# Presentation: 090493

## The JPARC neutrino target

- KEK
- Yoshinari Hayato
- (For J-PARC target/monitor Group)

- High-power targetry for future accelerators
- Ronkonkoma, NY.

## Next generation LBL experiments in Japan	“J-PARC - Kamioka neutrino project”

- Beam Energy ~1GeV

- Will be adjusted to
- the oscillation maximum

- Baseline ~295km

-  0.75MW

- Beam power

- Far detector

- Super
- Kamiokande(50kt)

- Physics

- disappearance

- appearance

- NC measurements

- Next generation LBL experiments in Japan	**“J-PARC - Kamioka neutrino project”**

**Notes:**
A.K.Ichikawa

## J-PARC facility

**400MeV Linac**

**3GeV PS**

**50GeV PS**
**(0.75MW)**

**N**

**FD**

**Neutrino Beam Line**

**To SK**

**Construction**
**2001****~****2006 JFY**

|  | J-PARC | K2K |
| --- | --- | --- |
| E (GeV) | 50 | 12 |
| Int. (1012ppp) | 330 | 6 |
| Rate (Hz) | 0.275 | 0.45 |
| Power (kW) | 750 | 5.2 |

**JAERI@Tokai-mura**
**(60km N.E. of KEK)**

**(Approved in Dec.2000)**

## JPARC neutrino beamline

- Proton beam kinetic energy

- # of protons / pulse

- Beam power

- Bunch structure

- Bunch length (full width)

- Bunch spacing

- Spill width

- Cycle

- 50GeV (40GeV@T=0)

- 3.3x1014

- 750kW

- 8 bunches

- 58ns

- 598ns

- ~5s

- 3.53sec

**Extraction**
**       ****point**

**Target**

**Target station**

**muon monitor**

**beam dump**

**Near neutrino **
**detector**

**Decay **
**volume**

**Primary Proton**
**        ****beam line**

## Off Axis Beam (another NBB option)

**WBB w/ intentionally misaligned beam line from det. axis**

- (ref.: BNL-E889 Proposal)

- ( a few degrees)

**Target and Horns**

**Decay Pipe**

- Far Det.

**Decay Kinematics**

**Quasi Monochromatic Beam**

## Target station

**Notes:**
3 horns

## Target for JHF neutrino

- melting point should be high enough.

- Solid target

- Easy to handle

- Graphite Target

- Melting point

- Thermal conductivity

- Thermal expansion

- Thermal shock resistance

- Requirements

- Young’s modulus

- Candidate

## Determination of the size (radius)  						of the target

-  Size of the beam
- 		at the target

- Larger than r~0.4cm
- 	(for 24 mm mrad beam)

- minimum

- (heat load from radiation)

- maximum

- rtarget~10mm

- rtarget~15mm

- (pions are not well focused)

**Z (cm)**

******T (degree)**

- Temperature rise / pulse

- of the inner conductor (1st horn)

- Radius of the target : 10~15mm

- Determination of the size (radius)  						of the target

- External conditions

- A.K.Ichikawa

- (Target needs to be embed
- in the 1st horn to focus pions efficiently.)

******

- inner

- conductor

## Determination of the size (radius)  						of the target

- Yield of pions (=neutrinos)

- Smaller is better ( reduce the absorption of pions)

- the difference of # of  is ~5%

- But even if we change diameter
- 	from 20mm to 30mm,

- diameter (mm)

- Typical angle of the 
-       focused by the horn   	~100mrad

- effect of the  absorption
-   in this region is fairly small

**Beam size ( ********r**** = r/2.5 )**

- A.K.Ichikawa

## Energy deposit in the target

- Target and beam size dependence

- Carbon

- (density 1.81g/cm3)

- This time, we used the target with ********=30mm**
-  		in the calculations and the simulations.

- A.K.Ichikawa

- A.K.Ichikawa

**Maximum>460J/cm****3**

## Estimation the temperature rise

- Temperature dependences
-       have to be taken into account.

- Specific heat
- 	increased at higher temp.

- Temperature rise is overestimated

- Maximum temperature rise (Tmax)

- Constant

- Temp. dependent

- ~170K

- ~240K

- Material properties used in the simulation

- Temperature (K)

- Temperature (K)

- (W/mK )

- Thermal conductivity
- 	decreased at higher temp.

- Temperature at the center
-    of the target is underestimated

- (Still, far below the melting point)

**(Tokai Carbon G347)**

**(Tokai Carbon G347)**

**Notes:**
of the t

## Estimation of the temperature rise

- 	(after 5s)

- Thermal convection coefficient

- Temperature of the surrounding area

- just before the next spill 		(after 3.53s)

- Parameters

- M.Minakawa, Y.H.

- = 6.5W/m2/K

- = 30oC (fixed)

## Time dependence of temperature

**r=15mm,z=700mm**

**r=0mm,z=161mm**

- 4

- 8

- 32

- 12

- (Sec.)

- Surface (r=15mm)

- Center (r=0mm)

- far below the melting point

- (temperature of
-   the surrounding area
-      was fixed at 30 oC)

- To keep the surface temperature below 100oC,

- Maximum temperature

- M.Minakawa, Y.H.

- Thermal convection coeff. needs to be larger than ~6kW/m2/K.

- Is it possible?

- water temperature should not exceed ~50oC.

- Consider direct water cooling

## Cooling test

- heat transfer rate

- According to the results from the calculations,

- larger than ~6kW/m2/k.

- Heat up the target with DC current

- and try to cool by the flowing water.

- measure water flow rate and temperature at various points

- estimate the heat transfer rate.

- water

- DC Current

**DC ~1.5kA**

**~20kW**

**Notes:**
2mm

## Cooling test set up

- Current feeds

- Water

- Thermocouples

- water

- Thickness of the water path : 2mm

- Radius of the target:             15mm

- Water temp. (in)                   ~25oC

- DC Current:                 up to 1.3kA

- ~ 20kW

- heat transfer rate measurement

- DC Current

- corresponds to

## Cooling test results

- Generated heat

- 5~20kW

- Results & calculations

- Data

- Calc.

- Measurements and theoretical calculations seem to agree

- cab be achieved when
-    the flow rate is more than 18l/m

-  > 6kW/m2/k

**This time we measured up to 12l/m.**

- Theoretical formula

- = 0.023 x Re 0.8 x Pr 0.4 x  x d-1

- Re

- Pr

- Prandtl number

- Reynolds number

- 

- Thermal conductivity

- equivalent diameter

- d

- (Re and Pr also depend
- 	on the surface temp.)

- S.Ueda

## Change of the material properties 

- The thermal conductivity is largely reduced
-   by the neutron irradiation effect ( about by factor 10.)

- T.Maruyama et al., J. of nucl. materials, 195(1992), 44-50

- Reduce the thermal conductivity by factor 10 in the simulation.

- Temperature at the center was increased
-    	but  it was saturated after 10 spills
- 	and the maximum temperature was less than 400 oC.

- Effect of the neutron irradiation on thermal conductivity
- 			will not be the problem.

- (Temperature of the surface did not change or slightly reduced.)

- by neutron irradiation

## Actual design of the target

- Direct cooling or put in the container?

- This time, we tested the “direct cooling”.

- It seems to be working.

-  The target will not be dissolved?

-  If water get into the deep inside of the target ...

- Boiled when the beam hits the target (?)

- But

-  90cm long target can not be made

- by using the best material.

- If we put the target in a metal container,

- water does not contact with the target,

- even if the target brakes up,

- it is possible to cut the target in small pieces,

- the target material does not flow away.

- We are planning to put the target in a container

- and measure the heat transfer rate.

## Material properties used in the simulation

- Thermal expansion coeff.

- Temperature (K)

- Temperature (K)

- Young’s modulus

- (GPa)

- Estimation of the thermal stress

- If these temperature dependences
- are taken into account,
- the estimated thermal stress will be increased.

**(Tokai Carbon G347)**

**(Tokai Carbon G347)**

## Estimation of the thermal stress (Analytical)

- 	       	ISO-88		~11		68.6
- Poco Graphite	ZXF-5Q  	~15		95.0

- Analytical calculations

- E

- 

- Poisson ratio

- 

- linear expansion coeff. (thermal)

- T0

- Temperature

- Young’s modulus

- Here, we do not have the data of temperature dependences of the material properties other than G347,
- we assume that the shape of the temperature dependences are the same.

- Manufacturer	Type	         Equivalent    Tensile
- 			           stress (MPa)      strength (MPa)

- Tokai Carbon	G347		~6		31.4

## Thermal stress estimation (ANSYS)

- Condition:

- Simulate the hottest part (z=100mm ~ 200mm)

- Both of the edges (z=100 & 200mm) are fixed
- 						(z direction).

- just after the spill (after 5s)

- 100

- 200

- Equivalent stress

- (Because both of the edges
- 	 	      were fixed)

- z (mm)

- maximum
- temperature

- @ r=0, z=200mm

- ~14.5MPa.

- @ maximum temperature
-                (r=0,z~170mm)

- ~8.8MPa.

- (r=0,z~170mm)

- r (mm)

- 0

- 15

- [Tensile strength (Tokai Carbon G347)
- 		            : 31.4MPa]

- slightly larger but consistent with the analytical calculations

- (analytical calc: 6.0MPa)

- (due to the approximation of the temperature distribution)

## Water system for the target cooling

- To the decay volume
- 	cooling system

- Buffer tank
-  (0.1m3)

- Degasser

- Filters
-   /Ion exchangers

- Underground machine pit

- Service pit

- Target Area

**Heat ~20kW**
**Water vol.= 1l**
**Flow 20l/min.**

- Target

- We have to remove H2,N ions and heavy metal ions.
- Also, the water have to be cooled.(T(water)~15oC@20l/min.)

## Radioactive residues

- (target and cooling water)

- size

**=30mm, L=900mm

- # of generated Be7

- 1.8g/cm3

- density

- 1) Target

- ~9x1012(Bq)

- after 1yr of running, cooled for 1day

- ~14Sv/h

- (By Nakano)

- 2) Cooling water

- (By K.Suzuki)

- after 20 days of running

- Tritium ~30(MBq)

## Summary (I)

- For the JPARC  experiment,

- solid target R&D is now ongoing.

- diameter ~30mm
- length      900mm (2 interaction length)

- cooling

- dimensions

- material

- Graphite ( or C/C composite ?)

- Water (direct or put in the case?)

- temperature rise

- ~ 175 oC (center)

- ~ 25oC (surface)

- thermal stress

- ~ 9MPa  (for G347)

- [Tensile strength (G347) ~ 31MPa]

- Heat transfer rate > ~ 6kW/m2/K

- cooling method

- Direct cooling

- Water flow rate ~20l/min.

- seems to work

## Summary (II)

- Beam test (with same energy concentration)

-  Irradiation effects other than the thermal conductivity

-  Stress test

- (Usually, graphite, whose tensile strength is large,
- 	has large Young’s modulus.
- 		the thermal stress is also getting larger.)

- Temperature dependences of the material properties.

-  Cooling test

- Measure the heat transfer rates with a target container.

- Set the water flow rate at 20l/min. and confirm the method.

- Where?

- R&D Items

- (We want to test/check the following items.)

## Summary (III)

- How to fix (support) the target, alignments etc...

-  Design of the entire system has to be fixed.

**Notes:**
Remove target in the waste area.

## Summary (IV)

-  Target handling

- How to remove the target from the horn remotely?

- (It may be necessary to remove the target from the horn
- 				when the target part is broken.)