P.K.A. de Witt Huberts

The ANTARES optical module

The ANTARES collaboration is building a deep sea neutrino telescope in the Mediterranean Sea. This detector will cover a sensitive area of typically 0.1 km-squared and will be equipped with about 1000 optical modules. Each of these optical modules consists of a large area photomultiplier and its associated electronics housed in a pressure resistant glass sphere. The design of the ANTARES optical module, which is a key element of the detector, has been finalized following extensive R & D studies and is reviewed here in detail.The ANTARES collaboration is building a deep sea neutrino telescope in the Mediterranean Sea. This detector will cover a sensitive area of typically 0.1 km-squared and will be equipped with about 1000 optical modules. Each of these optical modules consists of a large area photomultiplier and its associated electronics housed in a pressure resistant glass sphere. The design of the ANTARES optical module, which is a key element of the detector, has been finalized following extensive R&D studies and is reviewed here in detail.

The 500 MeV electron-scattering facility at NIKHEF-K

The 500 MeV electron-scattering facility, designed and built in conjunction with the 500 MeV, 2.5% duty factor electron linear accelerator (MEA), has been completed. It allows high-resolution (1 × 10−4) single-arm (e,e′) experiments with a QDD spectrometer and single-arm hadron detection [(γ, π) and (γ,p) reactions] with a large solid angle (17 msr) QDQ spectrometer. With both specrometers coincidence experiments (e,e′x) can be performed with a 225 keV missing energy resolution and a 1 ns timing resolution. A comprehensive description is given of the beam-handling system, spectrometers, detection system, data handling techniques and other instrumentation. Finally, test results obtained at energies ranging from 70 to 460 MeV are presented.

On the radial distribution of the 1f72 proton orbit

Abstract Cross sections for magnetic elastic electron scattering of high multipolarity from 51 V and 59 Co have been measured. They are interpreted in terms of the rms radius of the 1f 7 2 proton orbit. The results for 51 V and 59 Co 1f 7 2 rms radii are smaller by 3% and 9%, respectively, than predicted by the Hartree-Fock-Bogoliubov theory.

An overlapping scintillator detection system for electron scattering

Abstract A high-resolution system for detecting high-energy electrons in the focal plane of a magnetic spectrometer is described. It consists of 10 overlapping scintillators which form 19 detection channels and a Cerenkov counter. The results obtained on logic circuitry are interpreted and processed by a small on-line computer. The total detection efficiency is independent of electron energy and the momentum resolution per channel is 0.1%. Construction and performance are described.

On the nature of low-lying electric dipole excitations in light and heavy deformed nuclei☆

Abstract Form factors from high-resolution inelastic electron scattering on 48 Ti, 164 Dy, 232 Th and 238 U display the fact that the E1 transition to the lowest lying J π = 1 − states is excited by the same mode in light and heavy nuclei. A description of the form factor in terms of surface octupole vibrations of the nucleus around a quadrupole deformed shape is shown to work quite well up to its second maximum. The E1 strength found at the photon point is explained satisfactorily by taking into account the mixing with the electric giant dipole resonance.

Search for nucleon-nucleon correlations in the proton spectral function of 208Pb

Abstract Cross sections for the reaction 208Pb(e,e′p) have been measured with the continuous electron beam from the Amsterdam Pulse-Stretcher facility at NIKHEF-K. The spectral function has been extracted for protons with initial momenta of 300 to 500 MeV/c and binding energies up to 26 MeV. The data are compared to calculations with and without inclusion of nucleon-nucleon correlations. Mean-field predictions significantly underestimate the data and the discrepancy increases with binding energy. For transitions to the valence states the discrepancy is removed by introducing long-range correlations. Above the two-nucleon emission threshold long-range and short-range correlations reduce the discrepancy, but are insufficient to fully account for the measured strength.

A fast and flexible focal-plane detection system for electron scattering experiments

Abstract A multiwire drift chamber detection system, with a total of 1800 sense wires, operated in the focal planes of a two-spectrometer set-up for intermediate energy electron scattering experiments, is discussed. Two-dimensional reconstruction of single-arm events with a spatial resolution of 250 μm is performed by dedicated hardware modules with a peak event rate of 5 MHz. The system is rather flexible and expandable in its applications. Special features of the system used for single-arm and coincidence reactions are discussed and test results are presented to illustrate the overall performance of the detection system.

The magnetic form factor of 51V at very high momentum transfer

Abstract The magnetic form factor of the 51 V nucleus has been measured between 3 and 4 fm −1 . These new data show a clear evidence for the diffraction structure of the M7 magnetic multipole. The data are compared to Hartree-Fock results including meson exchange currents and core polarization effects.

Elastic electron scattering from the magnetization distribution of 4193Nb

Abstract Cross sections of elastic magnetic electron scattering from 41 93 Nb have been obtained at momentum transfers from 1.7 to 2.5 fm −1 . The observed deviation of the dominant M9 amplitude from the 1 g 9 2 single-proton value can be explained by large-space shell model calculations.

The Amsterdam pulse stretcher and storage ring AmPS A C.W., (800–900) MeV, high luminosity electron beam facility

Abstract At NIKHEF (Amsterdam) the existing 500 MeV, 1 % duty factor linear electron accelerator (MEA) has been upgraded with a pulse stretcher - storage ring. This dual-function device will provide electrons with up to 900 MeV energy in a 100 % duty factor beam with tens of microamps in extraction mode, and up to 200 mA circulating current in storage mode. Commissioning recently commenced, less than three years after the start of the project. First operational results of the AmPS facility are discussed.