EXOGAM

EXOGAM
Name	EXOGAM
Caption	High-purity germanium detector array EXOGAM at a radioactive ion beam facility
Type	Gamma-ray spectrometer
Location	GANIL
Installed	2001
Detectors	Clover high-purity germanium
Operators	CNRS, CEA, GANIL collaboration

EXOGAM

Introduction

EXOGAM is a high-resolution gamma-ray spectrometer developed for nuclear structure research at accelerator facilities. The array was commissioned to perform spectroscopy of exotic nuclei produced by reactions at GANIL, enabling studies that connect to topics investigated at GSI Helmholtz Centre for Heavy Ion Research, ISOLDE, RIKEN, TRIUMF, FRIB, CERN, Oak Ridge National Laboratory, Lawrence Berkeley National Laboratory, Argonne National Laboratory, Brookhaven National Laboratory, Michigan State University, University of Jyväskylä, University of Manchester, University of Oslo, CEA Saclay, CNRS, IPN Orsay, University of Strasbourg, University of Liverpool, University of York, University of Edinburgh, University of Notre Dame, Institut Laue-Langevin, Max Planck Society, Helmholtz Association, European Commission, Niels Bohr Institute, Universität Köln, University of Warsaw, University of Padua, University of Milano-Bicocca, Université Paris-Sud, Université Grenoble Alpes, Madrid Complutense University, University of Tokyo, Tohoku University, Kyoto University, University of Manchester, University of Birmingham.

Design and Components

The detector array uses segmented high-purity germanium clover detectors mounted in a configurable geometry, incorporating electronics and cryogenic systems from collaborators including CEA Saclay, CNRS, IPN Orsay, STFC, ECFA, INFN, GANIL and vendors with heritage from projects such as EUROBALL, MINIBALL, GASP, AGATA, DALI2, TIGRESS, HORUS, CLARION, RISING, PRISMA, SPIRAL, LISE3, and SPEG. Each clover module houses four crystals, preamplifiers, and digitizers patterned after designs used at ISOLDE and GSI; the mechanical support and vacuum chambers were engineered in collaboration with institutes including CEA, CNRS, IPN Orsay, INFN, Universität Köln, and industrial partners in France and Germany. Cooling is provided by liquid-nitrogen dewars patterned after systems used at Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory, while the digital data acquisition borrows firmware concepts tested on AGATA and GRETA development programs.

Operation and Performance

EXOGAM operated at GANIL in configurations optimized for in-beam and decay spectroscopy, often coupled to ancillary devices such as VAMOS, SPEG, ALPHA, DIAMANT, NEDA, Neutron Wall, MINIBALL ancillary detectors, ZeroDegree Spectrometer, RITU, FMA, S800, SHARAQ, PRISMA, and MUST2 charged-particle arrays. In-beam experiments used heavy-ion beams from the GANIL cyclotrons to populate states of interest, enabling coincidence measurements with particle detectors and recoil separators similar to setups at GSI and ISOLDE. Energy resolution, peak-to-total ratios, and photopeak efficiency matched expectations for clover detectors, allowing Doppler-corrected spectroscopy of fast beams and lifetime measurements using recoil-distance and Doppler-shift attenuation techniques employed at NSCL and LNL. The system recorded gamma-gamma, gamma-particle, and gamma-neutron coincidences, supporting studies comparable to those from TAMU Cyclotron Institute, Michigan State University’s NSCL, and RIBF.

Scientific Achievements and Experiments

EXOGAM contributed to the mapping of shell evolution, shape coexistence, and collectivity in nuclei far from stability, producing results relevant to research themes pursued at FRIB, ISOLDE, RIKEN, GSI, TRIUMF, NSCL, JYFL, GANIL-SPIRAL, and University of Jyväskylä. Notable topics include investigation of magic numbers near N=20 and N=28, studies of proton-rich nuclei relevant to the rp-process, neutron-rich isotopes pertinent to the r-process, and spectroscopic studies informing theoretical frameworks developed at CEA, CNRS, Oak Ridge, Brookhaven National Laboratory, Argonne National Laboratory, Lawrence Livermore National Laboratory, University of Tennessee Knoxville, University of California Berkeley, IReS Strasbourg, and Universidad Complutense de Madrid. Experiments produced high-spin spectroscopy, isomer studies, and measurements of electromagnetic transition probabilities that fed comparisons with shell-model calculations from groups at MSU, University of York, Institut de Physique Nucléaire, University of Liverpool, University of Milano-Bicocca, Università di Padova, GANIL theory unit, and collaborations with theorists at GSI Theory Department and RIKEN Nishina Center.

Upgrades and Successor Instruments

Experience with EXOGAM informed design and commissioning of next-generation arrays such as AGATA and influenced development at GRETA and PARIS. Lessons learned about clover segmentation, electronics, and data acquisition were integrated into upgrade paths at GANIL and guided ancillary detector improvements at ISOLDE and TRIUMF. Components and expertise migrated into collaborative projects including AGATA-Phase1, AGATA-Phase2, FAIR-related instrumentation at GSI, and international detector development networks supported by the European Commission Horizon programs and national funding agencies such as CNRS, CEA, INFN, STFC, DFG, RSNZ, and NSERC.

Collaboration and Facility Context

EXOGAM was realized by a consortium of European and international institutes coordinated through GANIL and funded by agencies including CNRS, CEA, INFN, STFC, DFG, European Commission, ANR, MIUR, Ministerio de Ciencia y Tecnología (Spain), and national research councils. The project involved close collaboration with accelerator facilities and detector groups at GSI, ISOLDE, RIKEN, TRIUMF, NSCL, LNL-INFN, JAEA, CEA Saclay, IPN Orsay, University of Liverpool, University of Manchester, Universität Köln, University of Warsaw, Université Grenoble Alpes, Institut Laue-Langevin, and industry partners in France and United Kingdom. The array’s operation contributed to the scientific output of user programs at GANIL-SPIRAL and supported visiting experimental campaigns from groups across Europe, North America, and Asia.

Category:Gamma-ray spectrometers Category:Nuclear physics experiments Category:GANIL