HB2012 - List of Keywords (synchrotron)

Paper	Title	Other Keywords	Page
MOI1B01	High Intensity Issues at FAIR	ion, emittance, heavy-ion, ion-source	11
	O.K. Kester GSI, Darmstadt, Germany O.K. Kester IAP, Frankfurt am Main, Germany
	Funding: Supported by the BMBF and Helmholtz International Center for FAIR The facility for antiproton and ion research - FAIR - will produce secondary beams of unprecedented intensities [1]. In order to produce such intense secondary beams and to provide intense beams for the CBM [2] and APPA [3] collaboration, primary heavy ion beams of highest intensities will be required. The main driver accelerator of FAIR will be the SIS100 synchrotron. The GSI heavy ion accelerator facility will be the injector of ion beams for SIS100. In order to reach the final intensities above 10¹¹ ions per cycle, the injector chain has to be modified accordingly and the SIS100 has to be tailored to the needs. Therefore an intensity upgrade program of the GSI accelerator facility has been started, which comprises improvements of ion sources, of the injector linacs and of the heavy ion synchrotron SIS18. In addition, high energy beam transport and the SIS100 need to have a dedicated design, in order to handle beam losses. The issues of the upgrade programme and of the SIS100 design will be addressed. [1] FAIR Green Paper- The Modularized Start Version, Oct.2009 [2] B.Friman et al.,The CBM physics Book, Series: Lecture Notes in Physics, Vol.814,2011 [3] http://www.fair-center.de/de/oeffentlichkeit/experimenteprogramm/appa-physics.html
	Slides MOI1B01 [15.662 MB]

MOP204	A Method to Measure the Incoherent Synchrotron Frequencies in Bunches	space-charge, simulation, dipole, injection	46
	O. Chorniy, H. Reeg GSI, Darmstadt, Germany
	The method of measuring the incoherent synchrotron frequencies in a stationary bunch is presented. It can be shown that by measuring the local current at a fixed coordinate in RF bucket the corresponding incoherent synchrotron frequency can be obtained. Test calculations were done using simulation data where longitudinal space charge effects were included. The incoherent frequencies obtained with method are in a good agreement with theory. In real experiment, the incoherent frequencies were determined from bunch profiles recorded in the SIS18 with low intensity beam at injection energy. Bunch profiles were measured with a new Fast Current Transformer which has a relatively broad frequency range. The profiles were recorded using 8 bit resolution oscilloscope. The frequency spectra of local current fluctuation at different longitudinal positions were obtained numerically. The strongest lines in these spectra were at positions of theoretically expected incoherent frequencies. In this paper the method is described in details, the comparison of incoherent frequencies obtained from the simulation and measurement data with theoretical solutions is shown.

MOP205	Intense Heavy-Ion Bunches in Dual-harmonic RF Systems	ion, impedance, factory, space-charge	51
	M. Mehler, O. Chorniy GSI, Darmstadt, Germany O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany O.K. Kester IAP, Frankfurt am Main, Germany
	For the synchrotron's SIS-18 and SIS-100 (FAIR) a dual-harmonic RF system with the harmonic numbers h1=2, h2=4 and h1=10, h2=20 respectively is planned. Such systems flatten the bunch form and increase the bunching factor Bf therefore reducing the transverse space charge force. For high currents cavity beam loading and potential-well distortion will deform the flattened bunch shape and lead to phase shifts. Optimized settings for the difference between the two RF phases and for the synchronous phase of the main RF harmonic are an option to reduce these effects. In this contribution we will analyse further aspects of the matched bunch distribution, possible instabilities of the obtained distribution will be discussed and results of machine experiments in SIS-18 will be presented.

MOP206	Numerical Calculation of Beam Coupling Impedances for the SIS-100 Synchrotron for FAIR	impedance, kicker, coupling, space-charge	54
	U. Niedermayer, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany
	The transverse impedance of kicker magnets is considered to be one of the main beam instability sources in the projected SIS-100 at FAIR and also in the SPS at CERN. The longitudinal impedance can contribute to the heat load, which is especially a concern in the cold sections of SIS-100 and LHC. In the high frequency range, time domain codes are commercially available to calculate the impedance but they become inapplicable at medium and low frequencies. We present the ongoing work of developing a Finite Integration (FIT) solver in frequency domain which is based on the Parallel and Extensible Toolkit for Scientific computing (PETSc) framework in C++. The code is applied to an inductive insert used to compensate the longitudinal space charge impedance in low energy machines. Another application focuses on the impedance contribution of a ferrite kicker with inductively coupled pulse forming network (PFN) and frequency dependent complex material permeability. In future we plan to confirm our simulations with dedicated wire or coil bench measurements.

MOP215	The Study on Measuring Beta Functions and Phase Advances in the CSNS/RCS	space-charge, kicker, betatron, lattice	85
	Y.W. An, S. Wang IHEP, Beijing, People's Republic of China
	As a key component of the China Spallation Neutron Source (CSNS) Project, the Rapid Cycling Synchrotron (RCS) will accumulate and accelerate the proton beams from 80 MeV to 1.6 GeV for extracting and striking the target with a repletion rate of 25 Hz. To check linear optics and locate the quadruple errors, beta function plays an important role in beam diagnostics of a particle accelerate system. The Independent Component Analysis (ICA) is a robust beam diagnosis method by decomposing the samples recorded by turn by turn BPMs (beam position monitors) into the independent components which represent the inherent motion of the beam. The beta functions and phase advances can be derived from the corresponding independent components. Because the linear part of the space charge gives a defocusing effect to the beam, beta function variation will be induced. We find that the ICA method can measure beta functions with a reasonable tolerance under the conditions of strong space charge effects.

MOP244	CERN High-Power Proton Synchrotron Design Study for LAGUNA-LBNO Neutrino Production	proton, linac, target, status	154
	R. Steerenberg, M. Benedikt, I. Efthymiopoulos, F. Gerigk, Y. Papaphilippou CERN, Geneva, Switzerland
	Within the framework of the LAGUNA-LBNO project, CERN has started design studies in view of producing neutrinos for future long base line neutrino experiments. These design studies foresee a staged approach in the increase of the primary proton beam power, used for the neutrino production. The first step consists of exploring the feasibility of a CERN SPS beam power upgrade from the existing 500 kW, presently available to CNGS, to 750 kW. This beam should then be transferred to a new to be built neutrino beam line that is dimensioned for a beam power of 2 MW. The 2 MW proton beam is to be provided at a subsequent stage by a 30 - 50 GeV High-Power Proton Synchrotron (HP-PS), which is a major part of the design studies. This paper will provide an overview of the project and then focus on the preliminary ideas for the HP-PS design study.

MOP252	Measurements of the LHC Longitudinal Resistive Impedance with Beam	impedance, electron, emittance, synchrotron-radiation	183
	J.F. Esteban Müller, T. Argyropoulos, T. Bohl, T. Mastoridis, N. Mounet, G. Papotti, B. Salvant, E.N. Shaposhnikova, D. Valuch CERN, Geneva, Switzerland
	The resistive part of the longitudinal impedance contributes to the heat deposition on different elements in the LHC ring including the beam screens, where it has to be absorbed by the cryogenic system and can be a practical limitation for the maximum beam intensity. In this paper, we present the first measurements of the LHC longitudinal resistive impedance with beam, done through synchronous phase shift measurements during Machine Development sessions in 2012. Synchronous phase shift is measured for different bunch intensities and lengths using the high-precision LHC Beam Phase Module and then data are post-processed to further increase the accuracy. The dependence of the energy loss per particle on bunch length is then obtained and compared with the expected values found using the LHC impedance model.

MOP257	Space Charge Limits on the ISIS Synchrotron including the Effects of Images	simulation, space-charge, resonance, injection	206
	B.G. Pine, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The ISIS synchrotron provides a pulsed, 50 Hz, 800 MeV proton beam for spallation neutron production. Each pulse from the synchrotron contains ~2.8×10¹³ ppp, and at this beam intensity space charge and image forces have a strong effect on transverse beam dynamics. In order to increase intensity in the present machine, and to prepare for possible upgrades running at a higher intensity, studies are under way aimed at understanding the most critical features of such forces and their impact on beam loss. These studies are focused on working point optimisation, including resonances due to space charge and images. A 2D simulation code, Set, has been developed to improve understanding of transverse dynamics at ISIS, using a particle-in-cell algorithm to include space charge and image forces self-consistently. The ISIS synchrotron has profiled vacuum vessels and RF shields which conform to the shape of the beam envelope, and have a distinctive influence on the beam dynamics. Set is specifically designed to include these image forces. A systematic simulation study of possible working points is presented, along with an assessment of the effect on apertures.

TUO1C05	Measurements and Interpretation of the Betatron Tune Spectra of High Intensity Bunched Beam at SIS-18	space-charge, ion, acceleration, injection	310
	R. Singh, O. Chorniy, P. Forck, R. Haseitl, W. Kaufmann, P. Kowina, K. Lang GSI, Darmstadt, Germany O. Boine-Frankenheim, R. Singh, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	The paper presents the status of the transverse tune measurements in the synchrotron SIS18 at GSI. Presently, there are two systems for tune measurements in operation in the SIS18, namely TOPOS (Tune, Orbit and POsition measurement System) and BBQ (Base Band tune measurement system). The first one is a digital system where the BPM signal is digitized and the bunch position is calculated numerically. The second system is an analog system, where the transverse bunch motion is detected using peak detector. Band limited noise and chirp excitations were used to excite the betatron oscillations. Measurements of the betatron tune spectra were done at injection energy at medium and high intensities. In the frequency spectra a number of peaks around the position of betatron tune were seen. The peaks can be attributed to different bunch head-tail modes which were observed in time domain. These modes were dependent on the beam intensity. In this paper we compare the tune spectra measured at high beam intensity with the theoretical model for the space charge affected head-tail modes.
	Slides TUO1C05 [1.315 MB]

WEO1A04	Longitudinal Instabilities in the SPS and Beam Dynamics Issues with High Harmonic RF Systems	emittance, beam-loading, damping, controls	358
	E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, J. Esteban Müller, H. Timko CERN, Geneva, Switzerland
	Even after a successful impedance reduction programme which eliminated the microwave instability in the SPS another longitudinal instability is still one of the main intensity limitations. It is observed during acceleration ramp for both single bunch and multibunch beams at intensities below the nominal LHC intensity. With the lower transition energy of the new SPS optics, under intensive studies now, the thresholds are increased. However, even in this case the operation of the 4th harmonic RF system is required for stability of the nominal beams. To cope with the higher intensity beams required for the future High Luminosity LHC an upgrade program for both RF systems is under way. The results of studies of the parameter space required for beam stability are presented and compared with operation modes of double RF systems in other accelerators.
	Slides WEO1A04 [6.135 MB]

WEO1C01	Effect of Self-consistency on Periodic Resonance Crossing	simulation, resonance, space-charge, ion	429
	G. Franchetti GSI, Darmstadt, Germany
	In high intensity bunched beams resonance crossing gives rise to emittance growth and beam loss. Both these effects build up after many synchrotron oscillations. Up to now long term modeling have relied on frozen models neglecting the physics of self-consistency. We address here this issue and present the state of the art of simulations also applied to the SIS100.
	Slides WEO1C01 [3.657 MB]

WEO1C02	Simulation and Measurement of Half Integer Resonance in Coasting Beams in the ISIS Ring	resonance, injection, simulation, space-charge	434
	C.M. Warsop, D.J. Adams, B. Jones, S.J. Payne, 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 a high intensity proton synchrotron, accelerating 3·10¹³ ppp from 70-800 MeV, at a repetition rate of 50 Hz. Present studies are looking at key aspects of high intensity behaviour with a view to increasing operational intensity, identifying optimal upgrade routes and understanding loss mechanisms. Of particular interest is the space charge limit imposed by half integer resonance: we present results from coasting beam experiments with the ISIS ring in storage ring mode, along with detailed 3D (ORBIT) simulations to help interpret observations. The methods for experimentally approaching resonance, and the implications on beam behaviour, measurement and interpretation are discussed. In addition, results from simpler 2D simulations and analytical models are used to help interpret expected beam loss and halo evolution. Plans and challenges for the measurement and understanding of this important beam loss mechanism are summarised, as are some closely related areas of high intensity work on ISIS.
	Slides WEO1C02 [2.224 MB]

WEO1C04	Acceleration of High-Intensity Protons in the J-PARC Synchrotrons	cavity, 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]

WEO3C01	Injection and Stripping Foil Studies for a 180 MeV Injection Upgrade at ISIS	injection, simulation, dipole, electron	456
	B. Jones, D.J. Adams, M.C. Hughes, S.J.S. Jago, B.G. Pine, H. V. Smith, C.M. Warsop, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The Rutherford Appleton Laboratory (RAL) is home to ISIS, the world's most productive spallation neutron source. ISIS has two neutron producing target stations (TS-1 and TS-2), operated at 40 Hz and 10 Hz respectively with a 50 Hz, 800 MeV proton beam from a rapid cycling synchrotron (RCS), which is fed by a 70 MeV H− drift tube linac. The multi-turn charge-exchange injection process used on ISIS has been the subject of a programme of detailed studies in recent years including benchmarked simulations and experiments. More recently, these studies have been expanded as plans for upgrading ISIS have focussed on replacement of the 70 MeV linac with a new, higher energy injector and a new synchrotron injection straight. Whilst much of these studies have been reported elsewhere, this paper presents a summary of the programme with some further details.
	Slides WEO3C01 [4.895 MB]

THO1A04	High Intensity Longitudinal Dynamics Studies for an ISIS Injection Upgrade	injection, simulation, bunching, 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]

THO1C02	Beam Loss Control in the ISIS Accelerator Facility	injection, controls, proton, acceleration	560
	D.J. Adams, B. Jones, A.H. Kershaw, S.J. Payne, B.G. Pine, H. V. Smith, C.M. Warsop, R.E. Williamson, M. Wright STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	The ISIS spallation neutron and muon source has been in operation since 1984. The accelerator complex consists of an H⁻ ion source, RFQ, 70 MeV linac, 800 MeV proton synchrotron and associated beam lines. The facility currently delivers ~2.8·10¹³ protons per pulse at 50 Hz, splitting the pulses 40/10 between two neutron target stations. High intensity performance and operation are dominated by the need to control beam loss, which is key to sustainable machine operation and hands on maintenance. Beam loss measurement systems on ISIS are described, along with typical operational levels. The dominant beam loss in the facility occurs in the synchrotron due to high intensity effects during the H⁻ injection and longitudinal trapping processes. These losses are localised in a single superperiod using a beam collector system. Emittance growth during acceleration also drives extraction and beam transport loss at 800 MeV. Measurements, simulation and correction systems for these processes are discussed, as are the implications for further intensity upgrades.
	Slides THO1C02 [4.759 MB]

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

Paper

Title

Other Keywords

Page

MOI1B01

High Intensity Issues at FAIR

ion, emittance, heavy-ion, ion-source

11

O.K. Kester
GSI, Darmstadt, Germany
O.K. Kester
IAP, Frankfurt am Main, Germany

Funding: Supported by the BMBF and Helmholtz International Center for FAIR
The facility for antiproton and ion research - FAIR - will produce secondary beams of unprecedented intensities [1]. In order to produce such intense secondary beams and to provide intense beams for the CBM [2] and APPA [3] collaboration, primary heavy ion beams of highest intensities will be required. The main driver accelerator of FAIR will be the SIS100 synchrotron. The GSI heavy ion accelerator facility will be the injector of ion beams for SIS100. In order to reach the final intensities above 10¹¹ ions per cycle, the injector chain has to be modified accordingly and the SIS100 has to be tailored to the needs. Therefore an intensity upgrade program of the GSI accelerator facility has been started, which comprises improvements of ion sources, of the injector linacs and of the heavy ion synchrotron SIS18. In addition, high energy beam transport and the SIS100 need to have a dedicated design, in order to handle beam losses. The issues of the upgrade programme and of the SIS100 design will be addressed.
[1] FAIR Green Paper- The Modularized Start Version, Oct.2009
[2] B.Friman et al.,The CBM physics Book, Series: Lecture Notes in Physics, Vol.814,2011
[3] http://www.fair-center.de/de/oeffentlichkeit/experimenteprogramm/appa-physics.html

Slides MOI1B01 [15.662 MB]

MOP204

A Method to Measure the Incoherent Synchrotron Frequencies in Bunches

space-charge, simulation, dipole, injection

46

O. Chorniy, H. Reeg
GSI, Darmstadt, Germany

The method of measuring the incoherent synchrotron frequencies in a stationary bunch is presented. It can be shown that by measuring the local current at a fixed coordinate in RF bucket the corresponding incoherent synchrotron frequency can be obtained. Test calculations were done using simulation data where longitudinal space charge effects were included. The incoherent frequencies obtained with method are in a good agreement with theory. In real experiment, the incoherent frequencies were determined from bunch profiles recorded in the SIS18 with low intensity beam at injection energy. Bunch profiles were measured with a new Fast Current Transformer which has a relatively broad frequency range. The profiles were recorded using 8 bit resolution oscilloscope. The frequency spectra of local current fluctuation at different longitudinal positions were obtained numerically. The strongest lines in these spectra were at positions of theoretically expected incoherent frequencies. In this paper the method is described in details, the comparison of incoherent frequencies obtained from the simulation and measurement data with theoretical solutions is shown.

MOP205

Intense Heavy-Ion Bunches in Dual-harmonic RF Systems

ion, impedance, factory, space-charge

51

M. Mehler, O. Chorniy
GSI, Darmstadt, Germany
O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
O.K. Kester
IAP, Frankfurt am Main, Germany

For the synchrotron's SIS-18 and SIS-100 (FAIR) a dual-harmonic RF system with the harmonic numbers h1=2, h2=4 and h1=10, h2=20 respectively is planned. Such systems flatten the bunch form and increase the bunching factor Bf therefore reducing the transverse space charge force. For high currents cavity beam loading and potential-well distortion will deform the flattened bunch shape and lead to phase shifts. Optimized settings for the difference between the two RF phases and for the synchronous phase of the main RF harmonic are an option to reduce these effects. In this contribution we will analyse further aspects of the matched bunch distribution, possible instabilities of the obtained distribution will be discussed and results of machine experiments in SIS-18 will be presented.

MOP206

Numerical Calculation of Beam Coupling Impedances for the SIS-100 Synchrotron for FAIR

impedance, kicker, coupling, space-charge

54

U. Niedermayer, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany

The transverse impedance of kicker magnets is considered to be one of the main beam instability sources in the projected SIS-100 at FAIR and also in the SPS at CERN. The longitudinal impedance can contribute to the heat load, which is especially a concern in the cold sections of SIS-100 and LHC. In the high frequency range, time domain codes are commercially available to calculate the impedance but they become inapplicable at medium and low frequencies. We present the ongoing work of developing a Finite Integration (FIT) solver in frequency domain which is based on the Parallel and Extensible Toolkit for Scientific computing (PETSc) framework in C++. The code is applied to an inductive insert used to compensate the longitudinal space charge impedance in low energy machines. Another application focuses on the impedance contribution of a ferrite kicker with inductively coupled pulse forming network (PFN) and frequency dependent complex material permeability. In future we plan to confirm our simulations with dedicated wire or coil bench measurements.

MOP215

The Study on Measuring Beta Functions and Phase Advances in the CSNS/RCS

space-charge, kicker, betatron, lattice

85

Y.W. An, S. Wang
IHEP, Beijing, People's Republic of China

As a key component of the China Spallation Neutron Source (CSNS) Project, the Rapid Cycling Synchrotron (RCS) will accumulate and accelerate the proton beams from 80 MeV to 1.6 GeV for extracting and striking the target with a repletion rate of 25 Hz. To check linear optics and locate the quadruple errors, beta function plays an important role in beam diagnostics of a particle accelerate system. The Independent Component Analysis (ICA) is a robust beam diagnosis method by decomposing the samples recorded by turn by turn BPMs (beam position monitors) into the independent components which represent the inherent motion of the beam. The beta functions and phase advances can be derived from the corresponding independent components. Because the linear part of the space charge gives a defocusing effect to the beam, beta function variation will be induced. We find that the ICA method can measure beta functions with a reasonable tolerance under the conditions of strong space charge effects.

MOP244

CERN High-Power Proton Synchrotron Design Study for LAGUNA-LBNO Neutrino Production

proton, linac, target, status

154

R. Steerenberg, M. Benedikt, I. Efthymiopoulos, F. Gerigk, Y. Papaphilippou
CERN, Geneva, Switzerland

Within the framework of the LAGUNA-LBNO project, CERN has started design studies in view of producing neutrinos for future long base line neutrino experiments. These design studies foresee a staged approach in the increase of the primary proton beam power, used for the neutrino production. The first step consists of exploring the feasibility of a CERN SPS beam power upgrade from the existing 500 kW, presently available to CNGS, to 750 kW. This beam should then be transferred to a new to be built neutrino beam line that is dimensioned for a beam power of 2 MW. The 2 MW proton beam is to be provided at a subsequent stage by a 30 - 50 GeV High-Power Proton Synchrotron (HP-PS), which is a major part of the design studies. This paper will provide an overview of the project and then focus on the preliminary ideas for the HP-PS design study.

MOP252

Measurements of the LHC Longitudinal Resistive Impedance with Beam

impedance, electron, emittance, synchrotron-radiation

183

J.F. Esteban Müller, T. Argyropoulos, T. Bohl, T. Mastoridis, N. Mounet, G. Papotti, B. Salvant, E.N. Shaposhnikova, D. Valuch
CERN, Geneva, Switzerland

The resistive part of the longitudinal impedance contributes to the heat deposition on different elements in the LHC ring including the beam screens, where it has to be absorbed by the cryogenic system and can be a practical limitation for the maximum beam intensity. In this paper, we present the first measurements of the LHC longitudinal resistive impedance with beam, done through synchronous phase shift measurements during Machine Development sessions in 2012. Synchronous phase shift is measured for different bunch intensities and lengths using the high-precision LHC Beam Phase Module and then data are post-processed to further increase the accuracy. The dependence of the energy loss per particle on bunch length is then obtained and compared with the expected values found using the LHC impedance model.

MOP257

Space Charge Limits on the ISIS Synchrotron including the Effects of Images

simulation, space-charge, resonance, injection

206

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

The ISIS synchrotron provides a pulsed, 50 Hz, 800 MeV proton beam for spallation neutron production. Each pulse from the synchrotron contains ~2.8×10¹³ ppp, and at this beam intensity space charge and image forces have a strong effect on transverse beam dynamics. In order to increase intensity in the present machine, and to prepare for possible upgrades running at a higher intensity, studies are under way aimed at understanding the most critical features of such forces and their impact on beam loss. These studies are focused on working point optimisation, including resonances due to space charge and images. A 2D simulation code, Set, has been developed to improve understanding of transverse dynamics at ISIS, using a particle-in-cell algorithm to include space charge and image forces self-consistently. The ISIS synchrotron has profiled vacuum vessels and RF shields which conform to the shape of the beam envelope, and have a distinctive influence on the beam dynamics. Set is specifically designed to include these image forces. A systematic simulation study of possible working points is presented, along with an assessment of the effect on apertures.

TUO1C05

Measurements and Interpretation of the Betatron Tune Spectra of High Intensity Bunched Beam at SIS-18

space-charge, ion, acceleration, injection

310

R. Singh, O. Chorniy, P. Forck, R. Haseitl, W. Kaufmann, P. Kowina, K. Lang
GSI, Darmstadt, Germany
O. Boine-Frankenheim, R. Singh, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

The paper presents the status of the transverse tune measurements in the synchrotron SIS18 at GSI. Presently, there are two systems for tune measurements in operation in the SIS18, namely TOPOS (Tune, Orbit and POsition measurement System) and BBQ (Base Band tune measurement system). The first one is a digital system where the BPM signal is digitized and the bunch position is calculated numerically. The second system is an analog system, where the transverse bunch motion is detected using peak detector. Band limited noise and chirp excitations were used to excite the betatron oscillations. Measurements of the betatron tune spectra were done at injection energy at medium and high intensities. In the frequency spectra a number of peaks around the position of betatron tune were seen. The peaks can be attributed to different bunch head-tail modes which were observed in time domain. These modes were dependent on the beam intensity. In this paper we compare the tune spectra measured at high beam intensity with the theoretical model for the space charge affected head-tail modes.

Slides TUO1C05 [1.315 MB]

WEO1A04

Longitudinal Instabilities in the SPS and Beam Dynamics Issues with High Harmonic RF Systems

emittance, beam-loading, damping, controls

358

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

Even after a successful impedance reduction programme which eliminated the microwave instability in the SPS another longitudinal instability is still one of the main intensity limitations. It is observed during acceleration ramp for both single bunch and multibunch beams at intensities below the nominal LHC intensity. With the lower transition energy of the new SPS optics, under intensive studies now, the thresholds are increased. However, even in this case the operation of the 4th harmonic RF system is required for stability of the nominal beams. To cope with the higher intensity beams required for the future High Luminosity LHC an upgrade program for both RF systems is under way. The results of studies of the parameter space required for beam stability are presented and compared with operation modes of double RF systems in other accelerators.

Slides WEO1A04 [6.135 MB]

WEO1C01

Effect of Self-consistency on Periodic Resonance Crossing

simulation, resonance, space-charge, ion

429

G. Franchetti
GSI, Darmstadt, Germany

In high intensity bunched beams resonance crossing gives rise to emittance growth and beam loss. Both these effects build up after many synchrotron oscillations. Up to now long term modeling have relied on frozen models neglecting the physics of self-consistency. We address here this issue and present the state of the art of simulations also applied to the SIS100.

Slides WEO1C01 [3.657 MB]

WEO1C02

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

resonance, injection, simulation, space-charge

434

C.M. Warsop, D.J. Adams, B. Jones, S.J. Payne, 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 a high intensity proton synchrotron, accelerating 3·10¹³ ppp from 70-800 MeV, at a repetition rate of 50 Hz. Present studies are looking at key aspects of high intensity behaviour with a view to increasing operational intensity, identifying optimal upgrade routes and understanding loss mechanisms. Of particular interest is the space charge limit imposed by half integer resonance: we present results from coasting beam experiments with the ISIS ring in storage ring mode, along with detailed 3D (ORBIT) simulations to help interpret observations. The methods for experimentally approaching resonance, and the implications on beam behaviour, measurement and interpretation are discussed. In addition, results from simpler 2D simulations and analytical models are used to help interpret expected beam loss and halo evolution. Plans and challenges for the measurement and understanding of this important beam loss mechanism are summarised, as are some closely related areas of high intensity work on ISIS.

Slides WEO1C02 [2.224 MB]

WEO1C04

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

cavity, 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]

WEO3C01

Injection and Stripping Foil Studies for a 180 MeV Injection Upgrade at ISIS

injection, simulation, dipole, electron

456

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

The Rutherford Appleton Laboratory (RAL) is home to ISIS, the world's most productive spallation neutron source. ISIS has two neutron producing target stations (TS-1 and TS-2), operated at 40 Hz and 10 Hz respectively with a 50 Hz, 800 MeV proton beam from a rapid cycling synchrotron (RCS), which is fed by a 70 MeV H− drift tube linac. The multi-turn charge-exchange injection process used on ISIS has been the subject of a programme of detailed studies in recent years including benchmarked simulations and experiments. More recently, these studies have been expanded as plans for upgrading ISIS have focussed on replacement of the 70 MeV linac with a new, higher energy injector and a new synchrotron injection straight. Whilst much of these studies have been reported elsewhere, this paper presents a summary of the programme with some further details.

Slides WEO3C01 [4.895 MB]

THO1A04

High Intensity Longitudinal Dynamics Studies for an ISIS Injection Upgrade

injection, simulation, bunching, 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]

THO1C02

Beam Loss Control in the ISIS Accelerator Facility

injection, controls, proton, acceleration

560

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

The ISIS spallation neutron and muon source has been in operation since 1984. The accelerator complex consists of an H⁻ ion source, RFQ, 70 MeV linac, 800 MeV proton synchrotron and associated beam lines. The facility currently delivers ~2.8·10¹³ protons per pulse at 50 Hz, splitting the pulses 40/10 between two neutron target stations. High intensity performance and operation are dominated by the need to control beam loss, which is key to sustainable machine operation and hands on maintenance. Beam loss measurement systems on ISIS are described, along with typical operational levels. The dominant beam loss in the facility occurs in the synchrotron due to high intensity effects during the H⁻ injection and longitudinal trapping processes. These losses are localised in a single superperiod using a beam collector system. Emittance growth during acceleration also drives extraction and beam transport loss at 800 MeV. Measurements, simulation and correction systems for these processes are discussed, as are the implications for further intensity upgrades.

Slides THO1C02 [4.759 MB]

THO3C02

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

cavity, linac, 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]