Status of the CALIFA/R$^{3}$B calorimeter

View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by GSI Repository PHN-ENNA-EXP-65 GSI SCIENTIFIC REPORT 2012 Status of the CALIFA/R3 B calorimeter∗ D. Cortina-Gil † 1 , H. Álvarez-Pol1 , T. Aumann2,5 , V. Avdeichikov3 , M. Bendel4 , J. Benlliure1 , D. Bertini5 , A. Bezbakh6 , T. Bloch2 , M. Böhmer4 , M.J.G. Borge7 , J.A. Briz7 , P. Cabanelas1 , E. Casarejos8 , M. Carmona Gallardo7 , J. Cederkäll3 , L. Chulkov9 , M. Dierigl4 , D. Di Julio3 , I. Durán1 , E. Fiori10 , A. Fomichev6 , D. Galaviz11 , M. Gascón1 , R. Gernhäuser4 , J. Gerl5 , P. Golubev3 , M. Golovkov6 , D. González1 , A. Gorshkov6 , A. Heinz12 , M. Heil5 , W. Henning4 , G. Ickert5 , A. Ignatov2 , B. Jakobsson3 , H.T. Johansson12 , Th. Kröll2 , R. Krücken ‡ 4 , S. Krupko6 , F. Kurz4 , T. Le Bleis4 , B. Löher10 , N. Montes1 , E. Nacher7 , T. Nilsson12 , C. Parrilla8 , A. Perea7 , N. Pietralla2 , B. Pietras1 , R. Reifarth13 , J. Sanchez del Rio7 , D. Savran10 , S. Sidorchuk6 , H. Simon5 , L. Schnorrenberger2 , O. Tengblad7 , P. Teubig11 , R. Thies12 , J.A. Vilán8 , M. von Schmid2 , M. Winkel4 , S. Winkler4 , F. Wamers2 , and P. Yañez8 1 Universidad de Santiago de Compostela; 2 Technische Universität Darmstadt; 3 Lund University; 4 Technische Universität München; 5 Helmholtzzentrum für Schwerionenforschung, Darmstadt; 6 Joint Institute for Nuclear Research, Dubna; 7 Instituto Estructura de la Materia, CSIC Madrid; 8 Universidad de Vigo; 9 National Research Centre, Kurchatov Institute Moscow; 10 Extreme Matter Institute and Research Division, GSI; 11 Centro de Física Nuclear da Universidade de Lisboa; 12 Chalmers University of Technology, Göteborg; 13 Goethe University Frankfurt am Main CALIFA (the CALorimeter for In Flight detection of γ rays and light charged pArticles) is one of the key detectors of the R3 B experiment. It surrounds the reaction target and is optimised according to the exacting requirements given by the ambitious physics program proposed for the R3 B facility [1]. CALIFA is a versatile detector and will be used in a wide spectrum of experiments. In certain spectroscopy experiments, high γ-ray energy resolution ( 5% at 1 MeV) as well as multiplicity determination is required. In other experiments the goal is to attain calorimetric response with high efficiency. Part of the complexity arises from the reaction kinematics which leads to large Lorentz boosts and broadening of the detected γ rays peaks, i.e. effects that the detector should be able to account for. Charged particles of moderate energy, e.g. protons up to 300 MeV, should also be identified with an energy resolution better than 1%. In order to meet these targets the detector is divided into two sections, a "Forward EndCap" covering polar angles between 7-43.2o and a cylindrical "Barrel" section that provides angular coverage up to 140.3o . The Technical Design Report (TDR) [2] of the Barrel section was recently approved (January 2013) by FAIR, following the recommendation of the Expert Committee for Experiments (ECE)1 . The adopted technical solution consists of 1952 CsI(Tl) crystals, readout by Large Area Avalanche Photodiodes (LAAPDs), and a very compact geometry (internal radius 30 cm) in order to maximise the calorimetric properties. To optimize the detector efficiency and to minimize energy straggling for inter-crystal proton scattering, the passive material must be kept at an absolute ∗ Work performed in the CALIFA/R3 B Working group and supported by the Helmholtz International Centre for FAIR † Convener of the CALIFA Working group ‡ Also affiliated to TRIUMF 1 Decision adopted in the ECE first meeting in November 2012 198 minimum. These demands have lead to an in-depth investigation of the best crystal housing, support structures and overall mechanical design. The coupling of LAAPDs to CsI crystals was found to fulfil many of the R3 B programme’s most challenging demands. Their ability to meet the energy resolution requirement has been proven via an extensive R&D program using standard radioactive sources. The performance over a wide dynamic range has been investigated via irradiation of smaller size prototypes with proton beams at 25 (MLL, 2011), 180 (TSL, 2009), 200 and 400 MeV (GSI, 2012). Readout support for the photosensors is provided by Mesytec MPC-16B preamplifiers, which feature an online temperature-gain correction. A custom digital FEBEX electronic support system, envisaged for use in the final CALIFA setup is currently undergoing tests. In addition to the compact, high performance design, this approach takes advantage of the different CsI decay times for pulse shape analysis for particle identification. The FEBEX setup is highly flexible and allows for easy reprogramming of the FPGA online processing to suit individual experimental requirements [3]. Detailed simulations of the response of the CALIFA Barrel have been performed within the R3BROOT analysis framework in order to guide the progression through each stage of the development process. These simulations have been validated by comparison to experimental data for a number of smaller scale prototypes for both γ-ray and proton irradiation over a wide range in energy. The next milestone as described in the TDR is the construction of the CALIFA Demonstrator. The Demonstrator will have a modular configuration of 8 petals each comprising 20 alveoli. The Demonstrator will cover a polar range of 32.5 – 65◦ , with 4 types of alveoli/crystals and 3 segments of 2 alveoli in the azimuthal direction and 10 alveoli in GSI SCIENTIFIC REPORT 2012 PHN-ENNA-EXP-65 polar direction. The design provides a significant section of the final calorimeter and will ultimately be incorporated into CALIFA [4]. In addition to detector characterisation, the Demonstrator is intended for use in a real experimental campaign. In Figure 1 an artistic view of the CALIFA Demonstrator is shown. Figure 2: An artistic representation of the complete CALIFA calorimeter. Figure 1: An artistic impression of the CALIFA Demonstrator. We are in parallel working on the R&D towards an optimal solution for the "Forward EndCap" section. This polar region will be subject to high energy charged particles in addition to γ rays boosted to several times their energy in the projectile rest frame. The long CsI(Tl) crystals employed for the CALIFA Barrel section would fulfil the R3 B physics requirements for the EndCap section, however this option would suffer from incident charged particles undergoing a large number of inelastic reactions, significantly reducing the full energy peak efficiency. This restriction may be overcome by the use of a phoswich concept with two, relatively short, high performance scintillator layers which provide two ∆E measurements as charged particles pass through them. From these measurements the particle’s incident energy can be determined. This approach reduces the detector volume significantly and several phoswich options are currently under investigation. One such concept proposes a combination of two novel scintillation materials: 4 cm of LaBr3 (Ce) followed by 6 cm LaCl3 (Ce). This configuration works as a telescope, the first section (LaBr3 (Ce)) provides a ∆E measurement whereas the total E is obtained by the two consecutive energy loss measurements (∆E LaBr3 +∆E LaCl3 ). An initial small size prototype consisting of an array of 2x2 phoswich LaBr3 +LaCl3 elements, formed by rectangular crystals, was recently irradiated with high energy protons (GSI, 2001000 MeV). Data analysis is currently under way. We have also progressed towards the final design of the segmentation of the Forward EndCap. The large segmentation present in the Barrel must be preserved in order to retain the spectrometric capabilities. A dedicated design places frustum shaped crystals into 10 branches, each one containing 5 alveoli. The alveoli are sub-divided into 15 sectors holding individual crystals which results in a total of 750 crystals. The performance of this system has been studied by means of Monte Carlo simulations [5]. Figure 2 shows an artistic conception of CALIFA where both sections: Barrel and Forward EndCap, are mounted on a common platform. CALIFA is currently entering a very exciting period, with the full implementation and commissioning of the CALIFA Demonstrator expected in the first quarter of 2014. The submission of the TDR for the forward section is foreseen by the end of 2014. According to our plans the complete CALIFA should be installed and operational in the R3 B cave by the end of 2016. This work was supported by Mineco (FPA2009-14604C02-01, FPA2009-14604-C02-02, FPA2009-07387), HIC /FAIR, BMBF (06DA9040I, 05P12RDFN8, 06MT9156, 05P12WOFNF), DFG (EXC153), GSI-TU Darmstadt cooperationn and the EraNet NupNet GANAS. References [1] T. Aumann et al., Technical Proposal for the design, construction, commissioning and operation of R3 B, A universal setup for kinematical complete measurements of Reactions with Relativistic Radioactive Beams (2005). [2] T. Aumann et al., Technical report for the Design, Construction and Commissioning of the CALIFA Barrel: The R3 B CALorimeter for In Flight detection of γ-rays and high energy charged particles (2011) [3] T. le Bleis et al., Test of Integration of CALIFA into R3B, GSI SCIENTIFIC REPORT 2012 [4] E. Casarejos et al., Mechanics of CALIFA Barrel, GSI SCIENTIFIC REPORT 2012 [5] J. Sanchez del Rio et al., CEPA: A LaBr3(Ce)/LaCl3(Ce) phoswich array for detection of high energy protons and gamma radiation, GSI SCIENTIFIC REPORT 2012 199