M. Vretenar

Conceptual design of the SPL II : A high-power superconducting

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.

H^-

The Neutrino Factory is a new concept for an accelerator that produces a high-intensity, high-energy beam of electron and muon neutrinos – the ultimate tool for neutrino oscillation studies and the only machine conceived up today that could help detect CP violation of leptons. The basic concept of the Neutrino Factory is the production of neutrinos from the decay of high-energy muons. Due to their short lifetime, these muons have to be accelerated very fast. Several new accelerator techniques, like a high-intenstiy proton linac, high-power targets, ionization cooling or recirculating muon linacs are required. This paper presents a snapshot of the accelerator design at CERN. Although some aspects of this European Neutrino Factory Scheme have been optimised for the CERN site, the basic principle is siteindependent.

linac at CERN

The main upgrades of the injector chain in the framework of the LIU Project will only be implemented in the second long shutdown (LS2), in particular the increase of the PSB-PS transfer energy to 2GeV or the implementation of cures/solutions against instabilities/e-cloud effects etc. in the SPS. On the other hand, Linac4 will become available by the end of 2014. Until the end of 2015 it may replace Linac2 at short notice, taking 50MeV protons into the PSB via the existing injection system but with reduced performance. Afterwards, the H− injection equipment will be ready and Linac4 could be connected for 160MeV H− injection into the PSB during a prolonged winter shutdown before LS2. The anticipated beam performance of the LHC injectors after LS1 in these different cases is presented. Space charge on the PS flat-bottom will remain a limitation because the PSB-PS transfer energy will stay at 1.4GeV. As a mitigation measure new RF manipulations are presented which can improve brightness for 25 ns bunch spacing, allowing for more than nominal luminosity in the LHC.

THE STUDY OF A EUROPEAN NEUTRINO FACTORY COMPLEX

The linac booster (LIBO) project aims to build a 3 GHz proton linac to give the beam from 50-70 MeV cyclotrons, which exist in several laboratories and hospitals, a final energy of 200 MeV. This will allow the treatment of deep-seated tumours. A prototype of the first LIBO module was designed, constructed and RF tested by a collaboration of CERN, University and INFN of Milan, University and INFN of Naples, and the TERA Foundation. Low power RF measurements have shown good field uniformity and stability along the axis of the four tanks composing the LIBO module. In December 2000, full power RF measurements at a repetition rate of 100 Hz have been performed at CERN. After a very short conditioning period, an accelerating gradient approaching 30 MV/m has been easily achieved in the tanks, well above the nominal 15.8 MV/m. The particularities of the design and the reasons for the successful performance are discussed.

Performance potential of the injectors after LS1

Abstract To prepare dense bunches of lead ions for the LHC it has been proposed to accumulate the 4.2 MeV/u linac beam in a storage ring with electron cooling. A series of experiments is being performed in the low-energy ring LEAR to test this technique. First results were already reported at the Beam Crystallisation Workshop in Erice in November 1995. Two more recent runs to complement these investigations were concerned with: further study of the beam lifetime; the dependence of the cooling time on optical settings of the storage ring and on neutralization of the electron beam; and tests in view of multiturn injection. New results obtained in these two runs in December 1995 and in April 1996 will be discussed in this contribution.

Successful high power test of a proton linac booster (LIBO) prototype for hadrontherapy

This report sums up in two volumes the first 50 years of operation of the CERN Proton Synchrotron. After an introduction on the genesis of the machine, and a description of its magnet and powering systems, the first volume focuses on some of the many innovations in accelerator physics and instrumentation that it has pioneered, such as transition crossing, RF gymnastics, extractions, phase space tomography, or transverse emittance measurement by wire scanners. The second volume describes the other machines in the PS complex: the proton linear accelerators, the PS Booster, the LEP pre-injector, the heavy-ion linac and accumulator, and the antiproton rings.

RECENT RESULTS ON LEAD-ION ACCUMULATION IN LEAR FOR THE LHC

Radio-frequency quadrupole (RFQ) linear accelerators appeared on the accelerator scene in the late 1970s and have since revolutionized the domain of low-energy proton and ion acceleration. The RFQ makes the reliable production of unprecedented ion beam intensities possible within a compact radio-frequency (RF) resonator which concentrates the three main functions of the low-energy linac section: focusing, bunching and accelerating. Its sophisticated electrode structure and strict beam dynamics and RF requirements, however, impose severe constraints on the mechanical and RF layout, making the construction of RFQs particularly challenging. This lecture will introduce the main beam optics, RF and mechanical features of a RFQ emphasizing how these three aspects are interrelated and how they contribute to the final performance of the RFQ.

Fifty years of the CERN Proton Synchrotron : Volume 2

With the completion of the antiproton physics program, the Low Energy Antiproton Ring is now available to be used as an accumulator ring for heavy ions in the LBC injector chain. The proposed scheme for the injection of Pb ions is given, where an intensity gain of 125 is obtained by accumulating Pb ions with electron cooling in the LEAR ring. With a linac cycling at 10 Hz and cooling times faster than 100 ms, 20 pulses can be accumulated in 2 s before transfer to the PS, the next machine in the chain. A number of machine experiments have been performed and will continue this year, in order to establish the techniques required. We discuss injection line tests, ion beam lifetime and vacuum measurements and cooling time measurements.

The radio-frequency quadrupole

This introductory lecture outlines the impressive progress of radio frequency technology, from the first table-top equipment to the present gigantic installations. The outcome of 83 years of evolution is subsequently submitted to an anatomical analysis, which allows identifying the main components of a modern RF system and their interrelations.

Recent lead ion storage tests on LEAR

The LIU project has as mandate the upgrade of the LHC injector chain to match the requirements of HLLHC. The present planning assumes that the upgrade work will be completed in LS2, for commissioning in the following operational year. The known limitations in the different injectors are described, together with the various upgrades planned to improve the performance. The expected performance reach after the upgrade with 25 and 50 ns beams is examined. The project planning is discussed in view of the present LS1 and LS2 planning. The main unresolved questions and associated decision points are presented, and the key issues to be addressed by the end of 2012 are detailed in the context of the machine development programs and hardware construction activities. HL-LHC REQUIREMENTS AFTER LS2 The stated performance objective of HL-LHC is to accumulate 3000 fb of integrated p-p luminosity at 14 TeV centre of mass collision energy [1]. In order to achieve this, an annual figure of 250-300 fb has been posited, requiring instantaneous luminosity capability of around 7–8×10 cms, levelling to 5×10 cms and high machine efficiency [2]. The present paper covers the first of these challenging requirements: how to deliver the beam from the injector complex for these luminosities almost an order of magnitude above LHC design. The HL-LHC project has previously outlined possible parameter sets for 25 and 50 ns spacing which give the required luminosity, summarised in Tab. 1, adapted from [2]. Strictly speaking the HL-LHC needs the specified beams from the SPS after LS3, when the major work for the HL-LHC project is planned. The LIU work will take place largely in LS2, so that the period LS2 to LS3 will be an important one in terms of achieving the maximum performance from the injector chain. The figures quoted are for beams at the start of the collision process at 7 TeV – any beam loss or emittance dilution after extraction from the SPS is not included. The assumptions on the beam loss and emittance dilution for all machines are given in Tab. 2, where it can be seen that the total assumed beamloss -ΔI/I0 is 27%, and the emittance growth Δε/ε0 is 33%, corresponding to a brightness which is reduced to 55% of the original value. Table 1: Parameters and requirements from HL-LHC Parameter Nom. HL 25 ns HL 50 ns N [e11 p+] 1.15 2.0 3.3