47 research outputs found
Nuclear Processes at Solar Energy
LUNA, Laboratory for Underground Nuclear Astrophysics at Gran Sasso, is
measuring fusion cross sections down to the energy of the nucleosynthesis
inside stars. Outstanding results obtained up to now are the cross-section
measurements within the Gamow peak of the Sun of and
the . The former plays a big role in the proton-proton
chain, largely affecting the calculated solar neutrino luminosity, whereas the
latter is the reaction that rules the proto-star life during the pre-main
sequence phase. The implications of such measurements will be discussed.
Preliminary results obtained last year on the study of
, the slowest reaction of the CNO cycle, will also be
shown.Comment: Invited talk at the XXIII Physics in Collisions Conference (PIC03),
Zeuthen, Germany, June 2003, 10 pages, LaTeX, 3 EPS figures. PSN THAT0
Search for correlations between solar flares and decay rate of radioactive nuclei
The deacay rate of three different radioactive sources 40K, 137Cs and natTh
has been measured with NaI and Ge detectors. Data have been analyzed to search
for possible variations in coincidence with the two strongest solar flares of
the years 2011 and 2012. No significant deviations from standard expectation
have been observed, with a few 10-4 sensitivity. As a consequence, we could not
find any effect like that recently reported by Jenkins and Fischbach: a few per
mil decrease in the decay rate of 54Mn during solar flares in December 2006.Comment: 5 pages, 3 figure
Precise measurement of the 222Rn half-life: a probe to monitor the stability of radioactivity
We give the results of a study on the 222Rn decay we performed in the Gran
Sasso Laboratory (LNGS) by detecting the gamma rays from the radon progeny. The
motivation was to monitor the stability of radioactivity measuring several
times per year the half-life of a short lifetime (days) source instead of
measuring over a long period the activity of a long lifetime (tens or hundreds
of years) source. In particular, we give a possible reason of the large
periodical fluctuations in the count rate of the gamma rays due to radon inside
a closed canister which has been described in literature and which has been
attributed to a possible influence of a component in the solar irradiation
affecting the nuclear decay rates. We then provide the result of four half-life
measurements we performed underground at LNGS in the period from May 2014 to
January 2015 with radon diffused into olive oil. Briefly, we did not measure
any change of the 222Rn half-life with a 8*10^-5 precision. Finally, we provide
the most precise value for the 222Rn half-life: 3.82146(16){stat}(4){syst}
days.Comment: Accepted for publication in Physics Letters B, 6 pages, 6 figure
The Luna experiment
LUNA is a pilot project initially focused on the 3 He ( 3 He , 2 p ) 4 He cross section measurement within the thermal energy region of the Sun (15–27 KeV ). A compact high current 50 KV ion accelerator facility including a windowless gas target system, a beam calorimeter and four detector telescopes has been built, tested and installed underground at the Laboratori Nazionali del Gran Sasso. The sensitivity has been improved by more than four orders of magnitude, as compared to the previous experiment. In particular, thanks to the cosmic ray suppression, we could attain a background level of less than 1 event per week, a rate similar to the one expected from 3 He ( 3 He ,2 p ) 4 He at the lower edge of the Sun thermal energy region
LUNA: Nuclear Astrophysics Deep Underground
Nuclear astrophysics strives for a comprehensive picture of the nuclear
reactions responsible for synthesizing the chemical elements and for powering
the stellar evolution engine. Deep underground in the Gran Sasso laboratory the
cross sections of the key reactions of the proton-proton chain and of the
Carbon-Nitrogen-Oxygen (CNO) cycle have been measured right down to the
energies of astrophysical interest. The salient features of underground nuclear
astrophysics are summarized here. The main results obtained by LUNA in the last
twenty years are reviewed, and their influence on the comprehension of the
properties of the neutrino, of the Sun and of the Universe itself are
discussed. Future directions of underground nuclear astrophysics towards the
study of helium and carbon burning and of stellar neutron sources in stars are
pointed out.Comment: Invited review, submitted to Annu. Rev. Nucl. Part. Scienc
Search for time modulations in the decay rate of 40K and 232Th
Time modulations at per mil level have been reported to take place in the
decay constant of about 15 nuclei with period of one year (most cases) but also
of about one month or one day. In this paper we give the results of the
activity measurement of a 40K source and a 232Th one. The two experiments have
been done at the Gran Sasso Laboratory during a period of about 500 days, above
ground (40K) and underground (232Th) with a target sensitivity of a few parts
over 10^5. We also give the results of the activity measurement at the time of
the X-class solar flares which took place in May 2013. Briefly, our
measurements do not show any evidence of unexpected time dependence in the
decay rate of 40K and 232Th.Comment: version accepted for publication (Astroparticle Physics
Search for time modulations in the decay constant of 40K and 226Ra at the underground Gran Sasso Laboratory
Time modulations at per mil level have been reported to take place in the
decay constant of several nuclei with period of one year (most cases) but also
of about one month or one day. On the other hand, experiments with similar or
better sensitivity have been unable to detect any modulation. In this letter we
give the results of the activity study of two different sources: 40K and 226Ra.
The two gamma spectrometry experiments have been performed underground at the
Gran Sasso Laboratory, this way suppressing the time dependent cosmic ray
background. Briefly, our measurements reached the sensitivity of 3.4 and 3.5
parts over 10^6 for 40K and 226Ra, respectively (1 sigma) and they do not show
any statistically significant evidence of time dependence in the decay
constant. We also give the results of the activity measurement at the time of
the two strong X-class solar flares which took place in September 2017. Our
data do not show any unexpected time dependence in the decay rate of 40K in
correspondence with the two flares. To the best of our knowledge, these are the
most precise and accurate results on the stability of the decay constant as
function of time.Comment: Accepted for publication in Physics Letters B, 6 pages, 8 figures.
arXiv admin note: text overlap with arXiv:1311.704
study of the time dependence of radioactivity
The activity of a 137Cs source was measured using a germanium detector installed deep underground in the Gran Sasso Laboratory. In total about 5100 energy spectra, one hour measuring time each, were collected and used to search for time variations of the decay constant with periods from a few hours to 1 year. No signal with amplitude larger than 9.6 × 10−5 at 95% C.L. was detected. These limits are more than one order of magnitude lower than the values on the oscillation amplitude reported in the literature. The same data give a value of 29.96±0.08 years for the 137Cs half life, which is in good agreement with the world mean value of 30.05 ± 0.08 years
Search for the time dependence of the 137Cs decay constant
Starting from June 2011, the activity of a 137Cs source has been measured by
means of a HPGe detector installed deep underground in the Gran Sasso
Laboratory. In total about 5100 energy spectra, one hour measuring time each,
have been collected. These data allowed the search for time variations of the
decay constant with periods from a few hours to 1 year. No signal with
amplitude larger than 9.6{\cdot}10-5 at 95% C.L. has been detected. These
limits are more than one order of magnitude lower than the values on the
oscillation amplitude reported in literature. In particular, for 1 year period
an oscillation amplitude larger than 8.5{\cdot}10-5 has been excluded at 95%
C.L., independently of the phase. The same data give a value of 29.96{\pm}0.08
years for the 137Cs half life, in good agreement with the world mean value of
30.05{\pm}0.08 years.Comment: 5 pages, 4 figure
The Luna experiment
One of the main ingredients of nuclear astrophysics is the cross section of the thermonuclear reactions which power the stars and synthesize the chemical elements in the Universe. Deep underground in the Gran Sasso Laboratory the cross section of the key reactions of the proton-proton chain and of the Carbon-Nitrogen-Oxygen (CNO) cycle have been measured right down to the energies of astrophysical interest. The main results obtained during the solar phase of LUNA are reviewed before describing the current LUNA program devoted to the study of the nucleosynthesis of the light elements in AGB stars and Classical Novae. Finally, the future of LUNA with the new 3.5 MV accelerator devoted to the study of helium and carbon burning is discussed