Report from the 1st meeting of Linac4 Machine Review Committee

1. Report from the1st meeting of Linac4 Machine Review Committee Günther Geschonke, Stuart Henderson, Alban Mosnier, Ulrich Ratzinger, Yoshishige Yamazaki Linac4 Review Committee

2. Charge • “Monitor progress and provide advice on technical and management issues”. Linac4 Review Committee

3. Introduction • LINAC4 = First step to guarantee the LHC performance and to implement the future upgrade of the Cern injector complex • its design and location fit well the possible later injection into the SPL Linac4 Review Committee

4. Parameters • Full consistent parameter list available • intensity in PSB improved by a factor 2 • Energy 160 MeV OK for PSB • Frequency change 700 (TDR06)  352 MHz MRC endorses the move to a single frequency ! • RF and Beam Dynamics advantages • But the different duty cycles are confusing for the design of the components (power sources, structures...) needs to be clarified for the specs Linac4 Review Committee

5. Beam Dynamics • looks on the safe side, in comparison with other similar projects (SNS, J-PARC) • however, concern about the RF tolerances(0.5% in amp, 0.5° in phase, as needed in DTL) • to check a larger longitudinal acceptance, study the sensitivity to the s law, field ramp ... • small safety margin in DTL • decision between 2 PMQ designs needed soon • think about steerers in empty DT (FFDD lattice) Linac4 Review Committee

6. Ion Source • DESY-type is a robust design and performances already achieved very close to the LINAC4 specs • good lifetime (RF antenna) • no cesium • MRC encourages beam measurements at the TestStand (expected end of 2008) Linac4 Review Committee

7. RFQ • home-made (drawings, machining, brazing) to master all the fabrication steps • tolerances look similar to IPHI RFQ • length divided by 2, but smaller aperture (1.8 mm) • can learn from the IPHI experience • especially, deformation during heat-treatment • concern about dipole modes • consider Pi-mode stabilizing loops to relax mechanical tolerances Linac4 Review Committee

8. Chopper • design looks fine • deflecting structure is OK • concern about the pulse driver • 0.5 kV in less than 2 ns ! • needs specialized FID technology • MRC encourages beam test ASAP • chopper line expected in operation in 2010is it realistic ? Linac4 Review Committee

9. Choice of structures • Question: Is the present choice optimal ? • trade-off between efficiency, beam dyn. & cost • the efficiency study was made, is that the cost optimum wrt energy ranges ? Linac4 Review Committee

10. Drift Tube Linac • Field looks fine (Killpatrick < 1.6) • Drift tubes alignment: mechanical tests could be done soon • Cooling issue: to prevent from local over-heating of the drift tube (PMQ & innertube) • power test ASAP, expected in Summer 2008 • thermal beam loss studies • Now two distinct approaches: decreases the technological risk Linac4 Review Committee

11. CC-DTL • LINAC4 will be the first Linac in the world to be equipped with CC-DTL structures • Sealing : Cu-plated Helicoflex gasketgood for vacuum but RF performance should be checked (alternative ?) • designed for which max. duty cycle ? • additional cooling is required in the tuners • Two distinct technological approaches: what is the conclusion ? Linac4 Review Committee

12. PIMS • robust design (LEP) and even better understood ... • Transient behaviour: well analysed and conclusion was positive • Choice of copper (3D forged or not ?) • in case metallurgical experts cannot answer, make two prototypes with different copperand compare before series production ... Linac4 Review Committee

13. RF power • 1 big 2.5MW klystron? compare the total cost : klystron + RF splitting + possibly High power Phase & Amp control and 2 x 1.3MW klystrons • Specs should allow the average power for SPL • Modulators: space should be enough for the upgrade to SPL requirements • Space issue: no room is left • consider vertical klystron Linac4 Review Committee

14. LLRF • choice: to start from the LHC systemnot far from the LINAC4 requirements • more study on the performance of the phase and amplitude (or I/Q) control • bandwidth of the feedback loops • operation close to saturation: enough margin on power overhead (at the expense of the efficiency) Linac4 Review Committee

15. Beam instrumentation • diagnostics plan looks very promising • but developments are needed to compact the devices Linac4 Review Committee

16. Magnets • even if some magnets are foreseen for the low duty cycle in the 1st stage for obvious economic reasons, a design for all magnets should exist for the SPL requirements Linac4 Review Committee

17. Test-Stand • MRC appreciates the possible extension to 10 MeV • A lot of tests are essential for the success of the project: Take care to additional delays ! Linac4 Review Committee

18. Resources • Time-schedule (5 years ½) is short • organisation: matrix structure of the project (Working Group coordinators / Workpackage responsibles) could optimise the manpower • In parallel, the TestStand, the Design and construction of Linac 4 : a big issuethe total manpower should not be underestimated !!! Linac4 Review Committee

19. Final comments • Very impressed with the new LHC injectors effort, now focused on the Linac4 • Has a complete 10-year scenario for the LHC luminosity upgrade 2007  2017 • Presentations were excellent • MRC appreciates the right approach adopted to meet this big challenge as well as the progress made so far by Maurizio and his Team • Thanks to All (especially to Cecile) Linac4 Review Committee