13c/ 12c pdf

It is the motivation for our choice of measurements here: irradiations with a 13C beam followed by measurement of activities at both surface and underground laboratory characterized by an ultra-low background radiation. The GammaSpec laboratory is an above ground installation in IFIN-HH main campus, in the same location as the tandem accelerators, consisting of a HpGe detector very well shielded, and carefully calibrated with sources and international inter-laboratory comparisons [10, 11].

In this mine a laboratory was built to perform measurements using gamma- ray spectrometry in ultralow radiation background. The average dose underground was found 1. Figure 1 compares -ray spectra measured above ground and underground. At higher energies, the background radiation originates mostly from cosmic rays.

The natural radioactivity is significantly reduced for measurements in the underground laboratory bottom spectrum. From Fig. This is the major advantage we want to test and use in the current measurements [13, 14]. The irradiated carbon targets were measured in the GammaSpec laboratory and in the underground laboratory. The cascading rays and keV were detected with germanium detectors.

The detection systems have been protected with lead castles to reduce ambient background radiation. The first case studied was a C target irradiated for 15 hours with an 8 MeV beam. We found an activity of 4. In the four the -ray spectra we could observe the decreasing activity of the irradiated target and the gradual relative increase of the background radiation.

The following two steps consisted of the activation of C targets at two different beam energies, 6 and 7 MeV, and from measuring them both in the underground laboratory and in the GammaSpec laboratory located at the surface. This spectrometric system is protected by a lead cylindrical shield 10 cm thick , covered on the inside with tin 1 mm thick and copper 1. Thus for rays of energies between 20 and keV in a 24 hours measurement one obtains a count rate of 1.

This activity was calculated after corrections were made for the efficiency and the time needed to transport the target from the reaction chamber to the GammaSpec laboratory. For measurements made in the underground laboratory another C target was irradiated using the same parameters, but for a longer irradiation time of about 25 hours. The minimum measurable cross section results to be about 3 nb using beam intensity around 0. That is an order of magnitude below the lowest value measured until now in other laboratories.

Increasing the beam intensity to approximately pPA, it is possible to decrease the limit of detection of 10 more times, so we can measure at the energies lower than those now existing in the literature. Barely in the surface lab, but clearly in the underground one see Fig. Reducing the limit by an order of magnitude is still possible by increasing the beam intensity. There will be, however, limitations on the extent to which the current intensity can be increased without damaging the targets.

A high current beam raises problems with sputtering effect some produced 24Na's are sputtered away from the target surface during irradiation and with heating effects. In a test at 10 PA we had visible signs of carbon sputtering from the target. For future measurements it will be necessary to construct a target cooling system.

But again there is a limitation on how heat can be dissipated in the target. This method allows to suppress the ambient background rays from natural radioactive isotopes such as 40 K and Tl. In the Notre Dame experiment the peaks at keV and keV of 24Na could be observed only in the gated -ray spectra.

It is obvious that this experimental setup made now at IFIN-HH, will allow decreasing the total fusion cross section from this measurement with another order of magnitude. To determine the optimum parameters of this experiment, stability and resolution tests of 12C beam obtained at the 3 MV accelerator of IFIN-HH were conducted last year.

Following these tests, it turns out that the accelerator has the characteristics required for nuclear astrophysics measurements, namely: allow the terminal voltage between 0. Activities of irradiated targets measured both in the underground and surface laboratories allowed to determine the limit of detection of cross sections of the order of nb.

However, this will imply a good cooling of the graphite targets. Calibrations and measurements performed in identical or similar conditions will also allow us to reduce the uncertainties associated with the experimental data corresponding with range Ec. In conclusion, the 3 MV accelerator is suitable for nuclear astrophysics measurements due to energies and intensities provided and stability in operation.

Low DFN and ultralow "PBq" Slanic background laboratories of the institute can be successfully used for measurements by activation with lifetime greater than ten minutes and several hours, respectively, necessary to transport the probes. These facilities have been included recently in a European project proposal Horizon program, called the European Laboratory Astrophysics Network ELAN as TA Transnational Access facility , in a select group of seven multi-disciplinary laboratories of atomic and molecular spectroscopy or radiation installations and of only two other nuclear astrophysics labs.

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