Production Of Secondary Beams Research Articles

Exploring the feasibility of magnetic moment measurements in the exotic 20C nucleus using LISE++ calculations

Nuclear magnetic moment measurements in neutron-rich isotopes require special techniques that have to be applied in the latest generation of RIB factories. Fragmentation reactions used in these labs can produce exotic species as secondary beams. Specialized fragment separators are used to optimize the production of secondary beams. In this work, a simulation code, LISE++, is used to explore the feasibility of a magnetic moment measurement in the exotic 20C nucleus, produced as a secondary beam in NSCL A1900 and RIKEN RIPS fragment separators, by optimizing the settings of operations in both.

Development of a cryogenic gas target system for intense radioisotope beam production at CRIB

A cryogenic gas target system was developed for the radioisotope (RI) beam production at CNS Radio Isotope Beam separator (CRIB). Hydrogen gas was cooled to 85–90K using liquid nitrogen and used as a secondary beam production target having a thickness of 2.3mg/cm2. An intense 7Be beam (2×108 particles per second) was successfully produced using this target. We observed a density-reduction effect at the gas target for high-current primary beams with about 7.5W heat deposition. One main feature of the target system is forced circulation of the target gas. We have found that the circulation of the target gas at a rate of 55 standard liters per minute (slm) was effective in eliminating the density reduction. The extent to which the forced flow can prevent the density reduction had not been known well. In this work, the relation between the density reduction and the forced circulation rate was quantitatively studied.

Elastic scattering of 6He + 27Al and 7Be + 51V at RIBRAS

A double superconducting solenoid system is installed at the Pelletron Laboratory of the Uni- versity of Sao Paulo, Brazil. This system allows the production of secondary beams of 8 Li, 6 He, 7 Be and others light exotic nuclei. The first results using this facility are presented.

Recoil spectrometers for heavy-ion identification and secondary-beam production: Pushing the low-energy limit

The feasibility of low-energy fragmentation experiments using a magnetic spectrometer is discussed. The main challenge is the multiplicity of the ionic charge states, which can hamper the identification in both Z and A of the fragments. Three topics are covered. First, a specific set-up for ionisation chambers, based on a very large gas thickness, is presented. Its satisfactory performances are discussed in light of the observations during a 500A MeV Pb+p experiment performed at the FRS (GSI). As a second topic, the possibility to use a thick layer of matter (a degrader) as a passive measurement device to identify the nuclear charge and the ionic charge state of fragments is discussed. This method, successfully used for Z identification in experiments such as Pb+p at 1A GeV, fails to measure the charge states at 500A MeV for the same system. It is shown that surface defects of the degrader are probably responsible for this failure. The third topic is the description of new analysis techniques developed in order to account for and subtract the contribution of polluting charge states in the spectrometer, thus making possible a clean estimation of the production cross-sections of all fragments. The combination of those new experimental and analysis techniques made the 500A MeV spallation experiment a success.

Secondary beam production in the nuclear and particle physics facility in J-PARC

At the Japan Proton Accelerator Research Complex (J-PARC), the world highest intensity secondary beams of kaons, pions, anti-protons, muons, and neutrinos will be produced by irradiating a target with the 50 GeV primary proton beam of 0.75 MW. Utilizing such high intensity secondary beams, various unique and interesting experimental studies in nuclear and particle physics can be carried out. We will describe the current R&D status of the target systems to be constructed in the Nuclear and Particle Physics Experimental Hall (NP-Hall) and the neutrino beam line of J-PARC. Some experimental studies proposed there will be also introduced.

Radioactive Ion beams in Brazil (RIBRAS)⋆

A double superconducting solenoid system is being installed at the Pelletron Laboratory of the University of S ao Paulo, Brazil. This system allows the production of secondary beams of light exotic nuclei like 8Li, 6He and others. The first results using this facility are presented.

Radioactive beams at Texas A&M University: recent results and future plans

Over the last decade, the combination of the K500 superconducting cyclotron and the recoil spectrometer MARS have been used to generate a wide range of secondary radioactive ion beams. The secondary beams, which typically are produced via transfer reactions in inverse kinematics, have been used primarily for reaction measurements relevant to nuclear astrophysics and β -decay studies. Recently the BigSol spectrometer system has been completed and first measurements of secondary beam production with it have been carried out. Future plans for secondary beam production call for recommissioning the existing K150 (88) cyclotron as a source of high intensity primary beams which would be used with MARS and as a driver for the production of radioactive isotopes which would then be accelerated in the K500 cyclotron up to energies of 70 MeV/A for light nuclei.

Fragmentation of 95 MeV/u 12C and 75 MeV/u 13C. Application to secondary-beam production

The fragmentation of 95 MeV/u 12C and 75 MeV/u 13C projectiles, interacting with natural targets of different elements (9Be, $^{\rm nat}$ Cu and 197Au for 12C, and 9Be, $^{\rm nat}$ Ni, and 181Ta for 13C) and of various thicknesses has been investigated at GANIL, using the doubly achromatic magnetic spectrometer LISE. The projectile-like fragments transmitted at 0 $^\circ$ have been analysed using a silicon $\Delta E$ -E telescope and the $\Delta E$ -time-of-flight method. The results obtained with the thinnest targets are discussed in the scope of radioactive nuclear beam production. The fragment momentum distributions can be fitted by Gaussian peaks associated with exponential tails towards low momentum values. The experimental production yields are compared with the results of the simulation code LISE. It appears that this code reproduces satisfactorily the yields of nuclei close to the stability line, but strongly overestimates the production of very neutron-deficient nuclei.

Radioactive ion beams in Brasil (RIBRAS)

The study of the so called exotic nuclei constitutes an important field of research in nuclear physics. The possibility of producing secondary beams of unstable nuclei(RIB) allows the investigation of nuclei at extreme conditions as low binding energies, high angular momentum and isospin. More laboratories are going through the process of re-direction of their experimental effort towards this activity. The nuclear physics community in Brazil has enthusiastically decided to join this endeavor to provide the Pelletron/LINAC complex with two superconducting solenoids which will permit the production of secondary beams of radioactive nuclei. A description of this facility and project RIBRAS follows.

Progress in RIBRAS radioactive ion beams in Brasil project

Nuclear physics has been going through a major evolution over the last decade. The realization that one can investigate nuclei at extreme conditions such as high density, temperature, and angular momentum using several sophisticated experimental innovations opened up the possibility of extending this activity to the study of these systems when more neutrons or more protons are added. The so called exotic nuclei constitute a major research activity in Japan, France, USA, Canada, Germany and other countries. More laboratories are going through the process of re-direction of their experimental effort towards this activity. The nuclear physics community in Brasil has enthusiastically decided to join this endeavor to provide the Pelletron/LINAC complex with two superconducting solenoids which will permit the production of secondary beams of radioactive nuclei. A description of this facility and project RIBRAS follows.

Future prospects for secondary-beam production

This contribution discusses the characteristics of different types of nuclear reactions and the influence of the beam energy in view of future prospects for secondary-beam production. First, electronic interactions in the target are considered because they define the usable target thickness. Rather high beam energies are advantageous. Secondly, the nuclear-reaction aspects are discussed. Three reaction mechanisms provide the most promising prospects for the production of secondary beams. Fusion is best suited for the production of nuclei near the proton drip line and for the heaviest elements. Fission specifically populates mid-mass neutron-rich isotopes. Fragmentation and spallation reactions represent rather universal production mechanisms for both neutron-deficient and neutron-rich exotic nuclei, since the fluctuations in the N-over- Z ratio are very important. Due to these large fluctuations, this is the most promising reaction mechanism to reach extremely exotic nuclei over the whole mass range, if sufficiently high primary-beam intensities are available. In particular, it seems to be a unique process for the production of extremely neutron-rich isotopes of elements above the region of fission fragments. These considerations are verified with experimental data. In particular, a systematic overview on the production of residual nuclei in reactions at relativistic energies has been obtained in several experiments recently performed at GSI in inverse kinematics. They allow to give a rather realistic estimate on the prospects for secondary-beam production in next-generation facilities.

A windowless gas target for secondary beam production

A windowless gas target was developed for the production of secondary high-spin isomer beams (HSIB). An 16 O target in the compound form of CO 2 gas was used to produce a 145 m Sm beam by using an 16 O ( 136 Xe , 7n) 145 m Sm reaction. The target gas pressure was kept constant at 50 Torr. A target thickness of about 1 mg/cm 2 was achieved with a 10 cm target length. Gas was recirculated and the consumption was very little.

Diagnostic imaging by energetic radioactive particle beams: Applications in Bragg peak cancer therapy

Researchers explore the use of Bragg Ionization Peak in radiotherapy for tumors. Considerations for the production of a high quality radioactive beam include secondary beam production efficiency, primary beam survival, and multiple scattering. A Positron Emitting Beam Analyzing camera was developed and tested at BEVALAC using a neon-19 beam stopping point. Results indicate that in homogeneous brain tissues, CT measurements and radioactive beam measurements are between 1-2 mm; there can be substantial difference between CT measurements and radioactive beam estimates if the beam stopping point crosses the fossae; random coincidences due to detector activation also appear as diffused images in the image plane of the beam stopping point; and further enhancements are necessary to make reliable measurements in the human trunk and complex brain regions.

SISSI at GANIL

In the continuation of secondary beam production studies started in the eighties, GANIL laboratory has been running for two years an efficient device called SISSI, dedicated to the production of exotic beams by projectile fragmentation. It consists of two supraconducting solenoids surrounding a thick target. The magnetic field is as high as 11T and the nominal angular acceptance of about 160 mr. SISSI is located at the CSS2 cyclotron exit that is upstream the alpha spectrometer and all the experimental rooms which can therefore receive secondary beams.

LISE 3: a magnetic spectrometer—Wien filter combination for secondary radioactive beam production

The doubly achromatic spectrometer LISE installed at GANIL has been running since six years for the study of exotic nuclei and the production of secondary beams obtained by the interaction of high energy heavy ions ( E/ A < 100 MeV) with thick targets (up to 1 g/cm 2). Essentially it is composed of two dipole magnets selecting the nuclear reaction products according to A/ Z at 0°. Combined with an achromatic degrader located in the intermediate focal plane, it provides a selection in A 3/ Z 2. Recently we have upgraded LISE by two major improvements: i) The angle of entry of the primary beam with respect to the axis of the spectrometer has been made variable (0° to 3.5°). This allows the suppression of remaining incompletely stripped beam-charge-states in experiments with heavy beams ( Z > 30). ii) A velocity filter based on an electrostatic field crossed with a magnetic one has been installed. This filter provides a third selection which is powerful in suppressing contaminants. Furthermore, the flight path between the target and the final focus is now increased to 43 m, which allows easy time-of-flight measurements also for heavy species. LISE 3 provides separated secondary beams of increased intensity and isotopic purity. We shall review the essential properties and present some recent experimental results for illustration.

Invited Paper-Progress Report on the 500 MeV Isochronous Cyclotron Meson Factory of ETH Zurich

The goal is a continous external proton beam of the order of 100 μA, the usable current depending mainly on extraction rate because of activation. The energy of 500 MeV is best suited to produce high fluxes of low energy or stopped mesons. The main fields of the research are planned to be: properties and interactions of mesons and nucleons, nuclear structure physics and medical and biological applications. The use of internal targets in field free regions as well as external targets should provide a great variety of beams for simultaneous experiments. The two-stage accelerator has a 70 MeV sector focussed cyclotron for injection into an isochronous ring accelerator consisting of eight spiral sector magnets. Four cavities operating at 50 MHz should provide at least 1 MeV energy gain per turn. In the course of present development the main fields of work are orbit dynamics and measurement on 1:5 scale magnets and design of a 1:1 model magnet sector. vZ is to be kept around 0.95 throughout acceleration and vr = 1.5 may be used for resonance extraction. Experiments to reach high gap voltage on a full scale cavity in vacuum are in progress (200-300 kV obtained at present). Remaining problems are some aspects of mechanical structure, in particular the vacuum chamber and schemes for quantitative extraction and secondary beam production from external targets at very high radioactivity levels. Funds of 21 Million Dollars have been approved for construction of accelerator and buildings.