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 α-resolutions of the reconstruction for 600 MeV electrons are 3 mrad for the angles, 3.2 mm for the vertex position, and 8.4 × 1

A recoil detector for the internal target facility of AmPS (NIKHEF).

A recoil detector has been built for internal target experiments with the Amsterdam Pulse Stretcher and storage ring, AmPS, of NIKHEF. The detector was designed to detect low-energy (1-20 MeV/nucleon) and low-mass (A ≤ 4) recoiling nuclei emerging from electron-induced reactions. The detector consists of 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 electronics and dedicated VME-based digitizer modules. The detector was operated successfully at the AmPS electron scattering facility with a gaseous He target of 1

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

The reactions He4(e,eâ€pHe3)Ï€- and He4(e,eâ€pHe3)Ï€0 were studied simultaneously, and for the first time, in a large kinematical domain including the Î"-resonance region. This was achieved by detecting the recoiling He3 and H3 nuclei instead of the emitted pions. The dependences of the cross section on the recoil momentum prec, the invariant mass WÏ€N, and the direction ÎÏ€,q†and Ï•Ï€,q†of the produced pion, are globally well described by the results of (quasifree) distorted-wave impulse approximation calculations. However, in the Î"-resonance region there are clear discrepancies, which point to medium modifications of the Î" in He4. © 2005 The American Physical Society

Recoil detection with a polarized He-3 target

The ultra-thin gas targets used in storage ring internal target experiments allow low energy, heavy nuclei to emerge from the target region. A detector capable of analyzing these nuclei provides unique access to many nuclear reactions. We report here the first use of such a detector in conjunction with a polarize