Higher Order Modes (HOMs) can severely limit the operation of superconducting cavities in a linac... more Higher Order Modes (HOMs) can severely limit the operation of superconducting cavities in a linac with high beam current, high duty factor and complex pulse structure. The full HOM spectrum has to be analyzed in order to identify potentially dangerous modes already during the design phase and to define their damping requirements. For this purpose a dedicated beam simulation code focused on beam-HOMinteraction was developed, taking into account important effects like the HOMfrequency spread, beam input jitter, different chopping patterns, as well as klystron and alignment errors. Here, the code is used to investigate in detail the HOM properties of the cavities foreseen in the Superconducting Proton Linac (SPL) at CERN and their potential to drive beam instabilities. Special attention is given to HOM excitation by chopped pulses with high repetition rate.
PIMS—A simple and robust accelerating structure for high intensity proton Linacs
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009
UK Neutrino Factory Collaboration Progress report number 2
Citeseer
... the proton-driver front-end test stand was laid by Dr. D. Findlay who was work-package-2 mana... more ... the proton-driver front-end test stand was laid by Dr. D. Findlay who was work-package-2 manager until Mr. A. Letchford took over ... Although a low frequency (ideally suited to the 4-rod type of RFQ) was initially thought preferable, questions remained over its suitability for generic ...
Linac4 is employing three types of accelerating structures after the RFQ: a Drift Tube Linac (DTL... more Linac4 is employing three types of accelerating structures after the RFQ: a Drift Tube Linac (DTL), a Cell- Coupled DTL (CCDTL), and a Pi-Mode Structure (PIMS) to accelerate the beam up to 160 MeV at 352.2MHz. The structures are designed for a peak power of approximately 1 MW per power coupler, which is transported via rectangular waveguides from the klystron
The Superconducting Proton Linac (SPL) at CERN is part of the planned injector upgrade of the LHC... more The Superconducting Proton Linac (SPL) at CERN is part of the planned injector upgrade of the LHC. Initially used at low duty cycle as LHC injector it has the potential to be upgraded as a high power proton driver for neutrino physics and/or radioactive ion beams. In this paper the influence of the beam parameters on the build-up of Higher
The pulse structure of proton linacs is determined by the linac energy, the RF system, and the ma... more The pulse structure of proton linacs is determined by the linac energy, the RF system, and the maximum duty cycle of the source. Short bursts of protons in the microsecond range can be achieved by adding an accumulator ring and a reduction of the bunch length to the order of nanoseconds can be accomplished with an additional bunch compressor ring.
The SPL (Superconducting Proton Linac) study at CERN foresees the construction of a 2.2 GeV linac... more The SPL (Superconducting Proton Linac) study at CERN foresees the construction of a 2.2 GeV linac as a high beam-power driver for applications such as a second-generation radioactive ion beam facility or a neutrino superbeam. At the same time such a high-performance injector would both modernize and improve the LHC injection chain. The 120 MeV normal-conducting section of the SPL
The ultimate luminosity (2.3 × 10 34 cm −2 s −1 ) in the LHC can only be reached or even exceeded... more The ultimate luminosity (2.3 × 10 34 cm −2 s −1 ) in the LHC can only be reached or even exceeded if a major upgrade of the CERN proton injector complex takes place. The first identified bottleneck towards higher brightness beams is the 50 MeV proton injection of Linac2 into the PS booster (PSB). Doubling the intensity in the PSB can be achieved with a new linac (Linac4), which increases the injection energy to 160 MeV. Linac4 will provide H − ions and use charge-exchange injection into the PSB instead of the present multi-turn injection. We present the current status of simulations with ACCSIM, ORBIT, and ESME for all three planes. We use different initial distributions, compare the results of ACCSIM and ORBIT and highlight their differences.
Linac4 is a normal conducting H- linac proposed at CERN to provide a higher proton flux to the CE... more Linac4 is a normal conducting H- linac proposed at CERN to provide a higher proton flux to the CERN accelerator chain. It should replace the existing Linac2 as injector for the PS booster (PSB). The same machine can also operate in the future as the front end of the SPL, a 2.2 GeV superconducting linac with 1.8 mA average current.
We present a summary of simulation results on a muon cooling experiment based on 88MHz cavities. ... more We present a summary of simulation results on a muon cooling experiment based on 88MHz cavities. The systems studied are subsections of the cooling channel in the CERN reference scheme for a neutrino factory. We present two different set-ups using 8 and 4 cavities. For each of these channels we have carried out a beam dynamics study based on engineering
The construction of the Large Hadron Collider at CERN is in its final phase, and commissioning wi... more The construction of the Large Hadron Collider at CERN is in its final phase, and commissioning with beam is scheduled to begin before the end of 2007. It is now time to prepare for increasing as much as possible the performance of this unique instrument to maximize the benefits for physics. An essential part of the proposed luminosity upgrade plan is the replacement of the CERN PS and its injectors by a 50 GeV proton synchrotron (PS2) and a 4 GeV superconducting linac (SPL). The design of the SPL has recently been updated and the optimization of its high-energy part will continue until ~2010. For the foreseen luminosity upgrade of the LHC a low-power version of the SPL (LP-SPL) is under study, which can be upgraded to a multi-megawatt machine providing beam to high-power proton users such as neutrino facilities and/or radio-active beam facilities. The construction start of the low-energy normal conducting SPL front-end, the 160 MeV "Linac4", is scheduled for January 2008, ...
PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268), 2001
The SPL working group at CERN is studying a 2.2 GeV Hlinac, which recuperates a large amount of R... more The SPL working group at CERN is studying a 2.2 GeV Hlinac, which recuperates a large amount of RF hardware from the now decommissioned LEP at CERN. During the ongoing design effort for an optimized layout, it was found that in some cases non-equipartitioned beams tend to exchange energy between the longitudinal and the transverse planes. Strict energy equipartition, however, imposes tight restrictions on such a high energy linac and often contradicts the goal of cost effective design. On the other hand, stability charts derived from 2D Vlasov analysis suggest the existence of stable non-equipartitioned equilibria in certain regions of parameter space. Due to the low bunch current (22 mA) in the SPL, these regions are large enough to ensure stable machine operation for nonequipartitioned beams. Systematic multiparticle simulations with IMPACT [2] are used to apply the stability charts to the beam dynamics design of a realistic high energy linac. Using the example of the SPL, it is shown that designs with stable non-equipartitioned bunches are feasible, and how these designs react to mismatched input beams.
The ultimate luminosity (2.3 x 10<sup>34</sup> cm<sup>-2</sup> s<sup&g... more The ultimate luminosity (2.3 x 10<sup>34</sup> cm<sup>-2</sup> s<sup>-1</sup>) in the LHC can only be reached or even exceeded if a major upgrade of the CERN proton injector complex takes place. The first identified bottleneck towards higher brightness beams is the 50 MeV proton injection of Linac2 into the PS booster (PSB). Doubling the intensity in the PSB can be achieved
An analysis of the revised physics needs and recent progress in the technology of superconducting... more An analysis of the revised physics needs and recent progress in the technology of superconducting RF cavities have led to major changes in the specification and in the design for a Superconducting Proton Linac (SPL) at CERN. Compared with the first conceptual design report (CERN 2000-012) the beam energy is almost doubled (3.5 GeV instead of 2.2 GeV), while the length of the linac is reduced by 40% and the repetition rate is reduced to 50 Hz. The basic beam power is at a level of 4-5 MW and the approach chosen offers enough margins for upgrades. With this high beam power, the SPL can be the proton driver for an ISOL-type radioactive ion beam facility of the next generation ('EURISOL'), and for a neutrino facility based on superbeam C beta-beam or on muon decay in a storage ring ('neutrino factory'). The SPL can also replace the Linac2 and PS Booster in the low-energy part of the CERN proton accelerator complex, improving significantly the beam performance in terms of brightness and intensity for the benefit of all users including the LHC and its luminosity upgrade. Decommissioned LEP klystrons and RF equipment are used to provide RF power at a frequency of 352.2 MHz in the lowenergy part of the accelerator. Beyond 90 MeV, the RF frequency is doubled to take advantage of more compact normal-conducting accelerating structures up to an energy of 180 MeV. From there, state-ofthe-art, high-gradient, bulk-niobium superconducting cavities accelerate the beam up to its final energy of 3.5 GeV. The overall design approach is presented, together with the progress that has been achieved since the publication of the first conceptual design report.
The design of the Drift Tube Linac (DTL) for the new linear accelerator Linac4 at CERN has been m... more The design of the Drift Tube Linac (DTL) for the new linear accelerator Linac4 at CERN has been made ready for production: H --ion beams of up to 40 mA average pulse current are to be accelerated from 3 to 50 MeV by three RF cavities operating at 352.2 MHz and at duty cycles of up to 10%. In order to provide a margin for longitudinal matching from the chopper line, the longitudinal acceptance has been increased. The synchronous phase starts at -35 deg in Tank1 and ramps linearly to -24 deg over the tank while it went from -30 to -20 deg in the previous design. The accelerating gradient has been reduced to 3.1 MV/m in Tank1 and increased to 3.3 MV/m in Tank2 and Tank3 for a better distribution of RF power between tanks that is compatible with a mechanical design. To make the transverse acceptance less sensitive to alignment and gradient errors, the focusing scheme is now FFDD over all 3 tanks. Design features that were demonstrated in earlier reports have been improved for series production. Results of high power RF tests of the DTL prototype equipped with permanent magnet quadrupoles (PMQs) are reported that test the voltage holding in the first gaps in presence of magnetic fields.
The PIMS (Pi-Mode-Structure) cavities for Linac4 are made of 7 coupled cells operating in !-mode ... more The PIMS (Pi-Mode-Structure) cavities for Linac4 are made of 7 coupled cells operating in !-mode at a frequency of 352 MHz. The mechanical concept is derived from the 5-cell cavities used in the LEP machine, whereas cell length and coupling are adapted for proton acceleration in the range from 50 to 160 MeV. Linac4 will be the first machine to employ this type of cavities for low-beta protons. During the first years of operation the PIMS will be used at low duty cycle (0.1%) as part of the consolidated LHC proton injector complex. It is designed, however, to operate eventually in a high duty cycle (10%) proton injector, which could be used as proton front-end for neutrino or RIB applications. To prepare for the series construction of the 12 PIMS units the first cavity (102 MeV beam energy) has been designed and constructed at CERN, to be used as a hot prototype for RF tests and as a pre-series mechanical unit. In this paper we report on some of the design features, the construction ...
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Papers by F. Gerigk