# Comments from the Review of Specs for Primary Beamline

# July 13, 2001

# 

## Specifications Driven by Physics, MI Parameters

## Presenter: P. Lucas

1.  ([Reviewer: D. Michael]{.underline}) The issue of 4 or 5 of 6
    batches should be pursued agressively and not simply accepted as
    inevitable.

2.  ([Reviewer: D. Michael]{.underline}) Technical issues and solutions
    to assure a 1.9 s (rather than 2.5s?) cycle time should be
    identified and personnel and resources assigned to do the necessary
    work.

3.  ([Reviewer: D. Michael]{.underline}) Technical issues and solutions
    necessary to go from 2x10\*\*13 ppp to 4\*10\*\*13 ppp must be
    identified soon and manpower and resources assigned to make this
    possible.

4.  ([Reviewer: D. Michael]{.underline}) The assumption of 40pi
    emittance for 95% of the beam with no non-Gaussian tails appears
    optimistic and could have a serious impact on groud-water
    irradition. It is important to invest effort to gain a better
    understanding of what we can expect.

5.  ([Reviewer: D. Michael]{.underline}) The momentum spread may be
    worse than planned, perhaps as much as 10\*\*-3 pulse-to-pulse
    variation? Likely to get worse under beam loading conditions. This
    requires further study on the design impacts it may present and
    better characterization of the likely quantities to be delivered.

6.  ([Reviewer: D. Michael]{.underline}) Quantitative ranges should be
    specified for the allowed variation in the beam spot size.

7.  ([Reviewer: D. Michael]{.underline}) Aperture plots which show
    10\*\*-2, 10\*\*-3 and 10\*\*-4 contours for beam should be
    produced. Better understanding and quantization of tails is
    essential. The possibility of adding addtional, stragic upstream
    scrapers should be pursued.

8.  ([Reviewer: D. McGinnis]{.underline}) The beam will have a halo
    (tails) - count on it! You need to have 2 scrapers per plane on the
    upstream end of the beam line.

9.  ([Reviewer: D. McGinnis]{.underline}) With such a huge dispersion in
    the beamline near tight apertures, you need to understand the
    longitudinal phase space of the Main Injector much better.

10. ([Reviewer: S. Mishra]{.underline}) The beam line being designed
    will have much more demand on its performance as compared to any
    standard beam line we are used to. This is mainly due to the beam
    loss requirement. I think the attention paid to the details in
    designing this beam line is at least minimal. Beam comes close to
    aperture at several location. Magnet quality, alignment etc. has not
    been taken into account

11. ([Reviewer: S. Mishra]{.underline}) There are a lot of misgiving
    about the Main Injector performance in this design. For example it
    was mentioned that the beam will have no or small tails. To date
    there has not been any beam without tails unless you put a scraper
    in front of the beam line. We have no clue how the beam will look
    when the intensity will be close to 2.5e13 ppp. We also do not know
    about dp/p of the beam at this intensity. I think NUMI designer
    needs to work with MI staff to get these parameters straight. Donor
    assume what is in the MI design report, we have real data or a data
    can/should be taken. Dispersion in the NUMI line is one concern.

12. ([Reviewer: S. Mishra]{.underline}) One general comment is that NUMI
    beam line designer needs to work on P1/P2 line on a daily basis to
    understand the details of the extraction line operation and problem.

13. ([Reviewer: A. Para]{.underline}) I am sure that better minds than
    mine have been working on this, but nevertheless I would like to
    hear the pros an cons. Given our geometry and sensitivities, is it
    possible to design a set of collimators to cut the tails and reduce
    the beam size to such a level that no losses in the carrier tunnel
    are possible? (It is not a trivial problem as improperly designed
    collimators may produce more background than reduce it).

14. ([Reviewer: A. Para]{.underline}) Very long drift space makes us
    sensitive to a momentum dispersion of the proton beam. Again, it
    seems that the Main Injector people are far less optimistic here. Is
    there anything one could do to reduce our sensitivity? I suppose it
    is maximal at the downstream end of the drift region. Can one have
    large aperture quadrupoles there to reduce the beam size?

## Parameters from Facility Construction, Radiation Control, Instrumentation

## Presenter: S. Childress

1.  ([Reviewer: D. Capista]{.underline}) Auto tuning for this beam line
    will require significant effort to make it work. In the 18 years I
    have been involved in operations, I have NEVER seen an auto tune
    program work completely correctly even under human control. These
    programs will diverge on solutions in some cases, range control
    devices, get bad detector data and steer the beam into a beam pipe,
    and various other problems. There have been many attempts at such
    programs in the past but when I look at the list of operational
    programs I believe many of the auto tune programs have been deleted.

2.  ([Reviewer: D. Capista]{.underline}) Since beam losses need to be
    kept very low in this beam line, the BPM system needs to be
    connected the beam permit system. BPMs will tell the permit system
    something is going wrong before beam loss occurs. It is true that
    BPM permits have been removed form the accelerators due to
    reliability issues, but the accelerators do not have the loss issues
    this beam line has.

3.  ([Reviewer: D. Michael]{.underline}) A vacuum window should not be
    placed between the MI and the NuMI beamline. However, an additional
    vacuum window at the upstream end of the transfer pipe region could
    help to avoid trouble and accelerate commissioning.

4.  ([Reviewer: D. Michael]{.underline}) It is likely that BPM
    monitoring as proposed will need improvement to provide sufficiently
    reliable information (on the location of the beam in the pipe).
    Design requirements for beam position measurement are appropriate.

5.  ([Reviewer: P. Martin]{.underline}) The beam position monitor system
    has to work reliably both during commissioning and operations. It
    must also work at both low intensity for commissioning and at high
    intensity for operations. Switchable amplifiers or attenuators may
    be required.

6.  ([Reviewer: P. Martin]{.underline}) For the physical layout of the
    NuMI beamline, I would recommend the addition of two vacuum valves
    (these could be hand-valves), one on each side of the beampipe that
    otherwise blocks vehicular access to the A1 line or NuMI stub. This
    would allow removal of the beampipe without letting up the section
    of NuMI beamline closest to the Main Injector. This will minimize
    the impact on MI vacuum following the need for access. Because there
    is no vacuum window separating the beamline from the MI vacuum
    system, the design goal should be substantially better than 10-7
    Torr, not the 10-6 Torr presented at the review. Further, the NuMI
    management should make a strong case for getting that section of
    beamline completely installed and under vacuum at least a year
    before first beam, along with taking the necessary steps before and
    during installation to achieve the higher vacuum levels desired. I
    realize that the installation cannot be completed right now, due to
    the interference with the Recycler, but that should be able to
    corrected sometime in the year or so following the fall shutdown. A
    reasonable goal would be to get your beamline under vacuum in 2003.
    This would be an appropriate time for the Lambertsons to be
    installed as well. On a somewhat related matter, the placement of
    kickers, needs to be firmed up with the Main Injector department,
    both in the case of two long kickers or three shorter kickers.

7.  ([Reviewer: P. Martin]{.underline}) Finally, although this isn't
    directly a NuMI project concern, it certainly is for the MINOS
    experiment. That is, understanding the losses in the Main Injector
    for NuMI operations. As I pointed out in one viewgraph, the losses
    associated with a multiwire being in the beam bring residual
    radiation levels in the nearly component up to over 1 R/hr.
    Extrapolating that to the Main Injector, beam losses of 1% would
    result in over 100 R/hr. The machine becomes unserviceable. The
    present \~90% efficiency needs to be improved. Just as the MiniBooNE
    people have worked with the Proton Source to help understand and
    reduce losses, the NuMI people need to look at the same issues in
    the MI.

8.  ([Reviewer: D. McGinnis]{.underline}) You need to have a way of
    making sure the BPM system is alive from the tunnel. The typical BPM
    system in the beams division is notoriously unreliable. I suggest
    that each BPM is connected to calibration system in the tunnel that
    measures offset and gain.

9.  ([Reviewer: D. McGinnis]{.underline}) The BPM system needs to work
    accurately at low (3e9/bunch) and high intensity (6e10/bunch) which
    is about 30 dB of dynamic range - tough but do-able.

10. ([Reviewer: D. McGinnis]{.underline}) You need to re-think your
    strategy on the auto-tune program and how the loop is closed (by a
    program or a human), how you commission such a system, and how
    robust the system is (BPMs, TRIMs, singular matrix, etc\...).

11. ([Reviewer: S. Mishra]{.underline}) Instrumentation of the beam line
    need more and clear thoughts. We heard hand waving arguments during
    the director\'s review and we did not get any answer to our
    questions raised during that review on BPM range etc.
    Instrumentation is a key for the commissioning and operation of this
    beam line.

12. ([Reviewer: S. Mishra]{.underline}) Power supply regulation and its
    control needs to be specified in great detail with beam stability in
    mind. You need to do simulations with beam size and several power
    supply errors together to understand its effect on the beam position
    and quality. MI\'s P1 and P2 line can be good place to study this.

13. ([Reviewer: S. Mishra]{.underline}) Need application programs for
    the operation of this line. NUMI needs to develop a clear plan for
    that.

14. ([Reviewer: A. Para]{.underline}) Delivering protons to the NuMI
    target seems to be more complicated than one could naively expect.
    This is due to the fact that we are transporting high intensity
    proton beam through a water table therefore raising a possibility of
    groundwater contamination. For financial reasons beam is designed to
    have a very long drift distance with no active elements. Such a
    design makes us sensitive to beam losses at the level of 10\*\*-6 -
    10\*\*-4, well beyond the range of usual concern.

15. ([Reviewer: A. Para]{.underline}) Detailed radiation calculations
    were performed using MARS and the results were presented in a form
    of limits on the stability of V105 and V104 magnets. It wasn\'t
    clear if these were truly the worst cases, or rather the examples.

16. ([Reviewer: A. Para]{.underline}) Great deal of discussion was
    devoted to the \'Auto-tune\' program. Opinions on different sides
    seem to be divided. I would like to understand better the expected
    role of this tool: is it just a convenience tool enabling to speed
    up the tuning and perhaps improve the efficiency of the running, or
    is it expected to be a critical part of our beam control system?

## Groundwater Requirements

## Presenter: N. Grossman

1.  ([Reviewer: D. Capista]{.underline}) Review the ground water
    radiation issue. Clearly we have to stick to what was presented but
    it would be interesting to know how much beam we really believe we
    can lose without causing well contamination. It may be a better
    position to say we can lose the larger amount of beam without a
    problem but will operate at this lower value.

2.  ([Reviewer: D. Michael]{.underline}) Groundwater irradiation
    simulations need to be updated with more complete beam conditions
    and more complete environmental conditions.

3.  ([Reviewer: D. Michael]{.underline}) The allowed regulatory
    conditions for groundwater protection must continue to be pursued to
    avoid over-simplified, and over-zealous enforcement.

4.  Additional local strageic shielding in the carrier tunnel should be
    considered. Additional strategic water inflow should be considered.

## Test Program/P150

## Presenter: A. Marchionni

1.  ([Reviewer: D. Michael]{.underline}) Additional beam extraction and
    characterization tests should be pursued.

2.  ([Reviewer: P. Martin]{.underline}) The beam loss budget is of
    course the most challenging aspect here. To this end, the studies
    discussed by A. Marchionni are extremely important. In addition to
    some of the items he discussed, measurements of the beam momentum
    spread are necessary. Along with the ACNET parameter for the bunch
    length, I:BLMON, the actual beam signal from which this is derived
    should be looked at. While this cannot be datalogged or
    fast-time-plotted, it contains much pertinent information on tails
    in E-t space, and bunch-to-bunch fluctuations. As I mentioned during
    the review, using 3-bumps in the P1 and P2 line to study tails and
    calibrate the BLMs will prove to be a useful tool, I suspect. I
    would be happy to meet with the NuMI people who will be working on
    these studies to help plan things further. As mentioned during the
    review, the Main Injector Dept. is extremely busy, and therefore
    NuMI personnel are going to have to take responsibility for these
    studies with minimal support from MID. But it is important to carry
    these studies out soon, to help set the specs on momentum stability,
    pulse to pulse and bunch to bunch.

3.  ([Reviewer: P. Martin]{.underline}) Apart from the studies with the
    MI beam and beamlines, design studies should continue for the NuMI
    beamline to verify that there are not combinations of mistunings of
    several power supplies that can in fact strike the beampipe in the
    carrier tunnel. Also, pursue a design of two scrapers per plane to
    clean up any beam tails or halo at a location where losses of a few
    percent can be tolerated. If the tails are already there coming out
    of the Booster, could they be cleaned up in the MI-8 line? Or would
    they grow again during acceleration? More studies!

4.  ([Reviewer: A. Para]{.underline}) A requirement of very low level of
    (average) beam losses leads to a very stringent requirements on
    power supplies stability and their monitoring. It also requires the
    knowledge of beam profiles and tails beyond our ability to measure
    them. It is worrisome that we (i.e. NuMI) seem to be far more
    optimistic about the proton beam properties than people from the
    Main Injector are. Our test program at P-150 is of great importance
    and interest, but this beam line is sufficiently different from the
    NuMI line that probably no conclusive results can be obtained.