1. Calorimetric System for Determining the Activity
of a Neutrino Source Based on 51Cr
Kozlova J. P., Gavrin V. N., Grekhov O.V., Ibragimova T. V., Kalichov A.V., Martynov A.A., Veretenkin E. P.
Institute for Nuclear Research of RAS
Russian Federation, Moscow
J.P.Kozlova. ICSSNP-2017

2. At the Gallium-germanium neutrino telescope at the Baksan Neutrino Observatory INR (Russia) the BEST project is proposed as a direct experimental test the hypothesis of the existence of sterile neutrinos - hypothetical particles whose interaction with matter is carried out through small admixtures of conventional (i.e. active) neutrinos.
Project BEST is an experiment to search for sterile neutrinos through using neutrino from a powerful compact artificial source based on 51Cr with initial activity of 3 MCi.
The source activity will be measured using calorimeter method and by measurement its gamma-rays using a Ge semi-conductor detector with accuracy of 1%.
J.P.Kozlova. ICSSNP-2017

3. Development of calorimetric system:
determination of the main factors that have an effect on the accuracy of the source activity measurement by calorimetric method,
creation of calorimeter prototype and heat imitator of neutrino source,
determination of calorimeter metrological characteristics (prototype calorimeter calibration),
development and creation of the final calorimeter system for experiment with artificial neutrino source,
development of the software for the calorimetric measurements,
calorimeter calibration in the dynamic mode.
J.P.Kozlova. ICSSNP-2017

4. Neutrino source based on 51CrW
51Cr
51Cr + e-  51V + e
Energy release – ± keV/decay.
Initial source heat release – 650 W.
Contribution of the impurity radioactive nuclides –
0.02% (after radiation), 0.11% (in 100 days).
Energy losses due to gamma-rays escaping < 0.03%.
3 MCi 51Cr
3 kg 97%-enriched 50Cr
Biological shield 30 mm
(W - 95%, Ni - 3%, Cu - 2%)
J.P.Kozlova. ICSSNP-2017

5. Flow diagram of the calorimeter1 c 3 a T2 2 d e 4 М f b 5 g T1 6
2 – flow meter
3 - thermostat
4 - bypass
5 - gear pump
6 – temperature damper
М - manometer
1 – MEASUREMENT CELL
a – thermal insulation
b – neutrino source
c – biological shield
d – output thermistor
e – heat exchanger
f – container
g – input thermistor
J.P.Kozlova. ICSSNP-2017

6. Electric power measurements
Shunt V1 V2
Power supply
Multimeter
Thermal simulator
N = U1U2/Rshunt,  = 0.03%
J.P.Kozlova. ICSSNP-2017

7. Calorimetric system flow meter multimeter power supply
measurement cell
with electric heated
simulator
temperature
damper
thermostat
J.P.Kozlova. ICSSNP-2017

8. Calorimetric system software
Used equipment
Platinum thermistors PTV-2-1 (VNIIFTRI) (with an temperature error less than K).
Coriolis mass flow meter Micro Motion (±0.05%).
Cooling thermostat Unistat (±0,01 К).
Gear pump Ismatec Reglo-Z Digital (± 0,05 %).
Power supply Sorensen XHR 300-3,5.
Two-channel digital multimeter ADVATEST R6452E (0,01 V).
Shunt (R= 52,14 ± 0,01 Ohm).
Calorimetric system software
Software is based on LabVIEW Package (National Instruments).
Software ensures reading and storing of the following data:
mass flow rate, density, total mass and temperature of the coolant through the flow meter;
Input and output temperatures of coolant through the heat simulator;
Voltage on the heat simulator and the shunt.
J.P.Kozlova. ICSSNP-2017

9. The heat release is proportional to the difference between the output and input temperatures of the coolant and it can be expressed by equation:
N = k x Q x (To – Ti),
where
N – heat release of the source, W.
k - the proportionality factor, which in the absence of heat losses is equal to the specific heat capacity of the coolant, J/(kg x K).
Q - the coolant flow rate, kg/s.
To – the temperature at the outlet of the heat exchanger, K.
Ti - the temperature at the inlet to the heat exchanger, K.
J.P.Kozlova. ICSSNP-2017

10. Prototype calorimeter calibration data
N (dT) = (69,677 ± 0.079)  dT + (0.62 ± 0.36)
the coefficient of determination: R^2 =
J.P.Kozlova. ICSSNP-2017

11. Calorimeter with biological shield
J.P.Kozlova. ICSSNP-2017

12. Calorimeter calibration data
(T2 – T1), K
σ (T2 – T1), K
P, W
σP, Вт
σP, % 1
0.950
0.002
47.05
0.45
0.96% 2
1.680
0.003
83.19
0.47
0.57% 3
2.707
0.001
134.65
0.48
0.36% 4
3.772
0.008
187.33
0.64
0.34% 5
5.353
266.80
0.58
0.22% 6
5.954
296.54
0.62
0.21% 7
6.432
0.004
320.12
0.65
0.20% 8
7.620
377.67
0.72
0.19% 9
9.380
0.006
465.60
0.83
0.18% 10
10.426
519.09
0.95
J.P.Kozlova. ICSSNP-2017

13. Calorimeter calibration data
J.P.Kozlova. ICSSNP-2017

14. Calorimeter calibration in dynamic mode
Р1 = Const  400 W
P2 = P1 exp(-ln2t/T1/2)
(T1/2 =27.7 d)
P3 = Const
dP = Pset - kstatdT
dP = 0,24 W,  = 0,09 W
0,06%
J.P.Kozlova. ICSSNP-2017

15. Conclusions
The calorimetric system for measurement of activity of high-intensity (3 MCi) neutrino source based on 51Cr has been created. The obtained uncertainty of the heat release measurement is less than 0.5% in the range of the heart power W and less than 0.25% in the range of the power W. Taking into account the obtained heat release uncertainty and the known uncertainty of the energy release from the 51Cr decay (0.23%) the activity of 51Cr neutrino source in the BEST project can be determined with accuracy of ~ 0.5%.
J.P.Kozlova. ICSSNP-2017