HB2012 - List of Keywords (cavity)

Paper	Title	Other Keywords	Page
MOI1C01	Intense-beam Issues in CSNS and C-ADS Accelerators	linac, emittance, lattice, simulation	25
	S. Fu, S.X. Fang, Z. Li, J. Peng, J.Y. Tang, S. Wang, F. Yan IHEP, Beijing, People's Republic of China
	In 2011 construction of two intense-beam accelerators were launched for China Spallation Neutron Source (CSNS) project and China Accelerator Driven System (C-ADS) project. CSNS uses a pulsed accelerator with an H⁻ linac and a rapid cycling synchrotron, and C-ADS has a CW proton linac with superconducting cavities. In both cases, the beam power is high and beam loss control is a key issue in beam dynamics. Beam emittance growth and beam halo formation must be carefully studied in beam dynamics and well controlled in machine design. This paper will present a brief introduction to the physics design of the two intense-beam accelerators, especially on the issue of beam instability. In their linac design equapartitioning focusing scheme is adopted to avoid coupling instability. Some beam halo formation experimental results due to mismatching will be compared with simulations. Beam halo generation due to the quench of superconducting cavity and magnet is investigated in detail and compensation scheme is also proposed. Beam loss study for the error effects and orbit correction will be presented.
	Slides MOI1C01 [3.747 MB]

MOP212	Simulation of Longitudinal Beam Instability caused by HOMs	HOM, simulation, linac, damping	73
	P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang IHEP, Beijing, People's Republic of China
	Superconducting cavities are employed in C-ADS linac to accelerate 10mA CW proton beams from 3.2 MeV to 1.5 GeV. High order modes in superconducting cavities are found by using the simulation tools CST and HFSS, then power dissipation caused by HOMs have been investigated, it is indicated that the Qext should not go beyond 10⁷} in order to limit the additional heat load. Beam instabilities caused by high order modes in elliptical cavity sections are investigated using the code offered by Dr. Jean-Luc Biarrotte (CNRS, IPN Orsay, France). Beam errors, linac errors and high order modes frequency spread are investigated in detail. It shows that the monopole modes do not affect the proton beam critically and need no HOM couplers (Q_ext=10⁵}) if high order modes frequency spread is more than 100 kHz.

MOP214	Test System and Characteristics Studies of Ferrite Cores for the CSNS RCS RF System	impedance, power-supply, controls, LLRF	81
	H. Shi, W.L. Huang, X. Li, W. Long, H. Sun, J.Y. Tang, C.L. Zhang IHEP, Beijing, People's Republic of China
	A two-ring ferrite test system for ferrite-loaded cavities of Rapid Cycling Synchrotron (RCS) of China Spallation Neutron Source (CSNS) has been developed. By this system, the RF characteristics of full-sized ferrite cores of RCS cavities have been studied. On dc bias current, the swept frequency range and thresholds of High Loss Effect (HLE) have been presented. On ac bias current of 25 Hz, although the shunt impedance of the cores satisfies the CSNS cavity, comparing with the dc bias, more power dissipation and more required bias current have been observed because the induced magnetic anisotropy of the ferrite cores disappears. Consequently, it is important to evaluate the dynamic features of the cores with 25 Hz bias current for designing the cavities, the power supplies and the bias current sources.

MOP219	Error Analysis and Correction Scheme in C-ADS Injector-I	emittance, linac, simulation, solenoid	99
	C. Meng, Z. Li, J.Y. Tang IHEP, Beijing, People's Republic of China
	Funding: Supported by the China ADS Project (XDA03020000) C-ADS Injector-I is a 10 mA 10 MeV CW proton linac. It uses a 3.2MeV normal conducting 4-Vane RFQ and 12 superconducting single-Spoke cavities. According to the detailed sensitivity analysis of alignment and RF errors, the error tolerance of both static and dynamic ones for Injector-I are presented. The simulation results show that with the error tolerance there are beam losses, the residual orbit is too large which will produce significant emittance growth, so the correction is necessary for Injector-I. After detailed numerical studies, a correction scheme and monitor distributions are proposed. After correction the RMS residual orbit can be controlled within 0.4mm and RMS emittance growth can be controlled within 10%, but it still has 1.7×10^-6 beam loss, which comes from the RF errors and low longitudinal acceptance. According to detailed analysis and simulations with 10⁸ macro particles, as a consequence, longitudinal emittance control and longitudinal distribution control as well as large longitudinal acceptance are the key to minimizing beam losses in low energy section. To minimize beam loss, a short period Injector-I lattice with larger longitudinal acceptance have been designed and performance very good error tolerance.

MOP220	Local Compensation-rematch for Major Element Failures in the C-ADS Accelerator	solenoid, quadrupole, emittance, focusing	102
	B. Sun, Z. Li, J.Y. Tang, F. Yan IHEP, Beijing, People's Republic of China
	In order to achieve the required reliability and availability for the C-ADS accelerator, a fault tolerance design is pursued. The effects of cavity failure in different locations have been studied and the schemes of compensation by means of local compensation have been investigated. After one cavity failure, by adjusting the settings of the neighboring cavities and the focusing elements to make sure that the Twiss parameters and energy are approximately recovered to that of the nominal ones at the matching point. We find the normalized RMS emittance and emittances including 99.9% and 100% particles have no obvious growth after applying the compensation with the RMS rematching in each section of the main linac. However, the conclusions above are drawn from the simulation results with the TraceWin code, which doesn't consider the phase difference. A code based on Matlab is under developing. By applying the code on the cavity failure in the middle part of spoke021 section, a fully compensated scheme with good dynamics results is obtained. The space charge effect is still not implanted in the code, and further study and optimization of the code will be performed in the next step.

MOP221	Physics Design of the C-ADS Main Linac Based on Two Different Injector Design Schemes	linac, emittance, simulation, lattice	107
	F. Yan, Z. Li, C. Meng, J.Y. Tang IHEP, Beijing, People's Republic of China
	Funding: Supported by Advanced Research Project of the Chinese Academy of Science Two design schemes for the main linac of C-ADS (China Accelerator Driven Subcritical system) are presented in this paper. They are corresponding to two different injector schemes. Injector-II scheme makes use of room-temperature RFQ and superconducting HWR cavities with the RF frequency of 162.5 MHz; Injector-I scheme makes use of higher-energy RFQ and superconducting spoke cavities with the RF frequency of 325 MHz. At the first choice, a relatively smaller longitudinal emittance is adopted for the RFQ designs with both the injector schemes to obtain more efficient acceleration. However, compared with the injector-I scheme, with the injector-II scheme, bunch current will be doubled in the main linac due to the half RF frequency in the injector-II. This means stronger space charge effects. Alternate design for the main linac with the injector-II scheme is to increase the longitudinal emittance by 50% so that the space charge effects will be alleviated. However, totally 30 cavities more and 36 m longer in the main linac have to be paid for this design scheme. The design considerations, the lattice designs, the simulation results including halo information are presented.

MOP235	Medium Energy Beam Transport Design Update for ESS	quadrupole, linac, DTL, rfq	128
	I. Bustinduy, F.J. Bermejo, A. Ghiglino, O. González, J.L. Muñoz, I. Rodríguez, A. Zugazaga ESS Bilbao, Bilbao, Spain B. Cheymol, M. Eshraqi, R. Miyamoto ESS, Lund, Sweden J. Stovall CERN, Geneva, Switzerland
	The major challenge of this part of the accelerator is to keep a high quality beam, with a pulse well defined in time, a low emittance and a minimized halo, so that the beam losses downstream the linac be limited and the overall ESS reliability be maximized. In order to minimize beam loss at high energy linac, and the consequent activation of components, a fast chopping scheme is presented for the medium energy beam transport section (MEBT). The considered versatile MEBT is being designed to achieve four main goals: First, to contain a fast chopper and its correspondent beam dump, that could serve in the commissioning as well as in the ramp up phases. Second, to serve as a halo scraping section by means of two adjustable blades. Third, to measure the beam phase and profile between the RFQ and the DTL, along with other beam monitors. And finally, to match the RFQ output beam characteristics to the DTL input both transversally and longitudinally. For this purpose a set of ten quadrupoles is used to match the beam characteristics transversally, combined with two 352.2 MHz buncher cavities, which are used to adjust the beam in order to fulfill the required longitudinal parameters.

TUO3B02	Beam Dynamics of the ESS Superconducting Linac	linac, proton, quadrupole, emittance	278
	M. Eshraqi, H. Danared, R. Miyamoto ESS, Lund, Sweden
	The European Spallation Source, ESS, uses a linear accelerator to deliver the high intensity proton beam to the target station. The nominal beam power is 5 MW at an energy of 2.5 GeV. The superconducting part covers more than 95\% of the energy gain and 90\% of the length. The beam dynamics criteria applied to the design of the superconducting part of the linac including the frequency jump at a medium energy of 200 MeV as well as the beam dynamics performance of this structure are described in this paper.
	Slides TUO3B02 [4.406 MB]

TUO3C02	FNAL Proton Source High Intensity Operations and Beam Loss Control	booster, proton, controls, injection	320
	F.G.G. Garcia, W. Pellico Fermilab, Batavia, USA
	Funding: U.S. Department of Energy The Proton Source (PS) has been the workhorse of the Fermi National Accelerator Laboratory (FNAL) for over 40 years. During that time the United States High Energy Physics program has continued to change with increasing demands put on the PS. The past 10 years saw an increase of over 10 fold in required hourly flux for the PS and plans are now underway to have the capability to double the output with continued operations until at least 2025. To meet these goals, effort in area of beam loss control has been a major part of the upgrades. Beam collimation and absorption systems as well as diagnostics used to mitigate and control losses have been implemented. The recent implementation of new correctors for orbit and higher harmonic control has also been very beneficial. A summary of recent and planned modification to these PS systems will be discussed.
	Slides TUO3C02 [16.766 MB]

WEO1A01	Impedance Studies of 2D Azimuthally Symmetric Devices of Finite Length	impedance, coupling, resonance, simulation	344
	N. Biancacci, E. Métral, B. Salvant CERN, Geneva, Switzerland N. Biancacci Rome University La Sapienza, Roma, Italy M. Migliorati, L. Palumbo URLS, Rome, Italy V.G. Vaccaro Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli, Italy
	In circular accelerators, the beam quality can be strongly affected by the self-induced electromagnetic fields excited by the beam in the passage through the elements of the accelerator. The beam coupling impedance quantifies this interaction and allows predicting the stability of the dynamics of high intensity, high brilliance beams. The coupling impedance can be evaluated with finite element methods or using analytical methods, such as Field Matching or Mode Matching. In this paper we present an application of the Mode Matching technique for an azimuthally uniform structure of finite length: a cylindrical cavity loaded with a toroidal slab of lossy dielectric, connected with cylindrical beam pipes. In order to take into account the finite length of the structure, with respect to the infinite length approximation, we decompose the fields in the cavity into a set of orthonormal modes. We obtain a complete set of equations using the magnetic field matching and the non-uniform convergence of the electric field on the cavity boundaries. We present benchmarks done with CST Particle Studio simulations and existing analytical formulas, pointing out the effect of finite length and non-relativistic beta.
	Slides WEO1A01 [6.689 MB]

WEO3B03	PXIE at FNAL	rfq, kicker, diagnostics, ion	414
	N. Solyak, C.M. Baffes, A.Z. Chen, Y.I. Eidelman, B.M. Hanna, S.D. Holmes, V.A. Lebedev, S. Nagaitsev, J.-F. Ostiguy, R.J. Pasquinelli, D.W. Peterson, L.R. Prost, G.W. Saewert, A. Saini, V.E. Scarpine, A.V. Shemyakin, D. Sun, V.P. Yakovlev Fermilab, Batavia, USA
	PXIE is the integrated systems test for the Project X frontend. It is expected to accelerate 1-2 mA CW beam up to 30 MeV. The major goal of the project is a validation of the Project X concept and elimination of technical risks. It is expected to be constructed in the period of 2012-2016. In presentation the conceptual design of the experimental test facility, lattice and beam dynamics studies will be discussed in details.
	Slides WEO3B03 [4.561 MB]

WEO1C03	Longitudinal Beam Loss Studies of the CERN PS-to-SPS Transfer	emittance, simulation, injection, impedance	439
	H. Timko, T. Argyropoulos, T. Bohl, H. Damerau, J. Esteban Müller, S. Hancock, E.N. Shaposhnikova CERN, Geneva, Switzerland
	Bunch-to-bucket transfer between the Proton Synchrotron (PS) and the Super Proton Synchrotron (SPS) is required before beams can enter the Large Hadron Collider. The overall beam loss at this transfer is currently around 5-10 %, and is increased for higher intensities or larger longitudinal emittances. Previous attempts to reduce the losses with additional RF voltage from spare cavities in the PS were unsuccessful. In this paper, we modelled the complete PS flat-top bunch splitting and rotation manipulations, PS-to-SPS transfer, SPS flat bottom and acceleration ramp using end-to-end simulations. Starting from the measured bunch distributions, the simulations provide an accurate insight into the problem and allow direct benchmarking with experiments. As a result, it was understood and confirmed by measurements that shorter bunches do not necessarily lead to better transmission. The particle distribution in longitudinal phase space at PS extraction should be optimised instead. A significant loss reduction of up to 50 % is expected from simulations; experimental studies are on-going to verify these theoretical findings.
	Slides WEO1C03 [3.903 MB]

WEO1C04	Acceleration of High-Intensity Protons in the J-PARC Synchrotrons	synchrotron, extraction, injection, proton	444
	M. Yoshii KEK/JAEA, Ibaraki-Ken, Japan
	The J-PARC consisting of the 181 MeV Linac, the 3GeV rapid cycling synchrotron (RCS) and the 50 GeV main synchrotron (MR), is the first high intensity proton synchrotron facility to use the high field gradient magnetic alloy (MA) loaded accelerating cavity. MA is a low-Q material. However, because of the high permeability and the high saturation magnetic flux density, the MA cores are the only materials to realize the required gradient. The MA loaded cavity can be considered as a stable passive load. No tuning control is necessary. 11 RF systems are installed in the RCS, and 8 RF systems in the MR. In addition, the RCS RF systems are operated in a dual harmonic mode to perform the acceleration and the longitudinal manipulation of the high intensity beam in the RCS available space. Beam loading compensation is an important issue. The feed-forward method using the RF beam signals from the wall current monitor has been established. The J-PARC synchrotrons realize stable, reproducible and clean acceleration of high intensity protons. A transition-free lattice and a precise digital timing system asynchronous to the AC-line are the distinctive features, which enable this achievement.
	Slides WEO1C04 [3.861 MB]

THO1A03	Dual-harmonic Acceleration Studies at CSNS RCS	injection, acceleration, simulation, bunching	487
	J.F. Chen, J.Y. Tang, X. Zhang IHEP, Beijing, People's Republic of China
	Dual harmonic acceleration is proposed to alleviate the space charge effects in the RCS (Rapid Cycling Synchrotron) at the upgrading stages of the CSNS (China Spallation Neutron Source). Different dual harmonic acceleration schemes have been studied by using a self-made parameter calculation code - RAMADH and the simulation code - ORBIT. Both complete and partial coverage of the dual harmonic RF system along the acceleration have been considered. The injection by combining beam chopping and off-momentum is used in the macro-particle tracking simulations by ORBIT. In addition, a new idea that unlocks the RF frequency and the magnetic field in the injection period is found very useful in obtaining a good longitudinal painting.
	Slides THO1A03 [1.343 MB]

THO3A02	Beam Dynamics of China ADS Linac	linac, rfq, lattice, emittance	502
	Z. Li Private Address, Beijing, People's Republic of China P. Cheng, H. Geng, Z. Guo, C. Meng, B. Sun, J.Y. Tang, F. Yan IHEP, Beijing, People's Republic of China
	Funding: Supported by China ADS Program(XDA03020000), National Natural Science Fundation of China (10875099) and IHEP Special Fundings(Y0515550U1) An ADS study program is approved by Chinese Academy of Sciences at 2011, which aims to design and built an ADS demonstration facility with the capability of more than 1000 MW thermal power within the following 25 years. The 15 MW driver accelerator will be designed and constructed by the Institute of High Energy Physics (IHEP) and Institute of Modern Physics (IMP) of China Academy of Sciences. This linac is characterized by the 1.5 GeV energy, 10 mA current and CW operation. It is composed by two parallel 10 MeV injectors and a main linac integrated with fault tolerance design. The superconducting acceleration structures are employed except the RFQ. The general considerations and the beam dynamics design of the driver accelerator will be presented.
	Slides THO3A02 [5.822 MB]

THO3B02	SRF Technology Challenge and Development	linac, SRF, HOM, ion	536
	A. Facco INFN/LNL, Legnaro (PD), Italy A. Facco FRIB, East Lansing, USA
	SRF technology in particle accelerators is in continuous evolution, providing a large variety of high gradient- low loss resonators with large apertures, suitable for many different beam current and energy regimes. Recent development was aiming not only at highest gradient and Q but also at improving field quality, reliability and cost reduction for large production. The SRF R&D effort, once concentrated mostly in the high energy electron machines, is increasingly focused to heavy ion linacs, energy recovery linacs and also to cavities for special applications. A concise overview of the present state of the art will be given.
	Slides THO3B02 [1.712 MB]

THO3B03	SRF Cavity Research for Project X	linac, SRF, cryomodule, proton	541
	R.D. Kephart Fermilab, Batavia, USA
	Project X is a new SRF linac based multi-MW class proton source proposed for construction at Fermilab. It consists of a 3 MW, 1 mA CW H⁻ SRF linac that feeds an intensity frontier Physics program and a 3-8 GeV pulsed linac that accelerates ~5% of the output of the CW linac to 8 GeV for injection into the Fermilab Main Injector synchrotron resulting in an additional 2 MW of beam power at 60-120 GeV in support of a world class long baseline neutrino program. The project has chosen operating frequencies that are sub-harmonics of 1.3 GHz and is developing 6 separate cavity designs for acceleration of H⁻ particles with various velocities. An R&D program is in progress to develop these cavities; the associated cryomodules; and the required fabrication and test infrastructure. A status and progress report on this R&D program will be presented.
	Slides THO3B03 [4.034 MB]

THO1C04	Performances and Future Plans of the LHC RF	klystron, injection, emittance, impedance	565
	P. Baudrenghien, T. Mastoridis CERN, Geneva, Switzerland
	The ramp-up of the LHC operation has been exceptionally fast: from the first acceleration of a single bunch at nominal intensity (1.1· E11 p) to 3.5 TeV/c on May 2010, to the accumulation of 11 fb-1 integrated luminosity two years later (June 2012). On the RF side this was made possible by a few key design choices and several developments, that allow reliable LHC operation with 0.35 A DC beam at 4 TeV/c (1380 bunches at 50 ns spacing, 1.5·10¹¹ p per bunch). This paper reviews the RF design and presents its performance. Plans are also outlined that would allow operation with 25 ns bunch spacing (doubling the beam current) and even increased bunch intensity with the target of above 1A DC current per beam, without big modification to the existing RF power system.
	Slides THO1C04 [9.945 MB]

THO3C02	Momentum Spread Determination of Linac Beams Using Incoherent Components of the Bunch Signals	linac, synchrotron, pick-up, bunching	583
	P. Kowina, P. Forck, M. Schwickert GSI, Darmstadt, Germany F. Caspers CERN, Geneva, Switzerland
	Measurements of the momentum spread of the beam particles are of great importance when optimizing linac settings for high current operation with controlled longitudinal phase space occupation. A new method of momentum spread determination was tested at the GSI heavy ion linear accelerator UNILAC. The method is based on an analysis of incoherent components of the bunch signal. A significant enhancement of the signal-to-noise ratio was achieved by means of a resonant pick-up of pill-box shape. Spectra were analyzed on the 36th harmonics of the linac rf-frequency, i.e. at 1.3 GHz. Thus, the contribution of coherent components in the frequency spectrum of the bunched beam, e.g. due to common mode, was significantly damped. Fast digital processing and gating synchronized to the bunch train allowed for a drastic reduction of the measurement time and, additionally, suppressed noise signals in the frequency spectrum. This contribution describes the measurement setup and discusses first results obtained with heavy ion beams.
	Slides THO3C02 [2.131 MB]

THO3C04	Longitudinal Beam Diagnosis with RF Chopper System	linac, neutron, acceleration, DTL	591
	T. Maruta JAEA/J-PARC, Tokai-mura, Japan M. Ikegami KEK, Ibaraki, Japan
	J-PARC linac has a chopper system between RFQ and DTL, which utilizes an RF deflector cavity instead of a usual slow wave kicker. Taking advantage of this unique feature of the chopper system, we have experimentally measured the longitudinal full width of phase direction at the chopper cavity. In this presentation, I would like to discuss the measurement technique and measurement results.
	Slides THO3C04 [2.495 MB]

Paper

Title

Other Keywords

Page

MOI1C01

Intense-beam Issues in CSNS and C-ADS Accelerators

linac, emittance, lattice, simulation

25

S. Fu, S.X. Fang, Z. Li, J. Peng, J.Y. Tang, S. Wang, F. Yan
IHEP, Beijing, People's Republic of China

In 2011 construction of two intense-beam accelerators were launched for China Spallation Neutron Source (CSNS) project and China Accelerator Driven System (C-ADS) project. CSNS uses a pulsed accelerator with an H⁻ linac and a rapid cycling synchrotron, and C-ADS has a CW proton linac with superconducting cavities. In both cases, the beam power is high and beam loss control is a key issue in beam dynamics. Beam emittance growth and beam halo formation must be carefully studied in beam dynamics and well controlled in machine design. This paper will present a brief introduction to the physics design of the two intense-beam accelerators, especially on the issue of beam instability. In their linac design equapartitioning focusing scheme is adopted to avoid coupling instability. Some beam halo formation experimental results due to mismatching will be compared with simulations. Beam halo generation due to the quench of superconducting cavity and magnet is investigated in detail and compensation scheme is also proposed. Beam loss study for the error effects and orbit correction will be presented.

Slides MOI1C01 [3.747 MB]

MOP212

Simulation of Longitudinal Beam Instability caused by HOMs

HOM, simulation, linac, damping

73

P. Cheng, Z. Li, J.Y. Tang, J.Q. Wang
IHEP, Beijing, People's Republic of China

Superconducting cavities are employed in C-ADS linac to accelerate 10mA CW proton beams from 3.2 MeV to 1.5 GeV. High order modes in superconducting cavities are found by using the simulation tools CST and HFSS, then power dissipation caused by HOMs have been investigated, it is indicated that the Qext should not go beyond 10⁷} in order to limit the additional heat load. Beam instabilities caused by high order modes in elliptical cavity sections are investigated using the code offered by Dr. Jean-Luc Biarrotte (CNRS, IPN Orsay, France). Beam errors, linac errors and high order modes frequency spread are investigated in detail. It shows that the monopole modes do not affect the proton beam critically and need no HOM couplers (Q_ext=10⁵}) if high order modes frequency spread is more than 100 kHz.

MOP214

Test System and Characteristics Studies of Ferrite Cores for the CSNS RCS RF System

impedance, power-supply, controls, LLRF

81

H. Shi, W.L. Huang, X. Li, W. Long, H. Sun, J.Y. Tang, C.L. Zhang
IHEP, Beijing, People's Republic of China

A two-ring ferrite test system for ferrite-loaded cavities of Rapid Cycling Synchrotron (RCS) of China Spallation Neutron Source (CSNS) has been developed. By this system, the RF characteristics of full-sized ferrite cores of RCS cavities have been studied. On dc bias current, the swept frequency range and thresholds of High Loss Effect (HLE) have been presented. On ac bias current of 25 Hz, although the shunt impedance of the cores satisfies the CSNS cavity, comparing with the dc bias, more power dissipation and more required bias current have been observed because the induced magnetic anisotropy of the ferrite cores disappears. Consequently, it is important to evaluate the dynamic features of the cores with 25 Hz bias current for designing the cavities, the power supplies and the bias current sources.

MOP219

Error Analysis and Correction Scheme in C-ADS Injector-I

emittance, linac, simulation, solenoid

99

C. Meng, Z. Li, J.Y. Tang
IHEP, Beijing, People's Republic of China

Funding: Supported by the China ADS Project (XDA03020000)
C-ADS Injector-I is a 10 mA 10 MeV CW proton linac. It uses a 3.2MeV normal conducting 4-Vane RFQ and 12 superconducting single-Spoke cavities. According to the detailed sensitivity analysis of alignment and RF errors, the error tolerance of both static and dynamic ones for Injector-I are presented. The simulation results show that with the error tolerance there are beam losses, the residual orbit is too large which will produce significant emittance growth, so the correction is necessary for Injector-I. After detailed numerical studies, a correction scheme and monitor distributions are proposed. After correction the RMS residual orbit can be controlled within 0.4mm and RMS emittance growth can be controlled within 10%, but it still has 1.7×10^-6 beam loss, which comes from the RF errors and low longitudinal acceptance. According to detailed analysis and simulations with 10⁸ macro particles, as a consequence, longitudinal emittance control and longitudinal distribution control as well as large longitudinal acceptance are the key to minimizing beam losses in low energy section. To minimize beam loss, a short period Injector-I lattice with larger longitudinal acceptance have been designed and performance very good error tolerance.

MOP220

Local Compensation-rematch for Major Element Failures in the C-ADS Accelerator

solenoid, quadrupole, emittance, focusing

102

B. Sun, Z. Li, J.Y. Tang, F. Yan
IHEP, Beijing, People's Republic of China

In order to achieve the required reliability and availability for the C-ADS accelerator, a fault tolerance design is pursued. The effects of cavity failure in different locations have been studied and the schemes of compensation by means of local compensation have been investigated. After one cavity failure, by adjusting the settings of the neighboring cavities and the focusing elements to make sure that the Twiss parameters and energy are approximately recovered to that of the nominal ones at the matching point. We find the normalized RMS emittance and emittances including 99.9% and 100% particles have no obvious growth after applying the compensation with the RMS rematching in each section of the main linac. However, the conclusions above are drawn from the simulation results with the TraceWin code, which doesn't consider the phase difference. A code based on Matlab is under developing. By applying the code on the cavity failure in the middle part of spoke021 section, a fully compensated scheme with good dynamics results is obtained. The space charge effect is still not implanted in the code, and further study and optimization of the code will be performed in the next step.

MOP221

Physics Design of the C-ADS Main Linac Based on Two Different Injector Design Schemes

linac, emittance, simulation, lattice

107

F. Yan, Z. Li, C. Meng, J.Y. Tang
IHEP, Beijing, People's Republic of China

Funding: Supported by Advanced Research Project of the Chinese Academy of Science
Two design schemes for the main linac of C-ADS (China Accelerator Driven Subcritical system) are presented in this paper. They are corresponding to two different injector schemes. Injector-II scheme makes use of room-temperature RFQ and superconducting HWR cavities with the RF frequency of 162.5 MHz; Injector-I scheme makes use of higher-energy RFQ and superconducting spoke cavities with the RF frequency of 325 MHz. At the first choice, a relatively smaller longitudinal emittance is adopted for the RFQ designs with both the injector schemes to obtain more efficient acceleration. However, compared with the injector-I scheme, with the injector-II scheme, bunch current will be doubled in the main linac due to the half RF frequency in the injector-II. This means stronger space charge effects. Alternate design for the main linac with the injector-II scheme is to increase the longitudinal emittance by 50% so that the space charge effects will be alleviated. However, totally 30 cavities more and 36 m longer in the main linac have to be paid for this design scheme. The design considerations, the lattice designs, the simulation results including halo information are presented.

MOP235

Medium Energy Beam Transport Design Update for ESS

quadrupole, linac, DTL, rfq

128

I. Bustinduy, F.J. Bermejo, A. Ghiglino, O. González, J.L. Muñoz, I. Rodríguez, A. Zugazaga
ESS Bilbao, Bilbao, Spain
B. Cheymol, M. Eshraqi, R. Miyamoto
ESS, Lund, Sweden
J. Stovall
CERN, Geneva, Switzerland

The major challenge of this part of the accelerator is to keep a high quality beam, with a pulse well defined in time, a low emittance and a minimized halo, so that the beam losses downstream the linac be limited and the overall ESS reliability be maximized. In order to minimize beam loss at high energy linac, and the consequent activation of components, a fast chopping scheme is presented for the medium energy beam transport section (MEBT). The considered versatile MEBT is being designed to achieve four main goals: First, to contain a fast chopper and its correspondent beam dump, that could serve in the commissioning as well as in the ramp up phases. Second, to serve as a halo scraping section by means of two adjustable blades. Third, to measure the beam phase and profile between the RFQ and the DTL, along with other beam monitors. And finally, to match the RFQ output beam characteristics to the DTL input both transversally and longitudinally. For this purpose a set of ten quadrupoles is used to match the beam characteristics transversally, combined with two 352.2 MHz buncher cavities, which are used to adjust the beam in order to fulfill the required longitudinal parameters.

TUO3B02

Beam Dynamics of the ESS Superconducting Linac

linac, proton, quadrupole, emittance

278

M. Eshraqi, H. Danared, R. Miyamoto
ESS, Lund, Sweden

The European Spallation Source, ESS, uses a linear accelerator to deliver the high intensity proton beam to the target station. The nominal beam power is 5 MW at an energy of 2.5 GeV. The superconducting part covers more than 95\% of the energy gain and 90\% of the length. The beam dynamics criteria applied to the design of the superconducting part of the linac including the frequency jump at a medium energy of 200 MeV as well as the beam dynamics performance of this structure are described in this paper.

Slides TUO3B02 [4.406 MB]

TUO3C02

FNAL Proton Source High Intensity Operations and Beam Loss Control

booster, proton, controls, injection

320

F.G.G. Garcia, W. Pellico
Fermilab, Batavia, USA

Funding: U.S. Department of Energy
The Proton Source (PS) has been the workhorse of the Fermi National Accelerator Laboratory (FNAL) for over 40 years. During that time the United States High Energy Physics program has continued to change with increasing demands put on the PS. The past 10 years saw an increase of over 10 fold in required hourly flux for the PS and plans are now underway to have the capability to double the output with continued operations until at least 2025. To meet these goals, effort in area of beam loss control has been a major part of the upgrades. Beam collimation and absorption systems as well as diagnostics used to mitigate and control losses have been implemented. The recent implementation of new correctors for orbit and higher harmonic control has also been very beneficial. A summary of recent and planned modification to these PS systems will be discussed.

Slides TUO3C02 [16.766 MB]

WEO1A01

Impedance Studies of 2D Azimuthally Symmetric Devices of Finite Length

impedance, coupling, resonance, simulation

344

N. Biancacci, E. Métral, B. Salvant
CERN, Geneva, Switzerland
N. Biancacci
Rome University La Sapienza, Roma, Italy
M. Migliorati, L. Palumbo
URLS, Rome, Italy
V.G. Vaccaro
Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli, Italy

In circular accelerators, the beam quality can be strongly affected by the self-induced electromagnetic fields excited by the beam in the passage through the elements of the accelerator. The beam coupling impedance quantifies this interaction and allows predicting the stability of the dynamics of high intensity, high brilliance beams. The coupling impedance can be evaluated with finite element methods or using analytical methods, such as Field Matching or Mode Matching. In this paper we present an application of the Mode Matching technique for an azimuthally uniform structure of finite length: a cylindrical cavity loaded with a toroidal slab of lossy dielectric, connected with cylindrical beam pipes. In order to take into account the finite length of the structure, with respect to the infinite length approximation, we decompose the fields in the cavity into a set of orthonormal modes. We obtain a complete set of equations using the magnetic field matching and the non-uniform convergence of the electric field on the cavity boundaries. We present benchmarks done with CST Particle Studio simulations and existing analytical formulas, pointing out the effect of finite length and non-relativistic beta.

Slides WEO1A01 [6.689 MB]

WEO3B03

PXIE at FNAL

rfq, kicker, diagnostics, ion

414

N. Solyak, C.M. Baffes, A.Z. Chen, Y.I. Eidelman, B.M. Hanna, S.D. Holmes, V.A. Lebedev, S. Nagaitsev, J.-F. Ostiguy, R.J. Pasquinelli, D.W. Peterson, L.R. Prost, G.W. Saewert, A. Saini, V.E. Scarpine, A.V. Shemyakin, D. Sun, V.P. Yakovlev
Fermilab, Batavia, USA

PXIE is the integrated systems test for the Project X frontend. It is expected to accelerate 1-2 mA CW beam up to 30 MeV. The major goal of the project is a validation of the Project X concept and elimination of technical risks. It is expected to be constructed in the period of 2012-2016. In presentation the conceptual design of the experimental test facility, lattice and beam dynamics studies will be discussed in details.

Slides WEO3B03 [4.561 MB]

WEO1C03

Longitudinal Beam Loss Studies of the CERN PS-to-SPS Transfer

emittance, simulation, injection, impedance

439

H. Timko, T. Argyropoulos, T. Bohl, H. Damerau, J. Esteban Müller, S. Hancock, E.N. Shaposhnikova
CERN, Geneva, Switzerland

Bunch-to-bucket transfer between the Proton Synchrotron (PS) and the Super Proton Synchrotron (SPS) is required before beams can enter the Large Hadron Collider. The overall beam loss at this transfer is currently around 5-10 %, and is increased for higher intensities or larger longitudinal emittances. Previous attempts to reduce the losses with additional RF voltage from spare cavities in the PS were unsuccessful. In this paper, we modelled the complete PS flat-top bunch splitting and rotation manipulations, PS-to-SPS transfer, SPS flat bottom and acceleration ramp using end-to-end simulations. Starting from the measured bunch distributions, the simulations provide an accurate insight into the problem and allow direct benchmarking with experiments. As a result, it was understood and confirmed by measurements that shorter bunches do not necessarily lead to better transmission. The particle distribution in longitudinal phase space at PS extraction should be optimised instead. A significant loss reduction of up to 50 % is expected from simulations; experimental studies are on-going to verify these theoretical findings.

Slides WEO1C03 [3.903 MB]

WEO1C04

Acceleration of High-Intensity Protons in the J-PARC Synchrotrons

synchrotron, extraction, injection, proton

444

M. Yoshii
KEK/JAEA, Ibaraki-Ken, Japan

The J-PARC consisting of the 181 MeV Linac, the 3GeV rapid cycling synchrotron (RCS) and the 50 GeV main synchrotron (MR), is the first high intensity proton synchrotron facility to use the high field gradient magnetic alloy (MA) loaded accelerating cavity. MA is a low-Q material. However, because of the high permeability and the high saturation magnetic flux density, the MA cores are the only materials to realize the required gradient. The MA loaded cavity can be considered as a stable passive load. No tuning control is necessary. 11 RF systems are installed in the RCS, and 8 RF systems in the MR. In addition, the RCS RF systems are operated in a dual harmonic mode to perform the acceleration and the longitudinal manipulation of the high intensity beam in the RCS available space. Beam loading compensation is an important issue. The feed-forward method using the RF beam signals from the wall current monitor has been established. The J-PARC synchrotrons realize stable, reproducible and clean acceleration of high intensity protons. A transition-free lattice and a precise digital timing system asynchronous to the AC-line are the distinctive features, which enable this achievement.

Slides WEO1C04 [3.861 MB]

THO1A03

Dual-harmonic Acceleration Studies at CSNS RCS

injection, acceleration, simulation, bunching

487

J.F. Chen, J.Y. Tang, X. Zhang
IHEP, Beijing, People's Republic of China

Dual harmonic acceleration is proposed to alleviate the space charge effects in the RCS (Rapid Cycling Synchrotron) at the upgrading stages of the CSNS (China Spallation Neutron Source). Different dual harmonic acceleration schemes have been studied by using a self-made parameter calculation code - RAMADH and the simulation code - ORBIT. Both complete and partial coverage of the dual harmonic RF system along the acceleration have been considered. The injection by combining beam chopping and off-momentum is used in the macro-particle tracking simulations by ORBIT. In addition, a new idea that unlocks the RF frequency and the magnetic field in the injection period is found very useful in obtaining a good longitudinal painting.

Slides THO1A03 [1.343 MB]

THO3A02

Beam Dynamics of China ADS Linac

linac, rfq, lattice, emittance

502

Z. Li
Private Address, Beijing, People's Republic of China
P. Cheng, H. Geng, Z. Guo, C. Meng, B. Sun, J.Y. Tang, F. Yan
IHEP, Beijing, People's Republic of China

Funding: Supported by China ADS Program(XDA03020000), National Natural Science Fundation of China (10875099) and IHEP Special Fundings(Y0515550U1)
An ADS study program is approved by Chinese Academy of Sciences at 2011, which aims to design and built an ADS demonstration facility with the capability of more than 1000 MW thermal power within the following 25 years. The 15 MW driver accelerator will be designed and constructed by the Institute of High Energy Physics (IHEP) and Institute of Modern Physics (IMP) of China Academy of Sciences. This linac is characterized by the 1.5 GeV energy, 10 mA current and CW operation. It is composed by two parallel 10 MeV injectors and a main linac integrated with fault tolerance design. The superconducting acceleration structures are employed except the RFQ. The general considerations and the beam dynamics design of the driver accelerator will be presented.

Slides THO3A02 [5.822 MB]

THO3B02

SRF Technology Challenge and Development

linac, SRF, HOM, ion

536

A. Facco
INFN/LNL, Legnaro (PD), Italy
A. Facco
FRIB, East Lansing, USA

SRF technology in particle accelerators is in continuous evolution, providing a large variety of high gradient- low loss resonators with large apertures, suitable for many different beam current and energy regimes. Recent development was aiming not only at highest gradient and Q but also at improving field quality, reliability and cost reduction for large production. The SRF R&D effort, once concentrated mostly in the high energy electron machines, is increasingly focused to heavy ion linacs, energy recovery linacs and also to cavities for special applications. A concise overview of the present state of the art will be given.

Slides THO3B02 [1.712 MB]

THO3B03

SRF Cavity Research for Project X

linac, SRF, cryomodule, proton

541

R.D. Kephart
Fermilab, Batavia, USA

Project X is a new SRF linac based multi-MW class proton source proposed for construction at Fermilab. It consists of a 3 MW, 1 mA CW H⁻ SRF linac that feeds an intensity frontier Physics program and a 3-8 GeV pulsed linac that accelerates ~5% of the output of the CW linac to 8 GeV for injection into the Fermilab Main Injector synchrotron resulting in an additional 2 MW of beam power at 60-120 GeV in support of a world class long baseline neutrino program. The project has chosen operating frequencies that are sub-harmonics of 1.3 GHz and is developing 6 separate cavity designs for acceleration of H⁻ particles with various velocities. An R&D program is in progress to develop these cavities; the associated cryomodules; and the required fabrication and test infrastructure. A status and progress report on this R&D program will be presented.

Slides THO3B03 [4.034 MB]

THO1C04

Performances and Future Plans of the LHC RF

klystron, injection, emittance, impedance

565

P. Baudrenghien, T. Mastoridis
CERN, Geneva, Switzerland

The ramp-up of the LHC operation has been exceptionally fast: from the first acceleration of a single bunch at nominal intensity (1.1· E11 p) to 3.5 TeV/c on May 2010, to the accumulation of 11 fb-1 integrated luminosity two years later (June 2012). On the RF side this was made possible by a few key design choices and several developments, that allow reliable LHC operation with 0.35 A DC beam at 4 TeV/c (1380 bunches at 50 ns spacing, 1.5·10¹¹ p per bunch). This paper reviews the RF design and presents its performance. Plans are also outlined that would allow operation with 25 ns bunch spacing (doubling the beam current) and even increased bunch intensity with the target of above 1A DC current per beam, without big modification to the existing RF power system.

Slides THO1C04 [9.945 MB]

THO3C02

Momentum Spread Determination of Linac Beams Using Incoherent Components of the Bunch Signals

linac, synchrotron, pick-up, bunching

583

P. Kowina, P. Forck, M. Schwickert
GSI, Darmstadt, Germany
F. Caspers
CERN, Geneva, Switzerland

Measurements of the momentum spread of the beam particles are of great importance when optimizing linac settings for high current operation with controlled longitudinal phase space occupation. A new method of momentum spread determination was tested at the GSI heavy ion linear accelerator UNILAC. The method is based on an analysis of incoherent components of the bunch signal. A significant enhancement of the signal-to-noise ratio was achieved by means of a resonant pick-up of pill-box shape. Spectra were analyzed on the 36th harmonics of the linac rf-frequency, i.e. at 1.3 GHz. Thus, the contribution of coherent components in the frequency spectrum of the bunched beam, e.g. due to common mode, was significantly damped. Fast digital processing and gating synchronized to the bunch train allowed for a drastic reduction of the measurement time and, additionally, suppressed noise signals in the frequency spectrum. This contribution describes the measurement setup and discusses first results obtained with heavy ion beams.

Slides THO3C02 [2.131 MB]

THO3C04

Longitudinal Beam Diagnosis with RF Chopper System

linac, neutron, acceleration, DTL

591

T. Maruta
JAEA/J-PARC, Tokai-mura, Japan
M. Ikegami
KEK, Ibaraki, Japan

J-PARC linac has a chopper system between RFQ and DTL, which utilizes an RF deflector cavity instead of a usual slow wave kicker. Taking advantage of this unique feature of the chopper system, we have experimentally measured the longitudinal full width of phase direction at the chopper cavity. In this presentation, I would like to discuss the measurement technique and measurement results.

Slides THO3C04 [2.495 MB]