Fermilab 11 th November 2015 1 Chris Densham STFC Rutherford Appleton Laboratory On behalf of the T2K beam collaboration 2 2015 Breakthrough Prize in Fundamental Physics awarded to Professor ID: 788362
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Slide1
T2K Target status
PASI Meeting Fermilab 11th November 2015
1
Chris Densham
STFC Rutherford Appleton Laboratory
On behalf of the T2K beam collaboration
Slide22
2015 Breakthrough Prize in Fundamental Physics awarded to Professor
Koichiro
Nishikawa on behalf of the K2K and T2K Collaborations for the achievements of K2K and T2K
$3M prize shared with
Kamland
,
Daya
-Bay, Super-
Kamiokande
and SNO experiments
Slide3Chris Densham HINT 15 October 20153
Slide4Pacific
30 GeV PS
3 GeV PS
400 MeV LINAC
T2K neutrino facility
T2K Target Station
295 km to Super-Kamiokande
Near detector
MLF
Beam dump
Slide5T2K operational history
Slide6T2K Secondary Beam-line
110m
Muon
Monitor
Target station
Beam window
Decay Volume
Hadron absorber
Target Station, Decay Volume and Beam Dump all enclosed in large water-cooled steel helium vessel.
He atmosphere prevents nitrogen oxide (NO
x
) production / oxidization of apparatus.
Beam dump and vessel walls cooled by water circuits.
Maintenance is not possible after beam operation due to activation.
Radiation shielding / cooling capacity were designed for
~4MW beam
.
Slide7T2K Secondary Beam-line
Baffle
1st horn
Target
2nd horn
3rd horn
BEAM
Iron shield (2.2m)
Concrete Blocks
Helium Vessel
Muon
Monitor
Target station
Beam window
Decay Volume
Hadron absorber
Slide8Horn & target system in Target Station
8
15.0m
10.6m
Baffle
Graphite
Collimator
Horn-1
Horn-2
Horn-3
Beam window
Ti-alloy
DV
collimator
Large flange, sealed with
Al plates, t= 120mm
1.0m
Concrete
blocks
Water-cooled
iron cast blocks
29pcs.
total 470t
Support
Module
2.3m
Horns / baffle supported within vessel by support modules.
Apparatus in beam-line highly irradiated after beam.
Remote maintenance required
.
Service Pit
Disassemble
@ maintenance area
OTR
Target
Beam
Slide9Horn transfer from beamline to remote maintenance area
Handling machine
for horns
Horn and target
Guide cell on
the maintenance area
Horn support module
Guide cell on
helium vessel
Slide10Target exchange system
Target & horn
Helium cooled graphite rod
Design beam power: 750 kW
Beam power so far:
330 kW
3% beam power deposited in target
1
st
target
& horn replaced after 4 years, 6.5e20 p.o.t.
2
nd
target being repaired after 5 e20 p.o.t.
π
π
p
Slide11Inspection of target/horn in Remote Maintenance Area
Cracked
ceramic
break diagnosed
Not a real technical problem (inside helium vessel)
Currently working on pipe replacement
Known issue with diffusion bonded ceramic-to-stainless joint has been fixed
Slide12Plan for remote replacement of helium pipe
Slide13Inlet pressure = 1.45 bar
(gauge)
Pressure drop = 0.792
bar
Need higher pressure helium for higher powers
Helium cooling velocity streamlines
Maximum velocity = 398 m/s
Current target – helium cooled solid graphite rod
Designed for old parameters of MR
750kW beam
: cycle: 2.1s, PPP: 3.3x10
14
Present expected parameters:
Doubled rep-rate, MR cycle: 1.3 s, PPP: 2.0x10
14
Stress wave amplitude decreased by 40%
-> What is maximum beam power possible for this design?
Slide14Effect of pulsed beam on T2K target
Inertial ‘violin modes
’
P. Loveridge
Stress distribution after off-centre
beam spill
Radial stress waves – on centre beam spill
8 MPa
0.5 µs beam spill
p
Slide15Stress wave magnitude determined by
t
spill
<
t
oscillation
period
Slide16Fast neutron radiation damage data for graphite
(IG 110, similar to IG 43)
Max temperature 736ºC assuming reduction in thermal conductivity by 75%
Slide17Beam Window
Separates He vessel from vacuum in primary line with pillow seals
Double skin of 0.3mm thick Ti-6Al-4V, cooled by He gas (0.8g/s)
300
C/200MPa,
Safety factor 2
for
750kW(3.3x10
14
)
~ Safer for 750kW(2.0x10
14
)
Reduction of Ductility
reported
with 0.24DPA
6x10
20pot≈1DPA?: Replacement cycle should be considered.Same window in front of Target, Same material with OTR, SSEM
17
Slide18Pulsed beam tolerance for candidate window materials
where
‘Thermal stress resistance’,
UTS – ultimate tensile strength
α – coefficient of thermal expansion
E – Young’s modulus
ΔT – temperature jump
EDD – energy deposition density
Cp – specific heat capacity
NOTE:
Δ
T depends on material density as well as specific heat capacity, so these are also important variables.
Slide19ANSYS static (time-averaged) stress
UTS Ti-6Al-4V ≈ 1GPa
NOTE: 100W/m
2
K
heat transfer coefficient applied to internal wall
Slide20Effects of elevated temperature, fatigue and radiation damage on beam window
U.T.S.
Safety Factor
N. Simos (BNL)
8.9x10
20
pot ~ 1.5
dpa
0.24
dpa
Significant loss of ductility at 0.24
dpa
Now likely to be entirely brittle at 1.5
dpa
Does it matter?
Low stress at moment
320 kW
750 kW
Slide21New collaboration led by P. Hurh on accelerator target materials as part of Proton
Accelerators for Science & I
nnovation (PASI) initiative.http://www-radiate.fnal.gov/index.html
Key objectives:
Introduce materials scientists with
expertise
in radiation
damage
to accelerator targets community
Apply expertise to target
and beam
window issues
Co-ordinate in-beam experiments and post-irradiation examination
12 members signed MoU – more welcome
21