1. Linac4 & SPL Status of preparation and Opportunities M. Vretenar (R
Linac4 & SPL Status of preparation and Opportunities M. Vretenar (R. Garoby)
End of the Trilogy on SPL-Linac4…
DAPNIA 9/01/2006

2. SPL = Superconducting Proton Linac
a 4 MW / 3.5 GeV linear accelerator to:
increase the performance of the CERN high energy accelerators (PS, SPS & LHC)
address the needs of future physics experiments with neutrinos and radio-active ion beams
DAPNIA 9/01/2006

3. SPL (2) Initial design (Conceptual Design Report 1):
“optimized” for a neutrino factory
assumed the use of LEP cavities & klystrons up to the highest energy
Revised design in progress
(CDR 2):
based on updated physics’ requests
using 704 MHz RF and bulk Niobium cavities
in collaboration with CEA-Saclay & INFN-Milano
to be published in 2005
Up-to-date information is available:
on the CERN EDMS
on the SPL site:
DAPNIA 9/01/2006

4. Three stages are planned:
SPL stages
Three stages are planned:
Stage 1: 3 MeV test place
Þ development and test of linac equipment, beam characterization
Stage 2: Linac4
New linac replacing the present injector of the PS Booster (Linac2)
Front-end of the future SPL
Þ improvement of the beams for physics (higher performance and easier operation for LHC, ISOLDE etc.)
Stage 3: SPL
New injector for the PS, replacing the PS Booster
New physics experiments using a high proton flux
Þ improvement of the beams for physics and possibility of new experiments
DAPNIA 9/01/2006

5. Linac4 design DTL CCDTL SCL Drift Tube Linac 352 MHz 13.6 m 3 tanks
3MeV
40MeV
90MeV
160MeV
DTL
CCDTL
SCL
Drift Tube
Linac
352 MHz
13.6 m
3 tanks
5 klystrons
4 MW
Cell-Coupled Drift Tube
Linac
352 MHz
25.2 m
24 tanks
8 klystrons
6.4 MW
Side Coupled
Linac
704 MHz
28 m
20 tanks
4 klystrons
12.5 MW
3MeV line
(H- source, IPHI RFQ, chopper line)
Duty cycle:
0.1% phase 1 (Linac4)
15% phase 2 (SPL)
4 different structures, (RFQ, DTL, CCDTL, SCL) 2 frequencies
Total Linac4:
86.3 m ,
18 klystrons
Beam current: 40 mA (avg. in pulse), 65 mA (bunch)
DAPNIA 9/01/2006

6. Linac4 Schedule
 Linac4 (160 MeV, H-) will double the intensity and brightness of the beam out of the PSB.
 Support by the DG for a decision on construction at end 2006.
Tentative schedule:
Continuation of R&D
2006 (end) Linac4 Design Report (basic design frozen)
2007 Detailed design (=execution drawings!), definition of construction strategy, attribution of contracts
Construction
2010 End of installation and commissioning
DAPNIA 9/01/2006

7. IPHI HIPPI ISTC # 2888 & 2889 ISTC # 2875
Linac4 collaborations
INDIA: klystron power supplies
CHINA: quadrupoles, bendings, buncher
IPHI
HIPPI
ISTC # 2888
& 2889
SCL
ISTC # 2875
Network of collaborations for the R&D phase, via EU-FP6, CERN-CEA/IN2P3, ISTC, CERN-India and CERN-China agreements.
The same network should support the construction of Linac4.
DAPNIA 9/01/2006

8. Shunt Impedance Effective shunt impedance ZT2 along Linac4
Superfish calculation, not scaled
The section between ~90 MeV and ~ 200 MeV is the most difficult for modern linacs:
DTL-like structures present a sharp decrease in shunt impedance.
Superconducting structures are not yet effective (low real estate gradient).
Usual p-mode NC structures (CCL, SCL) at double frequency are considered expensive.
DAPNIA 9/01/2006

9. The nominal Linac4 solution: a Side Coupled Linac
Klystron
[#]
Tanks/Kly.
Gradient E0
[MV/m]
Power/Kly.
[MW]
Energy
[MeV]
N cells/tank 1 5 4
3.00
107.42 11
3.06
125.16
3.15
144.16
2.59
160.2
Tot. Klystr.
Tot. tanks
Average Grad.
Tot. Power
Tot. Length.
[m] 20
12.46
28.02
RF power source: 4 MW, 704 MHz klystrons similar to SNS –
(offer from Thales)
DAPNIA 9/01/2006

10. More on the SCL
Chain of cells, coupled via slots and off-axis coupling cells.
Invented at Los Alamos in the 60’s.
Operates in the p/2 mode (stability).
CERN SCL design:
Each klystron feeds 5 tanks of 11 accelerating cells each, connected by 3-cell bridge couplers.
Quadrupoles are placed between tanks.
How it looks like
DAPNIA 9/01/2006

11. Example: the SCL for SNS
DAPNIA 9/01/2006

12. Side Coupled cells
Copper units made of one half accelerating cell and one half coupling cell, precisely machined (0.03mm) and brazed.
2 half cells with magnetic field lines
1 half cell with one half bridge coupler
DAPNIA 9/01/2006

13. SNS SCL Construction
Cell precision machining on a lathe – RF measurements after machining and before brazing
DAPNIA 9/01/2006
Vertical brazing in the oven – final RF tuning, bead-pull measurement of field in the module

14. Options for CERN SCL construction
Present status of Side Coupled Linac studies:
* Studied inside HIPPI, jointly by CERN and LPSC Grenoble.
Linac design (CERN), thermal analysis (LPSC), RF errors (LPSC, CERN), cell design.
* Cold model will be built by LPSC (2006).
* Technological model (Cu, brazed) will be built by BINP-Novossibirsk (2006).
* INFN-Naples joins now the collaboration (bridge coupler design, stability).
The construction of a Side Coupled Linac requires a difficult integration of technologies:
Procurement of forged copper - Precision machining on Cu – First RF tuning before brazing – Brazing – Final RF tuning.
Note that these technologies are very similar to those used for RFQ’s!
Options for construction ( ):
Contract with ACCEL (has built the SNS SCL).
Construction in Russia (some interest by BINP).
Construction in Italy (INFN-Na ready, INFN interest still to be checked)
Construction in France…?
DAPNIA 9/01/2006

15. A superconducting alternative to the SCL?
SCL can have another meaning:
Super Conducting Linac.
A SC section could replace the Side-Coupled, providing that we can obtain real-estate gradients ~2.5 MV/m.
Needs investment for the cryogenic infrastructure, justified in the optics of an SPL following Linac4.
SCL tanks
(700 MHz)
Spoke
cavities
(SC)
(350 MHz)
RF requirements:
beam power 2.8 MW 
- 20 units 100 kW, 352 MHz
- 3 klystrons 1 MW, 352 MHz
- 1 klystron 4 MW, 704 MHz
DAPNIA 9/01/2006

16. Spoke, 352 MHz
Focusing period in present design MeV (FODO): ~ 1.5 m  compatible with Triple-spoke
Triple-spoke designed at FZJ for HIPPI (E. Zaplatine):
0.78 m cavity length for b=0.5
E0T = 6.4 MV/m
no freq. jump
* Low efficiency at 90 MeV.
* Do we need a double spoke at lower energy (but b=0.35 probably too low)?
* Can we fit it in a cryostat ~ 1.2m long (to keep focusing distance)?
* Can we feed 8 of these cavities from a single LEP klystron?
DAPNIA 9/01/2006

17. Elliptical, 704 MHz
Elliptical cavities at b=0.5 (CEA, INFN) are giving excellent results.
Length ~ 0.9m
Designed for 12 MV/m.
* Require longer focusing period (~1.5 m).
* Low efficiency at 90 MeV.
* How many cavities can we feed with one klystron?
* We could use the SPL-CDR2 layout, with superconducting quadrupoles and long cryostats, but long R&D time for superconducting quadrupoles.
DAPNIA 9/01/2006

18. Summary for SC options
A superconducting option is attractive for the high-energy part of Linac4, but has to compete with the conventional Side Coupled Linac.
As a preliminary step in order to compare options we need layouts (mid 2006 ?) for both spoke and elliptical cavities, with a first beam dynamics analysis to be done in the frame of the HIPPI Activity (see ESAC recommendations).
To compete with the SCL, average real estate gradient should be > 2.2 MeV/m.
The option of cold quadrupoles (as for SPL) can be considered, but time is short to have it fully developed by end 2006.
The RF power system can be a cost driver even for a SC linac, if one cannot drive at least 8 cavities/klystron.
DAPNIA 9/01/2006

19. RF tests in SM 18 of prototype structures* for Linac4
Global planning
RF tests in SM 18 of prototype structures* for Linac4
* Quotes from R. Aymar (Jan.2005)
3 MeV test place ready
SPL approval *
“in , to review and redefine the strategy for CERN activities in the next decade in the light of the first results from LHC and of progress and results from the previous actions. “
Linac4 approval *
“… in , to decide on the implementation of the Linac 4 and any increased R&D programme, depending on new funds made available and on a new HR policy”
CDR 2
DAPNIA 9/01/2006