Axial Ionization Chamber Research Articles

Performance validation of the first arm of FALSTAFF: 252Cf and 235U fission fragment characterisation

The renewed interest for the study of nuclear fission is mainly motivated by the development of GEN-IV reactor concepts, mostly foreseen to operate in the fast neutron energy domain. To support this development, new high-quality nuclear data are needed. In this context, a new experimental setup, the FALSTAFF spectrometer, dedicated to the study of nuclear fission is under development. Employing the double-velocity (2V) and energy-velocity (EV) methods, the fission fragment mass before and after neutron evaporation will be deduced and the correlation between prompt neutron multiplicity and fragment mass will be determined. The first arm of the spectrometer is achieved. It is composed of two SED-MWPC detectors (a combination of a foil to produce secondary electrons and a Multi-Wire Proportional Chamber to detect them) and an axial ionization chamber. The SED-MWPC give access to the velocity (V) via time-of-flight and position measurements. The ionization chamber measures the fragment kinetic energy (E) and the energy loss profile. Preliminary results for spontaneous fission of 252Cf and from the thermal-neutron induced fission experiment on 235U, performed at the Orphée reactor (CEA-Saclay, France), are presented.

Impact of material thicknesses on fission observables obtained with the FALSTAFF experimental setup

In the past years, the fission studies have been mainly focused on thermal fission because most of the current nuclear reactors work in this energy domain. With the development of GEN-IV reactor concepts, mainly working in the fast energy domain, new nuclear data are needed. The FALSTAFF spectrometer under development at CEA-Saclay, France, is a two-arm spectrometer which will provide mass yields before (2V method) and after (EV method) neutron evaporation and consequently will have access to the neutron multiplicity as a function of mass. The axial ionization chamber, in addition to the kinetic energy value, will measure the energy loss profile of the fragment along its track. This energy loss profile will give information about the fragment nuclear charge. This paper will focus on recent developments on the FALSTAFF design. A special attention will be paid to the impact of the detector material thickness on the uncertainty of different observables.

PISA – an experiment for fragment spectroscopy at the Internal Beam of COSY: application of an Axial Ionization Chamber

The Proton-Induced SpAllation (PISA) experiment performed at the internal beam facility of the COSY storage ring in Jülich, Germany, which is aimed at the precise measurement of double differential cross-sections over a broad range of energies and angles for spallation reactions induced by protons of 200– 2500 MeV energy in various targets, is presented. In this paper the emphasis is put on the design, principles of operation and performance of a Bragg Curve Detector (BCD) optimized for internal beam experiments at storage rings. Very clean and distinct product identification (with Z up to ∼14) from reactions, in which a Ni target was bombarded with a 1.9 GeV circulating proton beam, is obtained. The individual elements are resolved for emission energies higher than 0.5 MeV/ nucleon . Moreover, due to the detector read-out achieved by coupling a specially designed current sensitive preamplifier directly to a sampling ADC, the shape analysis of the signals from the BCD allows the isotope identification of light particles with A up to ∼11. It is also found that the BCD can be used efficiently as a thin Δ E detector for the telescope consisting of the BCD and a series of silicon detectors.

A logarithmic detection system for heavy ion experiments

The performance of a logarithmic detection system is investigated for the 25 MeV/u 40Ar induced reaction. The detection system consists of four parts: an axial ionization chamber (IC), a position sensitive silicon detector (PSSD), a large area PIN silicon photodiode (SPD) and a 16 element CsI(Tl) scintillator array. The energy resolutions for IC and PSSD tested with241Am (5.486 MeV) sources were 3 and 2.6% (FWHM), respectively. Fragments with Z values from Z = 2 to Z = 21 were identified in the reaction 40Ar+ 115In. A Z resolving power of Z/ΔZ∼ 44.5 (FWHM) for Z = 18 has been achieved, and the energy dynamic range for α-particles was about 2–130 MeV. A position resolution of 0.86±0.03mm (FWHM) for PSSD was obtained for the reaction 40Ar+ 27Al with 1 μs amplifier shaping time.

A spectrometer for prompt mass identification of fragments from low-energy fission

A spectrometer for prompt mass identification of fragments from low-energy fission having a large effective solid angle of 35.2 msr is described. The mass identification is obtained by time-of-flight measurement using a pair of microchannel plate detectors and kinetic energy measurement using an axial ionization chamber. A mass resolution of 3.8 u at 100 u was obtained from experiments which observed coincidences between fragments and γ rays from a 252Cf spontaneous fission source.

A twin axial ionization chamber for studies of multiple intermediate-mass-fragment production in 1 GeV proton-nucleus collisions

A twin axial ionization chamber consisting of 16 cm deep parts was constructed. Two anode signals arising from the same particle trace were simultaneously recorded by two Flash ADCs. The on-line data handling procedure allows the determination of energy, energy loss, range and nuclear charge of the fragments. The energy resolution was better than 1.5%. A charge resolution ΔZ/ Z < 2.5% was found for nuclear charges within the range 2 ≤ Z ≤ 18. Isotopic separation for Li, Be and B is based on the determination of the range and the energy of the fragments as well as on the ΔE − E method. The mass resolution for these elements was about 3%. The twin axial ionization chamber was employed as precise detector in an arrangement which warrants large geometric coverage. The data acquisition system allows the simultaneous measurements of inclusive data as well as correlations between intermediate mass fragments from multiple events.

An axial ionization chamber for heavy ion identification

The design and performance of an axial ionization chamber is described. The contribution of straggling to the energy resolution of this detector is inv

Energy calibration of surface barrier detectors and ionization chambers for fission fragments

Abstract The pulseheight response X of surface barrier detectors and an axial ionization chamber has been taken for fission fragments of given mass M and energy E. Fragments of accurately known M and E were obtained from the mass separator Lohengrin at the ILL. The energies on Lohengrin were calibrated by a time-of-flight technique. Pulse-height spectra from 252Cf (sf) were recorded in parallel. It could again be shown that the Energy E is well described by the relationship E = (a+a'M)X + (b+b'M). In the case of surface barrier detectors, the calibration constants desired differ, however, markedly from previously reported values. The new constants yield for the reaction 235U(nth, f) kinetic energies of the fission fragments which are in perfect agreement with recent velocity measurements.

High resolution axial ionization chamber for fission products

The construction of an ionization chamber with the electrical field parallel to the particle beam (axial chamber) is described. The energy resolution achieved for typical light and heavy mass fragments from the thermal neutron induced fission of 235U is 385 keV and 510 keV, respectively.

A new method to identify nuclear charges of fission fragments

For a mass and velocity selected beam of fission fragments, the elemental components of the beam have been determined by measuring the difference between the time the fragments enter an axial ionization chamber (with the electrical field lines parallel to the particle trajectory) and the time the anode pulse crosses a given level. The nuclear charge resolution achieved for typical fission fragments out of the light mass group in thermal neutron induced fission of 235U is Z/ ΔZ = 43 for a nuclear charge Z = 39.