Total Reaction Cross Sections for 6,8 He and 9 Li Nuclei on 28 Si, 59 Co, and 181 Ta Targets
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l Reaction Cross Sections for 6,8He and 9Li Nuclei on 28Si, 59Co, and 181Ta Targets Yu. G. Soboleva, *, Yu. E. Penionzhkevicha, b, V. V. Samarina, c, M. A. Naumenkoa, S. S. Stukalova, I. Siváčeka, d, S. A. Krupkoa, A. Kuglerd, and J. Loukoe aJoint
Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia National Research Nuclear University (MEPhI), Moscow, 115409 Russia c Dubna State University, Dubna, Moscow oblast, 141982 Russia d Nuclear Physics Institute, Czech Academy of Sciences, Řež, 250 68 Czech Republic eCyclotron Laboratory, University of Jyväskylä, Jyväskylä, 40351 Finland *e-mail: [email protected] b
Received March 2, 2020; revised April 15, 2020; accepted April 27, 2020
Abstract—Experiments with 6,8He, 9Li + 28Si, 59Co, and 181Ta reactions in the energy range of 6,8He and 9Li beams 6–36 A MeV have been preformed. Prompt neutrons and gamma radiation were registered by a 12-detector gamma spectrometer. The values of the total reaction cross sections and the multiplicity distributions for the emission of γ-quanta and neutrons were calculated taking into account the distributions over the number of triggered detectors. DOI: 10.3103/S1062873820080286
INTRODUCTION Research on the structure of light exotic nuclei that lie at the boundary of the region of stability and specific features of the reactions with their participation is an important problem of today’s nuclear physics [1‒6]. The unusual nature of light neutron-rich nuclei with halos is apparent from their surprisingly large reaction cross sections [1] and specific energy dependences [4–9]. The use of silicon and plastic scintillation detectors as targets (with 28Si and 12C nuclei, respectively) in most experiments performed earlier (see, e.g., [5, 9]) did not allow results for heavier targets to be obtained. In this work, heavier 59Co and 181Ta nuclei were used along with 28Si nuclei as targets for 6,8He and 9Li beams. METHODS OF MEASURING TOTAL REACTION CROSS SECTIONS Total reaction cross section σR can be found by measuring the number I 0 of particles flown into a target and the number I of particles flown out of it without interaction:
I = I 0 exp ( −nd σR ) ,
(1)
where nd is the reduced number of nuclei of a target with thickness d, and n is the concentration of atomic nuclei. When nσR 1, we can restrict ourselves with
fair accuracy with the first terms of the series expansion of the exponent:
nd σR ≈ (I 0 − I ) I 0 ,
(2)
nd σR ≈ I R I 0 ,
(3)
where I R = I 0 − I is the number of reaction events. Formula (2) is used to determine the total reaction cross section in the beam attenuation method first proposed and implemented in [10]. In experiments with the beam attenuation method, the values of I and I0 are measured. Formula (3) is used to determine the total reaction cross section in the method of registration of reaction products first proposed and implemented in [11]. In experiments with this method, the values of IR and I0 are measured. The great variety of implementations of this method is due to the different ways of mea
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