Minutes from February 21-22 Meetings
February 21 Targeting Discussion Lead by Kirk McDonald
First, a list of links with the plots that were shown:
The general repository for documents on targetry for neutrino factories and
muon colliders is
The NLC positron source page is
Kirk's talk was loosely based on 2 recent presentations:
Additional info on results from beam tests is in
More info on the FEA simulations is in
Futuristic targets for neutron spallation sources are discussed at
Brief Synopsis of Talk:
The important thing to remember about targeting issues is that you will
worry much more about radiation effects and infrastructure than you
will worry about the target itself. The amount of cement needed in
these targeting facilities Kirk describes is staggering.
General Structure of Talk:
800kw beam from Los Alamos:
- High Power Targets not associated with Neutrino Beam Production
- Neutrino Targets Built and Almost Built
- Future Targets
on a 1 interaction length Tungsten Target
--cooling water is flowing on that target. Another idea (used by
g-2 experiment) is a rorating target.
Results from the SNS at Oak Ridge:
the baseline design was flowing Hg
in a stainless steel jacket, but a single pulse puts a pit in the entrance
window which is stainless steel. This was 1-2MW 1 microsecond pulse,
50Hz, 1GeV protons. conclusion: putting liquid target in pipe
requires extreme care.
3.5MW Deuterium source at Hanford Reactor:
35MeV Deuterium was to be put on a flowing Li target, with a free
surface facing the beam to not have this pitting problem mentioned
above. This project was cancelled though.
Targets for Making Neutrino Beams:
What target you want depends on what neutrino energy you want.
Optimization is different if you want high versus if you want
low energies. For 8GeV protons, pion production is constant vs. A
of the target material. But for 30GeV protong the production
is not constant--you win by going to higher A material.
Studies of Sublimation of targets have been done: if target is in
vacuum this is the limiting factor and it happens very quickly (1 day).
If target is at 1atm of He gas, then longer-term
radiation damage is the worry.
- MiniBooNE: they are using a Be target, 100kwatts, solid target
with Air cooling.
- MINOS: graphite target, 400kwatts, solid target with water cooling
along the edges (fin target).
- CERN SPL: 2GeV, 4MW, 50Hz, idea is to send a Hg jet down the
throat of a horn, which is pulsed at 500kAmps. Horn is only 1 inch
from the 4MW source!
- US neutrino factory design: want all conductors outside
of where the particles of interest are. 20T tapered to 0.1T solenoid is
current design: this gives a factor of 15 reduction in transverse momentum.
There is a carbon carbon composite with 0 thermal expansion.
With liquid targets in high magnetic fields, magnetohydrodynamics
becomes an issue.
With solid targets there is good agreement between measured strain
and the calculations. Single pulse accidents are NOT an issue
at the considered intensity.
February 22 Theory Overview Talk by Andre de Gouvea
On Feb. 22 Andre de Gouvea gave a thorough overview of the current
status of neutrino oscillation measurements and where things are going.
One topic which inspired lots of discussion was showing the effect of
the CHOOZ limit on the atmospheric allowed regions...for certain values
of sin2 2theta_13. For example, if sin2 2theta_13 is large, then this
effectively means that delta m^2 (23) is "low", since the chooz limit
is very quikly changing as a function of delta in the interesting region.
Also different parts of the solar allowed regions change when you dial in
different sin2 2theta_13 values in conjunction with the CHOOZ bound.
One interesting way to look at this that Andre mentioned
is that theta_13 may actually be
bigger than the cabibbo angle--we don't know that it's not right now!
There was much discussion about KAMLAND, and the sensitivity they may
actually have for delta m2 measurements--he showed some energy spectra
that would be expected for different delta m2 values. Without the
solar measurements KAMLAND can't determine if the mixing angle is on the
"dark" side or the "light" side.
Andre also showed how one must keep all these different terms in the
oscillation probabilities when one is trying to determine what the
reach of off-axis (or other future) experiments are: it's not enough
just to keep the largest term and the
CP violating, there's the cosine delta term, and of
course the higher mass splitting term. The question "how well can a minos
off-axis experiment do in CP" can be answered in a few ways:
recall that you can do disappearance with the on-axis detector, as well
as appearance and disappearance with the off-axis detectors. The
variables we have to play with are as follows: would we be better off
running in antineutrino and neutrino, or having two detectors at the same
energy but different baselines, or two detectors at different angles which
would give you slightly different energies as well?
Last modified: Tue Feb 26 13:51:47 CST 2002