Minutes of the Linac4 Technical Design Committee

meeting no. 5

date: 5 September 2006

present:

AB/RF M. Pasini, R. Wegner, C. Rossi, M. Paoluzzi, M. Vretenar
AB/ABP G. Bellodi, A. Lombardi, E. Sargsyan, Th. Meinschad, S. Maury
AB/BI R. Garoby
AB/OP K. Hanke
AB/BT W. Weterings
TS/CV Y. Body
TS/MME M. Timmins, Y. Cuvet
TS/CE A. Lopez
TS/SU M. Jones, T. Dobers
AT/MTM W. Venturini

agenda

1. Progress in the South Hall Layout (M. Timmins)
2. Progress in civil engineering for the South Hall option (L.A. Lopez- Hernandez)
3. The option of Linac4 in the position of Linac2 (L.A. Lopez- Hernandez)
4. Status of Technical Design Report preparation (M. Vretenar)
5. Tour de table
6. next meeting

1. Progress in the South Hall Layout (M. Timmins)

The integration of the different linac components in the South Hall (accelerating structures, klystrons, shielding, transfer line,…) has been studied to a certain extent. Among the problems that have appeared and the solutions that have been proposed during the discussion:

  • The linac is now shorter by about 5 m with respect to what was assumed in the first drawings. At first, was considered moving forward the Front End (3 MeV test stand), but then it was preferred to keep a spare length of 5 m at the end of the linac. This distance could be used for additional diagnostics, or could allow reducing the gradient in some accelerating structures, with advantages in terms of RF power consumption. Another option could be starting the transfer line from a more backward point, with the advantage of avoiding the interference with the kicker platform.
  • If the starting position of the transfer line is maintained, the LEIR kicker platform has to be removed and equipment moved either on the LEIR visitors’ platform, or in front of the Linac4 shielding. Both options are feasible, but they risk having a high cost.
  • The clearance between the overhead crane and the shielding blocks at the high-energy end is only 40 cm. Positioning of the waveguides over the shielding can be impossible and the crane could not be used for the installation of the concrete blocks on the roof. The conclusion is that the height of the linac tunnel should be reduced (to 2.5 – 2.7 m) at the high energy side, to increase the clearance for the crane.
  • An access platform for maintenance can be provided on the right side of the linac tunnel. This platform is however incompatible with a reduced tunnel height in the high-energy part.
  • A platform for installing the klystron over the equipment racks has been studied, but on one hand its cost is high (about 400 kCHF) and on the other hand there is now enough space on the floor for placing klystrons, circulators and power supplies. In conclusion, the idea of the platform is abandoned, but one has still to find the place for about 80 racks for the linac. One option is the area below the MCR, which is either air conditioned or easy to air condition (stabilized temperature appears to be a requirement for the low-level RF). The MCR itself should be reserved for the Linac4 control room.
  • Survey has been considered, and one is looking for solutions to provide a free line of sight for survey on the left of the linac (looking towards high energy). At the moment on that side there is interference with the RFQ input waveguides.

2. Progress in civil engineering for the South Hall option (L.A. Lopez- Hernandez)

The installation of Linac4 in the South Hall still presents many open questions (asbestos removal, preparation work, status of the building roof, etc.). Moreover, it is very difficult to estimate the cost of rehabilitation for an old building. The list of water and electrical requirements has been received, and the estimations are going to be prepared by TS. In the discussion, it turned out that it is very difficult to estimate the safety margin to be applied to the bare consumption figures in order to compute the required installed electrical power and water flow. In some cases, it is even proposed to apply a factor 4. It was decided that a consistent safety margin should be applied, unless it gives a too a high increase in the costs (for example, use of another cooling station or similar).

3. The option of Linac4 in the position of Linac2 (L.A. Lopez- Hernandez)

The ST has a certain preference for making new buildings instead of recuperating old ones, because of the better control of all the costs. The option of reusing the Linac2 building foresees the construction of a 35m long tunnel or surface building for machine and klystrons in the extension of Linac2 under the Mont Citron. A surface building (363) could be extended and used for the klystrons.

Discussion:

  • The length of 35m is not fixed yet, and the new tunnel could be longer, up to the limit given by the road.
  • This layout has still to be checked by the radioprotection, which has to see how much shielding has to be added to the “triangle” area of the South Hall and towards Linac3. Another concern is the shielding towards the present Linac2 equipment and amplifier galleries.
  • Commissioning of Linac4 in the position of Linac2 could be done in two steps. The low-energy part of Linac4 up to 50 MeV could be commissioned in the new building while Linac2 is running. Successively, during a first shut-down Linac2 could be removed and replaced by a transfer line, to inject from the new linac a 50 MeV beam into the PSB. Lately, during a second shut-down the rest of Linac4 could be installed and commissioned.

4. Status of Technical Design Report preparation (M. Vretenar)

Unfortunately, only few more contributions have been received in the last month. The deadline for the complete report is now approaching quickly, and a first complete draft should be ready by mid-October for the first Council meeting (1 month from now!). The most notable missing contributions are:
  • the low level RF
  • the magnets
  • the power supplies
  • the vacuum
  • the measurement and dump line
  • the booster injection simulations

The contributors are strongly required to send their document as soon as possible. The TS contribution has an extended deadline to September 15th, and this date should be by all means respected. Moreover, we need an updated cost estimate (material and manpower) by end of September. Some old numbers are going too far (in particular, the old TS estimates by M. Pohler), and we have to provide soon new numbers, before it is too late.

Tour de table

  • W. Weterings reminded that the PFN for the booster distributor are too large for the existing building, and a new building has to be foreseen near the PSB. A. Lopez will look at it.

next meeting:

Tuesday October 10th, 14:00, room 354 1-001

-- MaurizioVretenar -

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