HB2012 - List of Keywords (bunching)

Paper	Title	Other Keywords	Page
MOP216	The Design Study on the Longitudinal Beam Dynamics for CSNS/RCS	injection, acceleration, simulation, space-charge	89
	N. Wang, M.Y. Huang, Y. Li, S. Wang, S.Y. Xu, Y.S. Yuan IHEP, Beijing, People's Republic of China
	Rapid Cycling Synchrotron (RCS) is the key part of China Spallation Neutron Source (CSNS) accelerators. The RCS accumulates and accelerates 80 MeV beam from linac to 1.6 GeV. The particle number is 1.56·10¹³ for each pulse, with repetition rate of 25 Hz. In the RCS, longitudinal beam dynamics plays a crucial role in achieving high intensity beam with low beam loss. Longitudinal parameters are studied and optimized for efficient RF trapping of the beam in the longitudinal phase space. Beam performance is investigated by particle tracking simulations. Beam dynamic issues related to the high order mode induced by the RF generator are studied with a new developed code. Primary study on the adoption of dual harmonic cavity for higher beam power is also addressed.

WEO3B04	RFQ Beam Dynamics Design for Large Science Facilities and Accelerator-Driven Systems	rfq, proton, linac, ion	419
	C. Zhang IAP, Frankfurt am Main, Germany
	Serving as the front-end of large science facilities and Accelerator-Driven Systems (ADS), the Radio-Frequency Quadrupole (RFQ) accelerator usually needs to reach low beam losses, good beam quality, high reliability, and cost savings such design goals at high beam intensities. To address the challenges for modern RFQs, a special beam dynamics design technique characterized by a reasonable and efficient bunching process with balanced space-charge forces has been developed as an alternative to the classic Four-Section Procedure proposed by Los Alamos National Laboratory (LANL). In this paper, the design studies of some recent RFQ projects will be presented as examples.
	Slides WEO3B04 [3.698 MB]

THO1A03	Dual-harmonic Acceleration Studies at CSNS RCS	injection, acceleration, simulation, cavity	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]

THO1A04	High Intensity Longitudinal Dynamics Studies for an ISIS Injection Upgrade	injection, simulation, synchrotron, space-charge	492
	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. Recent upgrade studies at ISIS have centred on a new 180 MeV linac for injection into the existing ring offering the possibility of beam powers in the 0.5 MW regime through reduction in space charge and optimized injection. A central and critical aspect of such an upgrade is the longitudinal dynamics including beam stability, associated RF parameters, space charge levels and stringent requirements on beam loss. This paper outlines possible longitudinal injection schemes for the injection upgrade meeting key design requirements such as minimising halo, bunching factor and satisfying the Keil-Schnell-Boussard (KSB) stability criterion throughout acceleration. Details of simulation models including calculation of KSB are given together with associated assumptions. Latest results from studies to understand and confirm stability limits on ISIS via simulation and experiment are presented.
	Slides THO1A04 [2.641 MB]

THO3C02	Momentum Spread Determination of Linac Beams Using Incoherent Components of the Bunch Signals	cavity, linac, synchrotron, pick-up	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]

Paper

Title

Other Keywords

Page

MOP216

The Design Study on the Longitudinal Beam Dynamics for CSNS/RCS

injection, acceleration, simulation, space-charge

89

N. Wang, M.Y. Huang, Y. Li, S. Wang, S.Y. Xu, Y.S. Yuan
IHEP, Beijing, People's Republic of China

Rapid Cycling Synchrotron (RCS) is the key part of China Spallation Neutron Source (CSNS) accelerators. The RCS accumulates and accelerates 80 MeV beam from linac to 1.6 GeV. The particle number is 1.56·10¹³ for each pulse, with repetition rate of 25 Hz. In the RCS, longitudinal beam dynamics plays a crucial role in achieving high intensity beam with low beam loss. Longitudinal parameters are studied and optimized for efficient RF trapping of the beam in the longitudinal phase space. Beam performance is investigated by particle tracking simulations. Beam dynamic issues related to the high order mode induced by the RF generator are studied with a new developed code. Primary study on the adoption of dual harmonic cavity for higher beam power is also addressed.

WEO3B04

RFQ Beam Dynamics Design for Large Science Facilities and Accelerator-Driven Systems

rfq, proton, linac, ion

419

C. Zhang
IAP, Frankfurt am Main, Germany

Serving as the front-end of large science facilities and Accelerator-Driven Systems (ADS), the Radio-Frequency Quadrupole (RFQ) accelerator usually needs to reach low beam losses, good beam quality, high reliability, and cost savings such design goals at high beam intensities. To address the challenges for modern RFQs, a special beam dynamics design technique characterized by a reasonable and efficient bunching process with balanced space-charge forces has been developed as an alternative to the classic Four-Section Procedure proposed by Los Alamos National Laboratory (LANL). In this paper, the design studies of some recent RFQ projects will be presented as examples.

Slides WEO3B04 [3.698 MB]

THO1A03

Dual-harmonic Acceleration Studies at CSNS RCS

injection, acceleration, simulation, cavity

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]

THO1A04

High Intensity Longitudinal Dynamics Studies for an ISIS Injection Upgrade

injection, simulation, synchrotron, space-charge

492

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. Recent upgrade studies at ISIS have centred on a new 180 MeV linac for injection into the existing ring offering the possibility of beam powers in the 0.5 MW regime through reduction in space charge and optimized injection. A central and critical aspect of such an upgrade is the longitudinal dynamics including beam stability, associated RF parameters, space charge levels and stringent requirements on beam loss. This paper outlines possible longitudinal injection schemes for the injection upgrade meeting key design requirements such as minimising halo, bunching factor and satisfying the Keil-Schnell-Boussard (KSB) stability criterion throughout acceleration. Details of simulation models including calculation of KSB are given together with associated assumptions. Latest results from studies to understand and confirm stability limits on ISIS via simulation and experiment are presented.

Slides THO1A04 [2.641 MB]

THO3C02

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

cavity, linac, synchrotron, pick-up

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]