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Conventional Neutrino Beams. Deborah Harris NuFact05 Summer Institute Anacapri, Italy June 12-13, 2005. Fundamentals. Conventional Neutrino Beam. Neutrino Factory. Using Pions to make Neutrinos. Major Components: Proton Beam Pion Production Target Focusing System Decay Region - PowerPoint PPT Presentation
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Conventional Neutrino Beams
Deborah HarrisNuFact05 Summer Institute
Anacapri, ItalyJune 12-13, 2005
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 2
Fundamentals
• Conventional Neutrino Beam
• Neutrino Factory
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 3
Using Pions to make Neutrinos
Major Components:•Proton Beam•Pion Production Target•Focusing System•Decay Region•Absorber•Shielding…
Most ’s from 2-body decays:
→
K+→
Most e’s from 3-body decays:
→ee
K+→ee
energy is onlyfunction of
angle and energy
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 4
Proton Beam• Rules of Thumb
– number of pions produced is roughly a function of “proton power” (or total number of protons on target x proton energy)
– The higher energy neutrino beam you want, the higher energy protons you have to start with…
• Proton Sources around the world…Name Proton Energy
(GeV)
p/yr Power
(MW)
Neutrino Energy
(GeV)
KEK 12 1e20/4 0.0052 1.4
FNAL Booster 8 5e20 0.05 1
FNAL
Main Injector
120 2.5e20 0.25 3-17
CNGS 400 4.5e19 0.12 25
J-PARC 40-50 1.1e21 0.75 0.77
BNL AGS 28 1.2e21 0.5-1.3 1-2
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 5
Directing Protons is not trivial…• Example from NuMI: extract
beam from between two other beamlines, then make it point down at 3.5o so it comes through the earth in Soudan MN:
• Example from T2K: Proton source on prime real estate, direction to K2K determined, need to bend HE protons in small space: “combined function” magnets (D and Q)
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 6
Neutrino Production Targets• Have to balance many
competing needs:– The longer the target, the
higher the probability the protons will interact
– The longer the target, the more the produced particles will scatter
– The more the protons interact, the hotter the target will get—targeting above ~1MW not easy!
– Rule of thumb: want target to be 3 times wider than +- 1 sigma of proton beam size
Target Material
Shape Size
(mm)
Length (cm)
Mini-BooNE
Be cylinder 10 70
K2K Al cylinder 30 66
MINOS graphite ruler 6.4x20 90
CNGS carbon ruler 4mm wide
200
J-PARC graphite cylinder 12-15 mm
90
BNL AGS
Carbon-carbon
cylinder 6.4mm to 12mm
60cm to 80
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 7
Target Photo Album
CNGSImage courtesy of Bartoszek
Engineering.
NuMI
MiniBooNE
Shapes are similar, but cooling methods vary…some water cooled, some air cooled
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 8
Focusing Systems
• Want to focus as many particles as possible for highest neutrino flux
• typical transverse momentum of secondaries:
approximately QCD, or about 200MeV• Minimize material in the way of the pions you’ve just
produced• What kinds of magnets are there?
– Dipoles—no, they won’t focus– Quadrupoles—has been done with High Energy neutrino
beams, but focus in vert. or horiz.
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 9
What focusing would work best?
• Imagine particles flying out from a target:– When particle gets to front face of horn, it has transverse
momentum proportional to radius at which it gets to horn
B Field from line source of current is
in the direction
but has a size proportional to 1/r
How do you get around this? (hint: pt B l )
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 10
What should the B-Field be?
• Make the particles at high radius go through a field for longer than the particles at low radius. (B1/r, but make dl r2)
• Horn: a 2-layered sheet conductor• No current inside inner conductor, no current outside outer conductor• Between conductors, toroidal field proportional to 1/r
• For the record, there are also conical horns—what effect would conical horns have?
FROM TO
tune
outert p
r
lr
cr
Iep
2
20
2
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 11
Tuning the Neutrino Beam Energy
• The farther upstream the target is, the higher momentum the horns can “perfectly focus”..see this by considering
( /kt/4e20 p)
CC
evt
s / k
t / 4
e20
p / G
eV
l
Rpp
r
lr
cr
Iep tunetune
outert
2
20
2As l gets longer, then ptune gets higher for the same R
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 12
Horn Photo AlbumLength
(m)
Diameter (m)
# in beam
K2K 2.4,2.7 0.6,1.5 2
MBooNE ~1.7 ~0.5 1
NuMI 3,3 0.3,0.7 2
CNGS 6.5m 0.7 2
T2K 1.4,2,2.5 .47,.9,1.4 3
BNL 2.2,1.5 up to .3 2 MiniBooNE
CNGS
K2K
T2K Horn 1
NUMI
Horn World Record (so far): MiniBooNE horn pulsed for 100M pulses before failing
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 13
•D
esig
ning
wha
t pro
vide
s th
e 18
0kA
is a
s im
port
ant a
s de
sign
ing
the
horn
itse
lf!
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 14
What happens if you have 2 Horns?
• Can pretty much predict components of spectra just from apertures of horns.
~ pT/p = rneck / zhorn.
Overfocused by Horn 1Underfocused by Horn 1Focused by Horn 1, through 2Hits only Horn 2Goes through Horns 1, 2
p
Rneck(cm)
Zhorn(meters)
Max pion momentum
focused (GeV)
Energy
(GeV)
Horn 1 0.9 ~1.0 ~16 6
Horn 2 4.0 10 38 15
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 15
Are there ways to change (lower) the neutrino energy?
• Reduce Current in the horns– Yes, but this mostly just gives you fewer neutrinos
in the peak but the same number in the tail
• Move target closer to the horn– Yes, but eventually you hit the inner conductor
• What happens if you move the detector off the main axis of the beamline?
B(in tail)
+ (in peak)p
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 16
Off Axis Strategy• Trick used by T2K, NOvA (first
proposed by BNL)– Fewer total number of neutrino events– More at one narrow region of energy– For to e oscillation searches,
backgrounds spread over broad energies
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 17
Decay Regions• How long a decay region you need
(and how wide) depends on what the energy of the pions you’re trying to focus.
• The longer the decay region, the more muon decays you’ll get (per pion decay) and the larger e contamination you’ll have
• Again, tradeoffs between evacuating the decay volume and needing thicker vacuum windows to hold the vacuum versus filling the decay volume with Helium and thin windows, or with air and no windows…
Length Diameter
MBoone 50m 1.8m
K2K 200m Up to 3m
MINOS 675m 2m
CNGS 1000m 2.45m
T2K 130m Up to 5.4m
BNL 200m Up to 4m
T2K Decay Region:Can accommodate off axis Angles from 2 to 3 degrees
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 18
Decay Pipe Photo Album
CNGST2K
NUMINUMINUMI
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 19
Decay Pipe CoolingSlide courtesy C.K.Jung
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 20
Beamline Decay Pipe Comparison
Length E(GeV) y y e(theoretical)
MiniBooNE 50m 2.5 0.36 0.3% 0.15%
K2K 200m 3.5 1.0 0.9% 0.5%
MINOS 675m 9 1.3 1.2% 0.8%
CNGS 1000m 50 0.36 0.3% 0.15%
T2K 130m 9 0.47 0.2% 0.10%
BNL 200m 5 0.72 0.6% 0.3%
cE
cLmy
2
Let y (y) be the number of pion (muon) lifetimes in one decay pipe…
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 21
Decay Pipe Effect Summary
05.0
01.0
rms
006.0
rms
Additional RMS
Loss from
Interactions
Filling Decay Pipe with Air: 0.007
1mm Aluminum Window: 0.002
9.01
12
22
Remember, for aFlux ratio of 0.9,
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 22
Absorbing Hadrons
• As proton power gets higher and higher, have to think more and more about what will collect all the un-interacted protons!
• MINOS Absorber (1kton):– Water-cooled Al core– Surround with Steel– Surround with concrete
• Note: for 1020 protons on target per year, roughly 1019 per year hit the absorber…
• For scale: NuTeV experiment “pre-oscillation era neutrino experiments” took about 3x1018 protons over entire run
12-13 June 2005 Deborah Harris, Conventional Neutrino Beamlines 23
Review of what was covered today
• Targets
• Horns
• Decay Volumes
• Hadron Absorber
Questions to answer tomorrow:
How can you look at what’s happening each time you send protons to the target?
How can you predict precisely how many neutrinos you are making?
207m