**NUMI Power Supply Review**

**[Comments from Gerry Jackson]{.underline}**

June 28, 2001

First, let me say that it was clear that a lot of work went into the
presentations, and I appreciate the open and professional manner in
which the review was carried out. Second, let me assure you that having
once been a recipient of a review (either internal, friendly, director,
or DOE) on average every three weeks during the Recycler project, I
fully appreciate how annoying it can be to have someone who has not
thought about the issues anywhere as much as you presume to give you
advice. Third, you will find that the following comments are not sugar
coated, and are intended to make subsequent reviews smoother.

Momentum Distribution of Main Injector Bunches

It was stated that the 5 Booster batches destined for the NUMI target
are extracted 90 degrees in longitudinal phase space rotation after the
batch aimed at the antiproton production target is extracted. The goal
is to obtain the absolute smallest momentum spread possible in the NUMI
primary beamline.

The problem is that the beam distribution during bunch rotation is not
rigid, but in fact deforms the longitudinal beam distribution into an
S-shaped phase space shape. By knowing the initial longitudinal bunch
emittance and the RF voltages during the rotation, it is possible to
precisely simulate this shape. This is a straightforward calculation
which would give you MUCH better estimates of the particle losses in the
transfer line.

It was stated that a fractional momentum spread was between 100 and 400
ppm. What is the longitudinal emittances before bunch rotation which
achieves these momentum spreads?

Tritium Production in Ground Water

I tried to attack this issue from two different directions. In the
first, I asked about pulling down the water table locally around the
beamline in the area above the dolomite layer. In the second, I asked
about the constraints on the beam permit system and operational
reliability imposed by accidental beam losses near the water table. In
both cases I received a response which for all practical purposes could
be interpreted by a reviewer as: "We professionals have looked at the
issue of tritium production in groundwater and you should trust our word
that we have thought about every contingency and this is the best
solution". This may not be the message you were trying to transmit, and
it could well be true anyway, but it is not a good way to present
information to reviewers.

You need to be prepared to present a very technical talk about the
groundwater and tritium production issues. Do not be afraid to quote
lots of facts and figures that support the science of groundwater
migration, tritium detection, and legal responsibilities. It is OK to
defend your particular solution, but you need to be prepared to show
alternative solutions, pointing out why they were not pursued in favor
of the official plan.

Magnet Misalignment

The collaboration did a good job of explaining the error tolerances of
the transverse placement of the magnets. What they missed was the
longitudinal positioning along the beamline. For example, while the
Recycler transverse magnet placement tolerance was 10 mils, the
tolerance for longitudinal magnet placement was almost 10 times bigger.
Error calculations should be expanded to include longitudinal placement
errors.

Beam Size Variations

During the review two facts were stated which were quite troubling.
First, it was stated that if the transverse beam size were to be reduced
by a factor of two that the target would be damaged. In other words, the
target has only a factor of four energy density safety factor. I was not
aware that the science/art of targetry had evolved to error bars down to
the size of pi.

Second, it was stated that the tolerance for random transverse beam size
changes is 20%, which corresponds to an emittance variation of 40%. Beam
instabilities, especially around transition crossing time and during
flattop, make such variations of this magnitude quite common. It is not
clear to me that any of the present emittance measurement devices in
existence can determine transverse emittance accurately or fast enough
to be an input in any kind of beam permit system.

Beam Steering Scans

There was a discussion during the review about beam steering scans and
the need to perform them on a regular basis. It was stated that the
tunnel "should" be stable enough to only need an initial alignment scan.
Because of interest in building the NLC and VLHC in the geography
surrounding Fermilab, there have been definitive measurements of
vertical tunnel movement in the same rock layer in which the NUMI tunnel
exists. A good reference is Physical Review Special Topics --
Accelerators and Beams, Vol. 1, 031001 (1998) by Lach, Shiltsev, and
others. Presenting data rather than opinions is always preferable.

Beam Permit System

How many abort triggers per hour are expected given the number of NUMI
permit channels and the signal to noise level of each channels? How many
cycles must the NUMI beam be disabled after a 10% accident in the upper
end of the sloped carrier pipe? I hope that the review on the beam
permit system is very quantitative and thorough!