SAGE and BEST V N Gavrin on behalf of the BEST collaboration Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Sciences Village Neutrino ID: 802008
Download The PPT/PDF document "BNO INR RAS June 22 to July 2, 2020" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
BNO INR RAS
June 22 to July 2, 2020
SAGE and BEST
V. N.
Gavrin
on behalf of
the BEST
collaboration
Baksan Neutrino Observatory
of the Institute for Nuclear Research of the Russian Academy of Sciences
Slide2Village Neutrino
mt
.
Andyrchi
North Caucasus
Kabardino-Balkar ian RepublicBaksan valleyBNO INR RAS location
Slide3Outline
Introduction and a little bit of history.
SAGE. Present
Ga
results.
Source experiments. The BEST. Intermediate Results Summary
BNO INR RAS
22 to July 2, 2020
Slide4BNO INR RAS
June 22 to July 2, 2020
The Russian-American experiment SAGE began to measure the solar neutrino capture rate with a target of gallium metal in December 1989
168 runs (Jan 1990 – Dec 2007) result
65.4
+4.0
-4.1
SNU
[
P
hys
.
Rev. C 80, 015807 (2009)]
(
1 SNU =
1 interaction/s in a target that contains 10
36
atoms of the neutrino absorbing isotope
).
GALLEX
(May 1991 – Jan 1997)
GNO
(May 1998 – Apr 2003
71
Ga(
v
e
, e
-
)
71
Ge, E
th
= 233 keV
30 t of
Ga
(103 tons of GaCl
3
acidic solution)
GALLEX,
65 runs:
7
3
.1+7.1-7.3 SNU (at TAUP2007) GNO, 58 runs: 62.9+5.5-5.3 SNU GALLEX + GNO : 67.5 ± 5.1 SNU
Ga experiments
The weighted average of the results of all Ga solar experiments is 66.1±3.1 SNU .Ga experiments have shown deficit of solar neutrino in the entire energy range.
SAGE50 tons of metallic Ga
The first Ga experiments results provided a direct indication of the neutrino oscillations existence that became a strong justification for the SNO experiment.
Slide5BNO INR RAS
June 22 to July 2, 2020
SAGE &
GALLEX
neutrino source experiments
Gallium anomaly
:
[
Mario A. Acero, Carlo Giunti, and Marco Laveder. Phys. Rev. D 78, 073009 (2008), arXiv:0711.4222v3]
The neutrino capture rate measured by the
Ga detectors SAGE with
51Cr and 37Ar artificial neutrino sources is considerably less than expected.
R
ave
-
Bahcall
= 0.8
7
± 0.05 (2.
6
σ
)
R
ave-
Frefers
= 0.84 ± 0.05 (2.9
σ
)
[S Gariazzo, C Giunti, M Laveder, Y F Li, E M Zavanin,
arXiv:1507.08204v1 [
hep
-ph]]
Neutrino sources
:
51
Cr:
747 keV (81.6%)
,
427 keV (9.0%), 752 keV (8.5%), 432 keV (0.9%)37Ar: 811 keV (90.2%), 813 keV (9.8%) 1994 –1995 A(Cr1) = 1.714 ± 0.036 MCi 1994 –1995 A(Cr) = 0.517 ± 0.006 MCi GALLEX: SAGE: 1995 –1996 A(Cr2) = 1.868 ± 0.073 MCi 2004 A(Ar) =
0.409 ± 0.002 MCiResults: PLB 342 (1995) R
1(Cr) = 0.953 ± 0.11 PRC 59 (1999) R3(Cr) = 0.95 ± 0.12
GALLEX: SAGE: PLB 420 (1998) R2(Cr) = 0.812 ± 0.10 PRC 73 (2006) R4(Ar) = 0.791 ± 0.084R – ratio of the measured production rate to that expected [Bahcall 97]
(no uncertainty on cross section included)
The differences of 4 times in activities and more then 2 times in target masses result in equal uncertainties of the experiments. The cause is different sensitivity of the targets to
ν
from sources and dimensions of the sources.
Slide6Region of allowed mixing parameters inferred from 4 gallium source experiments assuming oscillations to a sterile neutrino
In
Ga
experiments
:
Eν
~ 1 MeV
L ~ 1 m
Oscillations affect
the capture rate with Δ
m2 ~ 1 eV2Limits for oscillation parameters obtained inthe four artificial neutrino source experiments:
the best-fit point (●) at Δm2 =
2.15
eV
2
and
sin
2
(2
θ
)
=0.24
χ
2
/
dof
=1.77/2, GOF=41%
BNO INR RAS
June 22 to July 2, 2020
[
arXiv:1006.2103 [nucl-ex]
]
Slide7Target:
50 т
Ga
metall
Masses of the zones: 8 t and
42 t
Path length in each zone:<L>
= 55
cm
σ – cross
sect.{5.8×10-45 cm2 [Bahcall]}
First proposal of two zone Ga experiment with
51
Cr (3MCi
)
source
The rate at SOE:
64.5 atoms/day
T
he region in
Δ
m
2
-
sin
2
(
2
θ
)
space to which
the new 3 MCi
51
Cr
experiment will
be sensitive
arXiv
:
1204.5379v1 [hep-ph] 18 Apr 2012
arXiv:1006.2103v2
[nucl-ex] BNO INR RASJune 22 to July 2, 2020 Since 2011 construction of the BEST experiment installation started [Physics of Particles and Nuclei. 2015. Vol.46, No.2. pp.131-137]
Slide8BEST
installation
scheme
Source activity measurement:
1) Moving the source into a lead container2) Measuring gamma spectrum at 21.65 m distance with a semiconductor detector ( 1h)3) Moving the source into a calorimeter4) Measuring the heat emitted by the source ( 20-21 h )
71Ge extraction (30 hours in total) : Pumping gallium from zones to chemical reactors: internal zone → 1 reactor, external zone → 6 reactors;
( 4.5 h).2) In each reactor the germanium carrier in the form of GeCl4 is extracted from the metal into aqueous phase.3) Concentration of the aqueous solution by evaporation. (16h)4) Synthesis of GeH4 and placing it into a proportional counter.
5) 71Ge decays are counted.( 60 – 150 days)
ν
e + 71
Ga → 71Ge + e-
BNO INR RAS
22 to July 2, 2020
Ga
Slide9BNO INR RAS
22 to July 2, 2020
2 zone gallium target
Source
Calorimetr
Lead chamber
Slide10BEST
installation
BNO INR RAS
22 to July 2, 2020
Slide11BEST: Neutrino source
4
kg 97%-enriched
50
Cr, 26 chrome metal disks
h = 4 mm, 84 and
88 mm.
BNO INR RAS
June 22 to July 2, 2020
26 chrome metal disks
Chromium disks from metallic
50
Cr enriched up to 97%
(the enrichment was performed by the JSC “PA “Electrochemical Plant” (
Zelenogorsk
) ) were
irradiated for
~ 100 days with thermal neutrons in the SM-3
reactor
(RIAR,
Dmitrovgrad
).
T
hermal
neutron
flux
density
– 5
×10
15
neutrons /(cm
2
sec
)
Stainless steel
Biological protection ,
tangsten
Stainless steel
Slide12The source was immediately placed at the center of the two-zone target of liquid gallium.
First stage of the BEST experiment began.
At 14:02 Moscow time the first irradiation of the two-zone gallium target has started.
BNO INR RAS
22 to July 2, 2020
In the photos you see the moment of source overload from a transport container into a two-zone
Ga
target.
Slide13The BEST stages
1. Working with the
51
Cr source (completed on October
2019):- 10 exposures of a 2-zone gallium target by the source 20 extractions from 2 zones of gallium target,
- 10 calorimetric measurements of the source activity,- 11 spectrometric measurements of the gamma spectrum of the source,- synthesis of germane (GeH4) and filling counters- installation of filled counters in the counting systems2. 71Ge decay measurements (completed on March 2020):- primary data collection and processing,- preliminary data analysis- comparative crosscheck data analysis3. Tests and checks (around the end of August ):
- production of 37Ar, 71
Ge isotopes- verification of counting systems,- measurement of the counters volumetric and peak efficiencies,- estimation of all systematic uncertainties4. Interpretation and presentation of results (September 2020)
BNO INR RAS
22 to July 2, 2020
Slide14BNO INR RAS
June 22 to July 2, 2020
Extraction schedule and related parameters
The times of exposure are given in days of year
2019
10 targets irradiations:
Mean exposure time - 9.18 d;
Masses : 7.4 t and 40.09 t;
Mean extraction eff. from
Ga
is 98
%;
Mean
the overall efficiency including synthesis into the counting gas GeH
4
- 96%;
The efficiency of extraction was measured by adding to the
Ga
a known mass of inactive
Ge
carrier before the start of exposure to the neutrino source and measuring the mass
of extracted
Ge
.
The mass of added carriers of ~2.4 µmol
of
72
Ge (92%) and
76
Ge(95%) were used.
Slide15BNO INR RAS
June 22 to July 2, 2020
Gamma-ray spectroscopy
Measured nuclide impurities in the
51
Cr source and their contribution to the source activity
measurement
at the reference time
14:02 on 05.07.2019From 11 spectrometric measurements of gamma radiation of the source was obtained:
- the total amount of heat release from impurity radionuclides is 2.9 ± 0.5 mW , which is ~ 4·10-6 of the initial 51
Cr source power
, and can be neglected;
- confirmation of a high purity of the material used to produce the
51
Cr
source
(V.V. Gorbachev, Poster session at
XXXV International Conference on Equations on State for Matter,
Elbrus, KBR, March 1-6, 2020
)
Full spectrum of photons from the source
Part spectrum of photons from the source (600-900 keV)
Slide16Source power measurements with the calorimeter
system
.
The source activity was measured by its heat release in the calorimetric system. 10 measurements of the 51Cr neutrino source activity were done.The obtained value of the neutrino source activity on 05.07.2019 at 14:02 is
3.4099 ± 0.008 МCi (total uncertainty includes the uncertainties of heat release (0.015%) and energy release (0.23%) added in quadrature).(Using a conversion factor of 217.857 W/MCi 51Cr the
heat power of the 51Cr source was 742.87 W on July 5, 2019
)For the first time, an artificial neutrino source of such high intensity was produced and for the first time so high accuracy in measuring such high activity was achieved.
According to the passport from RIAR an estimated source activity was
3.55 MCi
on July 2, 2019 at 09:40 (which corresponds 3.28 MCi
at the delivered time to BNO on July 5, 2019)
BNO INR RAS
22 to July 2, 2020
[
Yu.P
.
Kozlova
.
Measurement
of
Neutrino
Source
Activity
in
the
experiment
BEST
by
calorimetric
method
. Session of the Department of Nuclear Physics, Novosibirsk, March 10-12, 2020]
Slide17BNO INR RAS
22 to July 2, 2020
V. Gavrin*, V.
Barinov
, S.
Danshin
, V. Gorbachev, D.
Gorbunov
, T.
Ibragimova
, Yu.
Kozlova, L. Kravchuk,V. Kuzminov, B. Lubsandorzhiev, Yu. Malyshkin, I. Mirmov
, A. Shikhin, E. Veretenkin Institute for Nuclear Research of the Russian Academy of Sciences, Moscow 117312, Russia
B. Cleveland
SNOLAB, Sudbury, ON P3Y 1N2, Canada
H.
Ejiri
Research Center for Nuclear Physics, Osaka University, Osaka, Japan
S. Elliott ,
I. Kim,
R.
Massarczyk
Los Alamos National Laboratory, Los Alamos NM 87545, USA
D.
Frekers
Institut für Kernphysik, Westfälische Wilhelms-Universität Munster, D-48149 Munster, Germany
W.
Haxton
Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
V.
Matveev
, D.
Naumov
, G.
Trubnikov
, D.
Filossov
, S.
Yakovenko
Joint Institute for Nuclear Research (JINR) Joliot-Curie 6, 141980,
Dubna
, Moscow Region, Russia
J.
NicoNational Institute of Standards and Technology, 100 Bureau Dr, Gaithersburg, MD 20899, USAA. Petelin, V. Tarasov, A. ZvirJSC “State Scientific Center Research Institute of Atomic Reactors”, Dimitrovgrad, 433510, Russia R. RobertsonCenter for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195, USAD. Sinclair Carleton University 1125 Colonel By Drive Ottawa, K1S 5B6, CanadaJ. WilkersonDepartment of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599, USABEST Collaboration:* Principal Investigator
Slide18Summary
●
The BEST experiment - first direct search for neutrino oscillations into 4-th flavor with radioactive source has started 5 July 2019 in BNO INR RAS
● The first stage of BEST is finished and the second stage is nearing completion. Currently preparatory works have begun for the implementation of the third final one.● Spectrometric measurements of gamma radiation of the source shown a high purity of the material used to production the 51
Cr source and therefore a negligible contributions (~ 10-6) from impurity radio nuclides to the calorimetric source activity measurements ● Obtained a precise value of the source activity from the calorimetric measurements which is 3.4099 ± 0.008 МCi on 05.07.2019 at 14:02● Results of data measurements analysis is expected in September 2020
BNO INR RAS
22 to July 2, 2020
Slide19BNO INR RAS
22 to July 2, 2020
The authors express their sincere gratitude to
Rosatom
for the comprehensive support and fruitful cooperation in the implementation of the BEST experiment
Slide20Thank you for your attention
BNO INR RAS
22 to July 2, 2020