GRAN SASSO’S HADRON STOP

Temperature’s behaviour under specified beam conditions

Barbara Calcagno

CNGS Facilities

Beam Conditions

2D Energy deposition map [FLUKA]

FORTRAN interpolation program to convert the energy deposition map: 2D 3D

Integration of the data over the whole volume

ET-2D = Total energy - 2D model=17 kWET-3D = Total energy - 3D model = 16.9 kWDifference < 0.6% negligible for the purpose of the calculations performed

BEAM ENERGY[GeV]

400

NUMBER OFPROTON ONTARGET IN 200DAYS [pot/year]

4.5x1019

MAXIMUM NUMBEROF PROTON ONTARGET IN 200DAYS [pot/year]

13.8x1019

MAXIMUM BEAMPOWER [kW]

512.64

MAXIMUM POWERDEPOSITED IN THEDUMP [kW]

52.13

PURPOSES OF THE BEAM DUMP

Contain in a relatively small volume the radioactivity introduced by the beam particles reaching the end of the decay tunnelShield the detectors from the beam particles reaching the end of the decay tunnelContain the energy deposited by the beam particles and keep the local temperature within acceptable limits, during the longest data taking period (200 days) at the highest possible beam intensity (13.8x1019 pot/year) and at a proton beam energy of 400 GeVContribute to the shield of a possible near detector against muons produced by pions decaying in the decay tunnel

PRELIMINARY CONSIDERATIONS

The mass of graphite and cast iron are made of blocks: the maximum roughness measured and, consequently, the maximum air gap between graphite and cast iron blocks is of 2 mm and 4 mm respectively. The contact between blocks, even if not perfect, is at least guaranteed over 50% of each surface. It has been decided to simplify the model making the pessimistic hypothesis that between blocks there is no contact but a layer of air, considered a solid with low conductivity, neglecting the effects of radiation and convection.Preliminary calculations without cooling system shown that the temperature reach a value of 700 oC needing of a cooling system

COOLING SYSTEM

Preliminary calculations without cooling system: 700 0C after 200 days

Destruction of concrete structures

Needing of a cooling system

HYPOTHESES- Cooling power 50 kW- diameter of the tubes = 4 cm- number of tubes = 12- Turbolent regime U = 0.2 m/s- Tbulk =17 0C - Flow rate for each tube = 6.5 l/min

-Nu=0.012 (Re0.87-280) Pr0.4 1.5 Pr 500 3x103 Re 106

- h 500 W/m2K

CALCULATIONS HYPOTHESES

COMMON ASSUMPTIONS STANDARD CASE: Graphite blocks - horizontal and longitudinal airgap = 2 mm Kxx = 7.9 W/mK Kzz =9.4 W/mK - vertical airgap = 0.5 mm Kyy = 26.4 W/mK Iron blocks - horizontal and longitudinal airgap = 4 mm Kxx = 6.0 W/mK Kzz =9.8 W/mK - vertical airgap = 2 mm Kyy = 10.9 W/mK INITIAL TEMPERATURE = 20 0C

EXTERNAL SURFACES OF THE MODEL INSULATED (worst case)

NO CONVECTION IN THE MUON PIT: the air is considered as “one block material”

A-GEOMETRY B-GEOMETRY

VERTICAL SIMMETRY NO FLUX THROUGH THE SURFACES OF SIMMETRY Only a quarter of the dump is modeled

1 COOLING SYSTEM located immediately below the aluminum box, with the same cooling power of 50 kW.

VERTICAL SIMMETRY - HORIZONTAL SIMMETRY NO FLUX THROUGH THE SURFACES OF SIMMETRY Only a quarter of the dump is modeled

2 COOLING SYSTEMS located immediately below and above the aluminum box, with the same cooling power of 50 kW.

2.6 m 4.0 m 2.8 m

0.2 m

6.0 m

5.0 m 18.2 m

5.0 m

3.0 m

23.8 m

GRAPHITE

ALLUMINUM

AIR

HEAT SINK

CAST IRON

CONCRETE

A-GEOMETRY of the HADRON STOP

TRANSVERSAL SECTION

LONGITUDINAL SECTION

1.3 m 1.6 m 2.0 m1.4 m

3.0 m3.2 m

18.2 m 5.0 m

B-GEOMETRY of the HADRON STOP

TRANSVERSALSECTION

LONGITUDINALSECTION

GRAPHITE

ALLUMINUM

HEAT SINK

CAST IRON

AIR

CONCRETE

5.0 m

A-Geometry.Temperature profile on the transversal section related to the maximum temperature reached in graphite after 200 days - 4.5x1019 pot/year

6 HOURS 10 DAYS 5 DAYS

50 DAYS 25 DAYS 100 DAYS 200 DAYS

12 HOURSTEMPERATURE[0C]

24 HOURS

A-Geometry.Temperature profile on the transversal section related to the maximum temperature reached in graphite after 200 days - 4.5x1019

pot/year

5 DAYS

100 DAYS 200 DAYS

TEMPERATURE[0C]

50 DAYS 10 DAYS

24 HOURS

A- Geometry: load cases studied

Model Load case TmaxGraphite

TmaxCast iron

TmaxAluminum

Withconcrete

4.5x1019

pot/ year110.3 86.4 81.2

Withoutconcrete

4.5x1019

pot/ year110.3 97.1 81.6

Withoutconcrete

13.8x1019

pot/ year298 256 211

The results of the “worst case” considered - 13.8x1019 pot/year-without concrete - show the needing of studying the possibility of using a second cooling system.

B-Geometry.Temperature profile on the transversal section related to the maximum temperature reached in the graphite after 200 days - 13.8x1019 pot/year

6 H 24 H 5 Days 3 Days 12 H

TEMPERATURE[0C]In 5 days the transient could be considered concluded: the maximum temperature in graphite (194 0C) is reached

10 Days 20 Days 200 Days

Starting from the 10th day, the temperature profile doesn’t change with the time

Temperature Profile after 200 days of running and comparison between the maximum temperatures obtained with 1 and 2 cooling systems

LONGITUDINAL Temperature Profile related to the maximum temperatures in iron and in graphite

TEMPERATURE[0C]

10 mCOMPONENT 2 COOLING SYSTEM

TEMP.MAX [0C]

1 COOLING SYSTEM

TEMP.MAX [0C]

Graphite 194 298

Aluminum 108 211

Cast-iron 137 256

Temperature Profile after 200 days of running on the external surfaces of the hadron stop

LONGITUDINAL VIEWFRONT VIEW

TOP VIEW

TEMPERATURE[0C]

CONCLUSIONS

The choice of two cooling systems allows to keep the maximum temperatures under reasonable limits, always below the values accepted for analogous structures used in previous experiments, also in the case of continuos running with the maximum number of protons on target: 13.8x1019 pot/year

Each assumption which has been adopted is referred to the worst case under the thermal point of view the results obtained guarantee that the structure modelled would work in safety conditions under the thermal loading previously specified.