Claude Bovet

The Fast Shaving Ejection for Beam Transfer from the CPS to the CERN 300 GeV Machine

A fast shaving ejection during 10 or 11 turns is the most promising system for the transfer of the CPS beam to the 300 GeV machine under construction for which the CPS is to be the injector. The scheme uses a pair of fast kickers which shift the beam in 10 or 11 steps across an electrostatic septum, located at a position where the amplitude function is increased to near 100m and the momentum compaction function reduced to near zero. A prototype system has been installed in the CPS and tests have been carried out at 10 GeV/c with bunched and adiabatically debunched beams. The stability of the operation, ejection efficiency, emittance and momentum spread of the ejected beam are of major interest and have been measured. The test results are in agreement with theory and no serious difficulties have been observed.

The Cedar (Cerenkov Differential Counters with Achromatic Ring Focus) Project

All hadron beams of the CERN SPS are being equipped with a mass identification facility. The project involves the construction of twelve differential Cerenkov counters specialized either for the energy range of 15 GeV/c to 150 GeV/c (CEDAR-W) or 30 GeV/c to 340 GeV/c (CEDAR-N). The performances of four W-type and one N-type CEDAR are reported.

Wire scanners at LEP

Two sets of wire scanners, each for measuring the horizontal and vertical profile, are installed in LEP in a straight section where the dispersion in both planes is zero. The authors present the design and discuss some limitations of the instrument. A carbon fiber with a diameter of 36 mu m moves through the beam with a speed of about 0.5 m/s. The bremsstrahlung photons generated by the passage of the wire through the beam are detected in scintillators located 80-m downstream. During the first months of LEP operation, the fibers were destroyed occasionally. The various causes, tests and remedies are discussed. At injection energy a significant blowup of the beam results from the wire scan and has to be taken into account for the estimation of the genuine emittance. A model of this blowup is proposed, where the effect is renormalized on the actual measured data. This provides an effective data treatment to obtain the unperturbed beam size.<<ETX>>

LHC beam instrumentation

Six years before the scheduled commissioning of the LHC at CERN, the basic list of beam instruments has been established. This early date is needed due to the impact of the mechanical design of some detectors (mainly the beam position detectors) on the cryogenic part of the machine as well as for other projects due to the long R&D period (emittance measurements, tune and chromaticity diagnostics and control). This paper gives a detailed overview of the basic requirements and specifications of all beam instruments foreseen for transfer lines and main rings.

Polarization of Beams in LEP

Plans are presented for the implementation of polarized beams in LEP Phase 1 up to about 50 GeV. They include polarimeters, enhancement of polarization rate, error correction methods.

The use of LEP beam instrumentation with bunch trains

Filling LEP with trains of bunches separated of only 247 ns instead of the present eight equidistant bunches (at 11 μs intervals) has important implications for the use of beam instrumentation. The BPM system will be limited in its measuring capabilities. Most other instruments will not be able to identify bunches unless further developments are made in their timing and acquisition electronics. A review of the situation is presented together with the planned actions to cope with the observation of individual bunches in trains.

Measurement and Monitoring of the Ejected Proton Beam "58" of the Cern Proton Synchrotron

Instantaneous Proton flux densities of the order of 1011 to 1020 p cm-2 s-1 have to be measured and monitored in this ejected proton beam, the mean fluxes being about 1010 to 1012 p s-1, the burst durations ranging from about 108 to 10-1 s and the beam cross sections from 10-1 to several cm2. These fluxes are much higher than those encountered previously in secondary beams but not yet high enough for macroscopic methods to be comfortably usable. Another difficulty results from the increased radiation damage. For the observation of the particle distribution in space and time, fluorescent screens and television, special nuclear emulsions and plastic counters are used; while current transformers and a secondary emission chamber serve for intensity measurements during normal operation. The choice of these detectors and monitors, their characteristics, their calibration, and experience with operation since Autumn 1965, are discussed.

A beam size monitor based on velocity spectrum measurements of the rest gas ions accelerated by the space-charge force

Abstract In the design stage of the LHC (Large Hadron Collider/CERN, Switzerland), it is necessary to develop non-destructive beam size monitors. In this framework a profile monitor (BIGP) was proposed based on velocity spectrum measurements of the rest gas ions accelerated by the beam space-charge force. The paper presents simulation studies of the detector, a description of the prototype installed in the SPS and first measurement results.

First results of the beam gas ionization profile monitor (BGIP) tested in the SPS ring

The BGIP is a proposal for a new, non-destructive beam profile monitor for the future Large Hadron Collider (LHC). This device provides the rms beam size value by means of the analysis of the velocity spectrum of the rest gas ions created and accelerated by the beam itself. After a thorough computer simulation study of the related physics, a first prototype of the BGIP has been conceived, built up and installed in the SPS main ring during 1999. This paper contains a short presentation of the simulation work and a description of the test set-up. The first experimental results are presented and compared with theoretical computations.

Present Performance of the CERN 800 MeV PS Booster (PSB)

The CERN 800 MeV PSB consists of four synchrotrons stacked one on top of the other. The injector is the present 50 MeV CERN Proton Synchrotron (CPS) linac. Its beam is injected sequentially into the four rings via a vertical distribution system. Monoturn or multiturn injection of up to fifteen turns is available. After acceleration to 800 MeV, the four beams are ejected sequentially and brought to a common level by a recombination system. All twenty bunches are then transferred to the CPS, thus potentially increasing its intensity to 1013 p/p. Construction started in 1968, running-in on 1 May, 1972. Experiments on injection, acceleration, and transfer to the CPS were carried out whilst completing the installation of beam observation systems, debugging the interface to the IBM 1800 control computer, and bringing the software to operational standard. Closed orbit deviations are less than anticipated (only a few mm). Linear coupling and sum resonances were studied with a beam coasting at injection energy: they can be compensated with a small fraction of the available correction strength. Multiturn injection, RF trapping efficiency, acceleration, synchronization, ejection, and transfer to the CPS are described in their latest stage. At the end of the year the design intensity of 2.5 × 1012 p/p was reached in one ring.