1. Challenges and Progress on the SB Horn Design
NuFact 08
Valencia-Spain, June 30 - July
Marcos DRACOS
IN2P3/CNRS Strasbourg
30 June 2008
M. Dracos, NuFact08

2. Super-Beam Studies in Europe
Super Proton Driver at CERN (SPL)
Target and collector integration
Hadron Collector
Pulser
Conclusion
30 June 2008
M. Dracos, NuFact08

3. Conventional Neutrino Beams
proton beam
Decay tunnel
physics
hadrons p p n
target
hadron collector
(focusing)
Detector
30 June 2008
M. Dracos, NuFact08

4. SPL Super-Beam Project
H- linac 2.2, 3.5 or 5 GeV, 4 MW
Accumulator
ring + bunch
compressor p
proton driver
Magnetic
horn capture
(collector) p
Target
hadrons
n, m
decay tunnel
~300 MeV nm beam to far detector
to be studied in EURO WP2
30 June 2008
M. Dracos, NuFact08

5. Super Proton Linac at CERN
SPL (
30 June 2008
M. Dracos, NuFact08

6. SPL (CDR2) main characteristics
Ion species H-
Kinetic energy
3.5
GeV
Mean current during the pulse 40 mA
Mean beam power 4 MW
Pulse repetition rate 50 Hz
Pulse duration
0.57 ms
Bunch frequency
352.2
MHz
Duty cycle during the pulse
62 (5/8) %
rms transverse emittances
0.4
p mm mrad
Longitudinal rms emittance
0.3
p deg MeV
Length
430 m
butch compressor to go down to 3.2 s (important parameter for hadron collector pulsing system)
(possible energy upgrade to 5 GeV could be the subject of a 3rd CDR)
30 June 2008
M. Dracos, NuFact08

7. Proton Target 300-1000 J cm-3/pulse
Severe problems from : sudden heating, stress, activation
Safety issues !
Baseline for Super-Beam is solid target, mercury is optional (baseline for NF)
Extremely difficult problem : need to pursue two approaches :
Liquid metal target (Merit experiment)
Solid target (extensive R/D program at CCLRC and BNL)
Envisage alternative solutions
very challenging task
30 June 2008
M. Dracos, NuFact08

8. Proposed collection system
proton beam
horn
3.7 cm
8.5°
300 kA
4 cm
target
16.6 cm
40 cm
80 cm
taking into account the proton energy and collection efficiency, the target must be inside the horn
30 June 2008
M. Dracos, NuFact08

9. Proton Target some ideas cooling is a main issue… CC target Horn
He IN
He OUT
Proposed rotating tantalum target ring (realistic?)
Horn
Helium cooling of target
fluidised jet of particles
Liquid Mercury (MERIT)
Work at BNL and RAL
Experience on T2K target (750 kW) very useful
cooling is a main issue…
30 June 2008
M. Dracos, NuFact08

10. Hadron production Particles coming out of the target 2.2 GeV protons
pT distribution not the same for all targets 
the choice of the target could influence the hadron collection system (horn shape) pT
From now on Hg will be considered
30 June 2008
M. Dracos, NuFact08

11. Hadron production uncertainties
2.2 GeV protons
disagreement between models
(Monte Carlo production, interaction and transport codes)
p+ momentum
more development is needed (simulation, measurements)
30 June 2008
M. Dracos, NuFact08

12. Proton Energy and Pion Spectra
pions per proton on target.
Kinetic energy spectrum
2.2 GeV:
<Ek>=300MeV
3.5 GeV:
<Ek>=378MeV
interesting region for SPL SB
Ekine (GeV)
1GeV
2GeV
cos q
hadrons boosted forward -1 1
30 June 2008
M. Dracos, NuFact08

13. Proposed design for SPL
for pions coming out of the target
500 < pp < 700 MeV/c
p+ angle
p+ momentum
horn region
for a Hg target, 30 cm length, 15 mm (x1016/sec)
relatively better collection when pproton
the target must be inside the horn
30 June 2008
M. Dracos, NuFact08

14. Horn geometry 2.2 GeV proton beam : I = 300 kAmp I = 300 kAmp r(m)
<pp> = 492 MeV/c
<qp> = 55°
2.2 GeV proton beam :
<pp> = 405 MeV/c
<qp> = 60°
I = 300 kAmp
I = 300 kAmp
r(m)
r(m)
B~1/r
B~1/r
B must be 0
B must be 0
4 cm
4 cm
target
target
30 cm
z(m)
30 cm
z(m)
30 June 2008
M. Dracos, NuFact08

15. Proposed design for SPL
reflector
Hg target
proton beam
horn
8.5°
40 cm
16.6 cm
4 cm
3.7 cm
20.3 cm
12.9°
80 cm
70 cm
600 kA
300 kA
very high current inducing severe problems
30 June 2008
M. Dracos, NuFact08

16. Focusing Power 20% more p+ with reflector p+ transverse momentum
(2.2 GeV option)
p- are deflected
20% more p+ with reflector
30 June 2008
M. Dracos, NuFact08

17. Present Collectors In operation In operation completed
(120 GeV)
In operation
(8 GeV)
completed
(12 GeV)
CERN horn prototype for SPL
Super-Beam
(3.5 GeV)
In operation
(400 GeV)
MiniBooNE
NUMI
CNGS
K2K
30 June 2008
M. Dracos, NuFact08

18. Decay Tunnel Flux vs decay tunnel length (2.2 GeV option)
short decay tunnel
30 June 2008
M. Dracos, NuFact08

19. More about previous studies
S. Gilardoni: Horn for Neutrino Factory and comparison with a solenoid
A. Cazes: Horn for SPL
30 June 2008
M. Dracos, NuFact08

20. Main Technical Challenges
Horn : as thin as possible (3 mm) to minimize energy deposition,
Longevity in a high power beam (currently estimated to be 6 weeks!),
50 Hz (vs a few Hz up to now),
Large electromagnetic wave, thermo-mechanical stress, vibrations, fatigue, radiation damage,
Currents: 300 kA (horn) and 600 kA (reflector)
design of a high current pulsed power supply (300 kA/100 μs/50 Hz),
cooling system in order to maintain the integrity of the horn despite of the heat amount generated by the energy deposition of the secondary particles provided by the impact of the primary proton beam onto the target,
definition of the radiation tolerance,
integration of the target.
30 June 2008
M. Dracos, NuFact08

21. CERN horn prototype cooling system Current of 300 kA p Protons
To decay channel
B = 0
Hg Target
B1/R
initial design satisfying both, neutrino factory and super-beam
30 June 2008
M. Dracos, NuFact08

22. Energy deposition in the conductors
MARS
48.2 kW
67kW
14.9kW
78.7kW
+8kW from Joule effect
4MW, 2.2GeV proton beam
(1MeV = 1.82 kW)
30 June 2008
M. Dracos, NuFact08

23. Localization of the energy deposition
P (kW)
target
z (cm)
z position of the particles coming out of the target
z (cm)
power deposited in the inner conductor as a function of z
30 June 2008
M. Dracos, NuFact08

24. Horn prototype …but Al not compatible with Mercury!
For the horn skin AA 6082-T6 / (AlMgSi1) is an acceptable compromise between the 4 main characteristics:
Mechanical properties
Welding abilities
Electrical properties
Resistance to corrosion
Same for CNGS
…but Al not compatible with Mercury!
tests done with: 30 kA and 1 Hz, pulse 100 ms long
new tests to be done with 50 Hz
Electrical and water connections
30 June 2008
M. Dracos, NuFact08

25. Power Supply for horn pulsing (major issue)
values considered by CERN
30 June 2008
M. Dracos, NuFact08

26. 3 Solutions proposed by ABB
schematic versions
at the capacitors ends
option 1
at the capacitors ends
option 2
in the charge
option 3 s
30 June 2008
M. Dracos, NuFact08

27. Pulser simulation parameters
magnetic field with electrical excitation (pulses 100 μs, 50 Hz)
induced current distributions
magnetic forces
temperature and expansion distributions
mechanical constraints and deformations (static+ dynamical), vibration modes
non-linear magnetic and thermal effects in the calculation of mechanical constraints
fatigue (and constraints from radiations if any)
studies are needed to make the right choice, increase the system lifetime, reduce the cost
30 June 2008
M. Dracos, NuFact08

28. New ideas minimize power dissipation and radiation problems
(pulser problems remain as before)
use the advantage of the small horn size
2.5 m
protons
protons
2.5 m
same decay tunnel Ø 3 m
protons
protons
to be studied in EURO
2 options:
send at the same time 1 MW per target/horn system
send 4 MW/system every 50/4 Hz
possibility to use solid target?
30 June 2008
M. Dracos, NuFact08

29. New (crazy) ideas to be studied in EURO
superconducting wire (1 mm Ø) in superfluid He,
DC power supply
use a cryogenic horn (toroidal coil)
blow gas He to avoid quenching problems
No problem with power supply (pulser no more needed)
Proton compressor no more needed
to be studied in EURO
30 June 2008
M. Dracos, NuFact08

30. Conclusions
Proton driver characteristics and target have to be fixed before horn design.
Preliminary studies about horn focusing performance for SPL already exist.
Collector studies are necessary to increase the system lifetime.
Target/horn integration to be considered since the beginning.
Multi-physics simulations would be very useful.
New studies will start soon in the framework of EURO FP7 project.
30 June 2008
M. Dracos, NuFact08

31. End
30 June 2008
M. Dracos, NuFact08