1. Operating the septa beyond their design specs
Aspects of septa operation in 2006 and beyond
With input from:
G. Arduini, B. Balhan, B. Goddard, M. Hourican, T. Masson, J. Uythoven

2. Agenda Brief review of recent failures
Preventive maintenance, and reviewed spares policy
Impact of 900 ms cycles
High intensity operation and additional interlocks
SPS Septa strategy during combined LHC/CNGS operation

3. Recent failures: PS SMH16
failed 19/5/2004; yielding 117 hours of down time; coil failure
failed 5/7/2004; 2 weeks at 1 SFTPRO cycle / supercycle + 1 week down time; brazing failure
Currently running with 1st septum again, where one out of the two magnets has been refurbished with a new coil.

4. Recent failures: PS SEH23
HV cable failure (pp300B); 2/9/2004; 3 hrs down time; end of cable life

5. Recent failures: SPS MS septa
Cooling water flow drop provoked various trips as from July until end of the year. Cause unknown up to now.
LSS6 MS septa water flow

6. LSS2 MS septa water flow

7. Summary MS flow variations
Added diagnostics will be installed on cooling circuits in 2005 (O2 level, pH level).
LSS2 flow remains critical in the future because of the slow extraction.
LSS6 will be less critical due to fast extraction only use: flow should be reduced to increase septum life time.
2006 start up strategy still to be decided

8. Preventive maintenance
SPS MS septa every 107 pulses or 10 years of operation
SPS ZS HV cable replacement every sparks
Annual replacement PS electrostatic septa short cable
PS complex pulsed magnetic septa flexible stripline exchange
Annual hydraulic filter replacement
Periodic refurbishment of PS electrostatic septa
Do more? Replace PS septa every x years?
What is the strategy?
Cost impact!

9. Consolidation requirements
PSB injection septa renovation (30 yrs)
Modified spare policy for most stressed septa in PSB and PS:
1 operational septum
1 hot spare
1 cold spare (for highly stressed septa)
HV cable consolidation for PS electrostatic septa
Revised strategy will cost a significant amount
+require add. Manpower if done in accelerated fashion

10. 900 ms repetition rate implications
FATIGUE EFFECTS ON MAGNET / STRIPLINE LIFETIMES
THERMAL
LIMITATIONS
VIBRATION EFFECTS
All together somewhat more maintenance likely to be needed
Accelerated fatigue as damage if vibration is not fully decayed before next pulse
Operating the septa beyond their design specs – / J.Borburgh

11. Injection Septum BISMH Extraction Septum BESMH
900 ms: BOOSTER SEPTA
No hardware problems for Injection and Extraction from PSB.
SMV 10 Vibration measurements show septum oscillation is damped after 250 ms.
Injection Septum BISMH
SMV20
SMV10
Extraction Septum BESMH
Recombination magnets SMV10 & 20
Replacement of 3 flexible striplines
Operating the septa beyond their design specs – / J.Borburgh

12. SMH16 : Vibration Measurements to be performed end April.
900 ms: PS SEPTA
SMH42 : Flexible stripline is currently changed every 2 years as a result of fatigue effect damage. New design needed.
SMH57: The magnet coil was redesigned in 1997 to dissipate 8 kW. Increasing Flat top to 850ms will cause more fluctuation around an increased average temperature.
SMH16 : flexible stripline will be redesigned to cope with increased power dissipation.
Fatigue effect may reduce the lifetime but stripline is sufficiently dimensioned.
SMH16 : Vibration Measurements to be performed end April.
Operating the septa beyond their design specs – / J.Borburgh

13. Status on 900 ms OPERATION PSB PS
New striplines required for 3 vertical recombination septa
Good results from vibration measurements in Dec. 2004 PS
SMH16: New stripline required; vibration measurements will be carried out towards end March / April.
SMH42: New stripline required
SMH57: More investigation needed with possible power testing of reserve septum, at present no power supply available.
Operating the septa beyond their design specs – / J.Borburgh

14. High Intensity operation: PS
Septum 31:
Increased losses on beam slicing electrostatic septum 31, will induce higher dose rates at equipment level:
Oil insulated HV feedthrough will have to be replaced by a permanent circulating and regenerated insulating liquid HV feedthrough. This will be operational for the 2006 start-up.
Additional posibility is to leave the oil insulated feedthrough running with increased risk of failing the feedthrough and polluting the PS acuum chamber with oil untill the new multi turn extraction comes active?
Or leave running and exchange oil even more often, and accept the higher dose taken by personnel?

15. High intensity operation: SPS
Need for improved passive protection elements (TPSG) upstream of MS septa of the fast extraction channels to protect septa in case beam mis-steering occurs
TPSG6
MS Septa
Blue line shows injection beam envelope at 8? sigma

16. TPSG6 temperature distribution in case of full impact of nominal LHC beam

17. High intensity operation: TPSG diluter performance
TPSG4 (LSS4)
Improved design with different absorbing materials and water cooling and additional length will be installed.
TPSG6 (LSS6)
New design validated by calculations performed by the ATB group.
Both diluters will be able to properly protect the downstream MS septa from full impact of the nominal LHC beam, but not beyond, due to so far unavailability of sufficient quantities of CC and γ-met 100 Ti on the market.

18. High intensity operation: results of TT40 extraction tests
Beam induced noise on PT100 temperature probes was transmitted to MSE interlock PLC
Erratic interlock sent from MSE interlock PLC to Power converter, with catastrophic result (broken vacuum chamber in Quad downstream of septa)
Measures taken:
Disconnecting temperature probes drastically and sufficiently reduces the noise in the MSE interlock PLC
Modification of the interlock system:
Direct signal from the MSE interlock controller (PLC) to the BIC.
Delay of 10 ms in the PLC before sending interlocks to the Power converter.
Outstanding:
Still need to include a MS girder position interlock to BIC
More accurate water temperature measurement

19. Multi cycling in the SPS
Until now, to avoid high spark rates induced by LHC type beam for example during MD’s
the girders of the SPS ZS septa were retracted
HV switched off
Ion traps kept at Unom
This graph shows that with CNGS beam at high intensity, the ZS have a high spark rate

20. Multi-cycling in the SPS
For combined SFTPRO and CNGS/LHC operation the following options are available:
Move girder when mode of operation changes: girder displacement not designed for multi-cycling (slow, risk of fatigue)
Ramp down the HV on the ZS during CNGS/LHC operation: not designed to do so, but response time may be faster, less risks of fatigue (on HV cable mainly)

21. Multi-cycling in the SPS
Outstanding issues:
Recent tests (2004) have shown less sparking with LHC type beam and ZS girder in and HV at Unom. Is this a result of scrubbing? More tests needed.
Total HV ramp down takes a long time, but a 20% HV decrease down to 180 kV may relieve stress during LHC/CNGS operation, and could be done in ~ 10 seconds. Additional time is needed to do a reset of the interlocks.
Add interlock (BIC?) to prevent bumped beam if during CNGS or LHC operation

22. Conclusions
Actual operational requirements challenging with present equipment.
Consolidation program reviewed, but comes at significant cost and requires additional manpower. However no consolidation strategy guarantees zero failures.
New modes of operation such as 900 ms cycles, and multi-cycling can probably be accommodated, but more tests are needed.
Demonstrated need for reliable and well-thought interlocks and passive safety devices to protect septa.
Consolidation strategies:
Faults are not foreseeable
No reliable statistics yet
Proper maintenance strategy not evident
Radiation impact