http://www.cern.ch/accelconf/e98/PAPERS/WEP08H.PDF

Tomographic measurements of longitudinal phase space density

A technique for splitting bunches into three has recently been proposed as an alternative to debunchingrebunching in a synchrotron[1]. The preservation of longitudinal emittance and the possibility of maintaining a gap in the bunch train are key features expected from this new process. A proof of principle has been established experimentally at the CERN PS in 1999. This showed that the nominal longitudinal characteristics of the proton beam for the LHC could be achieved at the exit of the PS with the help of triple splitting. The method is described and experimental results presented. Other possible applications are sketched.

/pdf/demonstration-of-bunch-triple-splitting-in-the-cern-ps-3b63ht61mw.pdf

Demonstration of bunch triple splitting in the cern ps

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.

/pdf/fifty-years-of-the-cern-proton-synchrotron-volume-2-3de7u29zph.pdf

Fifty years of the CERN Proton Synchrotron : Volume 2

We describe commonly used strategies for the control of charged particle beams and the manipulation of their properties. Emphasis is placed on relativistic beams in linear accelerators and storage rings. After a brief review of linear optics, we discuss basic and advanced beam control techniques, such as transverse and longitudinal lattice diagnostics, matching, orbit correction and steering, beam-based alignment, and linac emittance preservation. A variety of methods for the manipulation of particle beam properties are also presented, for instance, bunch length and energy compression, bunch rotation, changes to the damping partition number, and beam collimation. The dierent procedures are illustrated by examples from various accelerators. Special topics include injection and extraction methods, beam cooling, spin transport and polarization.

/pdf/beam-techniques-beam-control-and-manipulation-5ga5j9mrx0.pdf

Beam Techniques - Beam Control and Manipulation

The usual formulas for the resistive-wall wake field are derived considering ultrarelativistic beams, traveling at the speed of light. This simplifies the calculation, and it leads to a cancellation between electric and magnetic fields. However, for proton beams below 10 GeV and for many heavy-ion beams, the velocities may significantly differ from the speed of light. In this paper, we compute the longitudinal and transverse wake fields for velocities smaller than $c$ and examine under which conditions nonrelativistic effects become important. We illustrate our results by a few examples.

/pdf/resistive-wall-wake-and-impedance-for-nonultrarelativistic-10aqtf8ari.pdf

Resistive-wall wake and impedance for nonultrarelativistic beams

M. Benedikt, A. Blas, J. Borburgh, R. Cappi, M. Chanel, V. Chohan, G. Daems, A. Fowler, R. Garoby, J. Gonzalez, D. Grier, J. Gruber, S. Hancock, C.E. Hill, A. Jansson, E. Jensen, A. Krusche, P. Maesen, K.D. Metzmacher, R. Losito, J. Olsfors, M. Paoluzzi, J. Pedersen, U. Raich, J.P. Riunaud, J.P. Royer, M. Sassowsky, K. Schindl, H. Schönauer, L. Sermeus, M. Thivent, H. Ullrich, W. Van Cauter, F. Völker, M. Vretenar.

The PS Complex as Proton Pre-Injector for the LHC - Design and Implementation Report

The LHC [1] will be supplied, via the SPS, with protons from the pre-injector chain comprising Linac2, PS Booster (PSB) and PS. These accelerators have undergone a major upgrading programme [2] during the last five years so as to meet the stringent requirements of the LHC. These imply that many high-intensity bunches of small emittance and tight spacing (25 ns) be available at the PS extraction energy (25 GeV). The upgrading project involved an increase of Linac2 current, new RF systems in the PSB and the PS, raising the PSB energy from 1 to 1.4 GeV, two-batch filling of the PS and the installation of high-resolution beam profile measurement devices. With the project entering its final phase and most of the newly installed hardware now being operational, the emphasis switches to producing the nominal LHC beam and tackling the associated beam physics problems. While a beam with transverse characteristics better than nominal has been obtained, the longitudinal density still needs to be increased. An alternative scheme to produce the 25 ns bunch spacing is outlined, together with other promising developments.

The ps complex produces the nominal lhc beam

In preparation for the Large Hadron Collider (LHC), extensive modifications have been made to the RF equipment of the PS Booster (PSB) and of the PS during the winter shut down ’97-98’. Low-frequency RF systems (0.6 - 1.8 MHz and 1.2 - 3.9 MHz) have been installed in the PSB and fixed frequency (40 and 80 MHz) systems in the PS. The longitudinal characteristics of all beams are changed to make the best use of the new capabilities. This paper summarises the characteristics of the new equipment and describes the RF gymnastics used to generate the various beams. The performances achieved so far are reported and compared to former results. Future plans are sketched. CERN/PS 98-022

/pdf/beams-in-the-cern-ps-complex-after-the-rf-upgrades-for-lhc-tds09kih6v.pdf

Beams in the cern ps complex after the rf upgrades for lhc

Bunches from the CERN PS Booster (PSB) with an improved bunching factor due to a hollow longitudinal distribution would facilitate the production of a highintensity (>7 10 12 /bunch) proton beam needed for the future neutron time-of-flight facility. It would also provide a safety margin for the Large Hadron Collider beam, where a double-batch transfer is used in which the first PSB batch waits for 1.2 seconds at 1.4 GeV in the PS for the second one to arrive. Since the earlier reports of the successful acceleration of low-intensity hollow bunches in the PSB, theoretical studies of the Beam Transfer Function (BTF) have led to a greatly improved understanding of the stability requirements of such beams. In addition, an experimental study of the capture of hollow coasting beams has revealed that structure resulting from the linac acceleration process persists for a remarkably long time. Any inhomogeneity has to be smeared out and the degree of hollowness carefully adjusted by a controlled longitudinal blow-up before a reproducible, stable bunch can be created. A method has been developed for reliably creating hollow distributions of up to 8 10 12 protons per bunch which have been routinely accelerated in the PSB.

/pdf/hollow-bunch-distributions-at-high-intensity-in-the-ps-1t38ek9tqx.pdf

Hollow bunch distributions at high intensity in the ps booster

The aim of the machine development sessions described in this note was to determine the type of instability involved when using the second harmonic cavity; and to explore the phenomenology of the instability under different conditions (eg beam intensity, cavity voltage-ratio and phase difference)

/pdf/diagnosis-of-longitudinal-instability-in-the-ps-booster-4hasdtmlws.pdf

Diagnosis of longitudinal instability in the ps booster occurring during dual harmonic acceleration

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