CERN
PROJECT DOCUMENT IDENTIFIER
FCC-ACC-MIN-0031
CH-1211 Geneva 23
Switzerland
Date :
FCC
EDMS NO.
1548459
2015-09-23
MEETING MINUTES – APPROVED
Subject: Infrastructure & Operation
Coordination Group #18
Date and Time: 2015-09-23, from 10:00 to 11:55
Place: 30/6-019
Participants: Michael Benedikt, Davide Bozzini, Charlie Cook, Eugenia Hatziangeli,
Philippe Lebrun, Volker Mertens (chair), John Osborne,
Guillermo Peon, Aniko Judit Rakai, Ingo Rühl, Peter Sollander
(secretary)
Excused: Paul Collier, Rende Steerenberg, Laurent Tavian
WBS:
File Location/Link: https://edms.cern.ch/document/1548459
Agenda
1. Minutes of the previous meeting
2
2. Combining FCC-hh and FCC-ee: CE challenges
2
3. Power estimates for cooling and ventilation
3
4. CFD simulations for the design of the FCC ventilation system
4
5. Status of ongoing work in IOWG (Tour de table)
6
6. Review of outstanding actions
6
7. AOB
9
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1. Minutes of the previous meeting
Volker welcomed to the 18th meeting. He suggested the following generic
sequence for future IOWG meetings, which was adopted: approval of minutes,
topical presentations, round-table and open actions, AOB. He has asked Peter
to update the list of working group members.
The minutes of the meeting held August 28th were approved with a few
corrections and will be published on EDMS 1537241.
Concerning the length of the machine Michael said that he will provide a short
list of more fine-grained length intervals in the range 93 to 100 km. He
commented that the most important input will come from the iteration of the
civil engineering study, which looks into the non-intersecting 100 km version
protruding more under the pre-Alps.
Volker reported that the Special Technologies Working Group meeting planned
for the beginning of September had been postponed to a later date and does no
longer demand a presentation from the FCC IOWG.
2. Combining FCC-hh and FCC-ee: CE challenges
Charlie presented some of the challenges faced by the civil engineering team
to accommodate both the FCC-hh and FCC-ee machines.
He listed three main issues:
1. Separating the beam lines by up to 13 m at the main interaction points would
require a 1.8 km stretch of double tunnel resp. an enlarged tunnel, on both
sides of the IPs (the rock between the two tunnels would have to be removed
and replaced by concrete once the distance would underpass 3 m).
Michael noted that one may not need a full 6 m diameter tunnel for the lepton
machine. On a question he explained that the current assumption is that we first
build the lepton machine and later the hadron machine and that the design
should allow to house both. John remarked that the civil engineering cost for
these enlarged parts could become enormous. The enlargements would typically
be excavated first with several road headers working simultaneously. The other
parts of the ring would subsequently be drilled with tunnel boring machines
(TBM); two TBMs could be used if a double tunnel option would be chosen, like
in the case of the Eurotunnel. Philippe asked where the top-up ring would be
located. Michael recalled that it is represented by the green line in the graph
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shown in the previous meeting. John proposed to make first cost estimates for
different options of the 4 x 1.8 km.
2. The swing of the FCC-hh ring across the tunnel cross-section by up to 2 m.
Early data indicate that there could be differences in transverse position which
would require a tunnel diameter of up to 8 m.
Michael said that the accelerator design people have to review the position of
the rings. A tunnel diameter of 8 m would be excluded. However there might be
no easy solution as the geometry varies strongly with the assumed cell length.
3. The required span of the experimental caverns is uncertain. Currently there
are two options for the FCC-hh experimental caverns, one with 38 m span
for a twin solenoid detector and one of 44 m for a toroid detector. The FCCee detector sizes are not yet known; 6 m are assumed as radius in the two
options shown.
Philippe suggested to use the ILC detectors as example and added that the
limit on the lepton detector comes from the top-up ring. Michael asked whether
the second tunnel could have a smaller diameter. John replied that 6 metres is
the standard European tunnel-boring diameter and that a smaller diameter may
actually be more expensive. Ingo asked whether the cavern size already
included the space for cranes. Charlie replied that the height will be defined by
the requirement to get the detectors into the caverns. John believed that there
is enough height above the detectors. Volker asked John to produce a more
detailed design of the cavern cross section. Guillermo asked whether there
would be separate service galleries; Volker confirmed that this should be
foreseen.
3. Power estimates for cooling and ventilation
Davide presented the latest results from the power consumption study of the
LHC, including data for this year’s very warm summer. In slide 3 the data for
June-July-August of 2012 (beam energy 4 TeV, blue data points) and 2015 (6.5
TeV, orange) are compared (without experiments which account for another ca.
20 MW). The power of the cooling and ventilation systems follows the ambient
temperature (slide 4), with a peak 12 MW daily average on the hottest day.
Overlaid are short-term variations from the machine operation. While the
cryogenics load is more or less constant the power consumption from magnet
powering or RF and consequently the thermal load can vary from one day to the
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next; this has not been detailed further. Volker noted that the latter seems to
dominate.
Davide explained that it would be interesting to dispose of a full year worth of
data, to derive more information on the dependencies. EN-EL will demand a
Fellow to study CERN’s power consumption in more detail.
Guillermo noted that there is a significant difference between the calculated
(i.e. expected) consumption for EN-CV and what EN-EL is measuring (slide 7).
Davide noted that the 10 MW for general services also include the power drawn
from all the sockets around the machine; cooling and ventilation is only a part
of it. Michael remarked that the 75 MW of power installed for CV include also
the spares, backup systems, etc. which are not running all the time; Guillermo
confirmed that. The 31 MW correspond to what is in principle all the time
running, resp. could be running; clearly services for which there was not demand
from the thermal load would be (automatically) switched off.
Peter inquired about the next steps. Guillermo said that one should look more
in detail what is running or not, and compare again the calculated and measured
values. Peter wondered how that would scale to FCC. Philippe commented that
to first order the ventilation needs scale with volume and the cooling needs by
dissipated power. He considered the cited peak consumption of 22 MW to be
wrong. The installed power and the average power consumption shall not be
mixed. Michael also cautioned against “over-designing” the system. Volker
suggested complementing the estimates by a bottom-up compilation departing
from the present draft specifications.
Action: EN-EL and EN-CV to understand better the consumption data and their
main contributors and reduce the apparent discrepancies.
4. CFD simulations for the design of the FCC ventilation system
Aniko Judit Rakai presented first results of numerical CFD simulations for the
design of the ventilation system (CFD = Computational Fluid Dynamics).
She noted that the FCC tunnel has neither a simple (pipes, supports, cable trays)
nor a regular (fire curtains) cross-section. To make the calculations less
complicated simplifications need to be made. The fire curtains are supposed to
be open during normal operation. Assuming isothermal conditions is another
start parameter.
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3D (software/computer based CFD) calculations have been carried out and
compared to values obtained using an analytical 2D approach (textbook
equations); in both cases the Navier-Stokes equations need to be solved all
along the length of the tunnel. Similar results have been obtained. It seems
therefore reasonable to use an analytical method to estimate the pressure drop
along the FCC tunnel.
Volker observed that the value of ACH = 0.5 (air change rate/h) is probably too
low. In LHC it would be closer to or above 1. Michael noted that the pressure
drop is dominated by tunnel friction and asked how important the surface quality
of the walls is. Aniko replied that it is important that the tunnel is “hydraulically
smooth”. Philippe commented that this condition is easy to reach and that the
habitual surface of accelerator tunnels can indeed be considered smooth. Volker
asked how equipment like cable ladders, support posts etc. can be included in
the model. Aniko answered that she can consider the equipment as an
obstruction, knowing the size of it.
Philippe noted that the electron machine should also be studied. It is different
in that it will bring heat into the tunnel, unless there is a way to absorb a
significant fraction of this heat, like as in LEP into the non-insulated cooling
pipes. The isothermal assumption may be too simplistic. The booster ring shall
be added as well.
On a question about the sensitivity of the results obtained with respect to the
tunnel lengths Aniko replied that it is linear with the length and pressure
assuming constant friction and curtains in regular intervals.
A priori the safe passage compartment should be slightly over-pressurised with
respect to the machine tunnel. Philippe remarked that the difference shall be
no larger than 50 Pa to allow opening (or closing) the doors to the safe passage.
To avoid the pressure difference to build up there must be several ventilation
feeding points into the tunnel sections. In case of loss of ventilation (power cut,
fault) relief valves should ensure that the safe passage can still be accessed
without too big difficulties. NDLR (following meeting on October 28th): André
commented that the over-pressure should be between 20 and 80 Pa. This is still
ok to open or close doors.
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5. Status of ongoing work in IOWG (Tour de table)
Michael suggested to start drafting the positions of technical infrastructure
around the ring. Civil engineers and FCC-ee machine designers shall discuss
together to converge on the layout. Michael recalled that an FCC-ee optics and
beam dynamics review is planned for October 14th (with an FCC-hh injection
energy review two days later) and that the tunnel integration question will come
up.
Volker noted that the preparation for the next FCC week has started. The
structure of the technical infrastructure session will soon need to be prepared.
Volker mentioned the goals listed by Philippe after the 2015 FCC week and
said that he has started to contact the people in charge of work packages to
know what has been done so far and what can be done before the FCC week in
April 2016.
Davide is looking for a contact person who has been involved in the electrical
work for the Gotthard tunnel. John has a contact at AMBERG who in turn can
find a person for questions about the electrical distribution system.
John is still collecting data for the geological tools. With that he will be able to
provide a more detailed risk study by the end of this year. Charlie noted that
Youri Robert has set up, in collaboration with GS-SE, an FCC-specific page
within the GIS system, where various tunnel footprints can be superimposed on
other layers of information (satellite image, topographic maps, height model,
etc.).
Peter reported that a collaboration with TU Delft has started in the area of the
RAMS study. A small workshop was held at CERN mid-September to define the
work for a more in-depth study of cryogenics reliability. Next week there will be
a RAMS workshop at the Tampere University which is part of the FCC RAMS
team. The first results from the RAMS study will be presented at the FCC I&O
meeting in October.
6. Review of outstanding actions
Actions are ordered by completion status, new and ongoing actions first. Status
is one of {New, Ongoing, On hold, Completed, Postponed or Cancelled}.
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Description and Comments
Develop a map indicating electrical power and water cooling
needs at different locations around FCC ring.
Status
Ongoing
Assigned
IOWG
Identify limits on sector lengths coming from technical
Ongoing
infrastructure and accelerator systems
Mauro: no hard limits, in the worst case add ventilation booster.
IOWG,
Accelerator
systems
Progress with study leading to selection on single or double
tunnel option for work towards CDR.
Ongoing
IOWG
Estimate radiation doses, “cooling” times and remote-handling
needs for removal of LHC insertions towards its use as FCC
high-energy injector (see Markus’ presentation on 29th July).
Ongoing
HSE
Define straight sections to detail level, which permits
documenting infrastructure requirements and constraints.
Michael will provide the list, lengths of RF sections, collimators
etc.
Ongoing
Accelerator
design
Study ground settling in newly excavated tunnel and impact on
machine alignment. Checking tunnel stability. Tunnel and
caverns are concerned.
Ongoing
M. Jones,
Accelerator
physics
Create a top-down operation model of the injector chain and
use for FCC availability studies.
Presentation in October 2015
Ongoing
RAMS team
Define work topics, work period and supervision line for all
personnel requests.
Ongoing
Supervisors
Review practical limits on magnet mass and length.
Not started
IOWG
Review and validate WBS items.
Long term.
Ongoing
IOWG
Elaborate and communicate work package descriptions
(identified by 4 digits in column A of the WBS) of the
Infrastructure & Operation study: 5 lines or about 100 words
Ongoing
IOWG
Pending input from magnet study group
with a general description and a focus on the work foreseen.
Long term.
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Description and Comments
Detail cooling and ventilation power consumption estimates.
Presentation in this meeting. To be refined.
Status
Ongoing
Assigned
G. Peon
D. Bozzini
Michael inquired about the option of the 2nd tunnel. Philippe said that RP had
indicated that the 2 tunnels should be separated by 7 m of rock; upon that the
2-tunnel option had been virtually abandoned. Doors were an issue; a chicane
and an air look would be needed at each connection between the tunnels. NDLR
(following meeting on October 28th; cf. comments from Ralf and Michael in
minutes of meeting #19): André commented that the demand for 7 m distance
applies only for the case that access was needed with beam on. Moreover the 2tunnel option should not be abandoned for some critical straight sections in order
to bypass highly radioactive areas, e.g. collimators. The main argument is
probably to have a separate fire-proof area (the “safe area”) and be able to
prove that access to it can be guaranteed under all conditions (pressure drop).
From the volume a single 6 m tunnel would roughly correspond to two 4.5 m
tunnels while providing more flexibility. John concurred, saying that the m3 to
excavate would be similar but the cost surely not. ILC and CLIC all concluded
that a single tunnel would be ok. Michael said that a summary presentation
listing the advantages and drawbacks of both solutions shall be foreseen towards
the end of the year. NDLR (following meeting on October 28th): André noted that
this had already been done for Safety. Also the accessibility matrix has already
been revised by HSE.
Philippe said that the regular arc cell shall be elaborated and integrated to a
greater level of detail, to include all known equipment. The cross section shall
also be refined including the transport gear for material as well as the “people
mover”. Guillermo argued that it would be difficult to know the requirements
for CV at this stage. Philippe replied that one should do an “educated guess” or
scale up.
Michael explained the idea to lump the RF section of the FCC-ee machine in two
zones, at 90 and 270° with respect to the experiments. To make up for the
energy loss along the circumference the power converters would be “tapered”,
i.e. the machine would be more sectorised, with different converter settings
along the arc.
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John and Charlie inquired about the timetable for the study of the nonintersecting 100 km option. Volker confirmed that the study shall be concluded
by December 2015, allowing a full risk/cost comparison between the all main
variants.
Michael and Volker noted that the registration for the FCC week 2016 will soon
open. The programme for the IO related session(s) needs to be worked out;
potential contributors shall be identified. Michael suggested to form various
working groups.
7. AOB
The next meeting will be held on October 28th with three main topics:
-
Update on the cryogenics study (L. Tavian);
-
Deformations and movements on CERN installations (M. Jones);
-
First results from the reliability study (A. Niemi).
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