The ^{12}C+^{12}C fusion reaction plays a critical role in the evolution of massive stars and also strongly impacts various explosive astrophysical scenarios. The presence of resonances in this ...reaction at energies around and below the Coulomb barrier makes it impossible to carry out a simple extrapolation down to the Gamow window-the energy regime relevant to carbon burning in massive stars. The ^{12}C+^{12}C system forms a unique laboratory for challenging the contemporary picture of deep sub-barrier fusion (possible sub-barrier hindrance) and its interplay with nuclear structure (sub-barrier resonances). Here, we show that direct measurements of the ^{12}C+^{12}C fusion cross section may be made into the Gamow window using an advanced particle-gamma coincidence technique. The sensitivity of this technique effectively removes ambiguities in existing measurements made with gamma ray or charged-particle detection alone. The present cross-section data span over 8 orders of magnitude and support the fusion-hindrance model at deep sub-barrier energies.
This paper updates the development of a warm front-end electronics (WFEE) dedicated to cryogenic sensors readout. It belongs to the X-ray integral field unit instrument of ESA’s future space ...observatory: ATHENA. This instrument integrates cryogenic elements such as 3168 transition edge sensors as detectors, multiplexed into 96 channels using time-division multiplexing (TDM). One TDM channel will be read out by two stages of superconducting quantum interference device (SQUID), followed by a WFEE and finally, a digital readout system, both two last stages operating at about 300 K. In the WFEE, 96 TDM channels will be distributed in 48 application-specific integrated circuits (ASIC). Each channel includes one low-noise amplifier to amplify the multiplexed signal and 5 configurable current sources to bias the SQUIDs and TES in the cryogenic stages. Additionally, two channels within the same ASIC share a serial bus “RS485/I
2
C” to configure the current sources (current SlowDACs) and housekeeping elements that monitor the temperature, current and voltage of the ASIC. The ASIC presented in this paper, “AwaXe_v3” (AwaXe: Athena Warm Asic for the X-ifu Electronics), is developed for the WFEE using an AMS 350 nm SiGe BiCMOS technology. It is the first prototype of the WFEE integrating two complete TDM channels. Representative measurement results that characterise the main components of the WFEE will be discussed in this paper as an update on the use of ASIC for the TES/SQUID readout.
Aims. The aim of this work is to furnish branching ratios (BRs) to the kinetic databases used in astrochemistry such as the KInetic Database for Astrochemistry (KIDA). This concerns CH y(+) ...$_y^{(+)}$ y (+) species (y = 2–4) excited by cosmic rays, electrons and photons, or the intermediate excited complexes CH y(+) $_y^{(+)}$ y (+) resulting from a chemical reaction. Methods. The full set of fragmentation branching ratios following CH y(+) $_y^{+}$ y + (y = 2,4) of constant velocity (250 keV uma−1) colliding with He atoms has been measured with the multidetector AGAT. Kinetic energy distributions of neutral fragments produced in each dissociation channel have been also measured. With these experimental inputs, and theoretical dissociation energies, semiempirical breakdown curves (BDCs) have been constructed. Results. Prediction of BRs with the present BDCs is found to agree with available BR measurements for electronic dissociative recombination, collision with fast electron and photodissociation. Dependence of BRs with the various UV fields relevant to interstellar medium and planetary atmospheres is predicted.
Synopsis We are studying small hydrocarbons produced in high velocity (3.4 a.u.) collision between CHy+ cations and He atoms. During the collision those hydrocarbons gain some energy and release this ...energy doing fragmentation. Thanks to the detector AGAT we have been able to measure fragmentation branching ratios for CHyq+ (y=2-4, q=0-3). We also constructed semi-empirical breakdown curves for CHyq+ using these experimental branching ratios.
We present
12
C+
12
C direct fusion measurements with STELLA UKFATIMA, that reach into the region of astrophysics interest relevant to massive stars (
M
⊙
≈ 25) using self-supporting thin rotating ...carbon foils 1. We demonstrate that detecting gammas and light charged particles in coincidence with nanosecond timing is key for effective background reduction achieving reliable measurements in the sub-nanobarn range. We give details about core developments of the detection apparatus as well as the coincidence-analysis procedure of low count statistics. The present data largely follows the phenomenological hindrance interpolation and shows indication for resonant behaviour at the lowest energy explored.
The calibration units of KM3NeT Le Breton, R.; Billault, M.; Boutonnet, C. ...
Journal of instrumentation,
09/2021, Letnik:
16, Številka:
9
Journal Article
Recenzirano
Odprti dostop
KM3NeT is a deep-sea infrastructure composed of two neutrino telescopes being deployed in the Mediterranean Sea: ARCA, near Sicily in Italy, designed for neutrino astronomy, and ORCA, near Toulon in ...France, designed for neutrino oscillation physics. To achieve the best performance, the exact location of the optical modules, affected by sea current, must be known at any time and the timing resolution between optical modules must reach the nanosecond. Moreover, the properties of the environment in which the telescopes are deployed must be continuously monitored because they affect the timing and positioning calibration. KM3NeT is going to deploy several dedicated Calibration Units to meet these calibration goals. Because of the difference in size between ARCA and ORCA, the design of the Calibration Unit is not the same for the two sites. This proceeding describes all the devices, features and purposes of the Calibration Units with a focus on the ORCA Calibration Unit.
The experimental setup STELLA (STELlar LAboratory) is designed for the measurement of deep sub-barrier light heavy ion fusion cross sections. For background suppression the γ-particle coincidence ...technique is used. In this project, LaBr3 detectors from the UK FATIMA (FAst TIMing Array) collaboration are combined with annular silicon strip detectors customized at IPHC-CNRS, Strasbourg, and the setup is located at Andromède, IPN, Orsay. The commissioning of the experimental approach as well as a sub-barrier 12C +12C → 24Mg∗ cross section measurement campaign are carried out.
The ALTO facility (Accélérateur Linéaire auprès du Tandem d’Orsay) has been built and is now under commissioning. The facility is intended for the production of low energy neutron-rich ion-beams by ...ISOL technique. This will open new perspectives in the study of nuclei very far from the valley of stability. Neutron-rich nuclei are produced by photofission in a thick uranium carbide target (UCx) using a 10μA, 50MeV electron beam. The target is the same as that already had been used on the previous deuteron based fission ISOL setup (PARRNE F. Clapier et al., Phys. Rev. ST-AB (1998) 013501.). The intended nominal fission rate is about 1011fissions/s. We have studied the adequacy of a thick carbide uranium target to produce neutron-rich nuclei by photofission by means of Monte-Carlo simulations. We present the production rates in the target and after extraction and mass separation steps. The results from Monte-Carlo simulations are compared to experimental data either with the ALTO facility (in the first step of commissioning, i.e. 100nA of the electron beam current intensity), or with fast-neutron-induced fission generated from a 26MeV deuteron beam. The results obtained support the suitability of FLUKA simulation code used to describe all the photofission process with an electron beam energy of 50MeV.
The 12C+12C fusion reaction is one of the most important for nuclear astrophysics since it determines the carbon ignition in stellar environments. Two experiments which make use of the gamma-particle ...coincidence technique to measure the 12C+12C S-factors at deep sub barrier energies are discussed. Results are presented showing a decrease of the S-factor below Ec.m. = 3 MeV.
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