Collection system optimisation for SPL at 3.5 GeV

1
Collectionsystem optimisation for SPL at 3.5 GeV

• Antoine Cazes
• Laboratori Nazionali di Frascati
• November 14th, 2006

2
Overview
3
Interaction between proton beam and target.

• Simulation done with FLUKA 2002.4 and MARS
• Proton beam
• Ek2.2GeV, 3.5GeV, 4.5GeV, 6.5GeV et 8GeV
• Target
• Liquid mercury
• Long 30cm
• ? 15mm
• Normalization 4MW
• 1.11016pot/s_at_2.2GeV
• 0.71016pot/s_at_3.5GeV

4
Particle Producion
p
K
p-
K0
K-
Ep(GeV)
Ep(GeV)

• 500 000 protons, Ek lt 5GeV
• at 2.2GeV
• 0.26 p/s
• 0.8 10-3 K/s

• at 4.5GeV
• 0.32 p/s
• 5.2 10-3 K/s

• at 3.5GeV
• 0.29 p/s
• 2.8 10-3 K/s

5
Horn optimisation

• Neutrinos Factory
• Decay tunnel solénoïde

• Momentum
• At the target

2 105 pot
SB
nFact

• Super Beam
• 130km beam
• Tunnel raduis

6
Collector

• 2 concentric horns
• 300kA et 600kA
• Conductor thickness 3mm

• Particles exit with large angle
• ltqpgt 60_at_2,2GeV
• ltqpgt 55_at_3,5GeV
• Target must be inside the horn.

7
Horn design
NuFact Note 138
x
2 optimisations studied

• En 350MeV
• (pp 800MeV/c)

• En 260MeV
• (pp 600MeV/c)

Oscillation Maximum
8
Horn design parameter
Conductor thickness 3mm horn
300kAmps reflector 600kAmps
HORN HORN
inner radius 3.4cm
neck length 40cm
outer radius 20.5cm
total length 120cm
REFLECTOR REFLECTOR
outer radius 40cm
total length 190cm
HORN HORN
inner radius 3.4cm
neck length 40cm
outer radius 20.5cm
total length 140cm
REFLECTOR REFLECTOR
outer radius 40cm
total length 220cm
En300MeV Ep800MeV
En260MeV Ep600MeV
9
Energy deposition (Geant 3.2.1)
4MW, 2.2GeV
7kW from Joule effect
Solution under investigation reduce the
Aluminium thickness (3mm Al) strength rings.
NuFact Note 134
10
Decay Tunnel Parameters

• Radius
• modify acceptance
• R1m, 1.5m and 2m have been Tested
• 1m ?2m (L40)
• nm , nm 50
• ne , ne 50 to 70
• 2m seems better

• Length
• modify purity
• L10m, 20m, 40m and 60m have been tested.
• 10m?40m
• nm , nm 50 to 70
• ne , ne 50 to 100
• 40m?60m
• nm , nm 5
• ne , ne 20
• 40m seems better

This results have been checked on sensitivity to
q13 and dCP
11
Flux computation

• Low energy ? Small boost ? low focusing
• Need a high number of events (1015 evts!!!)
• Use probability (M. Donega thesis approach)
• Each time a pion, a muon, or a kaon is decayed by
  Geant, compute the probability for the neutrino
  to reach the detector
• Use this probability as a weight, and fill an
  histogram with the neutrino energy
• Gives neutrino spectrum.

12
Probability method . Pions

• Pion is tracked by Geant
• When it decays, The probability for the neutrino
  to reach the detector is computed
• p?mnm (2-body decay)

L distance to detector A detector surface
To reach the detector d -a
13
Probability method . Muons

• m?enmne
• But muons have small decay probability.
• for each muon
• loop on the phase space (q,f,E)
• compute decay probability e-x/gct
• if it decays, compute probability for the
  neutrino to reach the detector

x 2En/mm
f0(x) f1(x)
nm 2x2(3-2x) 2x2(1-2x)
ne 12x2(1-x) 12x2(1-x)

• P is the muon polarisation coming from the
  pion/kaon decay

14
Probability method . Kaons

• Very few kaons
• kaon produced in the target is duplicated many
  times 100.
• Decay using Geant
• Choose the decay channel
• Probability computed depending on the decay
  channel
• 2 body decay
• 3 body decay

15
Neutrino flux _at_ 130km

• 3.5GeV Kinetic proton beam
• 800MeV p focusing
• 300MeV neutrinos
• 40m decay tunnel length
• 2m decay tunnel radius

16
Proton beam energy comparizon
5 year positive focussing
10 years mixte focussing (8y and 2y -)
Campagne, Cazes Eur Phys J C45643-657,2006
3.5GeV better !!!
17
Conclusion

• Choice of the beam energy is delicate
• Tools exist to do another simulation
• Proton interaction on target should be better
  with new version of fluka
• Shape of the horns is crucial.
• Technical feasability should be taken into
  account...

18
Thats all folks !!!
19
Project optimisation
- Old result - New optimization
2yrs () 8yrs (-)

• mixte Focalisation
• Acces to dCP
• To balance
• 20 positive
• 80 négative

Used values dCP0, q130, sin22q120.82, q23p/4
, Dm2218.1 10-5, Dm2312.2 10-3 5 precision on
q12 and Dm221
Campagne, Cazes Eur Phys J C45643-657,2006
dun factor 4 Gain on the sensitivity