1. Antifreeze design for Muon Detector of LHAASO
ICRC2017
Antifreeze design for Muon Detector of LHAASO
Shaohui Feng,IHEP,CAS

2. Outline Necessity of Antifreeze design for MD1
Necessity of Antifreeze design for MD 2
Study water temperature at Yangbajing Tibet 3
Study water temperature at Mt. Haizi, Sichuan 4
Conclusions

3. Necessity of Antifreeze design for MDP
art 1
Necessity of Antifreeze design for MD

4. 1. Necessity of Antifreeze design for MD
MD array
MD array would be built at 4400m , Mt. Haizi, Sichuan, China
2. MD array infrastructure construction has started.
3. 44 tons of ultra-pure water should be infused into
MD.
Environment
1. The deepest of the permafrost is 1.67m at 4400m.
2. Once the freezes, consequence would be severe.
Feasibility
The average annual air temperature on the surface of
soil is 1.2℃.
The average annual temperature of under ground 1.2m is 4℃.
MD underneath soil

5. 1. Necessity of Antifreeze design for MD
LHAASO infrastructure construction has started
Road in site
Drainage system
The accommodation area
Electric supply station

6. Study water temperature at Yangbajing Tibet
art 2
Study water temperature at Yangbajing Tibet

7. 2. Study water temperature at Yangbajing Tibet
Finite element simulation
Finite element mode：
Muon Detectors are buried underground;
The temperature field is very complicated;
Finite element mode
The temperature field is simplified:
a)The soil is a complex mixture, It belongs to the heterogeneous medium, in order to ease
of calculation, The soil around MD is reduced to isotropic homogeneous medium;
b)Because of the symmetry on both sides of the MD，half of the vertical axis of the MD
tank had been taken as a calculation area;
c)Assume that the MD tank is not moved after been set, and Water transfer in soil is not
been considered;
d)Assume that the temperature of MD water only affects the surrounding soil temperature,
there is no affects when the distance is more than 15m.

8. 2. Study water temperature at Yangbajing Tibet
Parameters Setting
Air temperature on the surface of soil
T is the air temperature on the surface of soil with corresponding time.
P0 is the Average annual air temperature on the surface of soil.
P1 is the amplitude for air temperature on the surface of soil;
P2 is the period for air temperature on the surface of soil;
P3 is the phase deviation for air temperature on the surface of soil;
TIME is time (day);
The air temperature on the surface of soil at Yangbajing Tibet
Yellow line is the average air temperature fitting function;
Red line is the limit air temperature fitting function.

9. 2. Study water temperature at Yangbajing Tibet
Parameters Setting
Thermodynamic calculation parameter
Parameters from the Yangbajing Tibet:
1. Initial temperature: Water 8℃，Soli 15℃，Air20℃
2. Air temperature on the surface of soil
3. According to the empirical formula, P0 should be
2 more than the real value;
5.8+

10. 2. Study water temperature at Yangbajing Tibet
The data analysis at Yangbajing Tibet MD MD
Water temperature comparison between simulated and measured.

11. 2. Study water temperature at Yangbajing Tibet
The data analysis at Yangbajing Tibet
Water temperature comparison between simulated and measured
One MD tank was placed on the ground, another MD tank was buried underground.
For Two MD prototypes, measured data is approximate to respective simulated data, it proves that the simulation model is correct.

12. Study water temperature at Mt. Haizi, Sichuan
art 3
Study water temperature at Mt. Haizi, Sichuan

13. 3. Study water temperature at Mt. Haizi, Sichuan
Parameters Setting
Thermodynamic calculation parameter
Parameters from the Mt. Haizi, Sichuan:
The annual average air temperature
of Yangbajing Tibet
Initial temperature: Water 8.5℃，Soli 8.5℃，Air -4℃, Antifreeze laye -8.5℃
Muon detectors will be built at 4400m,
Daocheng Sichuan province.
A simulation which is the same model
as Yangbajing Tibet has been made
using the new site basic parameters.
3. The annual average 5 ℃ temperature
drop are considered in the simulation.
2. Air temperature on the surface of soil
3. According to the empirical formula,
P0 should be 2 more than the real value;

14. 3. Study water temperature at Mt. Haizi, Sichuan
Simulation results
Simulation resul for Mt. Haizi, Sichuan
Base on the bottom of the MD tank:
Marsh type, The MD can be placed on the ground;
Shallow type, The MD should be buried at 1.2 m underground;
Deep type, The MD should be buried at 4.2 m underground.
Consider the simulation errors:
Marsh type, 15cm antifreeze layer should be adopted, the lowest water temperature of MD is 2-4 ℃;
Shallow type, 10cm antifreeze layer should be adopted, the lowest water temperature of MD is 2-4 ℃;
Deep type, 10cm antifreeze layer should be adopted, the lowest water temperature of MD is 2-4 ℃;
Extreme temperature ≥ 0 ℃;

15. 3. Study water temperature at Mt. Haizi, Sichuan
Marsh Type temperature varying with time
Marsh soil temperature sensor
Soil0 is the bottom of tank
Soil7 is surface of soil
Each sensor distance is 0.5 m
Blue lines are the water temperature in the MD center,
Red lines are the water temperature of the water in the MD boundary
Black lines are the soil temperature outside the MD
Each sensor distance is 0.5 m

16. 3. Study water temperature at Mt. Haizi, Sichuan
Temperature varying with time
(Marsh Type)
(Shallow Type)
(Deep Type)
Measured data of water temperature in MD

17. P
art 4
Conclusions

18. 4. Conclusions
By studying the water temperature of two MD prototypes at Yangbajing Tibet, measured data is approximate to respective simulated data, it proves that the MD model is correct.
By studying the water temperature of three MD prototypes at Mt. Haizi, Sichuan, measured data is approximate to respective simulated data, it proves that antifreeze design is feasible.
Consider the Antifreeze performance and price, Polyurethane is used as an anti-freeze material for MDs array.
Marsh type, 15cm antifreeze layer should be adopted; Shallow type, 10cm antifreeze layer should be adopted; Deep type, 10cm antifreeze layer should be adopted.