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Register a new userBeam Particle Identification and Tagging of Incompletely Stripped Heavy Beams with HEIST
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A challenge preventing successful inverse kinematics measurements with heavy nuclei that are not fully stripped is identifying and tagging the beam particles. For this purpose, the HEavy ISotope Tagger (HEIST) has been developed. HEIST utilizes two micro-channel plate timing detectors to measure time of flight, a multi-sampling ion chamber to measure energy loss, and a high purity Ge detector to identify isomer decays and calibrate the isotope identification system. HEIST has successfully identified $^{198}$Pb and other nearby nuclei at energies of about 75 MeV/A. In the experiment discussed, a typical cut containing 89% of all $^{198}$Pb$^{+80}$ in the beam had a purity of 86%. We examine the issues of charge state contamination. The observed charge state populations of these ions are presented and are moderately well described by the charge state model GLOBAL.
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The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. Optimized for use with low-energy radioactive beams (< 5 MeV/A) the detector presents only three 0.5 $mu$m/cm$^2$ foils to the beam in addition to the detector gas. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a risetime of 60-70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate. Tests with an $alpha$ source establish the detector energy resolution as $sim$8 $%$ for an energy deposit of $sim$3.5 MeV. The energy resolution with beams of 2.5 and 4.0 MeV/A $^{39}$K ions and the dependence of the energy resolution on beam intensity is measured. At an instantaneous rate of 3 x 10$^5$ ions/s the energy resolution has degraded to 14% with a pileup of 12%. The good energy resolution of this detector at rates up to 3 x 10$^5$ ions/s makes it an effective tool in the characterization of low-energy radioactive beams.
To improve the ability of particle identification of the RIBLL2 separator at the HIRFL-CSR complex, a new high-performance detector for measuring fragment starting time and position at the F1 dispersive plane has been constructed and installed, and a method for achieving precise Br{ho} determination has been developed using the experimentally derived ion-optical transfer matrix elements from the measured position and ToF information. Using the high-performance detectors and the precise Br{ho} determination method, the fragments produced by the fragmentation of 78Kr at 300 MeV/nucleon were identified clearly at the RIBLL2-ETF under full momentum acceptance. The atomic number Z resolution of {sigma}Z~0.19 and the mass-to-charge ratio A/Q resolution of {sigma}A/Q~5.8e-3 were obtained for the 75As33+ fragment. This great improvement will increase the collection efficiency of exotic nuclei, extend the range of nuclei of interest from the A<40 mass region up to the A~80 mass region, and promote the development of radioactive nuclear beam experiments at the RIBLL2 separator.
We have developed a method for achieving excellent resolving power in in-flight particle identification of radioactive isotope (RI) beams at the BigRIPS fragment separator at the RIKEN Nishina Center RI Beam Factory (RIBF). In the BigRIPS separator, RI beams are identified by their atomic number Z and mass-to-charge ratio A/Q which are deduced from the measurements of time of flight (TOF), magnetic rigidity (Brho) and energy loss (delta-E), and delivered as tagged RI beams to a variety of experiments including secondary reaction measurements. High A/Q resolution is an essential requirement for this scheme, because the charge state Q of RI beams has to be identified at RIBF energies such as 200-300 MeV/nucleon. By precisely determining the Brho and TOF values, we have achieved relative A/Q resolution as good as 0.034% (root-mean-square value). The achieved A/Q resolution is high enough to clearly identify the charge state Q in the Z versus A/Q particle identification plot, where fully-stripped and hydrogen-like peaks are very closely located. The precise Brho determination is achieved by refined particle trajectory reconstruction, while a slew correction is performed to precisely determine the TOF value. Furthermore background events are thoroughly removed to improve reliability of the particle identification. In the present paper we present the details of the particle identification scheme in the BigRIPS separator. The isotope separation in the BigRIPS separator is also briefly introduced.
Production of a GeV photon beam by laser backward-Compton scattering has been playing an important role as a tool for nuclear and particle physics experiments. Its production techniques are now established at electron storage rings, which are increasing worldwide. A typical photon intensity has reached $sim$ 10 $^6$ sec$^{-1}$. In the present article, the LEPS beamline facility at SPring-8 is mainly described with an overview of experimental applications, for the purpose to summarize the GeV photon beam production. Finally, possible future upgrades are discussed with new developments of laser injection.
High electronic excitations in radiation of metallic targets with swift heavy ion beams at the coulomb barrier play a dominant role in the damaging processes of some metals. The inelastic thermal spike model was developed to describe tracks in materials and is applied in this paper to some systems beams/targets employed recently in some nuclear physics experiments. Taking into account the experimental conditions and the approved electron-phonon coupling factors, the results of the calculation enable to interpret the observation of the fast deformation of some targets.
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