F. Balestra

FIRST experiment: Fragmentation of Ions Relevant for Space and Therapy

Nuclear fragmentation processes are relevant in different fields of basic research and applied physics and are of particular interest for tumor therapy and for space radiation protection applications. The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment at SIS accelerator of GSI laboratory in Darmstadt, has been designed for the measurement of different ions fragmentation cross sections at different energies between 100 and 1000 MeV/nucleon. The experiment is performed by an international collaboration made of institutions from Germany, France, Italy and Spain. The experimental apparatus is partly based on an already existing setup made of the ALADIN magnet, the MUSIC IV TPC, the LAND2 neutron detector and the TOFWALL scintillator TOF system, integrated with newly designed detectors in the interaction Region (IR) around the carbon removable target: a scintillator Start Counter, a Beam Monitor drift chamber, a silicon Vertex Detector and a Proton Tagger for detection of light fragments emitted at large angles (KENTROS). The scientific program of the FIRST experiment started on summer 2011 with the study of the 400 MeV/nucleon 12C beam fragmentation on thin (8mm) carbon target.

Project of an internal target for the antiproton ring at FAIR

The case of the internal target for the hyper-nuclear experiment of the PANDA (antiproton Annihilation at Darmstadt) Collaboration at the High Energy Storage Ring of Facility for Antiproton and Ion Research is illustrated. After a discussion of the problems arising from the interaction of a solid internal target with an antiproton beam, the design of material, shape and sizes of a target satisfying the experimental requirements is presented. The techniques used to produce a prototype of this target are illustrated. Then the results of the tests performed on the prototype for investigating the properties (purity, radiation hardness, structure modifications after shaping) are reported and the plan of the future activity is pointed out.

Characteristic study of the internal target for the Double Hypernuclei physics at PANDA

The case of the internal target for the hypernuclear experiment of the PANDA (antiproton Annihilation at Darmstadt) Collaboration at the HESR (High Energy Storage Ring) of FAIR (Facility for Antiproton and Ion Research) is illustrated. The main aspects of the experiment designed for the production of Double Hypernuclei are initially summarized. The problems arising from the interaction of a solid internal target with an antiproton beam inside a ring are briefly discussed, together with the constraints in making such a set up. The design of material, shape and size of a target satisfying the experimental requirements is presented. The techniques used to produce a prototype of this target are illustrated. Then the results of the tests performed on the prototype to investigate the properties (purity, radiation hardness, structure modifications after shaping) are reported and the plan of the future activity is presented.

Production of a thin diamond target by laser for HESR at FAIR

In the future hadron facility FAIR, the HESR ring will supply antiprotons in the momentum range 1.5-15 GeV/c as projectiles to study charm, strangeness and a wide range of other Physics topics. For all these reactions it will be necessary to use internal targets and in particular, for the production of systems with double strangeness, a solid 12C target will be used. Inserting a solid target inside an antiproton ring creates two main problems: a large background on the detectors due to the overwhelming amount of annihilations and a strong depletion of the beam due to all the hadronic and Coulomb interactions of the antiprotons with the 12C nuclei. The width of the target plays a crucial role in minimizing these unwanted effects. Two wire-shaped prototypes have been already realized, starting from a thin diamond disk. The wire shape has been obtained by using a femto-edge laser. One prototype has been submitted to irradiation by protons of 1.5 MeV and to simultaneous Back-Scattering control to test the impurity level, the 12C density, the radiation hardness and possible phase modifications during irradiation. Both the prototypes have been submitted to Micro-Raman spectroscopy in order to scan the carbon phases along the width. The results show performances which satisfy the experimental requirements.

The antiproton interaction with an internal 12C target inside the HESR ring at FAIR

In order to fulfill the goal of producing higher rates of doubly strange hyperons, the ANDA collaboration will use the antiproton ring HESR at the future facility FAIR. The low energy hyperon production by an antiproton beam requires to insert a solid target inside the ring. Unwanted side effects of such an insertion are the overwhelming amount of annihilations, which would make the detectors blind, and the fast depletion of the bunch, which circulates inside the ring. The choice of the target material impacts the hyperon production yield: Carbon turned out to provide enough initial hyperon deceleration and keep secondary interactions below a tolerable level. The use of a very thin Diamond target, together with beam steering techniques, seems to be a satisfactory solution to the above problems and will be described hereafter.

Production of a thin diamond target by LASER for nuclear reactions inside storage rings

Abstract A brief review of the double hypernuclei physics and state of the art of the todays available data is reported. The production of the prototype of diamond target is illustrated together with the tests to check its impurity level, the surface density, the radiation hardness and the phase modification. Finally the devised way to optimize the interaction between the bunch and the target, minimizing the detector damage, through the so-called “steering beam” technique is presented.

Experiment FIRST: Fragmentation of 12 C beam at 400 MeV/u

The knowledge about fragmentation processes in ion-ion interactions is fundamental in hadrontherapy and radiation protection in space missions. Hadrontherapy, based on 12C, features many advantages with respect to conventional radiation therapy with photons due to the possibility to shape the dose delivery region in tissues but side effects of the projectile fragmentation in healthy tissues are not negligible. NASA recently pointed out that measurements for some light ions and kinetic energies are missing in nuclear fragmentation databases. FIRST experiment aims to measure the fragmentation double differential cross section of 12C in the energy range 1001000 MeV/u on several elements, constituents of organic tissues and electronic devices, in order to fill some of the mentioned lack of information on light ions. A first set of data has been taken in 2011 at GSI (Darmstadt), using 12C beam at 400 MeV/u on C and Au targets. About 3·107 events with C target and 5 · 106 with Au target were recorded. Together with these data other sets of runs have been collected to calibrate the forward part of the whole experimental setup, the ToF-Wall. The calibration procedure and the detector performances, which fit the experiment requirements for what concerns efficiency, resolution and stability, will be illustrated. Moreover, some preliminary results concerning the 12C-12C elastic scattering, in agreement with the Rutherford model, will be presented.

The KENTROS detector for identification and kinetic energy measurements of nuclear fragments at polar angles between 5 and 90 degrees

KENTROS (Kinetic ENergy and Time Resolution Optimized on Scintillator) is a relatively compact detector has been projected and constructed in the framework of the INFN FRAG and TPS experiments. KENTROS has been designed for energy deposition and time of flight measurements of charged particles. The detector ensures an angular coverage from about 5 degrees up to about 90 degrees polar angle in the laboratory frame. Recently KENTROS has been used as part of the FIRST experiment, devoted to measure double differential fragmentation cross sections, with the aim to detect light fragments produced in the nuclear fragmentation process.