γ -spectroscopy group

The Gamma Spectroscopy group performs nuclear structure studies using stable beams provided by the PIAVE-ALPI-TANDEM accelerators of Legnaro National Laboratory, and high-resolution Ge arrays coupled to different ancillary detectors. The group works in close collaboration with the "Galileo Galilei" physics department of the University of Padova and INFN-Padova. Furthermore, the group belongs to the GAMMA collaboration for nuclear physics. This collaboration is part of the INFN - National Scientific Committee 3 (CSN3) initiative, which involves 5 INFN divisions: INFN - Laboratori Nazionali di Legnaro (LNL),

• INFN - Sezione di Firenze (FI),
• INFN - Sezione di Milano (MI),
• INFN - Sezione di Padova (PD),
• University of Camerino.

The group is also involved with SPES, which is a next generation ISOL-type accelerator that together with the operation of existing machines, is the future of LNL. SPES will provide Radioactive Ion Beam for nuclear physics and astrophysics research, as well as for interdisciplinary applications.

Currently, the AGATA array is being employed to detect γ radiation emitted after reactions such as fusion-evaporation, and low-energy Coulomb excitation. You can find more information on the installation and performance of AGATA@LNL here. At the moment, GALILEO, the native array for detection γ-ray radiation, is not operational as all efforts are focused on AGATA.

The physics program of the group is focused, but not limited, on following topics:

• Shell structure in n-rich nuclei
• Isospin symmetries and n-p pairing
• Pigmy resonance of interest in astrophysics
• Structure of nuclei at the proton-drip line
• Critical points and phase transitions between different nuclear shapes

In addition to the local activities, the group also performs research in collaboration with different laboratories such as GANIL, ISOLDE, JYU, the RIKEN Nishina Center, and GSI which is at the moment evolving into FAIR .

GALILEO

GALILEO (Gamma Array of Legnaro INFN Laboratories for nuclEar spectrOscopy) is the current high-resolution Ge array for advanced in-beam γ-ray spectroscopy studies constructed and installed at LNL.

The first phase of GALILEO was operational between 2015 and 2019 and consisted of 25 GASP tapered detectors coupled to Neutron Wall as shown in the picture. In a second stage of this phase, 10 GASP detectors were moved to the forward angles (replacing Neutron Wall) and LaBr₃ detectors were mounted at 90° to optimize the setup for measurements using the Plunger.

In its second phase, GALILEO will consist of 25 GASP tapered detectors at 90° and forward angles, and 10 triple clusters built using capsules of EUROBALL, mounted at backward angles. At the moment 20 GASP detectors and one triple cluster are mounted in the structure. Keep updated on the progress of the array following the latest news.

The HPGe detectors are surrounded by anti-Compton shields in order to reach, for the whole array, a peak-to-total ratio of about 55%. A 5cm thick heavy-metal shield improves Compton rejection, avoiding direct γ -ray interactions in the BGO shields. The geometry of the array is designed to maximize the photo-peak efficiency under typical in-beam medium-high γ-ray multiplicity conditions, achieving a value of 6.4%. GALILEO can be coupled to different ancillary devices.

Check out the list of GALILEO physics publications, or take a look at some of the technical publications . You can also see previous thesis regarding GALILEO or its ancillary devices.

A full list of the experiments approved and performed with GALILEO can be found here

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Previous Arrays

The group has a well-established expertise in nuclear spectroscopy with high-resolution gamma-arrays. Since the first experiments performed in the 90s, the group has hosted GASP, EUROBALL, CLARA, as well as the first stage of the last-generation European gamma-array, the AGATA demonstrator.

Ancillary devices

PRISMA

Nucl. Phys. A

PRISMA is a large-acceptance magnetic spectrometer for heavy ions. Its design is based on a simple quadrupole-dipole configuration, with no hardware elements correcting for the optical aberrations, which are corrected instead via a software reconstruction of the trajectories of the nuclei inside the spectrometer. The trajectories are deduced from the point of entrance in the spectrometer and in the focal plane, where position-sensitive detectors are placed. The start detector of PRISMA is based on an MCP, while the focal plane detector is based on a MWPPAC. These detectors provide also a time-of-flight measurement. An ionisation chamber placed after the MWPPAC measures the charge and total energy of the incoming ions.

#agata #clara

Plunger device

NIM A

A dedicated Plunger device for lifetime measurements using RDDS technique. Maximum distance of the plunger from the target is 1.2cm. Usage of"reversed plunger" was successfully tested.

#agata #galileo

EUCLIDES

Eur. Phys. J. A

The EUCLIDES array is based on dE-E telescopes, the silicon thickness is 130 μm and 1000 μm for dE and E layers respectively. This allows the discrimination between light charged particles. 40 telescopes form a self-supported structure with the solid angle coverage close to 80% of 4π sr. Detector is made out of pentagonal and hexagonal detectors, the surface of each telescope is approximately 10cm².

#agata #galileo

SPIDER

NIM A

SPIDER is an array of segmented silicon detectors primarily made for heavy-ion detection in low-energy Coulomb-excitation experiments. The array is made out of 7 trapezoidal 300μm thick detectors, each composed of 8 strips. Angular coverage is 124-161° covers 17% of 4π. These values can be however adjusted by changing the distance of the array from the target.

#agata #galileo

SAURON

Micron Semiconductor Ltd

SAURON is an annular double-sided silicon stripped ion detector for detection of light charged particles. Junction side is divided into 4 quadrants, each with 16 radial strips; ohmic side is divided into 16 azimuthal strips. Placing detector at standard 5cm distance from the target provides angular coverage of 25-44° if mounted forward, or 136-154° if mounted backward. The distance from the target may be adjusted. Available are 300, 500, 1000 and 1500 μm thick detectors.

#agata

DANTE

LNL Annual Report

DANTE is a position-sensitive array of MCP detectors. Each MCP has, 40 x 60mm² with position resolution below 1mm and time resolution of 130ps. Individual detectors are mounted on a ring in chevron configuration. Five support rings are available covering various angles, from near-zero to 90°.

#agata

TRACE

Eur. Phys. J. A

TRACE is an array of highly-segmented silicon telescopes aimed at performing spectroscopy and discrimination of charged particles and light ions in transfer reactions. It is made out of 60 4x4mm square pads arranged in 12x5 configurations. The dE layer is 200μm thick while the E layer is 1-1.5mm thick.

#agata #galileo

Oscar

NIM A

Oscar is an array of 128 δE-E pseudo-telescopes for identification of light charged particles. It is 2 arrays, each composed of 20μm thick silicon detector segmented into 16 strips, and a 16 500μm thick silicon pads arrange in 4x4 matrix.

#agata

LaBr₃

NIM A

Array of LaBr₃:Ce scintillators is couled with AGATA to provide fast timing measurements and high-energy γ-ray spectroscopy. Array consist of four 3"x3" detectors and four 2"x2" detectors.

#agata #galileo