November 13, 2002

Jim Hylen

DRAFT

Re Nov. 18, 2002 Review of NuMI Target Hall Instrumentation:

Responses to comments from previous (Oct .18, 2001) review

*Replies are in italics, original comments in normal type.*

Comments from Sam Childress

1\. Overall Remarks

Due to the very intense radiation environment in the target / horn
chase, besides design choices with rad hard components, it is prudent to
both:

\- Develop alternative monitoring plans using instrumentation more
remote from this environment which can be cross-calibrated in early
running with the direct target region monitors

*The plans for the hadron and muon monitors already existed. We have now
added two ionization chambers for the "cross hairs alignment system"
that will very likely provide redundancy for the target Budal monitor.
The cross-calibration of these will be done during commissioning.*

\- Review carefully the needs for motion control of components, and
minimize these where feasible.

*The addition of the cross-hair system will now allow for horn 1
location study by scanning beam rather than motion of horn 1, so we have
minimized this about as much as feasible.*

2\. Itemized suggestions, questions and concerns

\(1\) A complement to the Budal target monitor should be the muon
monitors, with an appropriate level of modeling done to understand their
performance as a beam on target monitor if/when the Budal monitor fails.

*Both the muon monitors and the cross hair ionization chambers will be
cross calibrated to the Budal monitor during commissioning. Since the
cross hair system can detect the secondaries from bean hitting a 2%
interaction length cross hair, detecting the signal from beam hitting a
200% interaction length target should be trival. The signal expected in
the cross hair chambers during normal beam operation is currently being
Monte Carloed.*

\(2\) Consider adding a microphone system (positioned outside the
shield) to give real time listening capability to the horn pulsing
during operation. This can probably be very sensitive to mechanical
system changes.

*This remains an interesting option, but we have not had the resources
to address it. It would be an excellent item to add if some money
remains at the end of the project.*

\(3\) Prior to beam operation, it is very important to understand
absolute positioning reference capability for baffle/target/horns by
survey efforts above the shield.

*A test of the accuracy obtained by lowering a long graphite pole
through shielding to tooling balls on the horns has been done in a
mock-up, and the accuracy obtained appears adequate.*

\(4\) A design plan was indicated to have the capability to sweep the
baffle completely to the side outside the beam. This transverse motion
of several inches adds considerable design complexity, and it is not
really clear that real benefit is provided. Suggest that commissioning
alternatives be considered which do not require large motions of target
chase components, except where this provides a significant clear
benefit.

A significant target motion capability along the beam direction is an
important design feature. Reducing other component motions can help
enable an easier more robust design for this.

*The motion of the baffle is now locked to that of the target. We retain
the capability to move the combined target/baffle carrier 8 inches to
move it out of the beam to allow for the cross hairs alignment checks.*

Comments from Rick Ford

1\. Overall Remarks

It seems that a lot of work has gone into understanding what the
potential issues are. There is a lot more work to do in some areas but
things everything in general seems on the right track based on the info
given.

2\. Itemized suggestions, questions and concerns

\(1\) I am concerned about the Budal monitor. During the beam tests was
proven that it works in principal, but I am concerned about the
proximity of the device to the horn. I would suggest testing it in MI-8
inside the horn if this hasn\'t already been done. Also, it doesn\'t
appear that the backup plan for using the muon monitors to monitor beam
on target was well thought out. If the Budal monitor fails 6 months into
the run, are you comfortable with not having one?

*The noise levels around the horn have been looked at (although not with
the Budal monitor) and the horn pulsing generates very little electrical
noise. The horn pulse is very low frequency, and the horn being
essentially a self-terminated coaxial cable is a very poor antenna. The
Budal signal is large (nearly a volt during beam tests) and should be
very robust against noise. In any case, the horn is not pulsed during
the essential operation of the Budal monitor, which is a position scan
of the beam across the target to check target alignment. The new cross
hairs ionization chamber will allow target alignment checks in case the
Budal fails.*

Comments from A. Marchionni

1\. Overall Remarks

The general scheme proposed for the instrumentation and monitoring in
the target hall is well thought, but more attention has to be focused on
the detailed implementation. In particular it was not clear how all the
different signals are transmitted to ACNET, read out by the experiment
\...

2\. Itemized suggestions, questions and concerns

\(1\) Horn current monitoring.

It is important to check the stability over time of the electronics for
the read out of the current transformers in the power supply, in order
to preserve the stability and the precision of the current transformers
themselves. A decision should be taken of whether to record the full
pulse shape of the stripline currents. I believe that, besides the peak
current, at least one additional point on the rising and one on the
falling edge of the signals would be very useful for diagnosis of
possible problems. The same requirements would apply to the signals from
the Bdot coils. These are particularly promising for the monitoring of
the magnetic field around the neck, and they can give indications of
movements or warping of the inner conductor. The stability of the Bdot
coil signal will be tested at the test stand in MI8. Nothing was said on
how to check the timing of the current pulses. The general design of
this horn monitoring system was done with both NuMI and MiniBoone in
mind, but we learned that some of the modules have to be adapted to the
peculiarities of each one of these systems and especially calibrated. It
is thus important to have readily available spares modules calibrated
and adjusted for NuMI.

*Some stability testing has now been done at MI8, but not a
recalibration of the DCCT coils, which would still be good to do. We
have not yet seen enough potential benefit from recording pulse shapes
to go to the added effort of building such a system. (Occasional
fast-time-plots will be easy to take using the ACNET controls system,
but the data would not be added to the MINOS data stream). A comparison
of beam time obtained with the Budal and cross hair ionization chambers
with the current pulse time of the horn will be read out every pulse,
although the precise implementation of this is not developed yet.*

\(2\) I think that the instrumentation presented for the horn support
module is adequate, but since this is quite a complicate system, enough
time should be devoted to test it, possibly rechecking the positioning
after pulsing the horn and measuring vibrations. No details of the
target support modules were given. Is there a way to prevent the target
case from accidentally hitting horn1 ? And if that happens, would we
know about ?

*An interlock is being developed to prevent the transverse positioning
motors from being activated when the target is located anywhere that
part of it extends into the horn. That is, transverse motors could only
be operated with the target retracted. As the target is inserted, a
simple ohm meter can tell if the target casing starts to touch the horn
inner conductor. The motor controls will be locked out at all times
except during special studies periods so that they are not accidentally
activated. The system is still not fool-proof, as one could deliberately
misalign the transverse motion and then drive the target into the horn
while not watching for contact, but we feel the level of precautions
taken above are reasonable.*

\(3\) How do we check that there is no water leak in the horn system ?

*During checkout, a leak check can be done by a modest overpressure of
the system with air. During operation, a leak will be seen by the
reduction of the level of water in the holding tank. Slow leaks will
prompt visual inspection of the water lines to the modules. Leaks above
the module will be fixed; we will continue running with slow leaks below
the module. A large leak will require replacement of the horn.*

Comments from Phil Martin

This review focused on the horn, horn power supply, target, and baffles.
Thus, it did not include anything on beam monitoring, either primary or
secondary.

It is proposed to monitor a fairly large number of parameters. This
includes numerous voltage and current monitor points in the horn power
supply, and thermocouples in many areas. While the overall concept
appears fine, there was little presented on what to do with all this
information. While some are important for protection of the horn and
horn power supply, most are mainly of importance to the MINOS
experiment. A block diagram should be generated, showing the overall
architecture of the data acquistion system and how this data is shipped
over to the MINOS experiment. Define which parameters need to be
interlocked to the beam permit system, which to the horn power supply,
and which need to be monitored (alarms and limits) in the Main Control
Room. One route to getting the data to MINOS would be to collect all
this information in ACNET, timestamping it, and then MINOS can read the
data pulse-by-pulse. Verify that this will really suffice.

*The block diagram is being generated. All data for MINOS will follow
the stated route, i.e. to ACNET, then ACNET to MINOS pulse by pulse.
Beam permit devices are identified. The three systems for getting data
into ACNET are identified (an MADC, an IRM, and a PLC). That the rate of
MINOS reads from ACNET required is OK has not been tested, but it is a
much lower rate than that required by MiniBOONE, so we should be able to
follow in their footsteps.*

Comments from Frank Nezrick

The presenters did a good job of giving us a lot of detailed information
in only two hours.

I realize that most of the presentations were primarily concerned with
the \"operational\" aspects of the instrumentation and monitoring rather
than the \"normalized neutrino flux\" aspects, but I still have a few
comments;

*(For 1, 2, 3 below, see replies to reviewers above)*

1\. Concerning the horn current maximum value-

a\. we need a digital value of the maximum current at the \~1/4 % level

b\. we need the time of the maximum with respect to some clock pulse.

2\. It would be useful to archive an indicator of the Horn current
waveform. Possibly the times (relative to some clock pulse) of the 1/2
current points.

3\. Concerning the Budal monitor-

a\. we should better understand it\'s lifetime (failure modes) with high
radiation dose, review previous experiences.

b\. what backup is reasonable if it fails - are the muon monitors a
realistic backup.

4\. What is the mechanical stability (straightness) of the LE target
under pulsed beam operation with top and bottom cooling of the fins?

*We plan to test this next February when the production target arrives.*

5\. Concerning the target pile air cooling system - I recommend an
additional pressure drop indicator across only the prefilter. Since
there is a big pressure drop across the HEPA filter it is sometimes
difficult to know the condition of the prefilter if a single PDIT is
used across both.

*This has been added.*

Comments from Ralph J. Pasquinelli

Overall Remarks

None of the systems reviewed was deemed critical, involved personnel or
environmental safety. This was to be considered a technical review, yet
several of the items reviewed were not sufficiently engineered at the
time of the review. Procedures of how to handle effects of failure of
the air cooling system or high temperature of the target baffle were not
outlined or understood at the time of this review.

*The baffle temperature with respect to the beam permit system and
normal operation is now well documented in the write-up for the
intervening baffle review. The beam permit and hardware interlocks
associated with the air cooling system have been documented for this
review.*

Overall, there appear to be no glaring problems or difficulties with the
instrumentation for the target area. In the future, such reviews should
be conducted when more thought has gone into some of the presentations.

2\. Itemized suggestions, questions and concerns

The work done on the horn power supply looks to be thorough. Many parts
of the instrumentation that are being developed will also aid in the
routine operation and troubleshooting of the system. This is just good
basic engineering practice.

For a technical review, very little technical engineering data was
presented.

Kris Anderson has presented much of the horn system in a previous
review. Location of thermal couples was presented this time around. This
is not a significant amount of additional information to warrant a
review.

Understanding procedures for dealing with a broken air flow system
should be developed. This was present for review before the NuMI
organization has figured out what to do in the event of a failure.

The target baffle provides protection to the horn. It is being
instrumented to monitor temperature. What is done with this
instrumentation data is not clearly known at this time. Here again, a
system was put up for review before much thought was given to the topic
from within the NuMI group.

It is my understanding that the NuMI/MINOS management desires to hold in
general three reviews of each system. The early review aids in gathering
input from stakeholders outside the project, for example in our case
people in beams controls and operations, with whom the designs being
developed must mesh. Such interface issues would be less of a problem if
the NuMI project were more closely integrated into the Beams Division.
The reviews also provide MINOS experimenters an opportunity to see that
designs being developed meet their requirements - the addition of the
cross hairs system is an example of such input. The resulting work
should be more focused and productive because of the early review.
Nevertheless, we understand that reviews consume resources and a balance
needs to be struck.