Comments for Review of NuMI Primary Beamline

## Sensitivities November 1, 2002

### 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}

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}.

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.

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}

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}

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

# 

# Comments on the NuMI Primary Deam 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?

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?

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?

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.

-   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

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?

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?

-   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.

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

[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.

-   

[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?

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?

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?

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

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

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.

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

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

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

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?

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

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

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?

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?

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

[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

-   did you look at any larger MI lattice errors?

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

    -   are all quads powered independently

    -   

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

    -   

# Position dependence on starting position

-   Where is the target?

-   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?

# Position dependence on starting angle

-   Not an issue?

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

-   Where is the start? Entrance to first lambertosn?

-   Do you mean a 0.5% field error?

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

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

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

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

    -   What about random alignment of all quads?

    -   Is this how one specified alignment tolerances?

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

    -   Same comments as the horizontal !

# Horizontal corrector ranges

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

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

-   What angle or current do these orbit distortions represent?

-   

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

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

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

    -   What angle or current do these orbit distortions represent?

    -   Are there specific correctors used for targeting?

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

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

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

-   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?

-   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.

-   

# 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?

[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.

5.  slide 4: nominal tuning of only max current, but need to specify
    rest and undershoot levels.

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

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?

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?

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).

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?

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.

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.