D. J. J. de Lange

Measurement of T20 in Elastic Electron-Deuteron Scattering

The authors report on a measurement of the tensor analyzing power T{sub 20} in elastic electron-deuteron scattering in the range of four-momentum transfer from 1.8 to 3.2 fm{sup {minus}1}. Electrons of 704 MeV were scattered from a polarized deuterium internal target. The tensor polarization of the deuterium nuclei was determined with an ion-extraction system, allowing an absolute measurement of T{sub 20}. The data are described well by a non-relativistic calculation that includes the effects of meson-exchange currents.

A large acceptance spectrometer for the internal target facility at NIKHEF

A non-focusing magnetic spectrometer, BigBite, has been built for use at the Internal Target Facility of the AmPS ring at NIKHEF. It allows detection of particles with momentum in the range of 200—900 MeV/c, with an angular resolution of about 4 mrad, and a design momentum resolution of 5]10~3.The track of a particle after passage through the field of a single dipole magnet is determined by two multi-wire drift chambers each of which has two planes. The four planes contain a total of 338 sense wires. For each plane, both sense wires and cathode strips are used to make measurements of each coordinate. The trigger consists of coincident signals from a single scintillator and a di⁄usely reflecting aerogel Cherenkov detector. The latter also provides discrimination between electrons and pions. Details of the signal handling and first results on the performance of the complete system will be discussed. ( 1998 Elsevier Science B.V. All rights reserved.

Tensor Analyzing Powers for Quasielastic Electron Scattering from Deuterium

We report on a first measurement of tensor analyzing powers in quasi-elastic electron-deuteron scattering at an average three-momentum transfer of 1.7 fm{sup -1}. Data sensitive to the spin-dependent nucleon density in the deuteron were obtained for missing momenta up to 150 MeV/c with a tensor polarized {sup 2}H target internal to an electron storage ring. The data are well described by a calculation that includes the effects of final-state interaction, meson-exchange and isobar currents, and leading-order relativistic contributions.

The optical properties of the BigBite spectrometer at NIKHEF.

The optical properties of the BigBite spectrometer currently in use at the Internal Target Facility of the AmPS ring at NIKHEF have been determined. The spectrometer, which consists of a single dipole magnet, combines a large solid angle with a large momentum acceptance. The track of a particle is determined from the information of two sets of drift chambers behind the magnet. Tracing this track through the magnetic field to the target yields the position of the scattering vertex and the size and direction of the momentum vector of the scattered particle at the target position. These quantities are calculated using an analytical approximation of the spectrometer, followed by a refinement with the matrix method. The p-resolutions of the reconstruction for 600 MeV electrons are 3 mrad for the angles, 3.2 mm for the vertex position, and 8.4]10~3 for dp/p. ( 1998 Elsevier Science B.V. All rights reserved.

Spin-dependent electromagnetic response of few-body systems.

We report on the experimental program with polarized electrons and polarized few-body systems at the internal target facility of the NIKHEF electron storage ring. n nWith a polarized deuterium internal target, absolute measurements of unprecedented accuracy have been performed for the analyzing powers T20 and T22 in elastic electron-deuteron scattering at transferred four-momenta 1.1 < Q < 2.8 fm−1. Results for a first measurement of the tensor analyzing power in quasi-elastic scattering are also presented. These data provide new constraints for descriptions of the deuteron spin structure and for reaction mechanism effects. n nQuasi-elastic electron scattering from polarized 3He may provide precise information on the S′ and the D-wave parts of the 3He ground-state wave function, the neutron form factors, and the role of spin-dependent reaction mechanism effects. We have started an experimental program at NIKHEF where polarized 3He and polarized electrons are used, in combination with large acceptance electron and hadron detectors. Data were taken for the transverse (Ay0) and longitudinal (A′z) asymmetries at Q ⋍ 2 fm−1. We outline the performance of the target and detectors.

A Recoil Detector for electron scattering experiments with internal targets

Abstract A Recoil Detector has been constructed for electron-scattering experiments with gas targets internal to the Amsterdam Pulse Stretcher and storage ring (AmPS) at NIKHEF. The detector was designed to detect low-energy (1–10 MeV/nucleon) and low-mass (A ≤ 4) recoiling nuclei emerging from electron-induced reactions. It consists of four sensitive elements: a low-pressure two-step avalanche chamber, two layers of silicon strip detectors of 100 and 475 μm thickness, and a scintillator. The signals from the separate detector elements are processed by custom-made analog and digital electronics. The detector was operated successfully at the AmPS electron scattering facility with a gaseous helium target of 1015 atoms cm−2 internal to the storage ring and beam currents of up to 200 mA.

A large-acceptance detector system for electron scattering from polarized internal targets

Abstract The design and the performance of a non-magnetic detector setup for internal target physics at the NIKHEF electron-scattering facility is described. The detector setup, used in the first internal-target experiment at the AmPS ring, measures the spin dependence in the elastic and break-up reaction channels from tensor polarized deuterium. It has been established that the detector setup can operate adequately in an internal target environment at luminosities up to 10 32 e − atoms cm −2 s −1 . Results and measured resolutions are presented.

Quasifree pi(0) and pi(-) electroproduction on He-4 in the Delta-resonance region

The reactions 4He(e, e p3He)pi- and 4He(e, e p3He)pi0 were studied simultaneously, and for the first time, in a large kinematical domain including the Delta-resonance region. This was achieved by detecting the recoiling 3He and 3H nuclei instead of the emitted pions. The dependences of the cross section on the recoil momentum p(rec), the invariant mass WpiN, and the direction thetapi,q and phipi,q of the produced pion, are globally well described by the results of (quasifree) distorted-wave impulse approximation calculations. However, in the Delta-resonance region there are clear discrepancies, which point to medium modifications of the Delta in 4He.

Measurement ofT20in Elastic Electron-Deuteron Scattering

The authors report on a measurement of the tensor analyzing power T{sub 20} in elastic electron-deuteron scattering in the range of four-momentum transfer from 1.8 to 3.2 fm{sup {minus}1}. Electrons of 704 MeV were scattered from a polarized deuterium internal target. The tensor polarization of the deuterium nuclei was determined with an ion-extraction system, allowing an absolute measurement of T{sub 20}. The data are described well by a non-relativistic calculation that includes the effects of meson-exchange currents.

Polarized deuterium internal target at AmPS (NIKHEF)

We describe the polarized deuterium target internal to the NIKHEF medium-energy electron storage ring. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage cell target. A Breit-Rabi polarimeter was used to monitor the injected atomic beam intensity and polarization. An electrostatic ion-extraction system and a Wien filter were utilized to measure on-line the atomic fraction of the target gas in the storage cell. This device was supplemented with a tensor polarization analyzer using the neutron anisotropy of the 3H(d,n)α reaction at 60 keV. This method allows determining the density-averaged nuclear polarization of the target gas, independent of spatial and temporal variations. We address issues important for polarized hydrogen/deuterium internal targets, such as the effects of spin-exchange collisions and resonant transitions induced by the RF fields of the charged particle beam.