2. SMH16 eddy current septum
J. Borburgh
20/6/2017
nABTEF

3. Outline Present PS extraction septum Eddy current septa
Related CERN developments
Consolidation proposal
Conclusions
20/6/2017
nABTEF

4. Present PS extraction septum
20/6/2017
nABTEF

5. PS fast extraction septum
SMH 16
20/6/2017
nABTEF

6. Principal septum parameters
Direct drive
Required deflection angle at 26 GeV/c 30
mrad
Lmagnetique
2174 mm
Lphysical
2x1125
Gap height
Gap width between conductors
55.5
Septum thickness 3
Max. operating current
28.5 kA
Max. field
1.2 T
Integrated field
2.6
T.m
Cooling water flow
l/min
Power dissipation
800 W
Pulse width
3.5 ms
Inductance
5.4 µH
Leak 10 mm 1 %
Leak 50 mm ‰
20/6/2017
nABTEF

7. SMH16 history Tank number Installed in PS Removed from PS
Cause for exchange
Smh16.1
4/1994
1/1999
Laminations sheared off
SMH16.2
2/1999
5/2004
Leak hydraulic circuit
SMH16.1
7/2004
2/2006
Preventive exchange
1/2010
Preventive exchange 6 M pulses
12/2011
Preventive exchange 8.6 M pulses
SMH16.3
1/2012
1/2013
Preventive exchange 9.7 M pulses
2/2014
12/2015
Preventive exchange 12.5 M pulses
SMH16.4
2/2016 -
7.5 M pulses in 2016 and counting
With the increased number of cycles, the expected life time of the septum is now around 2 years only. A significant amount of cost and accumulated dose is involved in the continuous rebuild and exchange of this device.
20/6/2017
nABTEF

8. Actual PS extraction septum layout
20/6/2017
nABTEF

9. Eddy current septa
20/6/2017
nABTEF

10. Eddy current septa
Experience with eddy current septa at CERN goes back to the early 1990s when the optimised topology was developed and constructed for use at ESRF [1].
Since then this topology worked reliably at ESRF as well as at Soleil, where a further developed versions are installed [2].
More recently this topology was studied for the PSB injection [3] and PS injection [4].
20/6/2017
nABTEF

11. Direct Drive vs Eddy Current Septum [5]
Eddy current septa deflectors can be constructed on a more robust way.
Current densities in the drive conductors can be lower, and the eddy current blade can be cooled indirectly.

12. Eddy current design
3 mm Cu septum pulse width corresponding to 0.6 mm skin depth δ δ= 2ρ ωμ → ω = 76 k (12.1 kHz) → 1 2 sine pulse width 41μs. Assuming present magnet impedance of 5.3 μH → 11.6 kV on magnet terminals.
20/6/2017
nABTEF

13. More realistic pulse lengths
½ sine pulse width [μs)
U on magnet (kV)
U on transformer primary (kV)
remarks 41
11.7
140
Both magnets in series
100
2.4
28.8
Powered individually
244
1.0
12.0
3500
0.093
1.1
Both magnets in series; present set up
Let’s choose arbitrarily a pulse length of 100μs, and power each magnet separately: 2.4 kV on each magnet.
20/6/2017
nABTEF

14. Frequency response Courtesy J.M. Cravero
The frequency response of laminated (0.35 mm) BISMV septa magnets is surprisingly linear, far above the common 10s of kHz.
Would this indicate that there would be no need for thinner laminations?
20/6/2017
nABTEF

15. Effect of current pulse shape on leak field [1]
Time function
Peak
∫Bydl [Tmm]
dt [µs]
dφ [˚]
ABS MAX
14.84
-223
-40.13
LOC MIN
-0.62
-226.7
-40.8
LOC MAX
1.87
ABS MIN
-1.37
ABSMAX
14.84
-218.1
-39.26
LOCMAX
14.28
Comparing the septum leak field integral of full sine with half sine excitation.
Full sine pulses reduce the leak field.
20/6/2017
nABTEF

16. Influence of shielding on leak field
Bruno presented [6] in the past the influence of shielding topologies on the leak field for the PS injection septa:
2D simulations were done in the time domain.
Comparing punctual field values, with 2 ms full sine excitation,
40 mm from the septum.
2: septum + Kapton + mu-metal screen
3: septum + Kapton + bumper
1: septum only
1: septum only
4: septum + Kapton + mu-metal screen + Kapton + bumper
5: non-uniform thickness septum
6: septum + Kapton + mu-metal box

17. Leak field @ 10 mm for various shielding options, simulated for LIU-PS injection septum [6]
2 ms full sine wave excitation

18. Related CERN developments
20/6/2017
nABTEF

19. BSW42 prototype
Several eddy current septa prototypes were built in the past in the section. Most recently Thierry presented the new PS injection proto [7].
A prototype magnet was built for the LIU- PS injection system in 2016.
Copper plate in galvanic contact with the magnet laminations and lateral as well as top and bottom screwed to the copper box

20. MSP
An attempt was made to design an eddy current septum for the SPS east extraction (LSS4) around the year 2000 [8].
Field
1.078 T
Gap size (h x w)
20 x 40 mm
Lmagnetic
3200
ʃB.dl
3.45
T.m
Pulse duration
250 μs
Flat top duration
7.8
Septum thickness
5 (Cu)+1(Fe)
Peak current
17.16 kA
Peak Voltage
3.40 kV
20/6/2017
nABTEF

21. MSP pulse generator A study was also done for the pulse generator.
Remarkable symmetries were present:
Ls/Lp = Cp/Cs = 3/4, the pulse duration is Tp = π⋅√(3LsCs) = π⋅√(3LpCp).
This symmetry is however lost when losses or the transmission cable are introduced.
Contrary to alternative third-harmonic circuits, the full stored electrical energy is available as magnetic energy at the time of beam deflection.
20/6/2017
nABTEF

22. MTE PS extraction septum (~2008)
As prepared for MTE study [9], but not retained because of cost. Aim was to design a (direct drive) thin SMH16. The design used a thin followed by a thick magnet, keeping mechanical stress level in thin septum comparable to present system.
A feasibility study to power the magnets separately was completed.
2 tanks are already equipped with the corresponding vacuum ports.
20/6/2017
nABTEF

23. MTE PS extraction septum
Magnet Parameters
Thin Septum (Upstream)
Thick Septum (downstream)
Physical Length
860
1390 mm
Septum thickness
1.7 5
Gap dimension (width × height)
62×30
79×30
Integrated magnetic Field
0.715
1.885
T.m
Magnetic length
800
1300
Peak current
21337
34616 A
Repetition rate
0.9 s
Deflection angle
8.25
21.75
mrad
Rear conductor thickness 9
Magnet resistance
0.55
0.26 mΩ
Magnet inductance
1.9
3.9 μH
Power dissipation
519
700 W
This set up displaced the centre of deflection by approximately 121 mm downstream.
The proposed set-up comes at the cost of additional complexity, since it uses two independent power supplies for the thin and thick septum.
Costing was done in 2008 and was estimated at 850 kCHF for the septum only.
20/6/2017
nABTEF

24. Consolidation proposal
20/6/2017
nABTEF

25. PE.SMH16 Consolidation proposal
As presented by Miro in [10].
If eddy current technology validated at PS injection septum, the SMH16 would be a good candidate to adopt this as well (present life time ~ 2 yrs + high activation).
Ideally would like to use faster pulse than TE/EPC can offer: ~ 200 µs (full sine), 30 kA, possibly with two generators (for thin and thick septum).
Would recover existing vacuum tanks and remote displacement systems.

26. SMH16 eddy current version Budget & Schedule
Material + Fellows + FSU (kCHF)
2020
2021
2022
2023
2024
2025
Manpower (Staff) [fte]
0.2
0.4
0.5
Manpower [TTE, Fellow, FSU] 1
0.7
Planned Expenditure 50
250
350
150
Excluding generator cost, nor (control) electronics
Installation
2020
2021
2022
2023
2024
2025
Design, simulations x
Mechanical designs
Part procurement X
Assembly, testing
Installation LS3, assumed to take place in 2025
20/6/2017
nABTEF

27. Conclusions
Experience from the LIU-PS injection septa should provide us with the necessary experience to confirm an increased MTBF.
The magnetic performance needs to be confirmed. In particular the feasibility of the leak field requirement still needs to be confirmed.
Magnet will have to be designed and build with the required voltage level in mind.
Magnet cost will be similar to direct drive septa magnets.
2 new generators (plus spare) will have to be designed and built. Much synergies from the MSP project can be expected.
A full sine pulse shape would be beneficial for the leak field. To see if this can be implemented in the pulse generator.
The project should be planned after LS2, with the aim to install in LS3.
20/6/2017
nABTEF

28. References
J.P. Perrine et al., The pulsed power converter and septum magnet system for injection into the electron storage ring at ESRF”, IPAC 1996,
P. Lebasque et al., “Eddy current septum magnets for booster injection and extraction, and storage ring injection at synchrotron Soleil”, EPAC 2006
Aiba, M. Barnes, “…”
Z. Szoke et al.,”Direct drive and Eddy current septa magnet designs for CERN’s PSB extraction at 2 GeV”, MT-22, IEEE Trans. On Applied Superconductivity, Volume 26, issue 4, June 2016.
B. Balhan, “PS Injection Septa”, LIU-ABT systems: PS review, Indico event , 1 October 2014
B. Balhan, “Magnetic design “, CERN PS injection septa for 2 GeV proton injection review, Indico event , 13 October 2016
T. Masson, “Prototype construction and magnetic measurements”, CERN PS injection septa for 2 GeV proton injection review, Indico event , 13 October 2016
G. Schroder et al.,”A novel eddy current septum magnet for the SPS extraction towards LHC and CNGS”, EPAC 2000
M. Giovannozzi et al., “The CERN PS multi-turn extraction based on beam splitting in stable islands of transverse phase space : Design Report”, CERN
M. Atanasov, “Additional Spare SMH16 + SMH 57”, Consolidation ABT Review, 10 May 2017, Indico event
20/6/2017
nABTEF