UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-23 17:56
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Conference: Bucharest University Faculty of Physics 2009 Meeting


Section: Nuclear and Elementary Particles Physics


Title:
Low background spectrometer for in–beam measurements of gamma rays and neutrons


Authors:
I. A. Precup, M. Petre, M. Duma, D. Moisa, C. Petre, E. Dragulescu


Affiliation:
Horia Hulubei National Institute of Physics and Nuclear Engineering IFIN-HH, P.O. Box MG-6, Bucharest, Romania


E-mail
edrag@nipne.ro


Keywords:


Abstract:
There are strong demands from various fields on high-resolution low backgrounds detectors for gamma-rays and neutrons. They are used to study extremely weak gamma-rays and /or associated with very important rare decays which are crucial for nuclear and particle physics. The purpose of this contribution is to report details of high-selectivity low- background selectivity spectrometer and its performance. The whole assembly is situated inside the low-background parallelipiped lead castle ( 85x56x55cm ) used as passive shield with 7.5 cm lateral and 10cm above depth to reduce cosmic background . Cu and Al layers with thickness of 2cm were used inside lead shield to reduce gamma-rays from lead bricks. Since the muon generated cosmic ray-rays contribution to the background spectrum is high due to neutrons produced in the spallation reactions the castle is covered by layers of 1 mm Cd layers and 10cm thick paraffin bricks. The main part of this spectrometer is represented by 4 NaI (Tl) summing detector placed on 7th beam line of IFIN-HH Tandem. This detector is a 22.5x22.9 cm annular “ Bicron “ NaI(Tl ). The detector is composed by two parts, either scintillation part is segmented in four sections and optically separated , viewed by a photomultiplier tube. The end of the hole can be closed by the 7.6x7.6 cm NaI (Tl) “ plug “ detector. This assembly can be operated as summing detector or as an active Anti-Compton shield mode with a closed–end coaxial HPGe detector of a high efficiency located inside the 7.62 cm diameter hole of the annular NaI(Tl). Target is situated in the detector center covering a solid angle of 4pi. The neutron detector based on NE213 scintillation detector (12cm diameterx5cm length) coupled with Photon XP04021 photomultiplier is positioned at 14cm from the target behind of NaI(Tl) detector. Due to different pulse shapes of neutrons and gammas, the n - discrimination offers the possibility to record both neutron and gamma pulses. This spectrometer was used in two modes (gamma prompt and delayed experiments) to measure cross-sections for different reactions.