondary electrons appear as the result of surface impacts of energetic primary electrons accelerated by the RF field. MP occurs in various microwave and RF systems and usually severely degrades their performance. Therefore, theoretical and experimental studies of MP are of great interest to researchers working in related areas of physics and engineering. In this paper we study MP in dielectric-loaded accelerating (DLA) structures. We started our work with the development of a self-consistent time-dependent 2D model of MP in such structures*. To benchmark that model, we compared its results with available experimental data**. The comparison showed good agreement between theory and experiment for DLA structures of larger diameter, however for structures of smaller diameter a significant discrepancy was observed. Therefore, we decided to develop a new quasi-3D model of MP that would allow us to take into account the effects ignored in our 2D studies. Results of our 3D analysis are presented in this paper.
* O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., Phys. Plasmas, 16, 073102 (2009).
** O. V. Sinitsyn, G. S. Nusinovich and T. M. Antonsen, Jr., AIP Conf. Proc., 1299, 302 (2010).

TUPC055

Strongly Space Charge Dominated Beam Transport at 50 keV

solenoid, beam-transport, simulation, electron

1123

D. Heiliger, W. Hillert, B. Neff
ELSA, Bonn, Germany

Funding: supported by DFG (SFB/TR16)
A pulsed (100 nC in 1 us), low energetic beam of polarized electrons is routinely provided by an inverted source of polarized electrons at ELSA. The beam transport to the linear accelerator is strongly space charge dominated due to the beam energy of 50 keV. Thus, the actual beam current has an impact on the beam dynamics, and the optics of the transfer line to the linear accelerator must be optimized with respect to the chosen beam intensity. Numerical simulations of the beam transport demonstrate that an intensity upgrade from 100 mA to 200 mA is feasible. In order to successfully adjust the focussing strength of the magnets according to the final results of the simulation, dedicated beam diagnostics like wire scanners suitable for extreme-high vacuum applications are required.

TUPC064

Transverse Phase Space Tomography in TRIUMF Injection Beamline

emittance, TRIUMF, quadrupole, injection

1144

Y.-N. Rao, R.A. Baartman
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Funding: TRIUMF receives funding via a contribution agreement through the National Research Council of Canada.
By tomography is meant the reconstruction of a 2-dimensional distribution from a number of 1-dimensional projections. In the case of transverse phase space, one records many profiles while varying a focusing device such as a quadrupole. Our aim was to investigate the two transverse phase space distributions in our 300keV H-minus beamline. We performed a series of measurements of beam profiles as a function of the voltage of an electrostatic quadrupole and used these along with the corresponding calculated transfer matrices in an iterative program based upon the Maximum Entropy algorithm, to find the phase space distributions. As well, we made measurements using an Allison-type emittance scanner to scan both planes. In this paper we present the details of these measurements, calculations, and we compare the two techniques.

TUPC098

Beam Profile Measurement using Flying Wire Monitors at the J-PARC Main Ring*

injection, simulation, proton, emittance

1239

S. Igarashi, K. Ohmi, Y. Sato, M.J. Shirakata, M. Tejima, T. Toyama
KEK, Ibaraki, Japan
Y. Hashimoto, K. Satou
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

Transverse beam profiles have been measured using flying wire monitors at the main ring of the Japan Proton Accelerator Research Complex (J-PARC). The flying wire is a beam profile monitor using a thin carbon fiber as a target. The beam is scanned with the wire target at the maximum speed of 5 m/s. The secondary particles from the beam-wire scattering are detected using a scintillation counter as a function of the wire position. The measurement has revealed a characteristic temporal change of the beam profile during the injection period of 120 ms. A multiparticle tracking simulation program, SCTR, taking account of space charge effects has successfully reproduced the beam profiles.

TUPC109

Electron Bunch Slice Emittance Measurement with the Space Charge Effects*

solenoid, emittance, electron, simulation

1272

C. Li, Y.-C. Du, W.-H. Huang, C.-X. Tang, L.X. Yan
TUB, Beijing, People's Republic of China

Funding: supported by the National Natural Science Foundation of China (Grant Nos. 10735050, 10805031, 10875070 and 10925523), and the National Basic Research Program of China (Grant No. 2007CB815102).
Since slice transverse emittance of the electron beam is critical to a high-gain short-wavelength FEL, its characterization is very important. For space charge dominated electron beam, conventional emittance measurement techniques, such as solenoid scanning and quadruple scanning, without considering space charge forces lead to large errors of emittance evaluations. This essay introduces a modified solenoid-scan method of slice emittance measurement for space charge dominated beam, and simulations show that the new method brings the emittance evaluations much closer to actual values.

TUPC150

The Effect of Space-Charge on the Tomographic Measurement of Transverse Phase-Space in the EMMA Injection Line

quadrupole, injection, emittance, simulation

1380

M.G. Ibison, M. Korostelev
The University of Liverpool, Liverpool, United Kingdom
K.M. Hock, D.J. Holder, B.D. Muratori, A. Wolski
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: STFC
Phase-space tomography for particle beams depends upon detailed knowledge of the particle transport through specified sections of a beam line. In the simplest case, only the effects of magnets (such as quadrupoles) and drift spaces need to be taken into account; however, in certain parameter regimes (high charge density and low energy) space charge forces may play a significant role. The ALICE accelerator is the electron source for EMMA, a prototype ns-FFAG machine. Results are presented of investigations into these effects on phase-space tomography in the injection line between ALICE and EMMA. The application of suitable correction techniques* to the EMMA injection line tomography measurements in the presence of space-charge is also discussed.
* D. Stratakis et al., Phys. Rev. ST Accel. Beams 9, 112801 (2006).

TUPO004

Generation of Attosecond Soft X-ray Pulses in a Longitudinal Space Charge Amplifier

undulator, electron, laser, radiation

1449

M. Dohlus, E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

A longitudinal space charge amplifier (LSCA), operating in soft x-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond x-ray pulses. It is shown that a compact and cheap addition to the soft x-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long x-ray pulses with the peak power at 100 MW level and a contrast above 98%.

TUPO028

Emittance Compensation Scheme for the BERLinPro Injector

emittance, solenoid, linac, booster

1497

A.V. Bondarenko, A.N. Matveenko
HZB, Berlin, Germany

Following funding approval late 2010, Helmholtz-Zentrum Berlin officially started Jan. 2011 the design and construction of the Berlin Energy Recovery Linac Project BERLinPro. The initial goal of this compact ERL is to develop the ERL accelerator physics and technology required to accelerate a high-current (100 mA) low emittance beam (1 mm•mrad normalized), as required for future ERL-based synchrotron light sources. Given the flexibility ERLs provides, a short bunch operation mode will also be investigated. The space charge is the main reason of emittance degradation in injector due to rather low injection energy (7 MeV). The implementation of emittance compensation scheme in the injector is necessary to achieve such low emittance. Since injector’s optics is axially non-symmetric, the 2D- emittance compensation scheme* is proposed to be used. Other sources of emittance growth are also discussed.
* S.V. Miginsky, "Emittance compensation of elliptical beam", NIM A 603 (2009) 32.

TUPO033

Emittance Minimization by Courant-Snyder Parameter Scan in Merger Section at the Compact Energy Recovery Linear Accelerator.

emittance, betatron, SRF, dipole

1506

J.G. Hwang
Kyungpook National University, Daegu, Republic of Korea
E.-S. Kim
KNU, Deagu, Republic of Korea
T. Miyajima
KEK, Tsukuba, Japan

The project of compact-Energy Recovery Linac(c-ERL) at Photon Factory in KEK is a test facility for the 5 GeV ERL, which is one of the candidates of next generation light source. It consists of injector system, merger section, main SRF section, return arc, long straight section and beam dump. The injector system produces beams with a low-energy of 5 MeV and low-emittance less than 1 mm-mrad. It causes the large emittance growth by space charge force in merger section, which consists of two rectangular type dipole magnets and one sector type magnet. Dispersion also causes the displacement of bunch sllice on horizontal plane. The displacement of bunch slice is laid on the kick angle induced by space charge force. Also, each slice has the orientation of the phase ellipse on horizontal phase space. Therefore, the emittance growth due to the displacement of bunch sllice induced by space charge force in the horizontal phase space can be minimized by matching the displacement to the orientation of the phase ellipse at the exit of merger. We present the results of the emittance minimization performed by mathcing of the angle of the phase ellipse by scan of CS (Courant-Snyder) parameter.

TUPS105

Beam Brightness Booster with Self-Stabilization of Electron-Proton Instability

ion, electron, brightness, proton

1789

V.G. Dudnikov, C.M. Ankenbrandt
Muons, Inc, Batavia, USA

The brightness and intensity of a circulating proton beam now can be increased up to the space charge tune shift limit by means of charge exchange injection or by electron cooling but cannot be increased above this limit. Significantly higher brightness can be produced by means of charge exchange injection with space charge compensation*. The brightness of the space charge compensated beam is limited at low level by an electron-proton (e-p) instability. Fortunately, the e-p instability can be self-stabilized at a high beam density. The “cesiation effect” significantly increases negative ion emission from gas discharges, and surface-plasma sources for intense high brightness negative ion beam production have been developed. These developments make it possible to produce stable “superintense” circulating beams with intensity and brightness far above the space charge limit. A beam brightness booster (BBB) for significant increases of accumulated beam brightness is discussed. Superintense beam production can be simplified by developing a nonlinear nearly-integrable focusing system with broad betatron tune spread and a broadband feedback system for e-p instability suppression.
* M. Reiser, “Theory and Design of Charged Particle Beam”, second edition, p. 565-570, Wiley-VCH, (2006).

WEPC003

Low-Beta Empirical Models used in Online Modeling and High Level Applications

cavity, solenoid, controls, simulation

2001

Y.-C. Chao, G. Goh
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

Using empirically models for elements generated by simulations codes such as Astra in low-beta beamline to provide efficient and more accurate models for machine diagnostic and tuning is discussed. Experience of such application in the framework of XAL may also be presented.

WEPC101

Simulation of the Interaction of an Electron Beam with Ionized Residual Gas

ion, simulation, electron, emittance

2250

G. Pöplau, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
A. Meseck
HZB, Berlin, Germany

Funding: Supported by BMBF under contract number 05K10HRC
Light sources of the next generation such as ERLs require minimal beam losses as well as a stable beam position and emittance over the time. Instabilities caused by ion accumulation have to be avoided. In Rostock the tracking code MOEVE PIC Tracking has been developed for the simulation of space charge influenced beam dynamics, which is recently applied for simulations of the interaction beam - e-cloud. In this paper we apply MOEVE PIC Tracking for simulation of the interaction of the ionized residual gas with an electron bunch. We demonstrate numerical results with parameters planed for the ERL BERLinPro.

WEPC102

Recent Developments for Efficient 3D Space Charge Computations Based on Adaptive Multigrid Discretizations

simulation, brightness, injection, optics

2253

G. Pöplau, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
M.J. de Loos
TUE, Eindhoven, The Netherlands
S.B. van der Geer
Pulsar Physics, Eindhoven, The Netherlands

Funding: Partly supported by BMBF under contract number 05K10HRC
Efficient and accurate space-charge computations are essential for the design of high-brightness charged particle sources. Recently a new adaptive meshing strategy based on multigrid was implemented in GPT and the capabilities were demonstrated. This new meshing scheme uses the solution of an intermediate step in the multigrid algorithm itself to define optimal mesh line positions. In this paper we discuss further developments of this adaptive meshing strategy. We compare the new algorithm with the current meshing scheme of GPT, where the mesh line positions are based upon the projected charge density.

WEPC107

Development of a Steady State Simulation Code for Klystron Amplifiers

cavity, simulation, klystron, electromagnetic-fields

2265

C. Marrelli
CERN, Geneva, Switzerland
M. Migliorati, A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma, Italy
B. Spataro
INFN/LNF, Frascati (Roma), Italy
S.G. Tantawi
SLAC, Menlo Park, California, USA

The design of klystrons is based on the intensive utilization of simulation codes, which can evaluate the complete beam-cavities interaction in the case of large signals. In the present work, we present the development of a 2-D steady state simulation code that can self-consistently evaluate the effects of the electromagnetic field on the particles and of the particles back on the field. The algorithm is based on the iterative solution of the power balance equation in the RF structures and allows determining the amplitude and phase of the electromagnetic field starting from the cavity modes. Some applications of the code to a single cavity and a two cavity klystron are presented and compared with the results obtained from other codes. The effect of the space charge forces in the klystron drift tubes is also evaluated.

WEPS018

The Proposed CERN Proton-Synchrotron Upgrade Program

injection, emittance, cavity, electron

2520

S.S. Gilardoni, S. Bart Pedersen, W. Bartmann, S. Bartolome, O.E. Berrig, C. Bertone, A. Blas, D. Bodart, J. Borburgh, R.J. Brown, A.C. Butterworth, M.C.L. Buzio, C. Carli, P. Chiggiato, H. Damerau, T. Dobers, R. Folch, R. Garoby, B. Goddard, M. Gourber-Pace, S. Hancock, M. Hourican, P. Le Roux, L.A. Lopez Hernandez, A. Masi, G. Metral, Y. Muttoni, E. Métral, M. Nonis, J. Pierlot, S. Pittet, C. Rossi, I. Ruehl, G. Rumolo, L. Sermeus, R.R. Steerenberg, M. Widorski
CERN, Geneva, Switzerland

In the framework of the High-Luminosity LHC project, the CERN Proton Synchrotron would require a major upgrade to match the future beam parameters requested as pre-injector of the collider. The different beam dynamics issues, from space-charge limitations to longitudinal instabilities are discussed, as well as the proposed technical solutions to overcome them, covering the increase of the injection energy to RF related improvements.

WEPS073

A Low Energy Cyclotron Injector for DAEdALUS Experiment

cyclotron, proton, extraction, cavity

2673

L.A.C. Piazza, M.M. Maggiore
INFN/LNL, Legnaro (PD), Italy
L. Calabretta, D. Campo, D. Rifuggiato
INFN/LNS, Catania, Italy
A. Calanna
CSFNSM, Catania, Italy

Multi Megawatt accelerators are today requested for different use. In particular the experiment DAEdALUS*, recently proposed by MIT scientist to search for CP violation in the neutrino sector, needs three accelerator with energy of about 800 MeV, average power of some MW and duty cycle of 20%. To reduce the cost of the accelerators a cyclotron complex consisting of an injector and of a booster ring cyclotron has been proposed**. The main characteristics of the new kind of a separated sector cyclotron injector able to accelerate a H²⁺ molecule beam up to 50 MeV/n will be presented. Due to the low duty cycle, the peak current to be accelerated is 5 mA. The problem related to the injection of a H²⁺ beam, delivered by a compact ion source, and to the space charge effects will be discussed. The main parameters of the magnetic sectors, RF cavities, the isochronous magnetic field and the beam dynamics along the injection and extraction path and during the acceleration will be presented, too.
* J. Alonso et al., “A Novel Search for CP Violation in the Neutrino Sector: DAEdALUS”, June 2010. e-Print: arXiv:10⁰⁶.0260
** L. Calabretta et al., ICCA, Lanzhou 2010; http://www. JACoW.org.

WEPS088

Space Charge Studies of a 1 GeV Isochronous Non-scaling FFAG Proton Driver

acceleration, lattice, simulation, emittance

2715

S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

The production of very high power proton drivers in the 10 MW range is a considerable challenge to the accelerator community. Non-scaling FFAGs have gained interest in this field, as they may be able to provide smaller, cheaper accelerators than existing options. The recent development of an isochronous non-scaling FFAG is a promising advance, but must be shown to have stable beam dynamics in the presence of space charge. Simulations of this design including space charge are presented and the implications discussed.

WEPS101

Lattice Design of a RCS as Possible Alternative to the PS Booster Upgrade

lattice, quadrupole, injection, booster

2745

M. Fitterer, M. Benedikt, H. Burkhardt, C. Carli, R. Garoby, B. Goddard, K. Hanke, H.O. Schönauer
CERN, Geneva, Switzerland
A.-S. Müller
KIT, Karlsruhe, Germany

In the framework of the LHC Injectors Upgrade (LIU) a new rapid cycling synchrotron as alternative to the PS Booster has been proposed. In this paper we present the lattice constraints and requirement as well as the current status of the RCS lattice design and beam dynamics studies.

WEPS104

Transverse Beam Dynamics for the ISIS Synchrotron with Higher Energy Injection

resonance, simulation, injection, synchrotron

2754

B.G. Pine, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on an 800 MeV rapid cycling synchrotron, which provides 3·10¹³ protons per pulse at 50 Hz, corresponding to a beam power of 200 kW. Studies are underway to increase the energy of the ISIS linac from 70 to 180 MeV. This would reduce space charge in the synchrotron, and enable a larger current to be accumulated, possibly up to 0.5 MW. As part of the study, transverse beam dynamics have been re-examined on ISIS, building up models from incoherent space charge tune shift, through smooth focusing models with space charge to 2D alternating gradient lattice simulations. These later simulations, using the in-house space charge code Set, include harmonic perturbations to the focusing lattice, closed orbits and images. A clearer picture of the dynamics is emerging, where there may be important constraints on the highest intensities, including half integer resonance, image induced structure resonances and transverse instabilities.

WEPS106

Status of Injection Upgrade Studies for the ISIS Synchrotron

injection, simulation, linac, synchrotron

2760

C.M. Warsop, D.J. Adams, D.J.S. Findlay, I.S.K. Gardner, S.J.S. Jago, B. Jones, R.J. Mathieson, S.J. Payne, B.G. Pine, A. Seville, H. V. Smith, J.W.G. Thomason, R.E. Williamson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J. Pasternak
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
C.R. Prior, G.H. Rees
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a high intensity proton accelerator, consisting of a 70 MeV linac and an 800 MeV rapid cycling synchrotron, which provides a beam power of 0.2 MW. Obsolescence issues are motivating plans to replace the ageing 70 MeV linac, and this paper summarises the status of studies looking at how a new, higher energy linac (~180 MeV) could be used to increase beam power in the existing synchrotron. Reduced space charge and optimized injection might allow beam powers in the 0.5 MW regime, thus providing a very cost effective upgrade. The key areas of study are: design of a practical injection straight and magnets; injection painting and dynamics; foil specifications; acceleration dynamics; transverse space charge; instabilities; RF beam loading; beam loss and activation; diagnostics and possible damping systems. Results from work on most of these topics suggest that beam powers of ~0.5 MW may well be possible, but a number of topics, particularly transverse stability, still look challenging. Conclusions so far are presented, as is progress on R&D on the main intensity limiting issues.

WEPZ021

Self-Consistent Dynamics of Electromagnetic Pulses and Wakefields in Laser-Plasma Interactions

laser, plasma, wakefield, simulation

2811

A. Bonatto, R. Pakter, F.B. Rizzato
IF-UFRGS, Porto Alegre, Brazil

In the present work we study the stability of laser pulses propagating in a cold relativistic plasma, which can be of interest for particle acceleration schemes. After obtaining a Lagrangian density from the one-dimensional equations for the laser pulse envelope and the plasma electron density, we define a trial function and apply the variational approach in order to obtain an analytical model which allows us to calculate an effective potential for the pulse width. Using this procedure, we analyze the stability of narrow and large laser pulses and then compare its results with numerical solutions for the envelope and density equations.

THPC101

Fitting Formulas for Space-charge Dominated Free-electron Lasers

FEL, electron, undulator, simulation

3122

G. Marcus, E. Hemsing, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

A simple power-fit formula for calculating the gain length of the fundamental Gaussian mode of a free-electron laser having strong space-charge effects in the 3D regime has been obtained. This tool allows for quick evaluation of the free-electron laser performance in the presence of diffraction, uncorrelated energy spread, and longitudinal space-charge effects. Here, we use it to evaluate the performance of high-gain FEL amplifiers considered candidates as high average power light sources. Results are compared with detailed numerical particle simulations using the free-electron laser code Genesis.

THPC135

Optimal Parameters of the Photocathode Gun Space Charge to Improve Beam Quality

laser, cathode, gun, electron

3203

M.G. Fedurin, C. Swinson, V. Yakimenko
BNL, Upton, Long Island, New York, USA

Accelerator Test Facility at Brookhaven National Laboratory operates with 5 MeV photocathode gun and 70 MeV linac for different range of experiments with a few picoseconds and a few micrometers emittance electron bunch. Many conducted experiments require beam with good spatial resolution and short length as well. NdYaG laser pulse turns to the electron bunch in the gun with space charge affecting on the own bunch length and transverse profile. Optimal beam loading parameters of the space charge in the photocathode RF gun could be found and used to improve bunch length and emittance. Simple model and experimental results on the Accelerator Test Facility at Brookhaven national Laboratory will be described

THPS001

Experimental Studies of Beam Loss during Low Energy Operation with Electron Cooled Heavy Ions in the ESR

ion, emittance, bunching, resonance

3424

P.A. Görgen, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
S. Appel, C. Dimopoulou, S.A. Litvinov, M. Steck
GSI, Darmstadt, Germany

At the ESR at GSI electron cooled heavy ion beams are decelerated to 4 MeV/u and extracted for the HITRAP experiment. We will report about cooling equilibrium measurements at 4 and 30 MeV/u for Ar¹⁸⁺ coasting beams. We compare the equilibrium beam parameters with results from beam dynamics simulations using the BETACOOL code and an analytic model of reduced complexity. The time slot in which HITRAP accepts beam is 2μs long. For optimum efficiency the beam has to be bunched to this length before extraction. The obtained bunch profiles are compared to longitudinal beam dynamics simulations. Our measurements show that at both energies bunching leads to severe beam loss. The estimated transverse space charge tune shifts during the rf bunching indicate that resonance crossing might be responsible for the observed the beam loss. The influence of the tune shift will be further evaluated through resonance measurements.

THPS034

Studies on Electron Cloud Dynamics for an Optimized Space Charge Lens Design

electron, plasma, ion, diagnostics

3493

K. Schulte, M. Droba, B. Glaeser, S. Klaproth, O. Meusel, U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: Work supported by HIC for FAIR.
Space charge lenses using a stable electron cloud for focusing low energy heavy ion beams are an alternative concept to conventional ion optics. Due to external fields electrons are confined inside the lens’ volume. In case of a homogeneously distributed electron cloud the linear electric space charge field enables beam focusing free of aberration. Since the mapping quality of the lens is related to the confinement, non-destructive diagnostics has been developed to determine the plasma parameters and to characterize the collective behavior of the confined nonneutral plasma. Moreover, a scaled up space charge lens was constructed for a detailed investigation of the nonneutral plasma properties as well as beam interactions with a stable confined electron cloud. Experimental results will be presented in comparison with numerical simulations.

THPS052

Studies on Transverse Painting for H⁻ Injection into the PSB

injection, emittance, linac, kicker

3544

C. Bracco, C. Carli, T. Fowler, B. Goddard, G. Gräwer, J.-B. Lallement, M. Martini, M. Scholz, W.J.M. Weterings
CERN, Geneva, Switzerland

Linac4 will inject 160 MeV H− ions in to the CERN PS Booster (PSB). This will allow to reduce space charge effects and increase beam intensity but will require a substantial upgrade of the injection region, with the implementation of a charge-exchange multi-turn injection scheme. The PSB has to provide beam to several users with different requirements in terms of beam intensity and emittance. Four kicker magnets (KSW), which are already installed in the PSB lattice, will be used to accomplish painting in the horizontal phase space to match the injected beams to the required emittances. Double linear functions, with varying slopes for each user, have been defined for the KSW generators waveforms according to detailed beam dynamic studies for all target intensities and emittances. Effect of space charge, injection offsets, dispersion and betatron mismatch have been taken into account. Preliminary studies have been carried out to evaluate how to obtain the required vertical emittance and the option of a transverse painting, also in the vertical plane, is explored.

THPS058

Third Integer Resonance Slow Extraction Using RFKO at High Space Charge.

extraction, resonance, dipole, betatron

3559

V.P. Nagaslaev, J.F. Amundson, J.A. Johnstone, C.S. Park, S.J. Werkema
Fermilab, Batavia, USA

A proposal to search for direct mu->e conversion at Fermilab requires slow, resonant extraction of an intense proton beam. Large space charge forces will present challenges, partly due to the substantial betatron tune spread. The main challenges will be maintaining a uniform spill shape and moderate losses at the septum. We propose to use "radio frequency knockout" (RFKO) for fine tuning the extraction. Strategies for the RFKO method will be discussed here in the context of the mu->e experiment. Feasibility of this method has been demonstrated using simulations.