1. CLIC Post-Collision Line and Dump
Edda Gschwendtner, CERN
for the
CLIC Post-Collision Line and Dumps WG

2. Outline Introduction Background Calculations to the IP Magnet Lifetime2 2
Outline
Introduction
Background Calculations to the IP
Magnet Lifetime
Main Beam Dump
Luminosity Monitoring
Summary
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

3. post-collision line Post-Collision Line Beam dump detector beam1 beam2
20mrad
detector
beam1
beam2
Beam
dump
post-collision line
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

4. Some Numbers 50 Hz repetition rate 156ns bunch train length4 4
Some Numbers
50 Hz repetition rate 156ns bunch train length
3.7E9 e/bunch bunches/pulse
14MW beam power
e+e- collision creates disrupted beam
Huge energy spread, large x,y div in outgoing beam
 total power of ~10MW
High power divergent beamstrahlung photons
2.2 photons/incoming e+e-
 2.5 E12 photons/bunch train
 total power of ~4MW
Coherent e+e- pairs
5E8 e+e- pairs/bunchX
170kW opposite charge
Incoherent e+e- pairs
4.4E5 e+e- pairs/bunchX
 78 W
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

5. Purpose of the Post-Collision Line
1 - transport spent beam safely to dump
Transport of all charged particles (disrupted beam, e+ e- pairs) as well as beamstrahlung photons to dump
Transport non-colliding particles to dump
Controlled beam losses in magnetic elements and collimators, with a minimal flux of backscattered particles at the interaction point
2 – implement beam based diagnostics
Monitor quality of collisions and luminosity for tuning purposes
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

6. Design Considerations
Long drift section required to allow expansion of the beam before hitting the dump.
Based upon the characteristics of the disrupted/undisrupted beam and requirements from the exit window and dump
Focusing of post-collision beam using quadrupoles not possible  long low energy tail
overfocusing would lead to large energy losses
Separate the charged particles from bremsstrahlung photons
luminosity monitoring
 Vertical chicane
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

7. Baseline Design side view7 7
Baseline Design
A. Ferrari, R. Appleby, M.D. Salt, V. Ziemann, PRST-AB 12, (2009)
intermediate dump
side view
27.5m
67m
1.5m
C-shape magnets
window-frame magnets
carbon based absorbers
ILC style
water dump 4m
315m 6m
5 window-frame dipoles and 4 C-shaped dipoles
Absorbers and an intermediate dump
To reduce beam losses in the magnets
Possible background sources:
Backscattered photons and neutrons from dump and along post-collision line
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

8. Background Calculations
Lawrence Deacon
Some changes/improvements done to the BDSIM model of the post-collision line
Thickness of elliptical beam pipes between the first 4 magnets
An accurate model of the beam pipe after the intermediate dump. complicated shape.
Main beam dump filled up with water
was 10m thick. These were unrealistic would have shielded the detector from back scattered particles. These have been replaced with beam pipe of the correct thickness.
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

9. Photon Background at IP
Lawrence Deacon
Per bunch crossing, within a 12x12m2 square plane 3.5m from the IP
Input particles
Flux [cm-2]
<E> [keV]
Disrupted beam
7.5± 1.1
360
Beamstrahlung photons
<0.5
Coherent pairs – wrong sign
8.4± 0.9
230
Coherent pairs – right sign
6.1± 0.6
300
All
Per bunch crossing, within a 2x2m2 square plane 3.5m from the IP:
All:
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

10. Neutron Background
Lawrence Deacon
Per bunch crossing, within a 12x12m2 square plane 3.5m from the IP
Input particles
Flux [cm-2]
<E> [keV]
Disrupted beam
1.6± 0.5
950
Beamstrahlung photons
<0.5
Coherent pairs – wrong sign
1.6± 0.4
350
Coherent pairs – right sign
0.7± 0.2
390
All
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

11. Origin of Backscattered Photons
Lawrence Deacon
intermediate dump
27.5m
67m
C-shape magnets
window-frame magnets
315m
Position of last scatter of backscattered photons
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

12. Background Calculations to IP
Preliminary results show that background particles at ‘outer edge’ of the LCD is low.
The detector yoke and calorimeter will further shield the vertex and tracker against
hits from background photons.
Even if additional absorbers are needed, space is available in the forward region between the detector (6m) and the first post-collision line magnet (27m) .
QD0
Kicker
BPM
Spent beam
Beamcal
Lumical
N.Siegrist, H.Gerwig
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

13. Energy Deposition in Beam-line Components
Lawrence Deacon
Magnets
2-4
Masks
Int.
dump
5-8
1a and 1b
Mask 1
Most magnets exceed 100W/m, many exceed kW/m
As much energy lost in magnets as masks
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

14. Impact on Magnet Lifetime
Lawrence Deacon, Michele Modena
Magnet lifetime limited by radiation damage to the coil insulation material.
Assume that conventional magnet coils (e.g. Cu insulated with epoxy impregnated fibre glass) can withstand 1E7 Gy.
Worst case: Magnet 5  ~6kW.
Mass is 6.9E4 kg, so it's dose rate is 8.7E-2 Gy/s.
Assuming a homogenous magnet and uniform particle distribution, the magnet lifetime would be only ~4 years.
 changes to Post-Collision Line Simulation:
Change material of absorbers for magnets 1-4 from graphite to iron
Lengthening the intermediate dump with 2 more metres of iron
 Assessment on specific CLIC radiation issues necessary
Robust coil fabrication technology for doses up to 1010 – 1011 Gy.
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

15. Results for Magnet Lifetime
Lawrence Deacon
intermediate dump
side view
27.5m
C-shape magnets
window-frame magnets
carbon based absorbers
ILC style
water dump 1a 1b 2 3 4 5 6 7 8
Magnet coil
Lifetime [year] - v1
Lifetime [year] - v2
1a + 1b
2500
200 2
5.7 36 3
1.2
7.6 4
8.4 5 11 26 6 13 20 7 19 33 8
170
230
Preliminary results
Simulations ongoing
Components downstream final dump were omitted
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

16. Main Beam Dump side view disrupted beam Right sign coherent beam
beamstrahlung photons
disrupted beam
+ right sign coherent pairs
1.5 TeV
300 GeV
90cm
side view
210m
to IP: 105m
ILC type
water dump
Right sign coherent beam
Beamstrahlung photons
Disrupted beam
Collided 1.5TeV Beam at water dump 315m from IP
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011 16

17. Luminosity Monitoring
Armen Apyan
m+m- pair production Main dump as converter muons  install detector behind dump  perform simulations of expected muon signals at different beam collision parameters
 See Armen’s talk
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

18. 30.0 cm diameter window (Ti)
Main Beam Dump
Alessio Mereghetti
Uncollided Beam Parameters
CLIC
ILC
TESLA
e- beam energy
[GeV]
1500
500
250
e- per bunch
[109]
3.72 20
bunches per bunch train
312
2820
bunch energy
[MJ]
0.28
4.51
2.26
frequency
[Hz] 50 4 5
beam power
[MW]
13.9
18.0
11.3 sx
[mm]
1.79
2.42
0.35 sy
3.15
0.27
0.5
Area1s = psxsy
[mm2]
17.76
2.05
0.55
ILC 18 MW water dump
Cylindrical vessel
Volume: 18m3, Length: 10m
Diameter of 1.8m
Water pressure at 10bar (boils at 180C)
Ti-window, 1mm thick, 30cm diameter
 baseline for CLIC 2011 main dump
Length 10.0 m
Diameter 1.5 m
30.0 cm diameter window (Ti)
1.0 mm thick
15.0 mm thick Ti vessel
Dump axis
ILC type
water dump
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

19. Energy Deposition in Main Beam Dump
Alessio Mereghetti
ILC: 240 J cm-3 /bunch train
(6 cm of beam sweep);
TESLA: ~20 kJ cm-3 / bunch train;
230 J cm-3 per bunch train
Dr=2.5 mm; Df=6.0 deg; Dz=20.0 mm;
Dx=0.45 mm; Dy=0.78 mm; Dz=20.0 mm;
Dr=2.5 mm; Df=6.0 deg; Dz=20.0 mm;
~40 kW cm-1
ILC: 54 kW cm-1;
TESLA: 32 kW cm-1;
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

20. Activation of Materials
Alessio Mereghetti
Rate of production of radio-nuclides for un-collided beam
(stable nuclides are not shown – collided beam: ~3% lower values):
Main species
in H2O: t½
R [s-1] 3H
12.3 y
7Be
53.6 d
11C
20 m
13N
10 m
15O
2 m
In the TESLA report, the production rates for 3H and 7Be are expected to be roughly a half of the present values.
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

21. Water - Thermodynamic Transient
Cesare Maglioni
Instantaneous p rise (kPa due to 1 bunch train) – whole dump, fast-transient analysis
Beam energy : 1.5 TeV
3.72E9 e-/bunch
dynamic pressure wave, estimated at
5-7 bar at walls (static bath, pin ~ bar) 
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

22. Window Thermo-Mechanics
Cesare Maglioni
With such a simplified preliminary design, the window cannot withstand the hydrostatic pressure (10bar) + dynamic wave : only energy deposition analysis
1 bunch-train Temperature rise
Steady-State Temperature rise
(multi bunch-trains)
Temperature rise per 1 pulse:
DT=1.44°C
Stable temperature after 3-4 sec with DT=24°C
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

23. Considerations & Next Steps
Cesare Maglioni
Min Water flow = 30 l/s, nominal is 60 v =1.5m/s, Tin = 22°C
TH2O,boil = 10bar  drive the choice of the hydraulics of the primary water loop, to be designed for high turbulence, mainly radial water flow and heat evacuation (orthogonal heat flux = 14MW/ps2)
If no water circulation is active (failure), water boils after few pulses
Energy density peak is at E=230 J/cm3/bunch train. The instantaneous T rise is 55°C. The interlock system must be as fast as 3 bunch trains.
The dynamic pressure wave inside the bath, estimated at 5-7bar at walls (in the case of a static bath) has to be taken into account for dimensioning the water tank, beam window, etc..  Hydrodynamic effects due to water flow have to be further analysed.
Of help : stiffeners on tank and window, sweeping system, shock absorber / diluter (gas bubbles?  this requires a detailed analysis and dedicated CFD simulations).
A steel / copper plate internal to the water bath, near to the end of it, and cooled by water directly, helps absorbing the tail of the beam.
Dump window  needs special care, detailed study and the design of a maintenance system
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

24. Summary Many new results achieved since last year Next steps24
Summary
Many new results achieved since last year
Background calculations to the IP
Magnet life-time estimates
Thermo-dynamical results on the beam dump and dump window
Muon monitoring for luminosity measurement
Next steps
Continue work on these issues to come up with a more detailled design
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

25. SPARE SLIDES
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

26. Post-Collision Line Magnets26
Post-Collision Line Magnets
Designed considerations:
average current density in copper conductor < 5 A/mm2.
magnetic flux density in magnet core is < 1.5 T.
temperature rise of cooling water < 20° K.
Dipole names
Magnetic length
Full magnet aperture
horiz. / vert. [m]
Full magnet dimensions
Power consumption
Mag1a1b 2m
0.22 / 0.57
1.0 / 1.48
65 kW
Mag2 4m
0.30 / 0.84
1.12 / 1.85
162.2 kW
Mag3
0.37 / 1.16
1.15 / 2.26
211 kW
Mag4
0.44 / 1.53
1.34 / 2.84
271 kW
MagC-type
0.45 / 0.75
1.92 / 1.85
254 kW
 All magnets strength of 0.8 T
 In total 18 magnets of 5 different types
Total consumption is 3.3MW
M. Modena, A. Vorozhtsov, TE-MSC
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

27. Magnets C-type Mag1a (window frame type) incoming beam 54.1cm 49 cm27
Magnets
C-type
Mag1a (window frame type)
incoming beam
54.1cm
40.8 cm
49 cm
34.3cm
20.1cm
5.1cm
11.1cm
Mag4
Mag3
Mag2
spent
beam
Inter-
mediate
dump
Mag1a
Mag1b C-
type
27.5m
30.5m
38m
46m
54m
67m
75m
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

28. Main Dump 1966: SLAC beam dump 2000: TESLA28 28
Main Dump
1966: SLAC beam dump
2.2 MW average beam power capacity
Power absorption medium is water
2000: TESLA
12 MW beam power capacity
Water dump
1.Radiation damage to the window material for long-term exposure to beam current.
2. Water quality. Particular attention should be given to chlorides in water, since they are a major factor in initiating stress corrosion cracking in stainless steel.
3. The radiolytically evolved hydrogen and oxygen can readily be recombined by a catalytic H2-O2 recombiner of modest size, using existing technology.
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

29. More Detailed View of Main Beam Dump
An internal (closed) water loop => heat dilution
Vortexes, turbulence, 30
An external water cooling system => heat removal
Safety confinement
Dump window
Dump shielding
Water bath Vessel
Internal primary water loop
External secondary Water cooling system
beam
10bar HE
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

30. Collided CLIC Beam at Main Dump
Alessio Mereghetti
Collided CLIC Beam at Main Dump
Distribution of secondary particles generated by the GUINEA-PIG code and transported up to the dump entrance via the DIMAD code (M. Salt).
Collided electrons
Coherent electrons
Photons
Window
Dump
IP-dump distance: 315 m;
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

31. Energy Deposition in CLIC Beam Dump Window31 31
Energy Deposition in CLIC Beam Dump Window
Titanium window:
1mm thick, 30cm diameter, cooling on internal surface by dump water at 180°C
 Total deposited Power: ~6.3W
max ≈ 4.3 J/cm3
uncollided beam
collided beam
max ≈ 0.13 J/cm3
uncollided beam
collided beam
A. Mereghetti, EN-STI
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

32. Assumptions Cesare Maglioni
Thermodynamic estimates – some easy numbers to get the feeling :
Input punctual values from FLUKA analysis
Symmetric un-disrupted beam adsorption (worst case)
(Static) water bath Thermodynamic Transient – preliminary simulations
Energy Density map from FLUKA analysis
Static water bath : meaningful of what may happen in case of major issues with the cooling / circulating system
Thermo Mechanics of the (simplified) dump window
Simplified geometry (circular ᴓ30cm, flat, Ti-6Al-4V), perfect convection
Only Energy Deposition analysis. Energy Density map from FLUKA
Symmetric un-disrupted beam adsorption (worst case ?)
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

33. Thermodynamic Estimates
Average Power deposited P = 14MW  mass flow :
= 60 l/s to keep reasonable DT (50°C)
= 25 l/s not to reach boiling point (180°C)
Energy Density Peak E* = 230 J/cm3/bunch train
 Peak Instantaneous T rise ~ 55 °C
interlock system as fast as 3 bunch trains (DT < 180°C)
rapid intervention of safety system and valves
 Peak Instantaneous p wave~ 560 bar
Proportional to initial pressure pi = 10 bar :
With exponential (radial) decay  6 – 7 bar at walls
Risk of cavitation
Edda Gschwendtner, CERN
LCWS11, Granada, Sept 2011

34. Considerations & Next Steps
Component
Issues
Possible Solution 1
Window design
Stresses due to :
Dynamic pressure wave
hydrostatic pressure
beam heating
Choice of material
Sweeping system
Stiffeners
Multiple window design
Additional water-jet cooling
Low pressure water and free surface 2
Tank integrity
Shock Absorbers / gas bubbles 3
Water circuit
... 5
Maintenance
Periodical window replacement
Management of radionuclides and radiolysis products
Remote handling System
Automated window exchange system
Local, separated storage of water 6
Safety
Containment of activated water in case of accident
Water tight dump enclosure
Safety enclosure + basin
Pre-window on beam pipe
Interlock and safety system for nuclear pressurized vessel
C. Maglioni CLIC Water Dump Thermo-Mechanical Analysis - September 7,