**[Executive Summary:]{.underline}**

A review of VLHC Draft Study Report" was carried out April 30 and May 1,
2001 at Fermilab. The report describes a scheme in which one first
builds a 40 TeV collider from superferric magnets in a very
large-circumference tunnel, followed some years later by a collider that
could reach 200 TeV in the center-of-mass. The review committee, charge,
and agenda are attached below.

The committee commends the contributors to the Study Report for the
large amount of high quality work contained in the report. The study
addresses the major issues associated with building a 40 TeV hadron
collider. However this study explores a set of parameter choices that is
very different than those selected for the SSC. The choice of low field
superferric magnets in a large circumference tunnel results in
accelerator estimates that are similar to those estimated for the SSC
when scaled to current dollars. However, substantial savings in the
injector complex and laboratory costs are realized by using the Tevatron
as the injector and taking advantage of existing FNAL laboratory
infrastructure. Another attractive feature of the proposed solution is
that it permits a future upgrade to above 175 TeV via the addition of a
second ring of high field magnets in the same tunnel. This option is
explored in the report but in much less detail than the stage 1
proposal.

**[Committee report:]{.underline}**

**General comments and findings:**

A detailed R&D plan for the project needs to be developed. The R&D plan
should list necessary R&D, establish priorities, and establish a
schedule for the required R&D. In addition to the R&D suggested below
for stage 1, the proponents should consider an R&D program to further
develop both Nb~3~Sn and HTS conductors for possible use in a Stage 2
VLHC. Magnet R&D for stage 2 should consider both common coil and cos
theta designs.

**1) Are there accelerator science, physics, or engineering issues that
could prevent the VLHC from operating that have not been addressed?**

General comments:

-   In the area of collective effects, the transverse mode-coupling
    instability and transverse resistive-wall instability have been
    correctly identified as major problem areas. Counter-measures, e.g.
    bunch coalescing in the VLHC design, and feedback systems in both
    stages against the resistive wall instability, should be
    incorporated in the design.

-   In the area of beam-beam effects, the choice of beam-beam parameter
    ξ=0.008 should be justified. Coherent beam-beam effects should be
    studied for various combinations of the tunes in the same plane in
    the two rings (M. P. Zorzano *et al.* claim that tune splits make a
    difference in LHC).

-   Will the feedback systems work in the presence of beam-beam
    collisions, with a multitude of collective modes?

More specifics: Stage 1:

-   Multibunch stability and coherent, incoherent tune shifts-

The distributed feedback systems which have been outlined, though
challenging and requiring more R&D for development, should in principle
be a solution. More R&D, experimental and theoretical, is needed on
detuning wakes in elliptical beam pipes. The "super-pipe" concept sounds
like it needs a lot of development. Conventional fast tune-control
schemes during injection may be able to handle the coherent tune shifts.

-   For single bunch (TMCI): the feedback is difficult; we recommend
    that a coalescing scheme be adopted as the baseline.

-   Dynamic aperture tracking for Stage 1 should be expanded to include
    synchrotron motion and tracking for a number of turns comparable to
    the injection time. Estimates of field errors should be put on a
    firm basis from measurements of several prototype magnets.

-   The stage 1 machine should be damped horizontally by slight changes
    of lengths and gradients in combined-function arc lattice (A.
    Hoffman, B. Zotter, ...)

More specifics: Stage 2:

-   The initial transverse emittances should be reduced. This should be
    possible since the bunch population is only about 1/3 that in
    Stage 1. This will reduce the waiting time for maximum luminosity,
    crossing-angle gymnastics, etc.

-   Multibuch stability seems OK-conventional feedback should work.

-   The single bunch-TMCI threshold is being approached with a 100 K, 10
    mm radius liner. It is aggravated by the impedance due to the photon
    catchers. Reducing the liner temperature (this may be possible if
    photon catchers work), making the liner thicker (but less than the
    thickness that will collapse under quench-induced forces), and/or
    increasing the injection energy to 20 TeV, should be considered.
    Trapped modes in photon catchers should be checked for.

-   Continued exploration of, and comparison between, flat and round
    beams is encouraged.(Comparisons should be made with technically
    comparable hardware). Tracking with field errors in IR magnets is
    needed to find magnet errors needed for acceptable dynamic aperture,
    and also to explore schemes for chromatic control.

-   The dynamic aperture at injection seems not to be an issue-what
    field errors for the arc magnets were assumed?

-   More effort is encouraged on the problem of IR magnets' tolerance to
    high heat load from IP collisions, as this may be the limiting
    technical issue for the luminosity. The exploration of novel ideas
    (HTS magnets?) may be useful.

**2) Have the civil construction issues been identified and addressed?**

[Findings]{.underline}:

-   Definition of scope for this stage in project development is
    reasonable.

-   The preliminary, conceptual-level cost estimate seem reasonable.
    Work is underway for preparation of an independent, conceptual-level
    cost estimate by an architect engineer, which should further
    increase reliability of the estimate.

-   The proposed "building-block" approach is sound, given that a
    specific site has not been selected and likely will not be for many
    years. The capability to rapidly produce estimates for specific
    candidate sites, based on an understanding of unit costs in various
    types of geology, will be essential.

[Recommendation]{.underline}:

In addition to the site options being explored, a third far west option
that cuts through the Troy Bedrock Valley should be included. This is
necessary to get the unit costs associated with such a site. It is also
the most attractive in terms of avoiding populated areas.

-   The project scale is certainly impressive. Project management during
    execution will be very challenging, both for civil construction and
    project as a whole.

(See related recommendation under Question 4.)

-   Given that the tunnel is sized for Phase II, the civil construction
    represents an unusually high proportion of overall project cost,
    making tunnel construction an attractive candidate for research and
    proposal that would reduce cost. Labor is generally about 40% of the
    cost of tunneling, so conducting R&D to reduce labor through
    automation might be an effective approach to reducing cost and would
    also reduce personnel exposure to the inherent hazards of
    underground work. How this R&D might best be done and the results
    might be incorporated into tunneling contracts is not clear.

> [Recommendation]{.underline}:
>
> Develop conceptual plans for accomplishment of R&D on tunnel
> construction and how R&D results would be incorporated into the VLHC
> effort.

**3) Are there technical issues with the planned low-field magnets and
associated accelerator systems that are unresolved?**

The planned use of 2 T magnets seems a very reasonable and cost

effective approach that doesn\'t appear to have any unsolvable technical

challenges.

An R&D plan is needed to build and measure phase 1 super-ferric magnets.
This program should include short magnets to demonstrate the required
field quality can be achieved, intermediate length magnets (of order 12
M) and full length 65 M long magnets. Other key features such as
achievable alignments, necessary cryo pipe-yoke alignment, and cryo pipe
support mechanisms should be demonstrated. A 65 M test article may be
useful for the development of handling and installation equipment. This
R&D program needs to be completed sufficiently early so that industry
involvement can be with completed designs and not R&D designs. This is
the best way to get cost effective involvement from industry. Longer
magnets should be developed to test both the

three-dimensional aspects of the calculations and to start learning how
to handle and construct long \"floppy\" magnets. Methods of moving the
magnets needs immediate attention as well, although the presented plans
are a good start.

The committee was concerned with the proposed internal welds that would
join the upper and lower magnet halves. A mechanical locking mechanism
may be able to do the same job without the risk of weld distortions and
the need to develop internal welding tooling.

Consider removing the ion pumps and taking advantage of the nearby
cryogenic lines that can act as cold pumps for the beam enclosures.

Use of SC transmission lines to excite special purpose magnets in which
the conductor experiences large electromagnetic forces requires R&D.

The difficult region of 1.8 to 2.0 T is used at the expense of
relatively

cheap corrector magnets to meet the beam stability requirements. In
addition,

it might be possible to go a little higher, to 2.1 T if necessary.
Careful attention to manufacturing tolerances of the field flattening
correction holes are recognized as critical issues. Some prototyping
will be necessary to demonstrate that thousands of tonnes of stamping
can be produced that will be of the required shape. The actual minimum
of field strength, tunnel length and number of corrector magnets can be
fine tuned to give the minimum, although data presented shows the
function to be shallow.

While basic field quality measurements on warm magnets are recommended,
detailed warm mapping of the assembled magnets does not appear to be of

sufficient use to justify the expense. It would be better to develop a

method of mechanical measurements that could be performed both in the
magnet

assembly area and after the transport to its place in the tunnel.

However, a basic check of field quality in each magnet would be prudent
as

insurance against mistakes in material selection. Efforts to develop a
fast and

reliable system would pay big dividends.

Several items require optimization and development:

Specifications and methods of verification of the more than 150 thousand
metric tonnes of low carbon iron need to be developed. Allowable
tolerances of batch-to-batch variations have to be developed and that
stability is not sacrificed.

The superconducting transmission line as presented should work,

but isn\'t optimized with respect to long term reliability. The
proponents should consider adding copper to the transmission line. This
would allow longer discharge times and reduced voltages during quenches.
It is likely that QPM could be made less sensitive to noise with longer
integration times if it did not have to act so rapidly to protect the
conductor. We also suggest the look at increasing the amount of
superconductor to provide more margin. This will allow both a
reliability improvement and a possible chance to optimize the planned
operating temperature of the liquid

helium to avoid critical regimes in the cryogenics. As the cost of the
conductor

is not a very big fraction of the cost of the magnets, there isn\'t much
to be gained by operating at the margin.

The magnet cooling scheme of the VLHC stage 1 operates with forced-flow
of

weakly supercritical helium over long distances; i.e., single phase
fluid

close to the two phase domain. This takes advantage of the large
sensible

heat of the cooling medium, but brings the risk of developing

instabilities, particularly through density-wave oscillations due to the

strong variation of fluid properties over the path evolution of the

thermodynamic state along the flow loop. This risk is also enhanced by
the

long delay times due to the length of the cooling loops. This risk
clearly

needs to be scrutinized in more detail, through stability analysis and

possibly by adequate scale modeling. Should it prove crucial to the VLHC

cooling loops, an issue could be made to move the design away from the

critical area; e.g., by increasing the pressure, at the cost of higher

mass flow rate taking away from the heat load.

The static linear heat loads estimates for the transmission line
cryostat,

although small, appear feasible and are comparable to the performance

achieved on cryogenic helium transfer lines of similar size. The dynamic

heat loads resulting from the Joule heating of the resistive splices -

every 65 m - in the superconducting cables carrying 100 kA, must be

contained by developing and enforcing reliable splicing techniques and

adequate quality assurance, suitable for in situ work in the tunnel

environment.

**4) Is the construction and installation plan credible?**

[Findings]{.underline}:

-   The plans are conceptual only at the stage, which makes them
    difficult to evaluate with much confidence.

-   The effort to minimize the work done in the tunnel is sound.

-   Challenges for construction and installation include:

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-   Large scale and high cost

-   Wide geographic dispersion of the work (long travel times and
    control issues)

-   Limited tunnel access (logistic choke points)

-   The sequential, inter-dependent nature of the civil construction,
    magnet production, installation and commissioning

[Conclusions]{.underline}:

-   Project management of this effort will be a daunting challenge

-   Demonstrating, in a credible way, that this project will be
    successfully managed will be critical to gaining support from the
    stakeholders (e.g., high energy physics community, general public
    (taxpayers), international partners, DOE and the authorizing and
    appropriating committees in Congress).

[Recommendation]{.underline}:

Begin now to develop, at least in written concept, the plan for project
management.

-   Expertise in successfully managing mega-projects lies primarily in
    the private sector (e.g., construction, aerospace, etc.) How can
    this private-sector expertise be incorporated into the proposed
    VLHC?

-   What are the logical blocks of effort for management of the work?

-   What is the procurement strategy? (In-house versus contract effort,
    etc)

-   What will the project management structure be? Where will the
    necessary talent come from?

**5) Have the major cost drivers been identified and is the preliminary
cost estimate for Stage 1 of the VLHC reasonable?**

The major cost drivers of high-energy hadron colliders are qualitatively
well known today based on available experience with previous studies and
projects spanning several generations of machines. Their relative
importance varies among projects based upon the choice of nominal
bending field and magnet technology.

The methodology applied for estimating costs is essentially analytical
from unit manpower and material costs and associated quantities. The
estimates for production or construction costs do not include
escalation, technical progress or increases in productivity, and are
therefore to be compared with present market prices. Moreover, they
strictly exclude R&D, EDIA, G&A and contingency, and are therefore
comparable with European cost estimate for similar projects.

Although they can and will be improved through focused R&D, the basic
technologies on which the Stage 1 VLHC rests are known today. The unit
costs quoted to support the estimates can be deemed as rather
conservative.

The largest single item in the cost estimate is civil construction.
Tunneling cost is the major contributor (see recommendation concerning
tunnel R&D under question 2) There is a large number of deep shafts
which will also be expensive:

Main ring 60

Beam Stop 2

> Klystron Gallery 1

Kicker magnet 1

Detector 1 4

Detector 2 4

There are obvious trade-offs between the number of shafts and ease of
installation and operational access. In A-E's estimates for typicall 15
foot and 30 foot diameter shafts can be used for trade-off studies. The
number of shafts should be as small as possible consistend with minimum
overall project cost and personnel safety concerns.

Additional analysis of the schem for handling tunnel drainage water
might be productive. Portable power and pumping capability might be
feasible to reduce size and cost of the proposed underground caverns for
holding drainage water during emergencies.

The second largest item concerns the magnet system. The cost of the
superferric magnets is driven by the cost of the low carbon steel
magnetic circuits. A large body of relevant experience exists for this
material.. The unprecedented quantities involved can only lead to
reduction of unit costs through economy of scale. The cost of NbTi
superconductor corresponds to current market prices.

**6) Does the plan to later install a second collider of higher energy
in the same tunnel make sense from the point of view of practical
accelerator issues?**

Such a plan makes sense if the required infrastructure is planned in
advance. Items such as bypass tunnels, injection lines to the later
machine, beam dump requirements and utilities must be considered. An
installation plans for the later machine must be developed that does not
materially disturb the Stage 1 machine. Allowance must be made for
cryogenic infrastructure needed in Stage 2. Some of these items will
cost money as Stage 1 is built, but for later efficiency and cost
containment they should be included. This does not imply that the Stage
2 infrastructure all be installed at Stage 1, but rather only those
items that if done early avoid excessive cost later. The committee saw
evidence that the proponents have considered many of these issues, but
ongoing planning is needed.

Particular and careful attention should be paid to all aspects of the
influence of the substantial stray magnetic fields from Stage 1 on the
Stage 2 beam.

**7) Are there any extraordinary or particularly difficult
environmental, safety or health issues either during the construction or
operational phase that have not been adequately addressed?**

[Environmental]{.underline}:

[Findings]{.underline}:

-   Little project-specific work has been done at this early stage. Some
    VLHC-specific issues have been identified in Section 7.8 of the
    Preliminary Draft Study. These will need to be fleshed out in
    greater detail as the project proceeds.

-   Tunnel egress was a significant issue for SSC. Several years of
    interaction with DOE were necessary to achieve agreement on issues
    such as egress spacing (\~2.7 miles) and refuges. VLHC is proposing
    a tunnel egress interval of approximately 3 miles, somewhat longer
    than that finally agreed upon for SSC.

-   The deep shafts of VLHC will be a significant cost.

-   Groundwater activation considerations should be explicitly included
    in site planning.

[Recommendation]{.underline}:

Develop specific proposals for tunnel egress and tunnel safety. Initiate
dialogue with DOE, so that conceptual cost estimates are consistent with
DOE egress requirements.

[Findings]{.underline}:

-   The Preliminary Draft VLHC Study (ed. 4/25/01) incorporates work
    done on ES&H issues for generic new accelerators by the Fermilab
    Committee on Site Studies. (See Section 5.3.7.) This work presents a
    concise catalog of the issues that will need to be addressed more
    specifically as the VLHC study matures.

-   The geographic extent of the VLHC means that an unusually large
    number of off-site people will be affected. Section 5.3.7, Part IIA,
    correctly recommends early coordination with State and Federal
    regulatory agencies to promote understanding of the nature and
    impact of the proposed VLHC. In addition, a vigorous outreach to
    affected communities and the general public will be essential to
    develop popular support for the VLHC and minimize opposition.

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-   The stored beam energy is at unprecedented levels. All failure modes
    involving the beam need to be carefully considered. Good work has
    been done in this regard in the study, but more work is needed: for
    example, loss of rf power at full energy in Stage 2, loss of single
    or multiple dipole correctors, beam loss during beam transfer
    operations.

-   The large scale of the machine will present new issues: e.g,
    search-and-secure strategies, redundancy requirements for extensive
    safety systems, etc.

[Recommendation]{.underline}:

Develop, at conceptual level, written VLHC-specific plans for
coordination with State and Federal regulatory agencies and conducting a
program of public outreach. Coordinate these plans with DOE to gain its
support for initiating this effort.

**[Review Committee:]{.underline}**

Bob Kephart Fermilab Chairman

Gerry Dugan Cornell Accelerator Physics

Jon Ives Consultant Conventional Facilities

Eberhard Keil CERN Acceleratror Physics

Philippe Lebrun CERN Cryogenics

Erich Willen BNL Magnets

Al Zeller MSU Magnets

Mike Anerella BNL Magnets

**[Charge:]{.underline}**

Review the information provided in the \"VLHC Study Draft Report\" that
may eventually evolve

into a proposal to construct a Very Large Hadron Collider (VLHC) at
Fermilab.

Address the following questions:

1\) Are there accelerator science, physics, or engineering issues that
could prevent the VLHC from operating that have not been addressed?

2\) Have the civil construction issues been identified and addressed?

3\) Are there technical issues with the planned low-field magnets and
associated accelerator systems that are unresolved?

4\) Is the construction and installation plan credible?

5\) Have the major cost drivers been identified and is the preliminary
cost estimate for Stage 1 of the VLHC reasonable?

6\) Does the plan to later install a second collider of higher energy in
the same tunnel make sense from the point of view of practical
accelerator issues?

7\) Are there any extraordinary or particularly difficult environmental,
safety or health issues either during the construction or operational
phase that have not been adequately addressed?

Agenda:

It is our desire to finish the presentations on the first day, April 30,
2001, and be available for questions and discussion on the second day of
the review. The report of the review is expected to be a few pages of
written material, plus a verbal close-out.

We have limited the number of speakers to keep things flowing, and to
give the impression that we are an organized and coherent group. Experts
in some of the details are also listed. We expect they will be present
to answer detailed questions at the review (at the discretion of the
speaker) during the times that their piece is presented. Some of these
experts may be called upon by the speaker top make short presentations.
We are also prepared to be present on Tuesday to answer questions or to
make additional presentations as requested.

8:30 **Executive session** (Working breakfast) 30 mins

9:00 **[Introduction:]{.underline}** Overview, machine parameters,
layout, issues

Speaker: P Limon 30 mins

9:30 **[Accelerator Physics:]{.underline}** Co-designing two machines,
lattice for Stage 1, dynamic aperture, other design issues Speaker: M.
Syphers 20 mins

Instabilities and their control Speaker: V. Shiltsev 15 mins

Stage 2 AP issues, lattice, etc Speaker: S. Peggs 15 mins

Other experts present: T. Sen, J. Johnstone, P. Bauer, J. Marriner,
Miquin Xiao

10:30 **[BREAK]{.underline}** 15 mins

10:45 [**Magnets**:]{.underline} Stage 1 arc magnets, correctors,
transmission line, mechanical & thermal design, production and testing,
R&D Status Speaker: V. Kashikhin 30 mins

[Special magnets]{.underline}: IR magnets, Installation I. Tereckine 40
mins

Other experts present: H. Piekarz, I. Novitski, J. Carson, R. Bossert,
P. Schlabach, J. Strait

> M. Lamm, G. Ambrosio, A. Zlobin, J. Volk, N. Andreev,
>
> L.Elementi, V.Tsvetkov, N. Mokhov

1:00 **[LUNCH]{.underline}** (Working Lunch)

1:45 **[Accelerator Systems:]{.underline}** Cryogenics, vacuum, power
supplies, quench protection, data communications, tunnel utilities
Speaker: G.W. Foster 45 mins

Other experts present: A. Klebaner, B. Norris, S. Hays, H. Piekarz, W.
Turner, N. Mokhov

T. Peterson

2:45 **[Conventional systems:]{.underline}** Underground and surface
construction, construction technique,

geology, access issues, detector halls, schedules; ground water, muck
removal/disposal;

service buildings, utilities

Speaker: P Garbincius 60 mins

Other experts present: one or more people from CNA, and A&E firm
designing and

estimating the tunnel, and FESS, the Fermilab construction organization.

3:45 **[BREAK]{.underline}**

4:00 **[Cost Drivers Analysis:]{.underline}** Basis for the estimates,
comparisons with SSC.

Bases for estimate: Speaker: J. Kerby 20 mins

Cost Drivers Analysis Speaker: P. Limon 30 mins

Many experts on costs; most of all the above experts and speakers

5:00 **[Summary:]{.underline}**

Necessary R&D for Stage-1 and Stage-2 Limon & others 30 mins

Upgrade to Stage 2; Magnet designs and R&D status A. Zlobin 20 mins

Conversion to Stage 2, switch-over time P. Limon 10 mins

Experts: Many of the above who worked on the Stage 2 design.

6:00 **[Executive Session]{.underline}**

8:00 **[Dinner]{.underline}**

**[Tuesday, May 1, 2001]{.underline}**

8:30 **[Executive Session]{.underline}** (Working breakfast)

9:00 Working on committee report and closeout statements.

Possible and various **[discussions]{.underline}** with the VLHC team,

as requested by committee members.

12:00 **[LUNCH]{.underline}** (working lunch), and continued working on
closeout.

1:30 **[Closeout]{.underline}**

3:00 **[Adjourn]{.underline}**