Future upgrade of the neutrino beam-line for multi-MW beam

5th Hyper-Kamiokande open meeting @ Vancouver

July-20-2014

Yuichi Oyama (KEK)(for T2K neutrino beam-line group)

Introduction

When the J-PARC project started, the primary goal of the beam power in the neutrino beam line was 750kW. Upgrade to 4MW was second step in the future.

~750kW beam from the accelerators will be within our reach by ~2017 if the budget is funded timely. It is possible to accept this beam power, with significant improvement for steady operation.

For operation beyond 750kW, critical improvements are needed.

In this talk, future upgrade required for ~2MW beam power is reported.

Beam History At the beginning, 750kW x 5year operation was officially approved,

where 1 year is defined as 107sec = 115.7days. For 30GeV proton beam, it corresponds to 7.81 x 1021 protons on target (pot).

Stable operation at ~230kW has been achieved. Until June 2014, 7.39x1020 pot is accumulated. It is ~9% of our goal.

3.2s3.04s145kW

2.56s190kW

2.48s235kW

2.48s235kW

[6 bunches]

Rep=3.52s50kW

Run 1

x1019

Run 2 Run 3 Run 4 Run 5

Recovery from the earthquake

Hadron Hall accident

Neutrino beamAnti-neutrino beam

1.43x1020potuntil Mar.11,’11

3.01x1020pot until Jun.9,’12

~7.3x1020pot until Jun.24,’14

6.63x1020pot until May.8,’13

Present expected beam parameters for ~750kW will be~1.3sec Main Ring cycle and ~2.0x1014 ppp (proton per pulse).

Future Improvements for higher beam power

T.Koseki in J-PARC symposium 2014 (http://j-parc jp/j-parc2014/) andT.Ishida in this HK open meeting

(if the budget is funded as we hoped)

5

BeamDump

PrimaryBeam-line

ExtractionExtractionPointPoint

MuonMonitors

110m110m

280m280m

295km295kmTo KamiokaTo Kamioka

Main

Main

RingRing

Target &Horns inTarget Station

PP

DecayVolume

Near NeutrinoDetectors

MLFMLF

RCSRCS

Neutrino experimental facility at J-PARC

Preparation section11 normal conducting magnets

Final focusing (FF) section10 normal conducting magnets

Arc section28 superconducting combined func. magnets

Primary Beam-line

Primary Beam-line All magnets in the primary beam-line , thickness of concrete tunnel and

surrounding soil are designed by assuming 1W/m energy loss in Arc section, 750W loss in the preparation section, and 250W loss in the final focusing section.

When the beam power become multi-MW, emittance of the beam may become drastically larger. Much larger energy loss would be generated.

A tuning of the beam orbit as well as the beam size is important to avoid radio-activation. Beam monitors are critical for the tuning.

If emittance of the beam becomes much larger, some of the magnets must be replaced with new design of large apertures.

Production of new magnets are not difficult from a viewpoint of technology. Production period of a few years, and shut-down for installation of a few month to one year, depending on the new beam parameters, are required.

Decay Volume

Target Station

Beam Dump

OA2o

OA2.5o

Beam TransportFrom RCS to MLF

6m-thick concrete wall OA3o

Helium Vessel

Target and 1st Horn

3rd Horn

Beam Window

Secondary beam-line

2nd Horn

For 3 Horns,See Sekiguchi-san’s talk

26mm x 910mm

Ti-6Al-4V(0.3mm-t)

Graphite

T~200K ~7MPa (Tensile strength 37MPa)

736oC

30GeV-750kW (~20kW heat load) CFX analyses CFX analyses

He gas cooling: 9Nm3/m (v=200m/s)Conductivity 14020W/mK(rad. damage)

Target Carbon Graphite of 26mmx 910mm

are embedded in Ti-6Al-4V of0.3mm thickness.

The design was based on calculationof thermal stress and flow of Heliumgas cooling.

The present design can accept 3.3x1014 (ppp) x 5 years with a safety factor of 2. This corresponds to 1.2MW if 1.3sec of Main Ring cycle is assumed. (750kW beam with 3.3x1014 ppp and 2.1s MR cycle was the initial plan.)

Larger beam diameter will be needed for future higher power.

Separate Helium vessel from vacuum in primary line.Double wall of 0.3mm thick Ti-6Al-4V, cooled by He gas (0.8g/s)

Stress by partial heat load at the beam spot may break the window !

The present design can accept 3.3x1014 (ppp) with a safety factor of 2 . This corresponds to 1.2MW if 1.3sec of Main Ring cycle is assumed.

Change the diameter of the beam and/or upgrade the cooling systemis needed for future beam.

Beam Window

Radiation damage may change the characteristics of the thermal stress of the material.

The radiation damage of the Ti -6Al-4V was reported up to 0.24DPA (displace per atom), which correspondsto ~1.5x1020 pot.We are already in unknown region.

Replacement cycle of the window shouldbe considered. However, 2MW x 1 yearbeam corresponds to 4x1021 pot.Replacement more than once per yearis impossible.

Test of radiation damage is needed.We are planning an internationalcollaboration for this test.Ask Ishida-san.

According to the results of the test,use of another target/window materialmight be needed.

Radiation damage for Ti-6Al-4V

0.24DPA

0 DPA1000MPa

Strain (%)

70MPa(220kW)

Limit:400MPa ? with fatigue & high temp.

200MPa

Ti-6Al-4V

Stre

ss (M

pa)

Helium Vessel, Decay Volume and Beam DumpLarge fractions of the beam

energy are absorbedin HV/DV/BD.

Thermal stress may damagethe structure of HV/DV.Their temperature must bekept less than 60 degree. The temperature of the beam dump core must be less than 400 degree.

They are cooled by cooling water system. At present, the system is adjusted for the 750kW operation.

Cooling power can be upgraded by increasing flow rate of the cooling water. Additional pumps and related components as well as the space for them in the machine room are needed.

Radioactivity of the cooling water will become higher.This is another serious problem.

750 kW

Fraction

Helium Vessel ~170 kW ~23%

Decay Volume ~130 kW ~17%

Beam Dump ~150 kW ~20%

(Neutrino) ~12 kW ~1.6%

Max. temp: 54 ºCMax. stress: 47 MPa

Thermal analysis shows that there is safetyfactor 3 for ~750kW beam.

Additional iron shields between the magnetic horns and side wall of the Helium Vessel are required for multi-MW beam.

Helium Vessel

XYZ

30.

40.

50.

60.

55.08

52.05

49.02

45.99

42.97

39.94

36.91

33.88

30.86Output Set: Case 9 Time 258232.3Contour: Temperature

Rectangular pipe of 3m(W) x 5m(H)x 100m(L), connected with TSHelium vessel. Total volume with TS Helium vessel is 1500m3.

Cooling water system for the iron walls.Ready for 750kW without any upgrade.Upgrade of cooling water flow rate is needed

for multi-MW.

Max. temp ： 55C

1414

Decay Volume

Graphite core of 2.8m(W) x 5.3m(H) x 3.2m(L),14blocks. Max. temperature < 400 degree.

Aluminum blocks are cooled by water Ready for 750kW without any upgradeUpgrade of cooling water flow rate is needed

for multi-MW.

Max. temp:180℃

1515

Beam Dump

Radiation IssueMany restrictions about radiation in the neutrino beam-line.

Radiation dose outside of the radiation control area:

< 0.5Sv/h

Radioactivity in disposed water:

for 3H < 60Bq/cc < 5000GBq/year (from J-PARC)

for 7Be < 30Bq/cc < 1200MBq/year (from neutrino facility)

Exhausted Air from stacks of buildings (Target Station):

for 3H < 5mBq/cc for others < 0.5mBq/cc (mainly 41Ar)

DV/BD cooling water systemHV/DV water system（ DV downstream and BD ）（ Helium Vessel and DV

upstream ）

Horn cooling water system

Three independent cooling water systems 　

Cooling Water system and Radioactivity

Neutrons and other beam products break Oxygen In H2O and many kinds of isotopes are produced as spallation products.They are 3H, 7Be,11C, 13N, 15O, 14O, 16N, 14C.

Lifetime 1/2 < 20minutes : 11C, 13N, 15O, 14O, 16N 1/2 = 5730 years : 14C 　Their contribution can be ignored.

The source of radioactivity is 3H (1/2 = 12.3 years) and 7Be (1/2 = 53.3 days).

B2 tank

DP tank

All drain water

(2 tanks are used together)

30m3 Drain tank

21m3 Buffer tank

Ion exchangers

H2SO4 NaOHpH control system

Only beam-off

Also beam-on

TSNU2

(effectively 84m3)

Horn CW

HV/DV CW

Ion exchangers

Ion exchangers

drainage

Off limit during beam

dilution water

Drainage of Radioactive Water

One drainage cycle per 3 business days.

42Bq/cc x 84m3 = 3.5GBq of 3H can be disposed per one drainage cycle.

Schematic flow of the drainagesystem for radioactive water

One “drainage cycle” is 1)Buffer Tank -> DP tank 2)dilution and measurement3)drainage from DP tank

Regulation/Requirement

FY2012 FY201X FY202X?

Beam power

3.10 x 1020pot(=149kW x 107s eqv.)

15.6 x 1020pot(=750kW x 107s eqv.)

41.6 x 1020pot(=2MW x 107s eqv.)

3H < 5000GBq/yr from J-PARC< 60Bq/cc(< 42Bq/cc for safety)

77.6GBq (NU2) 30.0GBq(Horn) 47.6GBq(HV/DV)15.9GBq (NU3) 93.5GBq (NU2+NU3)

390GBq (NU2) 151GBq(Horn) 239GBq(HV/DV) 95GBq (NU3) 485GBq (NU2+NU3)

1040GBq (NU2) 403GBq(Horn) 637GBq(HV/DV) 253GBq (NU3) 1293GBq (NU2+NU3)

Drain-age

1 drainage per3 business day

27 times x 84m3

(NU2)25 times x 17m3 (NU3)

87 times x 84m3

(NU2) and12 times x 16GBq (Tank Truck)

~200 times x ~100m3

(NU5) and ** times x 16GBq (Tank Truck)

Prospect for Radioactive Water Drainage

We can ask a part of drainage to another section in JAEA by using a tank truck. Ready for 750kW beam.

3 parallel drainage system with larger disposal tanks are needed for 2MW beam.

20

BeamDump

PrimaryBeam-line

ExtractionExtractionPointPoint

MuonMonitors

110m110m

280m280m

295km295kmTo KamiokaTo Kamioka

Main

Main

RingRing

Target &Horns inTarget Station

PP

DecayVolume

Near NeutrinoDetectors

MLFMLF

RCSRCS

We are planning to build new facility buildings for new cooling water system, new disposal tanks, and other facilities.

We need ~2 years for construction, and full 1-year shutdown?

Present facility buildings are too small to install upgraded facilities.

New Buildings in the neutrino beam-line

Radioactivity in Exhausted Air

~1000mBq/cc in machine room

~5000mBq/cc in service pit

Leakage of radioactive air through gaps

~3mBq/cc in ground floor

Negative pressure

~0.3mBq/cc at stack

Ventilation system 13000m3/h

(must be < 0.5mBq/cc. This radioactivity ismonitored in real-time)

@230kW beam (after many efforts)

Air-tight work in Target Station Caulking betweenconcrete shields

Air-tight sheet(made of the samematerial for balloon)

Protection sheet(over air-tight sheet)

Protection sheet under air-tight sheet

Air-tight lamination(in future)

Caulking + Air-tight sheet

More careful air-tight in future !

Ventilation flow rate 13000m3/hcannot be changed

Bypass of Ventilation in Target Station

By making bypass route of the air,ventilation rate of TS ground floorreduced to be 1/10.

Radioactivity in the exhausted air become 1/3 of non-bypass mode.

About 60% of 41Ar (1/2~110mins) decay in ground floor. Radioactivity in the ground floor increased by factor ~3.

Further change of the bypass rate will be needed for higher beam power…

Many works are definitely neededto accept ~2MW beam…….

Summary

Replacement of some of the magnets in the primarybeam-line?

New design of the target?New design of the Beam Window, and study of the

radiation damage?Additional iron plate in Helium Vessel.Upgrade of the cooling water system -> New buildingsUpgrade of radioactive water drainage -> New buildingUpgrade of Air-tight in the Target station buildingBypass ventilation systemOther works not covered in my talk……

List of works to accept ~2MW beam

END