Internal Target Facility Research Articles

Electron elastic scattering off a Tensor-polarized Deuterium Internal Target

The tensor analyzing power Γ20 in elastic electron-deuteron scattering has been measured in the four momentum transfer region between 1.4 and 3.2 fm~l using the Internal Target Facility at NIKHEF. Tensor-polarized deuterium is produced in an Atomic Beam Source and injected into a storage cell. Scattered electrons and recoil deuterons were detected in coincidence with two large acceptance nonmagnetic detectors.

The development of high resolution coordinate detectors for the DEUTERON facility

The DEUTERON internal target facility at the VEPP-3 storage ring at BINP is intended for the experiments on interaction of electrons and positrons with proton and deuteron. These experiments require high resolution tracking detectors which can provide the energy and angles of scattered electron.The prototype detector with a sensitive area of 160 × 40 mm2 was built and proved to be operational. It consists ofthree cascades of gaseous electron multiplier (GEM), the readoutstructure and detector electronics. Readout structure has 640 stripswhich are uniformly distributed in two layers skewed by 30degrees. Electronics of the detector includes APC128 ASICs, AlteraCyclone III FPGA, 100 MBit ethernet. In the APC128 ASIC each channelhas a separate analog pipeline consisting of 32 cells which arecyclically switched by a global clock synchronized to the bunchcrossing rate ( ∼ 4 MHz).For the needs of DEUTERON facility the expected resolution of lessthan 100 μm and thickness of ∼ 0.15% of radiation lengthare considered to be quite satisfactory. The latest results obtainedat the test beam facility at the VEPP-4M collider show that detectoris fully operational with maximum detection efficiency reached98%.

Prospects for searching the η→e+e− rare decay at the CSR

We study the possibility of searching the η→e+e− rare decay on the Cooling Storage Ring (CSR) at Lanzhou. The main features of the proposed Internal Target Experiment (ITE) and External Target Facility (ETF) are included in the Monte Carlo simulation. Both the beam condition at the CSR and the major physics backgrounds are carefully taken into account. We conclude that the ITE is more suitable for such a study due to better detector acceptance and higher beam density. At the maximum designed luminosity (1034 cm−2 s−1), η→e+e− events can be collected every ∼400 seconds at the CSR. With a mass resolution of 1 MeV, the expected signal-to-background (S/B) ratio is around 1.

重离子加速器实验环内靶控制系统

This paper describes the control system for HIRFL-CSRe internal target facility based on VAC800, VAC600 and TC hardware platform which integrates temperature control, vacuum and valve control and molecular pump control. It is able to realize remote monitor and control on temperature and vacuum and meets the requirements of physical experiments in the internal target facility. In the help of this system, Xe54+-N2 collisions experiments have been finished successfully. The whole system has been working for six months stably and safely.

A polarized [formula omitted] internal target for storage rings

A polarized 3 He internal target was employed at the internal target facility of the Amsterdam electron Pulse Stretcher and Storage ring (AmPS) at the Dutch National Institute for Nuclear and High-Energy Physics (NIKHEF). The unique features of internal targets such as chemical and isotopic purity, high and rapidly reversible polarization, and the ability to manipulate the target spin orientation were successfully demonstrated. A nuclear polarization of 0.50 (0.42) at a 3 He gas flow of 1.0 (2.0)×10 17 at s −1 could be obtained. Operation at a nominal flow of 1×10 17 at s −1 resulted in a target thickness of 0.7×10 15 at cm −2 at a target temperature of 17 K.

Electron scattering at NIKHEF with polarized beam and targets

We present the Internal Target Facility of the NIKHEF 900 MeV polarized electron storage ring. We give some results which illustrate the presently unique opportunity offered by this facility to study the spin structure of the nucleon, 2-body and 3-body system by the measurement of spin-dependent electron scattering observables.

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 σ-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 δp/ p.

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 (1–20MeV/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 475μm 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 1015atoms/cm2 internal to the storage ring and beam currents up to 200mA of 660MeV electrons. Unambiguous particle separation was achieved.

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 diffusely 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.

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 diffusely 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.

Coherent π0 electroproduction on 4He in the Δ region

Coherent π 0 electroproduction on 4He was studied using the internal target facility of the AmPS electron storage ring at NIKHEF. This 4He( e, e 14He π 0 experiment is the first on exclusive π 0 electroproduction on a complex nucleus. The experiment was performed at a luminosity of about 10 33 cm −2s −1 with a stored beam of about 150 mA 676 MeV electrons and a 4He gas target of 10 15 atoms/cm 2. The observation of neutral pions was avoided by detecting in coincidence with scattered electrons the recoiling 4He nuclei with a dedicated detector. A clear signature for π 0 knockout was achieved and the differential cross sections were measured as a function of the π 0 CM-angle over the full Δ-resonance region at two values of Q 2 of 0.07 and 0.15 (GeV/ c) 2.

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. With a polarized deuterium internal target, absolute measurements of unprecedented accuracy have been performed for the analyzing powers T 20 and T 22 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. Quasi-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 ( A y 0) and longitudinal ( A′ z ) asymmetries at Q ⋍ 2 fm −1 . We outline the performance of the target and detectors.

SPITFIRE: Spin physics with an internal-Target facility for international research

SPITFIRE: Spin physics with an internal-Target facility for international research

Thermal neutron capture gamma rays from sulfur isotopes: Experiment and theory.

We have carried out a systematic investigation of $\ensuremath{\gamma}$ rays after thermal neutron capture by all stable sulfur isotopes ($^{32}\mathrm{S}$, $^{33}\mathrm{S}$, $^{34}\mathrm{S}$, and $^{36}\mathrm{S}$). The measurements were made at the internal target facility at the Los Alamos Omega West Reactor. We detected a larger number of $\ensuremath{\gamma}$ rays: \ensuremath{\sim}100 in $^{33}\mathrm{S}$, \ensuremath{\sim}270 in $^{34}\mathrm{S}$, \ensuremath{\sim}60 in $^{35}\mathrm{S}$, and \ensuremath{\sim}15 in $^{37}\mathrm{S}$. Before developing detailed level schemes, we culled and then consolidated the existing information on energies and ${J}^{\ensuremath{\pi}}$ values for levels of these nuclides. Based on the current data, we have constructed detailed decay schemes, which imply that there are significant populations of 26 excited states in $^{33}\mathrm{S}$, 70 states in $^{34}\mathrm{S}$, 20 states in $^{35}\mathrm{S}$, and 7 states in $^{37}\mathrm{S}$. By checking the intensity balance for these levels and by comparing the total intensity of primary transitions with the total intensity of secondary $\ensuremath{\gamma}$ rays feeding the ground state, we have demonstrated the relative completeness of these decay schemes. For strongly populated levels, the branching ratios based on the current measurements are generally better than those available from previous measurements. In all four cases, a few primary electric dipole ($E1$) transitions account for a large fraction of the capture cross section for that particular nuclide. To understand and explain these transitions, we have recapitulated and further developed the theory of potential capture. Toward this end, we reviewed the theory relating off-resonance neutron capture to the optical-model capture. We studied a range of model-dependent effects (nature and magnitude of imaginary potential, surface diffuseness, etc.) on the potential capture cross section, and we have shown how experimental data may be analyzed using the expression for channel capture suitably modified by a factor that takes into account the model-dependent effects. The calculations of cross sections for most of the primary transitions in the sulfur isotopes are in good agreement with the data. Some discrepancies for weaker transitions can be explained well by an interfering compound-nucleus contribution to capture. This contribution is of the magnitude expected from statistical surveys of resonance capture data. Estimates of the cross section due to the valencecapture mechanism in $s$-wave resonances show that this cross section should dominate the more complicated compound-nucleus contributions.

A Comparison of the Gamma-Ray Spectra from 2.8-keV Neutron Capture and Thermal-Neutron Capture in Sodium-23

The gamma-ray spectrum resulting from neutron capture in the 2.8-keV resonance of /sup 23/Na has been measured with the high-resolution annihilation pair spectrometer at the internal-target facility of the CP-5 reactor. The 2.8-keV resonance was populated by using the boron-shielded target technique: A /sup 1///sub 2/-in.-thick filter of /sup 10/B surrounding the sodium sample selectively removes low-energy neutrons from the spectrum; the 1/E dependence of the incident neutron flux assures a low intensity of high-energy neutrons. Capture, predominantly in the 2.8-keV resonance, is indicated by a 2- to 3-keV shift in the energies of the primary transitions relative to those observed in thermal-neutron capture. The correlation between the absolute intensities of the resonance transitions and the thermal transitions (measured by others) is computed and discussed in terms of a numerical analysis. (The resonance and thermal intensities are identical within the precision of the measurement.) The results indicate that the resonance total radiation width is 0.24 eV less than or equal to GAMMA/sub ..gamma../ less than or equal to 0.40 eV.