Upload
rita-dickinson
View
219
Download
0
Tags:
Embed Size (px)
Citation preview
Matt Rooney
RAL
The T2K Beam Window
Matt RooneyRutherford Appleton Laboratory
BENE November 2006
Matt Rooney
RAL
Contents
• The T2K target station beam window
- Design
- Dynamic stress analysis
• Implications for beam windows at higher powers
- T2K upgrade
- Limits of windows
Matt Rooney
RAL
T2K Beam Window Overview
Matt Rooney
RAL
T2K Target Station
Proton beamFocusing horns
Target
Window
Matt Rooney
RAL
Beam Parameters
- 0.75 MW beam energy
- Gaussian profile with 4 mm rad rms beam spot
- 5 µs pulse = 8 x 58ns bunches
- 1 pulse every 2 seconds at 30 GeV
Matt Rooney
RAL
Beam Window - Requirements
• Withstand 1 atm pressure difference
• Endurance against temperature rise and thermal stress due to pulsed proton beam
• Beam loss must be less than 1%, i.e. it must be thin
• Structure should be remotely maintained
Pulsed proton beam
Vacuum
He @ 1 atm
Window
Graphite target
Matt Rooney
RAL
Beam Window Assembly
Window Overview
- Double skinned partial hemispheres, 0.3 mm thick.- Helium cooling through annulus.- Ti-6Al-4V.- Inflatable pillow seal on either side.- Inserted and removed remotely from above.
Matt Rooney
RAL
Window Assembling
Side plates-Provide a firm support for the beam window to hold it in position
Top plate- Used for inserting and removing window- Protects pillow seals and mating flanges- Provides a connection point for services
Pillow seals-Seal helium vessel and beam line(leak rate spec, 1 x 10-7 Pa……)
Ti-6Al-4V beam window
Matt Rooney
RAL
Helium cooling
He in He out
Titanium - 0.3mm
Titanium -0.3mm
Helium3mm Gap
Upstream
Annulus
Downstream
Helium velocity ≈ 5 m/sHeat transfer coefficient ≈ 150 W/m2K
Matt Rooney
RAL
Remote handling
Beam Position Monitorchamber
Target station
Matt Rooney
RAL
Dynamic Stress Analysis
Matt Rooney
RAL
Transient window temperature
Simulation shows temperature distribution over 5 pulses (15 seconds)
0
50
100
150
200
250
0 5 10 15 20 25 30
Time (s)
Te
mp
(o
C)
Heat transfer coefficient = 140 Wm2/K external and 10 W/m2K internalBeam energy = 50 GeVFrequency = 0.284
Matt Rooney
RAL
Stress Waves
Stress wave development in 0.6 mm constant thickness hemispherical window over first 2 microbunches.
Matt Rooney
RAL
0.62mm Window - Constructive Interference
-200
-150
-100
-50
0
50
100
150
200
0 1 2 3 4 5
Time from beginning of pulse (μs)
Str
es
s (
MP
a)
Von Mises
Hoop
Longitudinal
Matt Rooney
RAL
0.3mm Window - Destructive interference
-200
-150
-100
-50
0
50
100
150
200
0 1 2 3 4 5
Time from beginning of pulse (μs)
Str
es
s (
MP
a)
Von Mises
Hoop
Longitudinal
Matt Rooney
RAL
Important lesson
• With a pulsed proton beam, window and target geometry can greatly affect the magnitude of stress.
• Be careful to check dynamic stress when changing beam parameters or target and window geometry!
Matt Rooney
RAL
Higher Power
Matt Rooney
RAL
T2K 3 MW upgrade
• Increased number of protons per pulse would push the limits of Ti-6Al-4V.
0.75 MW pulse ~ 100 MPa shock stress3.0 MW pulse ~ 500 MPa shock stress
• Room temp yield strength Ti-6Al-4V = 900 MPa.• But higher power could also be achieved through a
higher beam frequency.
0
100
200
300
400
500
600
0 50000 100000 150000 200000 250000 300000 350000
Heat deposit (J/g)
Pe
ak
str
es
s (
MP
a)
VM centre
Long centre
VM edge
Matt Rooney
RAL
Future Neutrino Factories and Super-beams
• Higher beam current through higher frequency.
• Less PPP, smaller beam spot.• Adequate cooling and material selection
can mitigate for high energy deposit and thermal shock.
• Radiation damage becomes dominant effect.
Matt Rooney
RAL
Radiation effects
• Irradiation affects different materials in different ways:
- Many metals lose ductility.
- Graphite loses thermal conductivity.
- Coefficient of Thermal Expansion of super invar increases, but low CTE can be recovered by annealing.
Matt Rooney
RAL
Conclusions
More R&D needed for beam power upgrades.
Irradiated material data is crucial. This should be a major research priority in the coming years.
Matt Rooney
RAL
THANK YOU!
QUESTIONS?