Comments for Review of NuMI Primary Beamline

## Sensitivities November 1, 2002

*Response comments by S.C., P.L., N.G., S.H.*

### By: David Johnson

December 10, 2002

[I. Overall Remarks:]{.underline}

I did not attend the oral presentations, but I have reviewed the slides
and the documents that were posted on the web site and briefly talked
with Steve Hays. I will make comments on these slides and documents. I
will note up front that some of my comments might have been answered in
the presentation and requires no further comment.

This review was for the Primary Beam Sensitivities. These ultimately
translate into aperture and power supply regulation and stability
requirements. I found the primary specifications in the design report
relating to position, angle, and spot size on target and in the
transport line and their stability. I believe these are:

-   The target position and angle specifications are 0.5+/- 0.1 mm and
    60 microradians.

-   The position variation in the transfer line \< 1 mm.

-   Dispersion at target \< 0.04 m (no spec on D')

-   The spot size sigma = 1 +/- 0.1 mm (due to beta and dispersion)

-   The target size is 6.4 mm x 15.0 mm (WxH)

-   The divergence at target \< 10% (alpha \~0.12)

-   Beam loss \<1E-6 in carrier tunnel and 1E-4 in pre-target (no spec's
    for MI tunnel)

From Sam's overview, he states the power supply stability must keep beam
stable to:

-   0.1 mm (rms) transport and 0.05 mm on target -- all supplies short
    term (\< 30 min)

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-   1.0 mm (rms) transport and 0.5 mm on target -- all supplies Long
    term (hrs to days)

-   0.4 mm (rms) transport and 0.2mm on target -- each supply Long term
    (hrs to days)

1\. The current design uses three kickers all located downstream of
Q602. This requires the re-arrangement of instrumentation. [This has
been discussed but a final solution has not been documented and
accepted. This needs to be done!]{.underline}

Strongly concur! Alberto Marcianni's document provides space
requirements and notes instrumentation currently in place. A solution as
to instrumentation re-arrangement must come from Main Injector
Department. This needs to be addressed very soon.

Phil Martin is writing up a plan as to how/when/where/who will move the
instrumentation with an eye to moving it in the summer 2003 shutdown,
but not precluding moving it in the summer 2004 shutdown. He should be
done with this plan by mid April.

2\. The current design contains quad magnet moves in the MI60 RF
straight section. These quad offsets are used to reduce the required
corrector current needed for the counterwave and circulating beam
position around the Lambertson. The offsets are larger than those used
in other locations of the MI. The numerical values of the quad offsets
and corrector strength are correct and this has been verified. The large
offsets through the RF section caused concern. Previous simulations have
showed that 18 A would be required for the corrector at 602 to produce
the necessary counterwave. This beyond the current corrector capability.
With the likelihood of converting these supplies to +/- 30 A will most
probably remove the requirement for the quad alignment offset in MI60.
[A revised design of the extraction region, which eliminates and/or
reduces the needed quad offset should be incorporated to assure that the
position and angle into the beamline remains constant]{.underline}.

Use of 30 A. corrector power supplies (now the BD/EE standard) would
enable reducing the quad (Need to maintain \< 12.5 A rms). These are now
the supplies planned for the NuMI transport. Additionally, the local
bumps can be turned up toward high field part of the ramp to minimize
beam offset thru RF at lower energies. Questions re. impact of beam
offsets thru RF region can and should be addressed empirically - in the
next several months.

3\. The H604:3 counterwave bump should be tested in MI as soon as
possible to determine the amplitude that can be achieved with existing
power supply, then install a new higher current supply to determine the
amplitude that can be attained. This will also verify that there are no
ill effects due to running beam off center through the RF.

Concur. This is as we have discussed previously, and in response to
previous comment.

4\. **The power supply names and power supply regulation requirements
are not consistent among all documents.** For example table 1 in Power
Supply Regulation Requirements lists V100 allowed instability as 670 ppm
while table on p 10 in Steve's presentation list a 400 ppm value. On
page 14 in Steve's he list the as built as 250 ppm.. Table 4 in design
document list various p.s. current regulation numbers (which to use?).
Also, Table 1 in Power Supply Regulation Requirements lists H117 which
is not discussed in any other document. [All of these documents should
be made consistent starting the positopn/angle requirement, power supply
stability spec., stability at the costed value, and if it doesn't meet
the spec., how much to bring it into spec.]{.underline}

This was in progress at time of the review. See Technical Design
Handbook, <http://www-numi.fnal.gov/numwork/tdh/tdh_index.html>,
Chapters 4.2 and 4.3.

5\. Currently, only the basic regulation system used in P1 has been
costed (i.e. no filter, no digital DAC, no DCCT upgrade, no temp
regulation). Some power supplies need additional regulation. [All of the
documentation needs to be clear on which power supplies will require
additional regulation and how much it will cost.]{.underline}

See Technical Design Handbook (
<http://www-numi.fnal.gov/numwork/tdh/tdh_index.html>, Chapter 4.3). A
CR has been processed and approved for the additional regulation
requirements, with cost \~ \$150k. Steve Hays has reviewed this cost and
agreed with it.

[II Itemized suggestions, comments, questions, concerns]{.underline}.

# 

# Comments on the NuMI Primary Beam Design Report:

1.[Positional precision and stability]{.underline}

The program Autotune has been advertised to keep the position on the
target to within +/-100 microns. Is this the same program that is being
commissioned in the MiniBoone beamline? If so, then you will get
experience in the operation of the program. [This is good]{.underline}!
Will the program look at both wire profiles and BPM's? It was stated
that Autotune should be able to correct for slow drifting, but not for
random pulse to pulse variations. Do the power supply specifications.
What happens if one of the target BPM's fails? Does the Auto tune
program rely on one or both?

This is the same program structure as for MiniBooNE, and used previously
in several beams (KteV, NE, and originally, Switchyard). The normal
Autotune algorithm uses both target BPM's, but this structure can be
readily changed on the application control page, to keep system function
if a detector problem cannot be readily addressed. The program does not
change magnet settings unless all specified detector data is provided
and verified as for most recent beam pulse. Power specifications do
address the stability needed for pulse to pulse variations. Autotune can
-- and has been used with both BPM's and wire profiles. The possible use
with wire profiles for NuMI will be understood when the beam control
algorithms are developed. The major importance for this control system
is at operational intensities and to be active for a large duty cycle --
ie with BPM's.

2\. [Beam angle]{.underline}

Is the specification for incident beam angle 600 ur ?

It has been stated that the real limitation on the targeting angle will
be the relative alignment of the 2 final target BPM's. What is the
alignment tolerance? How are they to be aligned? What is the
relationship of the alignment of the BPM's to the target to the horn, to
the decay pipe? Which is most important in determining the neutrino beam
trajectory to Soudan? What are the relative mis-alignment tolerances and
how are these to be achieved?

Incident beam angle on target is at zero degrees -- relative to the
target, horn, decay pipe and Soudan detector line. Specified is an angle
tolerance for primary beam of +/- 60 μrad.

*Alignment tolerance is 0.25 mm (transverse). Alignment is with laser
tracker. A global beam alignment network will be established; then all
components are positioned w.r.t. this system.*

3\. [Beam size]{.underline}

The beam size has been specified as a sigma of 1 mm. If this a sigma of
a Gaussian, then one expects 99% of the beam to be contained in 6 sigma
. What is the specification on how much beam can miss the target? If the
target width is 6.4 mm, this would imply that the position tolerance of
+/- 0.2 mm for 99% of the beam to be on the target. Can this be achieved
with current supplies?

Position tolerance for beam on target (given in overview presentation)
is consistent with this. This can NOT be achieved with current supplies
as is -- but is achieved with the PS regulation improvements planned
(included in the approved CR).

4\. [Loss levels]{.underline}

III [Beamline elements]{.underline}

1.  [Kickers]{.underline}

2.  [Extraction Region]{.underline}

A more detailed discussion of the extraction region setting will be sent
later.

3.  [Transport and targeting]{.underline}

> No comments:

4.  [Layout]{.underline}

-   Table 3 lists the MI IDH correctors as having aperture increased
    from 1" to 1.5". I believe these numbers are half aperture.

> *Yes, these are half-apertures.*

-   The multiwire wire spacing in the beamline be1 mm. What is the sigma
    of say a 95% 40 pi beam? I see a sigma of about .7mm with a beta of
    10 m. It is likely that you will start out with an emittance x2
    smaller which gives a sigma of .5mm. Are you going to use these
    wires for only steering or are you going to do lattice
    measurement/verification? If you are going to look at profiles, the
    profile will be rather small

*The multiwire wire spacing is 1 mm along the transport, but 0.5 mm for
the targeting -- smaller wire spacing is used here for the reason you
note. Wires will be used as a diagnostic for both purposes.*

5.  [Focusing Sensitivity]{.underline}

-   Simulations with db/b were 25 units of random quad errors. The
    figure F shows a +/- .1 db/b variation at the end of the plot. Is
    this the position of the target? This correspond to a 5% variation
    in the beam size at target. Is this 0.05 mm a change in sigma or a
    change in beam size (see page 13)? If so, then 6X1.05mm is 6.3mm for
    a 99% beam size on a 6.4 mm target. What fraction of this 25 units
    is due to transfer function uncertainty and what part due to
    mis-powering?

*First, the end of the plot is slightly beyond the target. Second, the
25 units of quad error is put into this simulation as the total
uncertainty from each quad. Thus it is supposed to encompass both
effects.*

6.  [Trajectory Sensitivity and correction]{.underline}

-   Page 17 shows the orbit due to .1% EPB error. The maximum excursion
    along the beamline is 4 mm when the specs are less than 1 mm. The
    target position error is small now with a large slope. What happens
    if the phase advance changes?

*Yes, this figure indicates excursions along the orbit greater than the
spec. That is why this level of regulation is inadequate. Studies have
been made of altering the focusing conditions, thus phase advances. The
line is seen to be stable to reasonable changes.*

-   The vertical bends on the other hand have a 3 mm error at the
    target. For a 1000 ppm error. To get to .5 mm one needs 166 ppm and
    to reach .2mm long term stability (presented in Sam's slides) the
    power supply needs to by \~67 ppm. I think this is consistent with
    requirements presented in another document.

-   If I look at table 4, I see for V109 a .01% number for Holec which
    is 100 ppm. This says that the power supply will not meet
    requirements. Also, its not clear in the table under columns marked
    current regulation and ripple as to if these are what the P.S can do
    or if these are specifications. My suspicion is that it is what the
    ps can do.

*For this entire table, this is what the PS can do under various
scenario*s.

-   In this section of text you don't specify what the regulation
    requirements are.

*The beam stability requirements are given elsewhere in the document and
are quoted correctly by you above. This section gives the beam variation
due to PS regulation effects. By comparing the PS effects with the beam
specs, one can see the level of PS improvement required. See Technical
Design Handbook ( <http://www-numi.fnal.gov/numwork/tdh/tdh_index.html>,
Chapter 4.3).*

[IV Aperture Analysis]{.underline}

-   You should include another figure showing typical 99.99% beam sizes
    for 20 and 40 pi emittances on a +/- 50 mm scale.

> *Concur. A figure similar to this is planned for inclusion in the
> TDH.*

[Comments on Overview: NuMI Primary Beamline Sensitivities
slides:]{.underline}

1.  page1: First bullet assumes that the standard mode of operation is
    the "mixed mode" where NuMI and pbar production share the same
    cycle. Has the momentum offset and bunch rotation issues been worked
    out?

Not fully. We have done some beam study looking at bunch rotation beyond
the stacking batch extraction point. A lot more remains to be done here.

2.  page 1: second bullet: one could ask why is there an unshielded
    tunnel passing directly thru the protected ground water resource...a
    design choice, compromise, construction reasons??? I agree that this
    isn't reviewed here, but since you bring it up, it begs the question
    why is it like this?

Predominantly for construction reasons. Construction constraints (read
\$\$\$) significantly limit the size of the beam tunnel through the till
and dolomite interface region. The target hall with shield pile is the
counter example of a completely shielded tunnel. For the tunnel size we
are able to have, minimal shielding would be feasible. An additional 5-6
ft. in added tunnel diameter with concrete shielding only gains x 10,
which is a very minimal shielding gain, but would be at very large cost.

> *Also, the ground water shielding requirements for current tunnel are
> well matched to what is very good to do to limit residual activation
> of components.*

3.  page 2: Has the MARS modeling already determined the beam loss
    limits? How do these calculations compare with reality? Are there
    other areas these calculations have been performed that agree with
    measurements?

Yes. MARS has been benchmarked to very good agreement for these types of
calculations -- many examples exist.

4.  page 3: where is the central half of the transport line? In MI
    tunnel, glacial till, or in the dolomite?

*All three.* *See Technical Design Handbook (
<http://www-numi.fnal.gov/numwork/tdh/tdh_index.html>, Chapter 5, Figure
5.2).*

5.  page 3: the DC average loss at any point \< 1E-4. What is the time
    scale? 5 pulses, 1 minute, 1 day?

> *The important time scale for groundwater is residency time of a water
> sample. See Radiation Safety section of TDH. See Technical Design
> Handbook ( <http://www-numi.fnal.gov/numwork/tdh/tdh_index.html>,
> Chapter 5, Table 5.2).*

6.  page 4: You specify the acceptance of the transport line. What is
    the acceptance of the MI, particularly the MI60 region, and the
    extraction channel? The smallest of these should be considered the
    acceptance.

> *These are matched. It was quite important to significantly improve
> the acceptance of the extraction channel -- by adding a 2^nd^
> Lambertson power supply and a 3^rd^ kicker.*

7.  page 4: what parameter choices? What are these parameters used for?

*The ones immediately above this --maximum beam envelope of 500 p and
dp/p = 3E-3.*

8.  page 5: are the requirement levels the same as power supply
    stability specifications?

Yes.

9.  page 5: what are beam control effects on physics sensitivity? Which
    physics?

The comparison of beam spectra seen in near and far detectors is
essential for quantitative determination of neutrino oscillation
parameters. Beam targeting specs are set to preclude a bias in this
measurement.

10. page 5; last bullet: do you mean that the specifications for the
    power supply stability is consistent with current operation
    supplies? Are there any supplies that you [must]{.underline} do
    better by an order of magnitude?

Yes. Specifications are consistent with results achieved previously.
Improvements over "standard" power supply stability at order of
magnitude level is needed for several supplies, but this does not
require a new development effort.

11. page 6: does the .5mm absolute mean +/- 0.25 mm?

No. It means maximum position excursions should be +/- 0.5 mm from
centered.

12. page 6: where did the target angle of 60 microradians come from?

The assigned error budget for beam targeting angle, to have minimal bias
on spectra comparison between near and far detectors.

13. page 9: You say that the bottom line is 0.05 mm targeting and 0.1 mm
    along the beamline in the short term and 0.5 mm and 1.0 mm on a
    longer time scale. You have a 0.2 mm and 0.4 mm for individual
    supply regulation. How did these numbers come about? Are these
    discussed later?

A list of the input constraints for determining these specifications is
summarized on the preceding page 8.

14. page 10: NuMI uses MI correctors. What is the maximum corrector
    strength needed? What current does this correspond to? Is this
    consistent with MI power supplies?

See responses to similar questions re. Peter's slides.

15. page 10: Is the activation threshold of 0.5 mm for transport
    consistent with the BPM functional(?) accuracy of 0.2 mm?

Yes.

[Comments on Peter's slides:]{.underline}

There was not text associated with his slides. It seems most came from
the design report?

Here are the slides and a few comments:

# Beta waves due to 10% injection optics

-   what about beam sizes

> *Fractional beam size change is one half the fractional beta change
> and is seen from this plot to be acceptable.*

-   did you look at any larger MI lattice errors?

> *Accelerator Physics tells us that these are reasonable variations to
> use. They also point out that trim quads in the MI can be used to
> change lattice parameters if necessary.*

-   [Betax fractional variations for 1e-3 gradient errors]{.underline}

    -   are all quads powered independently

> *Yes, all are independent.*

-   

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-   [Betay fractional variations for 1e-3 gradient errors]{.underline}

    -   

# Position dependence on starting position

-   Where is the target?

> *Target is at station 356 meters.*

-   It looks like the vertical target position is within spec, but not
    the horizontal.

-   What does this imply about the accuracy of MI closed orbit at the
    lambertsons?

> *For the assumed 1mm offset at the Lambertsons, neither horizontal nor
> vertical is acceptable at the target. If the closed orbit were off by
> this much, the NuMI beam would have to be retuned onto the target.
> Specs on kicker stability can also be inferred from this plot.*

# Position dependence on starting angle

-   Not an issue?

> *This plot also shows the limit on closed orbit angular offset and
> kicker angle.*

# Horizontal position wave due to kicker at .5% spec

-   Where is the start? Entrance to first lambertosn?

> *Yes.*

-   Do you mean a 0.5% field error?

> *Yes.*

-   What happens if one of the three doesn't fire?

> *Much of the beam is lost on the first Lambertson. The rest is lost in
> the upstream part of the line.*

-   Its clear that the kicker-target are modulo 180 degrees for the
    design optics. What happens if there is an optics error?

> *Any major optics error in the MI or the line would have to be
> corrected. As was noted above, the line is stable to relatively small
> changes.*

-   [Sensitivity to quad motion (horizontal)]{.underline}

    -   Does this represent trajectories for each quad independently
        offset by 1 mm and all others on design orbit.

> *Yes.*

-   What about random alignment of all quads?

> *These curves add in quadrature. Note that the curves are drawn for
> 1mm offsets. 0.25 mm offsets are the goal. A major use of correctors
> is to correct for such effects*.

-   Is this how one specified alignment tolerances?

> *Yes, both alignment tolerances and corrector strengths.*

-   [Sensitivity to quad motion (vertical)]{.underline}

    -   Same comments as the horizontal !

> *Same responses.*

# Horizontal corrector ranges

-   What do you mean kicks reduced by 1/3?

> *At the indicated locations the BdL of the magnet is reduced to 2/3 of
> nominal by opening magnet gap by 50%.*

-   Have these been tested to 25 amps. Are they linear?

> *Projection is that they can be run at up to 30 amps with the planned
> ramp file (gives 12.6 A. rms for 30 A. peak) This is currently being
> tested. Field vs. current is linear to 25 amps for both 2" and 3"
> gaps.*

-   What angle or current do these orbit distortions represent?

> *The figure notes that it is plotted for 25 amps.*

-   [Vertical corrector ranges (2 plots one with IDH and one with
    IDV)]{.underline}

    -   So, which type corrector is being used for the vertical?

> *The plot is made with MI vertical correctors and indicates that they
> are inadequate. Thus rolled IDH horizontal correctors are to be used.*

-   Have these been tested to 25 amps. Are they linear?

#### See previous response

-   What angle or current do these orbit distortions represent?

#### See previous response

-   Are there specific correctors used for targeting?

> *Yes, the last magnetic elements are two correctors.*

# Maximal beam sizes, 500 pi, 3e-3 vs clearance

-   How many sigma is this? What fraction of beam is contained?

> *The 500 pi and 3E-3 are the acceptance of the MI. Thus 100% of the
> beam is contained within this envelope regardless of sigma. Since
> losses at the 10-4 level are important, no assumption is made as to
> the shape of beam tails.*

-   The total horizontal size is too big in the up bend. And the baffle.

*An up to date version of this plot improves the situation in the
upbend. As to the baffle, the text explains that 500 pi beam with a 40
pi tune is considered errant and is supposed to hit the baffle.*

-   The vertical look better but still to big for baffle.

-   It might be better to use more realistic emittances for looking at
    aperture.

# Horizontal beam sensitivity to nominal ps drifts

-   It seems that the EPB *PS as is* does not meet your requirements
    along transport. Is this true? What's to be done? What do you mean
    "PS AS IS"? Is there a ps solution? How much more does it cost than
    the base line?

> *These points are all discussed above.*

-   It looks like the EPB meets the requirements at the target for the
    design optics. What if there is an optical error ? How large of an
    optical error can be tolerated?

*Plots above indicate effects of MI beta function errors and NuMI line
quad errors*.

-   I assume you include the Lambertson because they are rolled? This
    essentially say's that you only have one horizontal supply to
    establish the horizontal trajectory to target.

> *Rolled Lambertsons induce minimal horizontal deflections. There are
> two horizontal bends (one at zero nominal) and ten horizontal
> correctors.*

# Vertical beam sensitivity to nominal ps drifts

-   Again what is meant by "PS AS IS"?

-   It is clear that the down bend and up bend do not meet the
    requirements. What to do? Is there a ps solution? How much more does
    it cost than the base line?

-   What are "nominal power supply drifts"?

-   Again the EPB meets the target, but not the transport. What happens
    for optical errors?

> *See previous responses.*

[Comments on NuMI Beamline Power Supplies slides:]{.underline}

1.  slide 1: no comments

2.  slide 2:

3.  slide 3: will all supplies invert? *Yes*

4.  slide 4: by max ps voltage, I assume that a voltage less than the
    max, say .8max, could be used. *Yes*

5.  slide 4: nominal tuning of only max current, but need to specify
    rest and undershoot levels. *I think this is a tune window question.
    But from a power supply design point of view the maximum current for
    the magnet loop is not the maximum current out of any supply so we
    have tuning range in the system. The DCCTs on order are the kind
    that we can change the turns ratio to best match the peak current
    needed. This will allows us to use the most of the bit steps from
    the DAC reference. SLH*

6.  slide 6: what is the current status of installing local DAC in P1
    and P2 supplies?

> *The P1 and P2 line power supplies: HVF12,HV703,Q703, V714, H703,LAM52
> and V701 have all been upgraded to the local DAC in the power
> supplies. This improves the signal noise level in the current
> reference and improves the 60Hz noise after the reference changes back
> to analog. SLH*

7.  slide 6: are these in 2^nd^ bullet improvements for NuMI or could
    these be used in P1/P2? Do any of these improve the regulation at 8
    Gev?

> *All of thee improvement could be added to the P1/P2 line power
> supplies. It is not clear that it would improve the 8Gev regulation.
> The DAC and reference supplied by the control card is only 16 bit
> which means that the smallest change is 153 micro volts. The LSB noise
> level can be two or three bits times the full-scale gain of the DCCT.
> So improving 8 Gev reference is a dynamic range issue for supplies
> that need 5000 amps at 150 Gev but only 250 amps at 8 Gev. SLH*

8.  slide 7: The design doc list supplies HV102,V109, and V119. This
    slide lists HV101, V108, V118A, V118B. Are there now two supplies on
    the up bend called V118 or V119? Is the stand alone temperature reg.
    DAC and filter part of the base line cost? Don't understand the last
    bullet, where is the BEST DAC system?

> *Nomenclature was not consistent at the presentation. I apologize. The
> TDH has everything consistent now. The baseline cost included 3
> filter/chokes that we could use where we wished. The Change Request
> (CR) adds 7 more filter/chokes. The temperature reg. DAC was not in
> the baseline, but is now in the CR for all large supplies. The BEST
> DAC system.*
>
> *The best DAC system is a Low Beta style regulation system that has
> been measured to be 4ppm stable pulse to pulse over long periods of
> time, months. The only addition to this is the BuLb system that can
> improve the pulse to pulse regulation on fast ramping systems. This
> was developed and used in the Main Ring Overpass system and learns to
> correct the systematic errors that the 20Hz bandwidth analog
> regulation system is not fast enough to correct. SLH*

9.  slide 8: 1^st^ bullet has 2 or 3 supplies on 3 magnet loops. The
    design report only has 2 magnet loops with multiple supplies (HV102
    and V119).

Nomenclature was not consistent at the presentation. I apologize. The
TDH has everything consistent now.

10. slide 9: will all dipole and quad supplies have this absolute value
    circuit? Does this look at the error during flattop or ramp? How is
    this value set?

> *The beam permit system consist of a C204 card that intercepts the
> MADC signals from the power supplies, we are grouping all the power
> supplies into one MADC to use this card. This allows us to not extract
> if any of the signal are out of the window at the extraction event.
> The plan is check the reference, current and current error signals.
> SLH*

11. slide 10: The table of target RMS in microns is not consistent with
    the table 1 power supply regulation requirements on the web page in
    ps names or values.

Nomenclature was not consistent in the presentation. I apologize. This
table was the table for the old beam optics. A new table was shown at
the review, but was not posted until later. The TDH has everything
consistent now.

12. slide 11 and 12:

13. slide 13: what has been costed?

14. slide 14: Are these As Built consistent with table 1 and table 4 in
    design doc? It looks like V108, V118A and V118B do not meet the
    requirements.

What was costed was 3 filter/chokes and nothing else additional. The CR
adds filter/chokes to all the main strings, special electronics and
DCCT's and costs for 3 BuLB or JITtER systems for the 3 main strings.
This is all documented in the TDH, Section 4.3.

**Subject: Comments on NuMI Primary Beamline Sensitivities Review**

**Date: Fri, 01 Nov 2002 19:30:57 -0600**

**From: Jim Hylen \<hylen@fnal.gov\>**

The Primary Beam Design Report and the presentations represent a large
amount of careful work. The resulting requirements from studies of beam
line sensitivities are becoming clearer, and quite a few component
tolerances can now be stated with good confidence. However, in some
areas it is still a work in progress. The work appears to be proceeding
in a very reasonable fashion, but obviously construction and
installation deadlines are going to be breathing down our necks soon.

I suggest adding the following two items to the written requirements in
the Beam Design Report, so that they are documented:

This documentation will be done in the TDH.

\(1\) the ability to scan beam the beam at least +/- 11 mm horizontally
and vertically from the beam line nominal position at the location of
the horn 1 neck. This is required as part of the recently added cross
hair system for horn position measurement.

A capability of transverse beam scans in either plane is incorporated
using the corrector dipoles.

\(2\) Beam tails should be less than 1% beam at radius greater than 5 mm
through the target hall baffle. Larger amounts will cause visible
changes to the neutrino spectrum. (The baffle is nominally r=5.5 mm; 5
mm thus gives some allowance for alignment tolerances)

Control of target focus is flexible, and this is a priority input in
determining settings. Beam modeling using a range of input distributions
indicate this should be achievable.

Peter showed quantitatively how M.I. beam position/angle offsets
translate into NuMI beam offsets, but the estimates for realistic M.I.
position/angle stability were not presented. Since the transfer function
appears relatively large, documenting the actual M.I. stability appears
to be an urgent task.

This will be done as part of a series of MI beam measurements relevant
to NuMI performance.

Sam argued that since the kicker may use up most of the beam jitter
tolerance, it makes sense to make the bend magnet power supply
regulation good enough that it will not be an additional big
contribution. The implementation of that better regulation is the
purchase of relatively inexpensive DCCTs. This does indeed appear to be
a prudent step.

Several contributions to beam offsets were described: beam
location/angle in Main Injector, kicker jitter, magnet position
tolerances, magnet regulation. Two tables (one for required corrector
strengths, another for operational tolerances) showing an error budget
with contributions listed would be a nice addition to the documentation,
and would aid in understanding the beam line as a system rather than
piecemeal.

The two tables are really the same thing. When the corrector is at its
maximum the tolerance is used up. This has been done for the correctors
in the TDH.

It was pointed out that the requirements derived for the kicker jitter
are a factor of 2 more stringent than the kicker designers are willing
to guarantee. The project should logically either figure out a plan to
improve the kicker, or else state that while not ideal, the less
stringent number is livable. Given the state of resources, the latter
course (if indeed livable, which I suspect may be true) may be
preferred.

What has been agreed to is a minimum specification plus a best effort
goal which is x2 more stringent than this.

**Comments for Review of NuMI Primary Beamline**

**Sensitivities November 1, 2002**

**From: Wes Smart**

1\. Overall Remarks

2\. Itemized suggestions, questions and concerns

1\) Use a common naming/numbering scheme for magnets and power supplies
in all documentation.

*This has been done- see Technical Design Handbook (
<http://www-numi.fnal.gov/numwork/tdh/tdh_index.html>,*

2\) Magnet stands and connections should allow for installing magnetic
shielding of the MI and recycler beams, should that prove to be
necessary.

Magnetic shielding for effects of NuMI fringe fields is being planned,
and can be installed using previously developed techniques.

3\) Any remaining extraction issues with MI should be resolved as soon
as possible, certainly before NuMI magnets are precisely aligned.

The remaining outstanding extraction issue, clearing MI insertion space
for the NuMI kickers, is actively being addressed.

4\) For a 250 micron transverse alignment tolerance to be effective,
quad field maps must be included. Before quads are moved into the
tunnel, verify that these field maps exist and can be included in the
alignment.

This is being done as part of the TD quadrupole refurbishment effort.