H. Harada, N. Hayashi, M. Kinsho, K. Okabe, P.K. Saha, Y. Shobuda, F. Tamura, K. Yamamoto, M. Yamamoto, M. Yoshimoto
JAEA/J-PARC, Tokai-mura, Japan
The J-PARC RCS have recently established a 1 MW beam operation with low fractional beam loss of the order of 10-3. In this talk, our approaches to beam loss issues that we faced in the course of beam power ramp-up are reviewed. Our recent efforts to further beam power ramp-up beyond 1 MW are also presented.
T.V. Gorlov, J.A. Holmes
ORNL, Oak Ridge, Tennessee, USA
A self-consistent beam maintains linear space charge forces under any linear transport, even with the inclusion of space charge in the dynamics. Simulation indicates that it is possible to approximate certain self-consistent distributions in a ring with the use of phase space painting. We focus on the so-called Danilov distribution, which is a uniform density, rotating, elliptical distribution in the transverse plane and a coasting beam in the longitudinal plane. Painting the beam requires measurement and control of the orbit at the injection point, and measuring the beam requires re- construction of the four-dimensional (4D) transverse phase space. We discuss efforts to meet these requirements in the Spallation Neutron Source (SNS) ring.
C.M. Bhat, S. Chaurize, P. Derwent, M.W. Domeier, V.M. Grzelak, W. Pellico, J. Reid, B.A. Schupbach, C.-Y. Tan, A.K. Triplett
Fermilab, Batavia, Illinois, USA
Funding:This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The Fermilab Booster is the oldest RCS in operation in the world. In current operations, it accelerates ~4.5E12ppp to 8 GeV at 15 Hz and will be upgraded to >6.7E12ppp at 20 Hz in the PIP-II era. Booster has 22 RF cavities with each capable of providing ~50 kV. These cavities are divided into two groups: A & B. In the tunnel, the cavities are cavities are placed in a BA, AB, ¿ sequence. At injection, A & B cavities have anti-parallel RF phase which results in a net zero RF voltage on the beam. During beam capture, the RF voltage is increased adiabatically by decreasing the relative phase between them. At the end of beam capture, the feedback is turned on for beam acceleration. It is vital that for current operations and in the PIP-II era that these cavities are properly matched in both magnitude and phase to preserve the longitudinal emittance during the early part of the beam cycle and to offer full RF voltage on the beam. In this paper we describe the how the cavities are distributed and how the phases are measured with beam and then corrected and balanced. Data with high intensity beam capture is also presented.
F. Asvesta, S.C.P. Albright, F. Antoniou, H. Bartosik, C. Bracco, G.P. Di Giovanni, E.H. Maclean, B. Mikulec, T. Prebibaj, E. Renner
CERN, Geneva, Switzerland
Resonance studies have been conducted during the recommissioning of the CERN Proton Synchrotron Booster (PSB) following the implementation of the LHC Injectors Upgrade (LIU) project. In particular, resonance identification through so-called loss maps has been applied on all four rings of the PSB, revealing various resonances up to fourth order. In a second step, compensation schemes for the observed resonances were developed using a combination of analytical methods, experimental data and machine learning tools. These resonance compensation schemes have been deployed in operation to minimize losses for reaching high intensity and high brightness, thereby achieving the target brightness for the LHC-type beams.
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C. Zannini, H. Bartosik, M. Carlà, K.S.B. Li, E. Métral, G. Rumolo, B. Salvant
CERN, Geneva, Switzerland
L.R. Carver
ESRF, Grenoble, France
M. Schenk
EPFL, Lausanne, Switzerland
At the end of 2018, an instability with multiple bunches has been consistently observed during high intensity studies at the CERN-SPS. This instability could be a significant limitation to achieve the bunch intensity expected after the LHC Injector Upgrade (LIU). Therefore, a deep understanding of the phenomena is essential to identify the best mitigation strategy. Extensive simulation studies have been performed to explore the consistency of the current SPS model, give a possible interpretation of the instability mechanism and outline some possible cures.
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F. Antoniou, F. Asvesta, H. Bartosik, J.F. Comblin, G.P. Di Giovanni, M. Hostettler, A. Huschauer, B. Mikulec, J.-M. Nonglaton, T. Prebibaj
CERN, Meyrin, Switzerland
The CERN PS Booster (PSB) has gone through major upgrades during the Long Shutdown 2 (LS2) and the recommissioning with beam started in December 2020. Two of the aspects leading to improved operation will be described in this paper: a new tune control implementation; and a full re-alignment campaign. The operation of the PSB requires a large range of working points to be accessible along the acceleration cycle. As part of the LIU project, the PSB main power supply was upgraded to raise the extraction energy from 1.4 GeV to 2 GeV, in order to improve the brightness reach of the downstream machines. A new tune control implementation was necessary to take into account saturation effects of the bending magnets and the reconfiguration of the main circuits, as well as the additional complexity of the new H⁻ charge exchange injection. The first part of the paper describes the implementation of the new tune control and its experimental verification and optimization. The second part describes the results of the PSB alignment campaign after LS2, giving emphasis to the method developed to perform a combined closed orbit correction through quadrupole alignments.
T. Prebibaj, S.C.P. Albright, F. Antoniou, F. Asvesta, H. Bartosik, C. Bracco, G.P. Di Giovanni, E.H. Maclean, B. Mikulec, E. Renner
CERN, Meyrin, Switzerland
T. Prebibaj
IAP, Frankfurt am Main, Germany
In the context of the LHC Injectors Upgrade Project (LIU), the Proton Synchrotron Booster (PSB) developed an H⁻ charge exchange injection system. The four short rectangular dipoles of the injection chicane induce focusing errors through edge focusing and Eddy currents. These errors excite the half-integer resonance 2Qy = 9 and cause a dynamically changing beta-beating in the first milliseconds after injection. Using the beta-beating at the positions of two individually powered quadrupoles, measured with k-modulation, correction functions based on a model response matrix have been calculated and applied. Minimizing the beta-beating at injection allows the machine to be operated with betatron tunes closer to the half-integer resonance and therefore with larger space charge tune spreads. In this contribution the results of the beta-beating compensation studies and the impact on the achievable beam brightness limit of the machine are presented.
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E. Renner, S.C.P. Albright, F. Antoniou, F. Asvesta, H. Bartosik, C. Bracco, G.P. Di Giovanni, B. Mikulec, T. Prebibaj, F.M. Velotti
CERN, Meyrin, Switzerland
A major aspect of the LHC Injectors Upgrade (LIU) project at CERN is the Proton Synchrotron Booster (PSB) connection to the newly built Linac4 and the related installation of a new 160 MeV H⁻ charge exchange injection. This contribution presents the first operational experience with the new injection system and its flexibility of applying horizontal phase space painting to tailor different beams to the respective user-defined brightness targets. The presented measurement and multi-particle simulation results focus on the optimisation of the required transverse injection settings to reduce losses when producing high-intensity beams, i.e. for the ISOLDE experiment. In this context, feasibility studies towards applying numerical optimisation algorithms for improving and efficiently adapting the respective injection settings online are presented.
C.M. Bhat, N. Eddy
Fermilab, Batavia, Illinois, USA
Funding:This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The Fermilab Booster is an RCS with h=84 and gammaT =5.47 and, during standard operation it accelerates ~4.5E12ppBc from 400 MeV to 8 GeV at 15 Hz. The Booster is being upgraded to handle higher beam intensity >6.7E12ppBc and repetition rate of 20Hz. In the current mode of operation, we perform multi-turn beam injection and capture beam in h=84 system adiabatically. However, we have observed coupled bunch (CB) instabilities in the extracted beam. This issue is expected to worsen at higher beam intensities. In principle, for h=84 one expects 41 modes of oscillations contributing to these CB instabilities. Currently, we have a digital mode damper to mitigate prominent CB modes [1]. We would like to understand at what time in the beam cycle a particular mode is going to originate and how much it contributes at a different time of the cycle. In this regard, we have collected wall current monitor data from injection to extraction and looked for the start of a particular mode of CB instability and its growth for different intensities. This paper presents the results from this study and future plans to mitigate the CB instability in Booster. [1] Nathan Eddy (private communications, 2020).
Funding:This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The SNS accelerator consist of a 1 GeV H⁻ linac and an accumulator ring producing a 1.4 MW pulsed proton beam which drives a spallation neutron source. The Proton Power Upgrade project will double the power capability from 1.4 to 2.8 MW by increasing the linac energy 30% and the beam current about 50%. Equipment upgrades include new superconducting RF cryomodules and supporting RF equipment, upgraded ring equipment, and upgraded high power target systems. An important aspect of the upgrade is a gradual power ramp-up starting in 2022 in which new equipment is installed during maintenance outages as it arrives.
Funding:SNS is managed by UT-Battelle, LLC, under contract DE- AC05-00OR22725 for the U.S. Department of Energy. The Spallation Neutron Source (SNS) uses 300-400μ g/cm2 nanocrystalline diamond foils grown in-house at the Center for Nanophase Materials Sciences to facilitate charge exchange injection (CEI) from the 1 GeV H⁻ linac into the 248~m circumference accumulation ring. These foils have performed exceptionally well with lifetimes of thousands of MW·hrs. This contribution shares some experience with the operation of these foils during 1.4 MW operation, and discusses current operational concerns including injection related losses, foil conditioning, deformation, and sublimation due to high temperatures. The implications for the SNS Proton Power Upgrade are also discussed.
M.Y. Huang, S. Wang, S.Y. Xu
IHEP, Beijing, People’s Republic of China
Funding:Work supported by National Natural Science Foundation of China (Project Nos. 12075134 and U1832210 ) In this paper, firstly, the beam commissioning of the injection system for CSNS/RCS will be studied, including: timing adjustment of the injection pulse powers, injection beam parameter matching, calibration of the injection painting bumps, measurement of the painting distribution, injection method adjustment, application of the main stripping foil, optimization of the injection beam loss and radiation dose, etc. Secondly, the painting methods for the CSNS/RCS will be studied, including: the fixed-point injection method, anti-correlated painting method and correlated painting method. The results of the beam commissioning will be compared with the simulation results. Combining with other precise optimizations, the beam power on the target has successfully reached the design value of 100kW and the stable operation of the accelerator has been achieved.
