1. Report from the 1st meeting of Linac4 Machine Review Committee
Günther Geschonke, Stuart Henderson, Alban Mosnier, Ulrich Ratzinger, Yoshishige Yamazaki
30 January 2008
Linac4 Review Committee

2. Linac4 Review Committee
Charge
“Monitor progress and provide advice on technical and management issues”.
30 January 2008
Linac4 Review Committee

3. Linac4 Review Committee
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
30 January 2008
Linac4 Review Committee

4. Linac4 Review Committee
for PSB
for LP-SPL
for HP-SPL
400 s
1.2 ms
1.1 Hz
2 Hz
50 Hz
0.044 %
0.24 %
2 %
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
30 January 2008
Linac4 Review Committee

5. Linac4 Review Committee
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)
30 January 2008
Linac4 Review Committee

6. Linac4 Review Committee
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)
30 January 2008
Linac4 Review Committee

7. Linac4 Review Committee
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
30 January 2008
Linac4 Review Committee

8. Linac4 Review Committee
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 2010 is it realistic ?
30 January 2008
Linac4 Review Committee

9. Linac4 Review Committee
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 ?
30 January 2008
Linac4 Review Committee

10. Linac4 Review Committee
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
30 January 2008
Linac4 Review Committee

11. Linac4 Review Committee
CC-DTL
LINAC4 will be the first Linac in the world to be equipped with CC-DTL structures
Sealing : Cu-plated Helicoflex gasket good 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 ?
30 January 2008
Linac4 Review Committee

12. Linac4 Review Committee
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 copper and compare before series production ...
30 January 2008
Linac4 Review Committee

13. Linac4 Review Committee
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
30 January 2008
Linac4 Review Committee

14. Linac4 Review Committee
LLRF
choice: to start from the LHC system not 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)
30 January 2008
Linac4 Review Committee

15. Linac4 Review Committee
Beam instrumentation
diagnostics plan looks very promising
but developments are needed to compact the devices
30 January 2008
Linac4 Review Committee

16. Linac4 Review Committee
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
30 January 2008
Linac4 Review Committee

17. Linac4 Review Committee
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 !
30 January 2008
Linac4 Review Committee

18. Linac4 Review Committee
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 issue the total manpower should not be underestimated !!!
30 January 2008
Linac4 Review Committee

19. Linac4 Review Committee
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)
30 January 2008
Linac4 Review Committee