1. Status of CIEMAT contribution to CLIC
M. Domínguez, ANTEC Magnets - D. Gavela, F. Toral CIEMAT
ECFA Linear Collider Workshop, May 30th, 2016

2. Outline Past CIEMAT contribution to CLIC
Dipole with longitudinally variable field
Accelerating structures
Summary 2

3. Past CIEMAT contribution to CLIC
CIEMAT contribution to CLIC started in 2004.
Different types of components are included, mainly magnets and RF structures.
It has allowed our group to consolidate research activities on RF structures.
Past CIEMAT contribution to CTF3/CLIC
COMPONENT
TYPE
QUANTITY
Septa Extraction Magnets
Resistive Magnet 2
Corrector Window-Frame Dipole 15
Precision Moving Tables (Quadrupole Movers)
Mechanics
Tail Clipper Kicker
Special Magnet 1
Stripline Kicker
Power Extraction Transfer Structures (PETS) for TBL RF
12 (Partial Contrib.)
Double Length PETS for CLIC 3

4. Outline Past CIEMAT contribution to CLIC
Dipole with longitudinally variable field
Accelerating structures
Summary 4

5. Technical specifications
96 dipoles with fixed longitudinal and transverse gradient
Possibility to include a small correction of the field amplitude (5%)
Good field region radius: 5 mm
Field quality  1*10-4
Transverse gradient: 11 T/m, vertical focusing
Longitudinal gradient: two possibilities, step and trapezoidal. Firstly, we will concentrate our efforts on the step, because the modelling is easier.

6. Permanent Magnets
Permanent magnets are the best choice to provide a fixed field: no power consumption and very compact.
Taking into account:
Temperature variation in the tunnel will be as low as ±0,1ºC
Sm-Co radiation tolerance is higher than Ne-Fe-B
Low radiation expected, but higher in the low field sections (magnet ends)
The magnet volume and weight reduction using Ne instead of Sm goes up to 45%.
The cost of Neodymium magnets is lower than SmCo.
We are pointing towards the use of:
Ne-Fe-B magnets in the high field region
Sm-Co magnets in the low field region
NO specific temperature compensation

7. 2-D Simulations: low field section
C-shaped magnets is the best layout for efficient use of space.
Gap is pointing outwards to ease synchrotron radiation evacuation.
Achieved:
1.01T, ΔB/B = 1*10-4, rGFR = 5mm

8. 2-D Simulations: high field section
Different configuration:
Three magnets working in parallel to preserve the pole dimensions within reasonable limits
Achieved:
1.77T, ΔB/B = 1*10-4, rGFR = 5mm
The above conditions were much more difficult to reach as the pole tip iron is saturated. The field quality is more sensitive to any minor change in the dimensions.

9. First 3-D magnetic simulations
Short magnet length (0.58m) makes 2-D simulations diverge from 3-D, specially in the case of the high field section (0.052 m long).
First simulations were made with Ansys-Maxwell. Very difficult to achieve numerical accuracy to evaluate the field harmonics, even with dense meshes: good quality field region is very close to curved surface of pole.

10. 3-D magnetic: Roxie (I)
Roxie is a magnetic field computation software specially developed at CERN to overcome problems of FEM codes to compute accurate field harmonics.
First results showed oscillations on the field profile without physical meaning.
It was solved decreasing the element size.
Execution time was decreased using M(B) algorithm.

11. 3-D magnetic: Roxie (II)
Good correlation with analytical models
Good field quality
1.7 T:
Field achieved higher than required to compensate the flux leakage in 3-D
Non-linear behaviour due to iron saturation: no good correlation with analytical models
Large b3 to be compensated by iron shaping.

12. 3-D magnetic simulations
In summary:
Ansys-Maxwell is not accurate enough to compute the field harmonics.
3-D modelling of magnets iron geometries extruded from several 2-D sections is very time consuming in Roxie.
We are following this strategy:
First model iterations will be made with Ansys, to achieve the required field profile.
The field quality will be evaluated with Roxie.
Alternatives to be studied:
Opera has not been considered by now, but likely the same problems than Ansys, because it is based on FEM.
Radia (ESRF) could be an alternative, it is based on boundary elements as Roxie.

13. Cross-talk (I) Interaction between 1T and 1.77T regions
1.77T pole longitudinal reduction and 1T pole extrusion to improve the field in the gap between the two magnet parts

14. Cross-talk (II) Lower d (d=11mm) Intermediate d (d=16mm)
Higher d (d=21mm)
Smooth transition from high to low field
Lowers the field in the central section
Base simulation, compromise solution regarding the flux exchange between the 1.77T and 1T regions
Higher field in the central section
Higher gap between different field regions

15. Summary
2-D simulations have been done achieving the requirements: longitudinal and transverse field gradient, field quality.
Tool for automatic calculation of the optimal magnet dimensions in 2-D based on analytical methods:
The optimal magnet working point (BHmax) is obtained and therefore the magnet volume needed is at minimum
We are confident now on results of 3-D simulations.
It is necessary to agree the longitudinal field profile to finish the calculations and go on with the fabrication design.

16. Schedule
Agreement
New schedule (May 2016)
WP2
- Technical specifications
- Magnetic and mechanical design
- Fabrication drawings of parts and tooling
- Fabrication of parts and tooling
- Assembly
- Characterization tests
- Final reporting
March 2015
September 2015
March 2016
September 2016
January 2017
May 2017
July 2017
July 2016
October 2016
February 2017
September 2017
A lot of problems to start activity, mainly to hire a new engineer. He started in November 2015.

17. Outline Past CIEMAT contribution to CLIC
Dipole with longitudinally variable field
Accelerating structures
Summary 17

18. Technical specifications
The aim of this activity is the fabrication of an accelerating structure for CLIC, mainly to compare the performance of structures developed by different teams/Institutes based on the same design.
The structure to be developed is known as TD26R05CC.
This task includes the RF low power characterization. 18

19. Furnace qualification for bonding (I)
A furnace able to perform bonding of copper discs is found in CEIT, a research Institute at San Sebastian, close to DMP.
Some problems were found to control the pressure of hydrogen gas during the thermal cycle.
First results are not good enough: aluminum and magnesium were found in the discs after the thermal cycle. It is likely due to wrong handling of the discs.
The test will be repeated in June. 19

20. Furnace qualification for bonding (II)20

21. Analysis of disc tolerances (I)21

22. Analysis of disc tolerances (II)
The discs will be hold at four points to be measured at the 3-D coordinate machine.
The origin of the problems to achieve the tolerance of the 0.5 mm fillet radius is the bending of the tool.
This problem can be overcome with the new design of accelerating structure, TD26R1CC.
Therefore, CIEMAT and CERN have agreed to move to this new design, which is better suited to the problems found during manufacturing. 22

23. Standard Disc of TD26R1CC 23

24. Schedule Important delay to start activities.
Agreement
Updated (May 2016)
WP1
- Fabrication drawings
- First disc
- Bonding dummy test
- Set of 26 discs
- Compact couplers
- Tooling: drawings and fabrication
- Assembly
- Characterization tests
- Tuning and baking out (at CERN premises)
- Final reporting
March - September 2015
July 2015
March - December 2015
July June 2016
July 2015 – June 2016
July 2016 – December 2016
January 2017 – March 2017
April 2017 – July 2017
September 2017
September 2016
October 2016
December 2016
June 2017
October 2017
December 2017
April 2018
May 2018
Important delay to start activities.
Difficulty to hire new people.
A lot of problems in other projects, which reduces the available manpower for this project.
Activities are now started and ongoing. 24