Status and Plans for the Upgrade of the CERN PS Booster
K. Hanke, LIU-PSB WP Holders
CERN’s Proton Synchrotron Booster (PSB) is undergoing a massive upgrade program in the frame of
the LHC Injectors Upgrade (LIU) project. During the first long LHC shutdown (LS1) some parts of the
upgrade have already been implemented, and the machine has been successfully re-commissioned.
More work is planned for the upcoming technical stops, notably in 2016/17, while most of the
upgrade is planned to take place during the second long LHC shutdown (LS2). We report on the
upgrade items already completed and commissioned, the first Run 2 beam performance and give a
status of the ongoing design and integration work.
Beam tests using a wide band RF system prototype in the CERN PS Booster
M.M. Paoluzzi, M.E. Angoletta, A.J. Findlay, M. Haase, M. Jaussi, A. Jones, J.Molendijk
Abstract: In the framework of the LHC Injectors Upgrade project (LIU) and in view of a complete
replacement of the existing CERN PS Booster (PSB) RF systems, a small scale, wide band prototype
cavity was installed in 2012 in the machine. Following the encouraging tests done using that limited
device, an almost full scale, RF system prototype has been built and installed in the PSB during the
Long Shutdown 1 (LS1). This modular, Finemet® loaded system covers the band 0.5 ÷ 4 MHz
corresponding to the h=1 and h=2 frequency ranges. It uses solidstate power stages and includes
fast RF feedback for beam loading compensation. New dedicated digital low level electronics
implement all loops required for beam acceleration and interfaces with the general PSB control
system. It allows using the new equipment at fundamental or second harmonic of the beam
revolution frequency as well as operating it in parallel with the existing RF systems. This paper
describes the low level and power sections of the project and reports about the achieved results and
experience built up so far.
Emittance measurements for future LHC beams using the PS Booster measurement line
J.L. Abelleira, W. Bartmann, G.P. Di Giovanni, K. Hanke, B. Mikulec.
The CERN PS Booster measurement line contains three pairs of SEM grids separated by drift space
that measure the beam size in both planes. The combined analysis of these grids allows calculating a
value for the transverse beam emittances. The precision of such a measurement depends on the
ratio of rms beam size and wire spacing. Within the LIU-PSB upgrade the extraction energy of the
PSB will be increased from currently 1.4 GeV to 2 GeV. This will result in smaller transverse beam
sizes for certain future beams. In this paper comparative measurements will be presented between
wire scanner measurements performed in the PSB rings before extraction and the SEM grid
measurements. Systematic errors will be evaluated, and it will be analysed if the present layout of
the transverse emittance measurement line will satisfy future requirements.
Transverse impedance model of the CERN-PSB
C. Zannini, B. Jones, K. Li, G. Rumolo
In the framework of the PS-Booster upgrade project an accurate impedance model is needed in
order to determine the effect on the beam stability and assess the impact of the new devices before
installation in the machine. This paper describes the PSB impedance model which includes resistive
wall, indirect space charge, flanges, step transitions, ejection kicker including cables, injection kickers
and cavities. Each impedance contribution has been computed for different energies in the PSB
cycle. Measurements of the coherent tune shifts have been performed and compared to calculations
based on the impedance model.
Longitudinal Injection Schemes For the CERN PS Booster at 160 MeV Including Space Charge
Effects
V. Forte (CERN and Universite’ Blaise Pascal, Clermont-Ferrand, France), E. Benedetto, A. Lombardi
(CERN)
In the framework of the LHC Injectors Upgrade (LIU) project, the CERN PS Booster will be upgraded
to the injection energy of 160 MeV after the connection with Linac4. A multi-turn H- charge
exchange injection is foreseen to tailor the initial beam profiles, both in the transverse and in the
longitudinal plane. We are here reviewing in details the different longitudinal schemes, from the
beam dynamics point of view, taking into account the needs of the large variety of the PS Booster
users, spanning in intensity from 5e9 to about 1.6e13 protons per bunch.
The baseline of the longitudinal injection has always been the longitudinal stacking with central
energy modulation: this scheme has the advantage of filling uniformly the RF bucket, and mitigate
transverse space charge, but it requires at least 40 turns of injection. A simpler injection protocol
(without energy modulation) is here also analysed more in detail to find the optimum initial
conditions in terms of bucket filling and reduction of transverse and longitudinal space charge
effects, with the advantage of minimizing the number of turns for the low intensity beams (i.e. for
the LHC). Simulations with space charge of the longitudinal capture process from different Linac4
trains are presented in this paper to fix different possible longitudinal injection scenarios during the
future commissioning and operation with Linac4.
Chromaticity Effects for Space Charge Dominated Beams in the CERN PS Booster
V. Forte (CERN and Universite’ Blaise Pascal, Clermont-Ferrand, France), E. Benedetto, F. Schmidt
(CERN)
In the prospect of the LHC Injectors Upgrade (LIU) project, an extensive campaign is on-going in the
CERN PS Booster to study collective effects for the future operation with the 160 MeV injection from
the Linac4. In operation, the machine is running with natural chromaticity. This paper focuses on the
study of the effects of chromaticity on losses and beam blow-up.
Measurement of Resonance Driving Terms in the CERN PS Booster Using AC Dipole
M. McAteer, J. Belleman, C. Carli, M. Gasior, B. Mikulec, R. Tomas
In order to ensure that the CERN PS Booster will be able to deliver the higher-intensity beams
required for high-luminosity LHC operation while adhering to strict limits on beam loss and
emittance growth, both linear and nonlinear optics will have to be well-understood and controlled.
For this purpose, a campaign has been undertaken to characterize resonance driving terms from
analysis of turn-by-turn trajectories with driven coherent transverse oscillations. This paper presents
the results of these measurements.
Orbit Correction in the CERN PS Booster
M. McAteer, E. Benedetto, C. Carli, G.P. Di Giovanni, B. Mikulec, R. Tomas
Prior to the Long Shutdown of 2013-2014, control of the closed orbit in the four rings of the CERN PS
Booster was achieved by adjusting the alignment of several focusing quadrupoles. Orbit corrector
magnets are now available, which made it possible to remove the intentional quadrupole magnet
misalignments and control the closed orbit using only the corrector dipoles. This paper summarizes
the results of measurements and simulations of closed orbit correction in the PSB.
CERN PS Booster Upgrade and LHC beams emittance
E. Benedetto, Chiara Bracco; Jose Abelleira; Bettina Mikulec; Giovanni Rumolo; Vincenzo Forte
By increasing the CERN PS Booster injection energy from 50 MeV to 160 MeV, the LHC Injector
Upgrade Project aims at producing twice as brighter beams for the LHC. Previous measurements
showed a linear dependence of the transverse emittance with the beam intensity and space-charge
simulations confirmed the linear scaling. This paper is discussing in details the curve dependence on
the longitudinal emittance and on the choice of the working point, with a special attention to the Hinjection process and to the beam dynamics in the first 5ms, during the fall of the injection chicane
bump.
New shaving scheme for low-intensity beams in the CERN PS Booster and feasibility at 160 MeV
M. Kowalska (CERN, Geneva, Switzerland, EPFL, Lausanne, Switzerland), E. Benedetto, B. Mikulec, G.
Rumolo (CERN, Geneva, Switzerland)
The PS Booster is the first synchrotron in the CERN proton accelerator chain, serving all downstream
machines. As part of the LHC Injector Upgrade Project, the PSB injection energy will increase from 50
MeV to 160 MeV and a new H- charge-exchange injection scheme will be implemented. Beam losses
are a concern due to the increased injection energy, and mitigation scenarios are under
investigation.
On the other hand it is desirable for low-intensity beams to have the possibility to precisely tailor
sub-micron beam emittances through controlled scraping (transverse shaving process) towards a
suitable aperture restriction. Challenges are the higher activation potential of the beam and the
smaller transverse beam sizes around 160 MeV as compared to 63 MeV, at which the shaving is
presently done.
This paper describes the proposal of a new shaving scheme, more robust with respect to the
steering errors and the choice of the working point, which localizes the scraping losses on the main
PS Booster aperture restriction. The robustness of the new method, together with the results of
simulations and measurements are discussed for the current (50 MeV) and future (160 MeV)
situation.