CCDTL 3d technical meeting for production of 7 CCDTL modules for Linac4 (#3888, #3889), March 8 - 10, 2010

Participants:

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,
• Ilya Semenev, Head of Workshop Division, VNIITF,
• Dimitry Vavasov, design engineer, VNIITF,

CERN, Geneva:

• Maurizio Vretenar, Linac4 Project leader, CERN,
• Frank Gerigk, ISTC Projects 3888/89 coordinator at CERN, work package leader for accelerating structures in Linac4,

ISTC, Moscow:

• Yuri Malakhov, Principal Senior Project Manager, ISTC

list of talks:

Indico meeting 88584

Technical Summary (A. Tribendis)

1. Current status of works
*2. Project schedule update*
*3. Tentative schedule for the next technical meetings*
*4. Technical aspects*
*5. Tours*
*6. Action List*

1. Current status of works

M.Vretenar gave an overview of the current status of the LHC upgrade program at CERN. According to the new strategy announced at Chamonix Workshop in January 2010

• LP-SPL and PS2 will not be built. The design study has to stop at end of 2010.
• Only Linac4 remains of Phase1 upgrade, injecting into the old machines.
• The booster (PSB) will be (probably) upgraded from 1.4 to 2 GeV and the PS will be consolidated.
• SPL (full power version, 5MW) will continue as a study aimed at a neutrino driver.
• The SPS will be upgraded for higher beam intensity and LHC luminosity.

New LHC schedule is

2010-2011	physics run at 3.5 TeV (per beam)
2012	shut down for splices repair
2013-q3 2014	physics run at up to 7 TeV (per beam)
q3 2014-q2 2015	shut down for Linac4 connection

This new schedule calls for the Linac4 construction would end up not later than q3 2014.

A.Tribendis reported on the current status of works at BINP.

• Drift tube mock-ups and a test vacuum vessel with drift tube girder are completed (in Feb 2010, planned in Dec 2009)
• Auxiliary tools (assembly table, drift tube alignment tools, aluminum dummy drift tubes for measuring resonant frequencies of the cavities upon their arrival from VNIITF) are completed (Dec 2009 as planned)
• Test and measurement area is completed (March 2010, planned in Dec 2009)

Figure1: Test and measurement area with support for test assemblies

M.Naumenko reported on the current status of works at VNIITF.

• Execution drawings have been transferred to the Workshop (January 2010)
• Preliminary machining of 6 half-tank buckets is completed (oversized by 5 mm)
• Manufacturing of the coupling cells has been started (both the parts which are welded to the accelerating cavities and the outer shells)
• Manufacturing of the transportation frames has been started

2. Project schedule update

Due to the delay of materials delivery from CERN and multiple design changes the beginning of manufacturing is delayed by ~5 months. This will require to shift shipment of the last CCDTL module to CERN by ~5 months and to extend the Project by 2 quarters. Although it is still within the Linac4 updated schedule it is important to speed up the 1st module production in order to test it ASAP. It was agreed that VNIITF will try to complete the 1st module cavities and send them to BINP to September 2010. Meanwhile BINP will start immediately manufacturing all 42 drift tube stems and bodies as well as accelerating and coupling cavity tuners. This will allow to have enough semi-finished parts at the time when the cavities arrive from VNIITF to BINP and so to finish the 1st module at BINP by November 2010. The goal is to have the 1st module shipped to CERN to the end of 2010.

At the moment an “optimistic” schedule is:

Milestones	Date
Cavities of module #1 are ready for copper plating at VNIITF *)	to be defined in May 2010
Cavities of module #1 are copper plated at VNIITF	to be defined in May 2010
Delivery of module #1 from VNIITF to BINP	planned for August 2010 (q5 of the project), to be confirmed in May 2010
Drift tubes and tuners for the cavities of module #1 semi-finished at BINP	August 2010 (q5 of the project)
Drift tubes installed in the cavities, cavities tuned, RF and vacuum tests completed at BINP *)	+3 after the cavities are delivered to BINP, November 2010 (q5 of the project)
Delivery of module #1 from BINP to CERN	December 2010 (q7 of the project)
Delivery schedule for modules 2-6 will be clear in the end of module #1 production
Delivery of module #7 from VNIITF to BINP	February 2012 (q11 of the project, project extension is needed)
Drift tubes installed in the cavities, cavities tuned, RF and vacuum tests completed at BINP	March-April 2012 (q12 of the project, project extension is needed)
Delivery of module #7 from BINP to CERN	May 2010, (q12 of the project, project extension is needed)

*) More water cooling channels were introduced to the cavity design based on new results of thermal simulations at 10% duty cycle. This require 50 more SERTO fittings for module #1. The fittings will be sent to VNIITF by CERN disregarding of the 2nd shipment of other missing materials.
**) A set of Helicoflex gaskets is needed for making vacuum tests of module #1 at BINP. The list of Helicoplex gaskets will be prepared by BINP. The gaskets will be provided by CERN.

Figure 2: updated planning

3. Tentative Schedule for the next technical meetings

Date	Place	Visitors	Purpose	Comment
June, 14-18	CERN	VNIITF, BINP	Design review of the support frames
July, 19-21	VNIITF	M.Vretenar (CERN), F.Gerigk (CERN), A.Tribendis (BINP), Yu.Malakhov (ISTC)	Inspection of the cavity production status at VNIITF
September	BINP	M.Vretenar (CERN), Yu.Malakhov (ISTC)	Inspection of the 1st module cavities delivered to BINP and DTs production status at BINP	Visit combined with SAC seminar
November	BINP	F.Gerigk (CERN), E.Page (CERN)	Participation in the rf and vacuum tests

4. Technical aspects

Design and production technology

Two drift tube mock-ups (one completely brazed, the other one electron beam welded at the stem-to-drift tube joint) have been made at BINP to verify new (compared to those used in the ISTC Project 2875) design and technological solutions. During the machining a drift tube body is fixed on a shaft with finger springs inside the beam hole (which is already machined and is used as a reference). This allows machining (turning) entire outer contour of the drift tube in one go (without changing position of the part on a lathe). Final pass is done with diamond machining. Drift tube to stem connection requires forming mating cylinder on the drift tube. This cylinder is machined from a sphere (a ball) on the center part of drift tube. The sphere is not milled off afterwards but remains on the drift tube and so has “diamond machining” surface quality.

Both drift tube mock-ups are vacuum tight and need to be water pressure tested.

As for the joining technique, the conclusions are:

• brazing the drift tube (DT) body (with golden alloy) is more favorable than electron beam welding (EBW) because it was accepted that DT is to be machined after joining the parts in order to get into the “tunable” frequency range (machining is not possible over EBW)
• brazing the stem upper joint (with silver alloy) is also preferable as it allows to machine it afterwards to ensure that it is straight (inclination of the stem in case EBW was used would bring the bottom end of the stem too far off the beam axis)
• electron beam welding of the stem to drift tube joint is quite an appropriate choice, especially taking into account that EBW machine at BINP undergoes an upgrade – a new aiming system has already been implemented (the system picks up backward electrons while scanning across the joint with low current beam; minimum reflection is seen at the welding gap), control system and driving motors are to be replaced. EB-welding is done in a single pass with no “smoothing” (no second pass over the weld with a defocused beam). Measured inclination of the stem after EBW is 4’.

Figure 3 and 4: drift tube prototypes

Quality assurance

• BINP and VNIITF will prepare and send to CERN somewhat generalized description of technological sequences of drift tubes and cavity bodies production.
• BINP and VNIITF will prepare and send to CERN templates of the travelers used to record critical operations and checks during drift tubes and cavity bodies production.
• 4 TIG welded stainless steel samples were presented by VNIITF. The samples were welded by 2 welders at VNIITF. They will be investigated at CERN and a conclusion about qualification of welders will be made.

Transport

For transport all drift tubes will dismounted and the cavities will be filled with nitrogen.

Intertank areas

The tables for the support of the inter-module elements are located on the upstream side. The support of the frames is on three legs, with one leg on the downstream side and legs on the upstream side

Coupling slots

It was agreed that the suggested larger coupling slots can be used for the last modules. The influence on the frequency has been checked by BINP and turns out to be minor. Technologically the larger slot size does not pose a problem.

Cooling simulations

• A flow speed of 0.5 m/s was used for the simulations. It was observed that the efficiency does not increase for larger speeds.
• The channels around the tuner ports have been re-introduced. For a 10% duty cycle and with the new channels the hottest spots reach 152 deg (assuming a Q value of 0.7 x Q0).
• CERN declined the proposal to add more cooling channels to reduce the temperature.

5. Tours

BINP CCDTL assembly and test area (see Figure 1) BINP Experimental Workshop BINP Free Electron Laser

6. Action list:

-- FrankGerigk - 18-Mar-2010