A.K.Ichiawa, Kyoto UniversityContents
 focus on ‘conventional superbeam’:  beamfrom meson decay
 focus on on‐going or future project Can’t cover great achievement by FNAL Booster and CERN CNGS Talk about challenges in High intensity Accelerator  beam facility

Components of the Long Baseline Neutrino Experiment
Neutrino beamline

ProtonAccelerator

Decay Volume

Target&Horns




Beam
dump

NearDetector

FarDetector

 monitor
A few 100m ~ a few kma few 100km ~ a few 1000 km

Example:~1/cm2/s at T2K Far detector(295km away)(@750kW proton beam power)
among which 10‐10 interact.

Feature of Superbeam  flux
 Wide band, but can be narrowed by•target‐horn distance (NuMI)•

off‐axis method (T2K, NOvA)

~10% uncertainty with p‐nucleus hadron production measurement (e.g.
NA61, MIPP)+beamline errora few % e contamination from the decay of Kaons and muons beam or anti‐ beam depending on the horn current polarity•

Yield difference is modest ( ~10%), but ‐nucleus cross section isdifferent::=2~3:1
Posc*ccT2K(arbitrary units)

NuMI/MINOS
‐fluence

CNGS

Proton Machine Intensity Frontier
EnergyPowerCurrent

PlanedFutureJ‐PARC/KEK30 GeV~0.25MW
T2K

0.75MW
T2K~2MWFNAL

120 GeV~0.36MW
MINOS

0.7MW
NOvA

~2MW
LBNE/LBNF

CERN

400 GeV/c

0.3MW~0.5MW
OPERA/ICARUS( 0.2MW for shortbaseline: CENF)

0.7~2MW(CN2PY)

BEAM POWER= (Energy) x (#Protons‐per‐pulse) x (acceleration‐rep‐rate)
Achieved = < 0.5 MW
Desired > 1 MW

What limits the intensity of proton accelerator?
++ + ++ + + ++ ++++ + ++ + +++ +Space Charge Effectcause blow up of beam
Larger at lower energy
effect increase non‐ linearlywith beam intensity

There can be many reasons. But here, let’s highlight Space Charge Effect
Space charge effect  beam loss  problem on shielding's andmaintenance
Bottle‐neck of existing facility• NuMI : Injection at booster, J‐PARC: Injection at Main Ring, see later slides

Possible solutions• Increase repetition rate , not increasing protons‐per‐pulse(PPP)• Increase injection energy• use Linac = one path accelerator (, but difficult to go to high energy)

J‐PARC
Hadron Experimental Facility

500 m

Neutrino Experimental
Facility
Rapid Cycle Synchrotron (RCS)
3 GeV ,25 Hz

Linac (330m)
180 MeV  400 MeV upgraded

Main Ring (MR)(30 GeV synchrotron)

J‐PARC power upgrade plan
JFY

2013

2014

power(kW)200‐240200‐300

Linac
Linac Front‐end
180MeV400MeV current

30mA50mA
2015

2016

2017
750

Main Ring rep. cycle
2.5s1.3s
w/ new Magnet Power supplies
and new high Impedance RFCurrent bottleneck

beam loss at injection to MR

can’t increase ppp (already world‐highest)

go higher rep. rate  0.75 MW

New RF R&D completed

Small prototype of 1 Hz PS is working.

Long‐term possibility under study

New 8 GeV BoosterTarget > 1~3MW
New high impedance RFFNAL power present upgrade plan
Booster is the current primary bottleneck.
 Main Injector (MI) Faster ramp
 Slip stack

Recycler Ring (using permanent
magnet to store 8 GeV beam) Put two batches from booster (fill bucket twice) Use recycler ring(RR) as injector
 booster  RR MI reduce injection time 280 kW 350kW
450kWby the end of this summer 700 kW in 2015

Main InjectorBooster (8 GeV)

Fermilab Accelerator Complex

FNAL future power upgrade plan‐Proton Improvement Plan(PIP) II‐ goal > 1MW (~2025)
 Linac 400 MeV New 800 MeV super conducting pulsedlinac
 Higher energy injection to Booster will reduce beam loss

CN2PY (CERN‐to‐Pyhasalmi)
 Initial beam from SPS(+) 400 GeV/750 kW
 Phase II: LP‐SPL(Superconducting Linac) to HP‐PS 50 GeV/2 MWESS 2 GeV linac as proton driver
for a neutrino Super Beam (proposal)

Neutron pspallation
HtargetESS linac

ESS: European Spallation
Source in Sweden
 2 GeV 5 MW
superconduction linac
 First beams 2019 Full power 2022

Accumulator

Proposal
rise frequency from 14 Hz to 28 Hz.
(duty 4.0%  8.0%, RF power 5 MW  10MW)

What limits the intensity of beamline?
 Beam loss (same as accelerator)
 Thermal shock Radiation damage
 Cooling power
 Dirty product in air(NOx) and water(Tritium,H2,Acid) Radiation shieldExample : 50 GeV 0.75 MW beam Residual radiation> 1000Sv/h

3.3E14 ppp w/ 5s pulsecm

When this beam hits an iron block,C ET  3GPacm

simulation by MARS

1100C(cf. melting point 1536C) Material heavier than iron would melt.
 Thermal shock stress(cf. strength ~300 MPa)
Material heavier than Ti might be destroyed.
 Target and beam window have to withstand the thermal shock.

Radiation damage
 Any high molecular material cannot withstand.
Only metal and ceramics.
 25% of carbon atom in target will be displaced bybeam hit in 1 year T2K 0.75MW operation.
 The material properties are changed.
 Dimension change
shrinkage by ~5mm in length in 5 years at max for
90cm long target Degradation of thermal conductivity
decreased by 97% @ 200 °C, 70~80% @ 400 °C

PSI fluence 1022 p/cm2

T2K Target
designed for 0.75 MW, He‐cooling to avoid water hammer
26mmx 910mm

Graphite
IG-430U

9Nm3/min(v=200m/s)

Ti-6Al-4V(0.3mmT)
He-gas cooling

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

736oC

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

LE target for MINOS(for 400kW)
water cooling pipeNuMI target
LE target : inserted into horn1
ME target: upstream of horn1
ProtonBeam

ME target for NOvA
Nominal max. beam power 700 kWtarget not inside Horn

Water Cooled
Clamping Plates

LBNE/LBNF target ideas
Minimal change from NuMI LE target
width: 6.4 mm  10mm, beam spot:1.1 mm 1.7mm
 aimed for 1.2 MW

Pressurized helium cooled beryllium sphere (RAL idea) aimed for 2.3 MW

CN2PY target study Phase‐I (400 GeV, 0.75 MW) : evolved version of the CNGS
graphite target Phase‐II (50 GeV 2 MW) : packed bed target (RAL idea)

ESS  proposed concept

packedbed of titanium spheres
cooled with cold helium gas

SplitProton
BeamRAL idea

Collimators

Horns andTargets

Decay Volume (He, 25 m)
Beam Dump

four systems to reduce the load

Neutrino
BeamDirection

What limits the intensity ofbeamline?
 Beam loss (same as accelerator)
 Thermal shock Radiation damage
 Cooling power
 Dirty product in air(NOx) and water(Tritium,H2,Acid) Radiation shield

Magnetic Hornp beam Toroidal Magnetic field Usually operated at 100~300 kAe.g. 1.8T @28,250

 a few ms pulsed current
 designed for ~700kW so far
 Radiation and Joule’s heating Recent horns are cooled by spray water
Issue on hydrogen, tritium NOx productions

Magnetic Horn

p beam Toroidal Magnetic field Usually operated at 100~300 kAe.g. 1.8T @28,250

 a few ms pulsed current
 designed for ~700kW so far
 Radiation and Joule’s heating Recent horns are cooled by spray water
Issue on hydrogen, tritium NOx productions

Decay Volume & Beam Dump
T2K (aimed for 3 MW)• Decay pipe: iron walls are water‐cooled• Beam dump: Graphite‐core• filled with Helium

LBNE current design (aimed for 2.3 MW)

T2K
DV&Dump• Target chase: air filled, air/water cooled• Decay pipe: helium filled/air cooled• Beam dump: Aluminum core/ water cooeld

LBNE Decay pipe
concept example

Summary
EnergyPowerCurrent

PlanedFutureJ‐PARC/KEK

30 GeV~0.25MW
T2K

0.75MW
T2K~2MWFNAL

120 GeV~0.36MW
MINOS

0.7MW
NOvA~2MW

CERN

400 GeV/c

0.3MW~0.5MW
OPERA/ICARUS( 0.2MW for shortbaseline: CENF)

0.7~2MW(CN2PY)

Achieved = < 0.5 MW
Desired > 1 MW
Need tough works to go
beyond 0.5 MW
Many innovative works arenecessary for power
beyond ~0.7 MW

MR Upgrade

2kW  3.5kW

J‐PARC power upgrade plan
JFY20132014

power(kW)200‐240200‐300

2015

2017
750

Linac
Linac Front‐end
180MeV400MeV current

30mA50mA

2016

Main Ring rep. rate
2.5s1.3s
w/ new Magnet Power supplies
and new high Impedance RFCurrent bottleneck

beam loss at injection to MR can’t increase ppp

8GeV Booster go higher rep. rate  0.75 MW
R&D of components succeeded.
Long‐term possibility under study

New 8 GeV Booster

reduce emittance and space‐charge
effect at MR injection



Target > 1~3MW

MR (30 GeV)RCS (3 GeV)

Accelerator complex status and plans Presently running with Main Injector only, 6 Booster batches 2.5E13, 1.67 s cycle time, 280 kW peak power Commissioning of Recycler ring (~ 4 months)
 peak power ≥ 500 kW in 2014
 at ~ 700 kW in 2015
 Project X (http://arxiv.org/abs/1306.5022) is a complete designconcept for 3 GeV CW superconducting H- linac with 1 mA average beam current
 3-8 GeV pulsed linac with 43 mA average beam current Recycler and Main Injector upgrades to provide ≥ 2 MW to the long
baseline neutrino target at 60-120 GeV
 Fermilab plans to reorient the Project X program to have a goal ofdelivering > 1 MW from Main Injector to the neutrino program by 2025
 800 MeV srf linac injecting into existing Booster
6.6E12 protons per batch @ at 12 batches/1.2 sec
12 batch slip-stacking in Recycler, providing 1.2 MW
 or 400 MeV srf linac appended to existing 400 MeV linac(“afterburner”)

Target‘Divide and Rule’ for increased power
Dividing material is favoured since: Better heat transfer
 Lower static thermal stresses
 Lower dynamic stresses from intense beam pulses
Helium cooling is favoured (cf water) since: No ‘water hammer’ or cavitation effects from pulsed beams
 Lower coolant activation, no radiolysis
 Negligible pion absorption – coolant can be within beam footprint For graphite, higher temperatures anneal radiation damage
Low‐Z target concepts preferred (static, easier)

Chris Densham (RAL) ICFA Neutrino European MeetingWhat limits the intensity ofbeamline?
 Beam loss (same as accelerator) : NOT LOSS but full power.
 Thermal shock Radiation damage
 Cooling power
 Dirty product in air(NOx) and water(Tritium,H2,Acid) Radiation shieldFight w/ the production of Nox,Tritium, acid etc.
Decay Volume

Target&Horns

All in one hugevessel(~1500m3) filled w/helium.

Cooling waterchannels

Remote maintenanceRadiation shieldings

2.2m thick iron shields remotely
installed

1mm thick concrete block.

On top of them, another 3~4 m thick concrete