CCDTL 4th technical meeting for production of 7 CCDTL modules for Linac4 (ISTC contract #3888 and #3889), 15-17 June 2010 at CERN


BINP Novosibirsk: Alexey Tribendis (ISTC Projects 3888/89 manager, deputy RF group leader BINP), Yaroslaw Kryuchkov (design group leader)
*VNIITF Snezhinsk:* Mikhail Naumenko (ISTC Projects 3888/89 sub-manager, design group leader VNIITF), Dmitry Vavasov (design engineer, VNIITF), Vladimir Lomakin (Production Supervisor)
*CERN:* Jean-Pierre Corso (responsible for integration for Linac4), Alessandro Dallocchio (responsible mechanical engineer for Linac4), Gilles Favre (Workshop Supervisor, Coordination of Linac4 Prototyping), Luca Gentini (mechanical engineer), Frank Gerigk (ISTC Projects 3888/89 coordinator at CERN, responsible for accelerating structures in Linac4), Jean-Michel Giguet (testing and installation of Linac4 accelerating structures), Mark Jones (Large Scale Metrology Linac4), Tadeusz Kurtyka (Project Office, External Relations), Luz Anastasia Lopez-Hernandez (responsible for civil engineering Linac4), Benoit Riffaud (mechanical engineer), Carlo Rossi (responsible for RFQ construction and 3 MeV test stand), Stefano Sgobba (material science, deputy group leader MME), Patricia Ugena (RF simulations Linac4), Maurizio Vretenar (Linac4 Project Leader), Rolf Wegner (responsible for PIMS design & construction)

List of talks:

Indico Meeting 97706

Supporting documents in EDMS:

Technical Summary

1. Construction Status at VNIITF
2. Construction Status at BINP
3. Water Cooling
4. Welding Qualification
5. Support Frame
6. Quality Assurance
7. Action List

The meeting was opened with a welcome by T. Kurtyka followed by a status report of the Linac4 project (M. Vretenar).

1. Construction Status at VNIITF

Presentation by M. Naumenko:
  • Slides in Indico
  • Approximately half of the modules are pre-machined,
  • The grooves for the water channels of the 1st module are machined and the workshop is now waiting for the approval of the welding procedures by CERN,
  • The SERTO fittings, which are connected to the cavity are bought by ISTC. This resolves the problem that these fittings cannot be bought in Russia directly. The purchase order has already been launched.
  • A solution was presented to avoid the trapping of chemicals (during copper plating) in the hidden volume between cavities and coupling cells. A water channel has been added, which can be used to press water through the hidden volume and flush out any remaining chemicals. This procedure was accepted by CERN. It was suggested by S. Sgobba to measure the PH value of the water which is flushed out to judge whether all chemical remains have been removed. After the water cleaning the warm gas (e.g. Nitrogen) should be used to dry the hidden volume.

Planning for July visit at VNIITF

  • The coupling cells and the half cells of the first tank will be machined. It was agreed that some of the half tanks and coupling cells will be copper plated for the visit.
  • There was concern that the copper plating might be damaged when doing a metrology check (with a rigid bar inserted in the beam pipe along a module) on the assembled module. However, several solutions were discussed how to avoid any damage.
  • A rough alignment check will have been done before the visit.

2. Construction Status at BINP

Presentation by A. Tribendis:
  • Slides in Indico
  • Altogether 50 drift tubes and stems will be prepared. This includes 8 spares, which will not be final machined, and the welding of drift tube to stem will not be done the spares to allow for final machining of the drift tubes on a turning machine.
  • Several aluminum dummy drift tubes with different sizes have been prepared for the tuning. These will be used to determine the precise dimensions of the copper drift tubes to arrive at 352.2 MHz.
  • Rough machining of drift tube bodies is ongoing.
  • It was calculated that around 700 g of gold will be used for the brazings..

Further construction planning

  • June/July: turning operations on drift tubes and stems.
  • July: machining of cooling channels,
  • August: brazing of drift tube bodies, rough machining of 50 drift tubes finished, machining operations of 50 stems finished,
  • The remaining fine machining will be done after measurements with aluminum dummies on the actual cavities.

3. Water Cooling

  • CERN announced that it does not want to install large manifolds, which can be used for the cooling for high duty-cycle (SPL type) operation. Instead a simplified cooling will be installed that only covers the needs of Linac4 operation.
  • CERN decided to reserve space for large manifolds on the ground close to the structures.
  • CERN needs to verify which hoses to connect to the foreseen SERTO fittings (SO 51429-12 weld-on, and SO51121-12-3/8 screw-on), and which connectors to use.
  • For the water pressure tests at BINP, BINP will use simple hoses and no special connectors are needed.
  • The final hoses will be ordered by CERN after a first mounting at BINP. From this test the total amount of hoses will be estimated.
  • BINP will calculate the pressure drop when connecting several channels of a module in series. Ideal would be 2 circuits for the 3 tanks and 2 circuits for the drift tubes. This would result in a "symmetric" heating pattern along the modules. The maximum pressure drop should not be more than 4 bars per circuit and the water flow speed should be ~1 m/s. At the PIMS CERN has calculated a pressure drop of 1.5 bar per circuit (4 discs) when assuming a flow speed of ~1 m/s.
  • BINP will make a suggestion for the design of a 4 fold splitter (mini-manifold) that can be used for the modules.
  • It was decided to place the 4-fold splitters on the ground, in order to block the space already for future, larger manifolds.
  • CERN will bring a sample hose to the visit at VNIITF.

4. Welding Qualification

  • After the tests of the welding samples EDMS 1072458, restricted access, which have been provided at the 3d technical meeting, new welding samples were presented according to the newly proposed welding procedure EDMS 1080835, restricted access.
  • The quality of the weldings and the approach was considered as valid for production by G. Favre and S. Sgobba.
  • For the qualification of the welders, however, it is necessary to obtain production drawings with specification of the welding depths. Only then can be judged if the welders actually did what they were asked to do. VNIITF will send these drawings and CERN will do the qualification of the pieces. It is foreseen to return the welding samples during the visit at VNIITF in July.
  • In order to proceed with the work at VNIITF, it was agreed that VNIITF can start the weldings with the proposed procedure. Nevertheless, the qualification process for the welders (see above) has to be concluded.

5. Support Frame

The current status of the support frame was presented by D. Vavasov. It shows all elements needed to fix intertank supports and water manifolds.

  • The maximum deformation of the frame will be in the range of 0.1 mm at one end of the frame. An effort should be made to reduce this deformation to ~0.05 mm. CERN will supply standard steel profiles, which can be used for the frame and VNIITF will make simulations to test the frame deformation with these profiles. Most gain is expected from profiles with more height (200 instead of 180) mm, while an increase in wall thickness will probably not have much effect (due to the simultaneous increase in weight).
  • For transport all water channels will be closed with an aluminum disk,
  • Quadrupole supports for quads between the cavities of a module can only be fixed on one side of the support, because a two-sided support would interfere with the coupling cells. At present these supports a screwed. It would be preferable to weld these supports to avoid any change in position over time. This however makes the dismounting of the modules difficult, because the longitudinal movement of the half tanks becomes restricted. A certain movement range, however, is needed to remove the cavity bodies from the coupling cells. VNIITF will check which beams can be welded, so that it is still possible to dismount the cavities. In case a welded solution is impossible, CERN will accept the screwed solution.
  • The tilt surfaces will have a distance of 310 -+ 0.5 mm from the axis. The exact distance and the position of the three holes for the laser-tracker target holders will be measured with a precision in the um range and given to CERN.

Assembly procedure:

The module is relatively flexible, which means that it will "find" its own position once it is assembled on a surface and once all bolts are tightened. It is assumed that each cavity of a module will "sit" on 2-3 points (out of 4 supports). The end cavities must be able to move longitudinally to account for heating effects. For alignment there is a precision machined guide rail
  1. The drift tubes are assembled in the half tanks,
  2. The half tanks are joined,
  3. The coupling cells are attached either to the central cavity or to the outer cavities.
  4. The cavities slide on the support into position.
  5. The center cavity is fixed into position longitudinally and transversally.
  6. The feet of the outer cavities are pressed against the guide rail on the support and blocked into their transverse position.

6. Quality Assurance

7. Action list:

action institute/person status/result completed
send drawings of welding samples (including foreseen welding penetrations) to CERN VNIITF, M. Naumenko urgent  
check which quadrupole supports can be welded, so that it is still possible to dismount the modules VNIITF, M. Naumenko in progress  
provide standard steel profiles, which can be used for the support frame CERN, Y. Cuvet done profiles 1, profiles 2 2010-06-17
increase rigidity of the support VNIITF, M. Naumenko in progress  

-- FrankGerigk - 17-Jun-2010

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