CCDTL: extension of #2875, new ISTC project on CCDTL series production, September 07 at CERN

list of talks:

• Current status of the ISTC project 2875 extension (M. Naumenko)
• CCDTL design (M. Naumenko)
• Assembly, tuning and commissioning experience of the CERN and ISTC CCDTL prototypes (M. Pasini)
• Experience with BINP/VNIITF CCDT prototype and proposed design modifications (A. Tribendis)
• CCDTL for Linac4 (A. Tribendis)
• CCDTL cavity layout (M. Pasini)

Technical summary (A. Tribendis)

of the meeting on the CCDTL at CERN, 08.09 – 14.09.2007

Participants:

BINP, Novosibirsk: A.Tribendis, Ya.Kryuchkov
VNIITF, Snezhinsk: M.Naumenko
CERN: M.Vretenar, M.Pasini, F.Gerigk, R.Wegner, Y.Cuvet, P.Bourquin, S.Ramberger

Main results:

1. Water cooling system

CCDTL will operate in 2 modes – with low (0.1%) duty cycle within Linac4 and with high (5%) duty cycle within SPL in the future. So thermal loading in the 2 modes of operation will be different. Water cooling channels of the CCDTL module section were designed to remove more heat than is now foreseen for SPL mode of operation and with a safety margin. So water cooling channels scheme should be revised in order to investigate the possibility to reduce the number of channels. Cooling channels connection schemes might be different for the 2 modes of operation. So the design should allow easy change of the connection scheme. In order to do this, each cooling channel should end up with threaded adapter located as close to the CCDTL shell as possible. SAGANA-type connections should not be used for series production. Cooling channels should be tested at 16 bars. Operating pressure at the supply side is 6-8 bars, at the return side – 2-3 bars. Inlets and outlets of the cooling channels on the CCDTL should be looking towards the waveguide feeding lines. Water manifolds will be mounted on the frame at the waveguide window side.

2. Drift tube connection

A design of dismountable drift tube connection was presented. The design allows adjustment of the drift tube position after it’s installation into the half-tank. This relaxes the manufacturing tolerances substantially. The design allows alignment of the drift tube with accuracy exceeding the CCDTL requirements. The drawbacks of the design are: 2 Helicoflex seals and the necessity to repeat the drift tube alignment procedure every time when the gasket is replaced. Another option with easier assembling procedure should be considered. Such a design might be based on the DTL design, where the alignment precision depends completely on the manufacturing accuracy.

3. Ports

CCDTL module will have the following ports. Each half-tank will have 1 side tuner port. Each coupling cell will have 2 (top and bottom) tuner ports. Each cavity (tanks and coupling cells) will have side rf pick-up port. Each tank will have bottom ion pump port. VARIAN ion pumps with pumping speed of 400 (200) liter/sec will be used. Each module will have one side rough pumping port and for vacuum gauge. Side tuner ports on the tanks should be looking towards the waveguide feeding lines. The number of vacuum ports will be defined by CERN vacuum experts.

4. Support frame

A new design of the support frame was presented. The design allows easier access to the components. The design allows having 2 tuner ports on the coupling cell. The design is acceptable in general. Mechanical properties of the frame with different load should be calculated. Bases for placing the 2 quadrupoles between the tanks in a module should be foreseen in the frame design.

5. Waveguide to half-tank connection

A new design of the waveguide to half-tank connection was presented. Brackets and guiding studs are used for lifting the WG T-section and for additional stability of the connection. The height of the half-tank cut-off waveguide piece is increased and the one on the T-section is decreased. This will make the assembly easier. Dimensions of the waveguide iris and waveguide short circuit position should be calculated for all 7 modules.

6. Analysis and improvement of copper plating technology

Model for copper plating technological studies was presented. The model is a full-size half-tank. During technological studies an electrolyte with higher copper content (СuSO₄ -250 g/liter, H₂SO₄ -70 g/liter) and modified tools will be used. The approach was accepted.

7. Analysis of the rectangular vacuum flanges production technology (surface preparation) Vacuum joint test model was presented. Test sequence was discussed. 2 HNV-type Helicoflex gaskets have been provided by CERN. 4 more HN-type Helicoflex gaskets will be purchased by CERN and sent to Snezhinsk. The tests should start with testing stainless steel surface right after machining with HNV-type gasket. Then the sealing surface should be copper plated and tested again with new HNV-type gasket. Then the test should be repeated with HN-type gasket. Then hand polishing should be applied to copper plated surface and the test should be repeated once again with HN-type gasket. Vacuum tightness of the joint should be tested by helium leak detector at sensitivity of 1×10−10 mbar×liter/sec.

8. Alignment Each half tank should have 2 perpendicular alignment reference pads to define the beam axis. Quadrupoles between the tanks will be installed on their own alignment tables which should be placed on the support frame. Quadrupoles between the modules will be installed independently of the CCDTL frames.

-- FrankGerigk - 17 Sep 2007