Comments on NuMI horn transmission line Review Feb. 26, 2002

                                      from Frank Nezrick, March 7, 2002



1. Overall Remarks
At every NuMI horn system review I have attended, I have been impressed
with the quantity and quality of the design and engineering effort
invested. This review has been no exception. Such thorough work will
certainly lead to a reliable, long lived focussing system.
My primary concerns lie with the need and reliability of the Flex Joint,
and the dearth of testing time for the final horn system before taking
beam.

2. Itemized suggestions, questions and concerns

(1) Flex Joint
 I again state that I seriously question the need of the flex joint for
Horn 1. Since the transverse position of Horn 1 most likely will not be
scanned to verify beam centring, I do not see a justification for the
flex joint. It adds extra cost, effort (time) and complexity.

(2) Flex Joint
In the note of Zhijing Tang of October, 2001 concerning the Finite
Element Analysis of the flex joint, he notes the importance of keeping
the slots at each bend to an equal length (also noted in Nancy's talk).
Also if I understand the calculation correctly the slots lengths are
always symmetric wrt the center of curvature for each bend of the
transmission line, e.g. Figs 4, 10-14. This implies drawings on page 1,
4, 5 and 9 of the Drawing Package handout by Boettinger are incorrect.

(3) Flex Joint
It is planned that the prototype flex joint and remote clamp will be
pulse tested at MI8. It is essential that the prototype survive the
testing. However we should require more.  The testing plan lacks
quantitative measurements (deflection at specific points, resonant
frequencies, etc.) which might demonstrate agreement with expectations
(ANSYS calculations, etc.) thus supporting an anticipated longevity.

(4) Vibrations
The transmission lines in the target hall when pulsed will act like
xylophone bars; they will undergo transverse and longitudinal
vibrations. There is probably time and space to develop appropriate
dampening methods after the TL system is installed. However, vibrations
from the transmission lines and flex joints in and under the horn module
should be better understood soon so space, e.g. for dampers, might be
allowed in the module design. Hints might be obtained during the flex
joint testing program at MI8.

(5) Nancy listed on Pg. 21 of her handout a Concern :::  "Schedule is a
bit tight."
In the part of the installation schedule not shown on Pg. 20, but
discussed at the review, it appeared that the amount of time allowed for
testing (pulsing) the horn system in its running position was about one
month. If no failures or major modifications are encountered, a month
may be sufficient. My concern is that for various reasons this testing
time might be reduced even more. It should be remembered this will be
the first time the horn system will be operated in this configuration
(supported from actual module with all appropriate motion controls and
monitors installed, target installed, target hall transmission line
attached, etc., etc.). Proper testing time must be rigidly scheduled,
even if only 3rd shift.