Edmund J N Wilson

Copious electron emission from PLZT ceramics with a high zirconium concentration

Abstract We describe the experimental method and report the results of electron emission from PLZT-2/95/5 ceramics subjected to rectangular HV pulses. The influence of HV amplitude, of gas pressure, and of temperature on electron beam current-density and charge was investigated. The kinetic energy was estimated by applying a decelerating field. Emitted current-density pulses of several A/cm2 and charges of 1 μC/cm2 are measured. A tentative interpretation is given.

Fast polarization changes in ferroelectrics and their application in accelerators

Abstract Several mechanisms are described which change the polarization in ferroelectric material. Provided the change is too rapid for the related surface charges to be screened or neutralized, the high charge density can lead to strong electric fields. The fields may possibly be used for emission and acceleration of electrons. First results of experiments are reported in which fast spontaneous polarization changes by reversal or phase transition have been demonstrated. Electrons of 25 keV energy have been observed, emitted from triglycine sulfate (TGS) crystals during phase transition while being slowly heated across the Curie temperature. With fast polarization changes, electron beams of even higher energy and density are expected.

THE STUDY OF A EUROPEAN NEUTRINO FACTORY COMPLEX

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.

Pulsed electron emission from PLZT ceramics

Abstract New experimental results on electron emission from PLZT ceramics of composition 2/95/5, subjected to rectangular high-voltage pulses are reported. The dependence of the emitted electron charge on the electric field strength and temperature was investigated. The energy of the emitted electrons was estimated by applying a decelerating potential to an auxiliary grid electrode. Emitted current densities of several A/cm2 and emitted charges up to ∼ 1 μC/cm2 (∼1013 electrons/cm2) were observed.

Design Concept for a 100 GeV E+-E- Storage Ring

A conceptual design of a 100 GeV e+-e- storage ring (LEP) being studied at CERN and some of the problems encountered are presented. The 20 GeV fastcycling injector synchrotron is studied at the Rutherford Laboratory.1 To obtain a luminosity L = 1 × 1032 cm-2 s-1 at 100 GeV, the product of bending radius ¿ and the RF power PB delivered to both beams must be PB ¿ = 136 GWm, assuming optimum coupling, a maximum permissible beam-beam tune shift ¿Q = 0.06, and a vertical amplitude function ßy* = 0.01 m at the crossings. The bending radius ¿ = 6.1 km was obtained by cost optimisation.2

Fast polarization changes in PZT ceramics by high-voltage pulses

Abstract Experiments on fast spontaneous polarization changes in PZT ceramics are described. The interactions between spontaneous polarization Ps and space-charge polarization Psp.ch. are discussed. The fast polarization changes are made with the aim of producing electron beam emission and acceleration from ferroelectric surfaces.

Acceleration and Storage of a Dense Single Bunch in the CERN SPS

First tests of the lifetime of a normal SPS beam stored for several hours at 200 and 270 GeV were encouraging. The natural logarithmic decay time is in excess of 24 hours. However, in the proton-antiproton scheme, 200 MHz bunches containing fifty times the normal design population of particles are to be injected into the SPS above transition at 26 GeV, accelerated and stored. Lacking the hardware to inject at so high an energy, we first injected bunches of 1011 protons at 10 GeV accelerating them through transition but found it difficult to pag transitionwith more than 40% of this design population . Nevertheless we report some interesting observations on head-tail and negative-mass effects which limited intensity during these tests.

Transverse Instabilities Due to Beam-Trapped Ions and Charged Matter in the CERN Antiproton Accumulator

At stack intensities above 10 antiprotons with transverse emittances of between and 2 mm.mrad at 3.5 GeV/c, three distinct transverse heating mechanisms caused by positive matter trapped in the negative beam potential have been observed and identified. Two effects are incoherent and one is coherent. The incoherent effects are of two kinds distinguishable by the rate at which emittance growth occurs, and by the sensitivity to tune changes. The first is a slow growth at a rate which is about equal to, or up to ten times faster than the intrabeam scattering growth rate at small emittances: this is attributed to the excitation of 11th and 15th order non-linear resonances by residual ion pockets, an effect very similar to the beam-beam effect in colliders. The second kind of incoherent effect is an intermittent, violent emittance growth, often associated with a substantial stack loss rate. This effect is believed to be due to multiple Coulomb scattering by highly charged tiny dust particles trapped in the beam potential. Observations of the coherent instability fit the known antiproton-ion (similar to proton-electron) theory. It leads to growth rates faster than the transverse damper presently installed in the AA can handle.

The use of ferroelectrics for acceleration of charged particles

Several mechanisms are described which lead to fast polarization changes in ferroelectric materials. The resulting surface charges may ultimately generate electric field spikes on the order of 1 GV/m. The fast response of ferroelectric materials to phase transitions under the influence of external electrical and/or mechanical stress allows the design of structures which emit and accelerate charged-particle beams. >

DESIGN STUDIES FOR A LARGE PROTON SYNCHROTRON AND ITS LABORATORY.

Abstract Analysis of the growth pattern of CERN-Meyrin leads to a model for the development of the proposed European 300 GeV Laboratory. The model must allow for flexibility in the development of the machine so that one may exploit future technological advances, e.g. pulsed superconducting magnets. The maximum use must be made of existing capital investment and infrastructure yet provision must also be made for a steady expansion in experimental utilization for 30 years to come. Various types of synchrotron with separated and combined-function lattices and missing-magnet, missing-power and fixed-energy configurations have been designed and costed. Their relative merits are discussed in the context of the model for the new laboratory.