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CLIC Technical Committee - Meeting #61
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Europe/Zurich
18/3-030 (CERN)
18/3-030
CERN
CLIC Technical Committee - Meeting #61 (26 Jun 2012)
Present: Nuria Catalan Lasheras; Roberto Corsini; Paolo Ferracin; Michele Modena; Germana Riddone; Alexandre Samochkine; Hermann Schmickler; Lars SobyChaired by: Dr. Schmickler, Hermann
General Information
Herman gave some information on the Japanese program for accelerator research. The goal of the program is to build a centre of excellence at KEK to work on already approved projects. The program would be funded equally by KEK and the Japanese science ministry and it will hire around 100 researchers. Marc Ross would lead the effort. A number of so called principal investigators may belong to another organization but have to spend 10% of their time at KEK. Hermann and Frank will represent CERN. Hermann has suggested to reduce the scope of the programme, currently aimed at general interest research, to a number of concrete projects. It this proposal is accepted, a document will have to be produced shortly specifying the areas of research useful to CLIC.Recall of the specifications and present design of multiple correctors. M. Modena
Michele reminded the current status of the MBQ and steering correctors (see slides). For the lab and CLEX modules, full size quadrupoles are being built as prototypes. However, in the CDR, the baseline quads are shorter to accommodate an eventual corrector. Steering coils were discarded as the field perturbation in the quadrupole field, already saturated, exceeds the tolerated values. Also, the quad is not designed to cope with the ramping of the dipole at 50Hz.Even if the current design is based on moving the quadrupoles to provide steering, the design and manufacture of dipole corrector prototypes is been done in parallel. Together with EPC, the magnet design was chosen and it was decided that the maximum stroke in a given cycle will be a fourth of the total range (EDMS 1058713).
The tooling for winding the coils is being prepared at CERN with the goal to use it also as part of the impregnation mould. The manufacture of the lamination stack is for the moment the biggest challenge as the required tolerances (0.01mm) cannot be achieved by laser cutting. For larger productions, fine blanking will be adopted. An independent test is going to be done at CERN where laminations with extra material are going to be machined by EDM (electro discharge machining).
The first dipole prototype will be ready by the end of the year.
Present integration studies of dipole correctors in main and driving beam. A. Samochkine
Alexander showed the studies made up to now to integrate the small dipole (83mm) inside the CLIC module (see slides). For the moment, the work has been done for T1 and T4 quadrupoles. The positioning of the dipole has to be done partially inside the quadrupole winding. Nevertheless, for T1, the quadrupole has to be shorten by 20 mm with respect to its original value. For the T4 case, the quadrupole has to be shortened by 63 mm.For the drive beam, there is no possibility to install a dipole corrector in the present module. Roberto pointed out that the field quality requirements can be relaxed for the drive beam and a steering coil could be envisaged. Technical specifications of the required dipole winding need to be provided (Action: Daniel)*. When discussing the possibility to move the quadrupoles using the existing actuators, it was recalled that both F and D quadrupoles sit in the same girder.
Hermann expressed his concern about the current baseline consisting of moving the girder with the existing piezos. When doing so, the BPMs also move and are recalibrated to the new estimated position through software. Given that the required movement is orders of magnitude larger than the BPM resolution, a random or systematic error in the actual displacement will spoil the BPM measurement adding noise and the steering may not converge. He proposed to test experimentally the accuracy of the displacement (Action: Kurt, Lars) and feed this result to a simulation of the steering (Action: Daniel).
Nuria asked if a similar effect could be expected from the perturbation of the quadrupole field when exciting the dipole as a consequence of their proximity in the module. The cross talk between both magnets has been calculated but not fed into simulations. However, this will not affect the BPM.
Eventually, for the last ten cells in the magnet for which the quadrupole field is saturated, T1 could be substituted by a T2 by sacrificing some acceleration structures.
In conclusion, as soon as the quadrupole is available, displacement of the full girder with the piezos should be tested and quantified. The first aim of the experiment should be to check that the final displacement of the quad is indeed orthogonal to the piezo plane. (Action: Michele, Kurt).
AOB.
Hermann inquired about the possibility to test the 010 configuration using the parts in the 1004 module. Germana replied that this would be prepared and tested before the assembly of the last 4 sub-module (Action: Germana).The summary of the thermal tests in the lab module will be presented during next CTC the 17th of July.
Nuria Catalan Lasheras
27 June 2012
27 June 2012
* After the meeting, Michele found a document from E. Adli dated 24 March 2009 stating:
"1.2 Beam-based correction
The Decelerator requires beam-based correction [1]. For this purpose either quadrupoles on movers or dipole corrector coils, in both the horizontal and the vertical plane, must be used. For movers we estimate a maximum displacement of ±1mm in each plane to be sufficient for normal operation as well as tune-up. The corresponding maximum corrector integrated field required is 12 mT m. Whether movers or corrector coils are to be used is still to be decided (cost issued needs to be addressed)."
"1.2 Beam-based correction
The Decelerator requires beam-based correction [1]. For this purpose either quadrupoles on movers or dipole corrector coils, in both the horizontal and the vertical plane, must be used. For movers we estimate a maximum displacement of ±1mm in each plane to be sufficient for normal operation as well as tune-up. The corresponding maximum corrector integrated field required is 12 mT m. Whether movers or corrector coils are to be used is still to be decided (cost issued needs to be addressed)."
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