MULTI-2, a 4π spectrometer for total reaction cross section measurements Siváček, I.; Penionzhkevich, Yu.E.; Sobolev, Yu.G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Letnik:
976
Journal Article
Recenzirano
A detection setup for the direct measurement of the total reaction cross section with exotic nuclei is presented. The setup consists of a multi-detector telescope for beam-particle identification and ...a 4π gamma-ray spectrometer for the detection of prompt photons and neutrons accompanying the nuclear reactions. Measurements are based on the modified transmission method and gamma-ray tagging of nuclear reaction events. Registration efficiency and response characteristics of the gamma-ray spectrometer are investigated by Monte Carlo simulations and measurement with 60Co spectroscopic source. Results show strong a dependence of the registration efficiency on gamma-ray multiplicity, with minimum registration efficiency value of 70%. Evaluation of the registration efficiency for data measured in the total reaction cross section experiments is discussed.
The 4π methods used to measure total reaction cross sections σ
R
are presented; they are based on the detection of prompt γ rays and neutrons by scintillation spectrometers with a solid angle Ω close ...to 4π. The experimental setup based on a 12-detector CsI(Tl) spectrometer (Ω = 0.96 × 4π) is described, which has been used in experiments on measuring σ
R
(
E
) for reactions with radioactive isotopes of He, Li, and Be. The above methods and the σ
R
(
E
) measurement results for the
6
He +
28
Si,
59
Co,
181
Ta reactions are analyzed. The advantage of the method allowing for multiplicity of γ rays is shown.
New semiconductor detectors based on CdZnTe and CeBr
3
crystals are tested. A spectrometer facility consisting of CdZnTe, CeBr
3
, and Si (for α–γ measurements) detectors is assembled for ...verification tests. The main parameters of the detectors such as energy resolution FWHM/
E
γ
keV and detection efficiency (%) are investigated and measured. The possibilities of measuring photon radiation in a wide energy range are verified. γ–γ and α–γ coincidences are measured using the detectors. The results of the measurements show that the detectors can be used to study nuclear reactions and properties of reaction products.
Two design options for a heat-recovery turbine unit (HRTU), which generates electricity for self-contained power supply of gas mains’ compressor stations (GMCSs) using the heat of exhaust gases from ...gas-turbine engines (GTEs) driving gas-pumping units (GPUs), are examined. The working fluid of the recovery circuit is octafluorocyclobutane (c-C
4
F
8
, engineering name is RC318) in one of the two HRTUs and the exhaust gases of GPU GTE in the other HRTU. The HRTU operating on RC318 has a three-circuit cycle, including three turbines, three recuperative heat exchangers, three RC318 heaters, and one common condenser. An alternative design of HRTU is a vacuum-type GTU consisting of an overexpansion gas turbine, whose inlet is connected with the exhaust of GPU GTE, exhaust gas coolers, a cooled gas compressor, and an induced-draft fan. The excess power of this HRTU above the current power demand at the GMCS is used to create a vacuum at the exhaust of the gas turbine of the GPU GTE. The results are presented of the comparative balance calculations of parameters and characteristics of both HRTUs as applied to a 16-MW Ural GPU GTE. They were performed using the updated initial data and the software library RefProp (in the CoolProp high-level interface) for the calculation of thermodynamic parameters of working fluids. It has been demonstrated that a more compact and easier to implement gas-type HRTU (with an overexpansion gas turbine), although having a lower power than the RC318-type HRTU, can still fully cover the demand of the GMCS for high-quality power and also to solve the problem of substituting imported gas piston and diesel generators at the GMCS within the shortest possible time and with the lowest capital and operating expenditures.
Two independent methods: Asymptotic Normalization Coefficients (ANC) and Modified Diffraction Model (MDM) were applied to new and existing experimental data to search for states with enhanced radii ...in isobaric analogue states (IAS) of 12B and 12N. The ANC analysis of the 11B(d,p)12B reaction at Ed = 21.5 MeV has confirmed neutron halo existence for two states of 12B: 2−, 1.67 MeV and 1−, 2.62 MeV 1. Some new results were obtained for higher excited states: halo-like states were observed for 0+, 2.72 MeV and 3−, 3.39 MeV states. It should be mentioned that the last one is unbound state, which is 19 keV above the neutron emission threshold and in both states last neutron has a non-zero orbital momentum (ln=1 and ln=2 correspondingly). We propose to use MDM to study isobaric analogue states of 12B in the mirror 12N nucleus and apply it to analyze the (3He,t) reaction data. The existing in the literature data are not completed enough to make definite conclusion about halo in the 2− and 1− states of 12N. This fact simulated us to carry out a new experiment on the 12C(3He,t)12N reaction at the end of 2018. The measurements were conducted at the University of Jyväskylä (Finland) using the K130 cyclotron to produce a 3He beam at E(3He)=40 MeV. The differential cross sections of the 12C(3He,t)12N reaction were measured in the c.m. angular range 8°-70°. Preliminary results for angular distributions are obtained. MDM analysis of preliminary (3He,t) experimental data is done.
The energy dependence of the total cross sections for the sup.6He + Si and sup.9Li + Si reactions was measured at beam energies between 5 and 20 MeV per nucleon. The results agree with experimental ...data published for the sup.6He + Si reaction. New data are obtained for the sup.9Li + Si reaction in the vicinity of a local enhancement of the total cross section. A theoretical analysis of the possible reasons behind the appearance of this peculiarity in the case of collisions of sup.6He and sup.9Li nuclei with silicon target nuclei is performed. In particular, the enhancement may owe its origin to the effect of loosely bound projectile nucleons.
The paper presents the results of measurement of the total cross sections for reactions 4,6He+Si and 6,7,9Li+Si in the beam energy range 5-50 A MeV. The enhancements of the total cross sections for ...reaction 6He+Si compared with reaction 4He+Si and 9Li+Si compared with reactions 6,7Li+Si have been observed. The performed microscopic analysis of total cross sections for reactions 6He+Si and 9Li+Si based on numerical solution of the time-dependent Schrödinger equation for external neutrons of projectile nuclei 6He and 9Li yielded good agreement with experimental data.
The differential cross sections for the
12
C(
3
He,
t
)
12
N reaction leading to formation of the 1
+
(ground state), 2
+
(0.96 MeV), 2
−
(1.19 MeV), and 1
−
(1.80 MeV) states of
12
N are measured at
...E
(
3
He) = 40 MeV. The analysis of the data is carried out within the modified diffraction model and distorted wave Born approximation. Increased rms radii have been obtained for the ground, 2
−
(1.19 MeV), and 1
−
(1.80 MeV) states. We revealed that
12
B,
12
N, and
12
C in the isobaric analogue states with
T
= 1, and spin-parities 2
−
and 1
−
have increased radii and exhibit properties of neutron and proton halo states.
Physical space anisotropy and the associated new interaction are investigated. These new physical characteristics of space are observed over a broad range of scales and are based on analyses of ...fluctuations in the β-decay (10
–17
cm) and α-decay (10
–13
cm) of radioactive elements, the motion of pulsars (the size of our Galaxy is 10
22
cm) and the anisotropy of ultrahigh energy cosmic rays (the size of our visible Universe is 10
28
cm). Experiments on using the new interaction as a source of propulsion for a model space vehicle are considered (Italy, 2012–2014). The coordinate of global anisotropy is determined: right ascension α ≈ 316° ± 5°.
A project of the high-resolution magnetic analyzer MAVR is proposed. The analyzer will comprise new magnetic optical and detecting systems for separation and identification of reaction products in a ...wide range of masses (5-150) and charges (1-60). The magnetic optical system consists of the MSP-144 magnet and a doublet of quadrupole lenses. This will allow the solid angle of the spectrometer to be increased by an order of magnitude up to 30 msr. The magnetic analyzer will have a high momentum resolution (10-4) and high focal-plane dispersion (1.9 m). It will allow products of nuclear reactions at energies up to 30 MeV nucleon to be detected with the charge resolution ∼1 60. Implementation of the project is divided into two stages: conversion of the magnetic analyzer proper and construction of the nuclear reaction products identification system. The MULTI detecting system is being developed for the MAVR magnetic analyzer to allow detection of nuclear reaction products and their identification by charge Q, atomic number Z, and mass A with a high absolute accuracy. The identification will be performed by measuring the energy loss (ΔE), time of flight (TOF), and total kinetic energy (TKE) of reaction products. The particle trajectories in the analyzer will also be determined using the drift chamber developed jointly with GANIL. The MAVR analyzer will operate in both primary beams of heavy ions and beams of radioactive nuclei produced by the U400 - U400M acceleration complex. It will also be used for measuring energy spectra of nuclear reaction products and as an energy monochromator.