1. Update on MKP Strategy ACKNOWLEDGEMENTS M.J. Barnes
A. Adraktas, M. Beck, L. Ducimetière, J.A. Ferreira Somoza,
B. Goddard, F. Maria Velotti, R. Noulibos, C. Pasquino, L. Sermeus,
L. Vega Cid, W. Weterings
4/10/2016
Update on MKP Strategy

2. Content Present MKP configuration
History and existing breakdown/flashover issues
Upgrades required to spare MKP-L
Planning
Exchange of installed MKP-L ??
Long-term plans for MKP-L
4/10/2016
Update on MKP Strategy

3. Present MKP Configuration
LSS1 Layout
MKP-S
MKP-L
Beam #1 #2 #3 #4
Magnet 7A
MKP-S: 2 tanks (#1 & #2) with 5 S-magnets each and 1 tank (#3) with 2 S-magnets
MKP-L: 1 tank (#4) with 4 L-magnets
Total kicker length: ~12.3 m
MKP-L exchanged during LS1. New version has:
PT100 sensors (on ground plate of 2 magnets);
Transition pieces (reduces heating of magnet);
Capacitive dividers.
MKP-L removed during LS1 is currently the spare.
4/10/2016
Update on MKP Strategy

4. MKP-L Vacuum Pressure
Since LS1 there have been periods of significant vacuum pressure rise in the MKP-L. The high pressure results in an important increase in the electrical breakdown (flashover/spark) rate.
Pressure rise is:
Slow pressure rise (temperature rise due to beam induced heating);
However, for a given measured temperature, there has been a reduction in pressure by a factor of 4-5 between Mar-Apr and Feb-Apr 2016 (4 at 30˚C; 4.5 at 45˚C).
Fast pressure rise (fast pressure rise with beam [ecloud]);
Normalized pressure, corrected to 30˚C measured, reduced from ~1x10-20 to ~4x10-21 mbar/proton – so some conditioning seen.
19/06/15 to 20/06/15 (25ns scrubbing run):
4/10/2016
Update on MKP Strategy

5. MKP-L breakdown rate
26/05/2016: tried to minimize number of breakdowns by reducing MKP-L PFN voltage (better for operation and decreased risk of permanent damage to MKP-L):
PFN voltage re-balancing between S and L type magnets implemented 26th May 2016.
Voltage on MKP-L magnets reduced from ~24.5kV to 21.5kV.
Voltage on MKP-S magnets increased from ~24.5kV to 25.5kV.
Note: Average spark-rate similar, during 2016, before and after 26/05/2016.
4/10/2016
Update on MKP Strategy

6. Spare MKP-L: Spare MKP-L needs upgrading: Notes:
presently no transition plates (required to significantly reduce beam impedance) or PT100s – these should be installed;
work on spare MKP-L must start before end of 2016 operation (e.g. at start of Pb run).
Notes:
Design of MKP-L is “non-bakeable”: ABT-FPS are working with vacuum team to reduce outgassing, e.g. by implementing a low-temperature bake-out….
Low-temperature to be tested e.g. on an MKE, e.g. MKE-L with unmodified serigraphy, later this month;
Vacuum team recommended that an upgraded MKP is transported to the tunnel with ion pumps already installed (to minimize time that the tank is vented and thus exposed to air) – FPS concern is that this could causing vacuum leaks. Wim/Luc to study possibility of a “support” for the pumps during transport;
Vacuum team recommend that ferrite is NOT cleaned with alcohol – this could be the cause of outgassing in MKP-L (and MKE4-S) [plates originally suspected, but their outgassing is OK];
Ferrites of spare MKP-L will be baked in air to 1000˚C;
“Test” capacitor plates, from Portugal, are out of specification and the material has not yet been delivered from the mill – hence series production cannot commence:
48 existing MKP plates have been found and machining at CERN will be launched this week.
4/10/2016
Update on MKP Strategy

7. Planning for spare MKP-L upgrade:
Note: at recent SPS coordination meeting it was mentioned that the SPS will be closed on the 24th of March, so one week earlier than previously announced.
4/10/2016
Update on MKP Strategy

8. Exchange of MKP-L ?? In the event of a vacuum problem:
it is not yet clear how much time the vacuum team would have to investigate etc. (due to commitments in the SPS during EYETS);
it is hoped that there would be a vacuum team member available for doing a low temperature bake-out:
If the vacuum does not improve, or no vacuum team member is available, the spare would NOT be installed (thus existing MKP-L would be left installed in the SPS).
Note:
Francesco is carrying out calculations to determine whether it is possible, in case of a serious problem with magnet 7A, to operate without MKP-L 7A 25.5 kV; kV) [terminated cables required]…..
Very preliminary results: 10 mm bump would be required. Thus it may not be feasible to run without MKP-L 7A.
4/10/2016
Update on MKP Strategy

9. Exchange of MKP-L ??
If vacuum of upgraded spare is good in lab (which should be evident within one-week of start of pump-down):
two weeks to HV condition in lab;
install in SPS as soon as possible to maximize pumping time in SPS (machine to be closed on 24th March 2017: vacuum installation 13/03 – 20/03 just fits);
C. Theis (RP): the expected radiation dose will be below 1 mSv between VBBA – start and MBA start (includes TIDVG & MKP), at 40 cm, but a well studied procedure is in any case necessary [IEFC 16/09/2016].
removed MKP-L – open and repair or keep “as is” – strategy to be decided.
4/10/2016
Update on MKP Strategy

10. Long-term plans for MKP
Design MKPs to be bakeable;
Transportable with ion pumps installed;
Carefully review beam induced power deposition estimates;
If required, install a beam screen:
Screen could consist of 2 mm thick ceramic sheet with serigraphy (and low SEY coating) at both top and bottom of aperture;
Mechanical studies commenced – it will be very challenging to connect transition pieces to serigraphy…..;
Thermal studies of installing only one serigraphed sheet, at bottom of aperture, commenced.
4/10/2016
Update on MKP Strategy

11. Conclusions
Plan to replace MKP-L during EYETS (due to problems with installed MKP-L);
Spare needs upgrading: refurbishment of spare MKP-L must start before end of 2016 operation (at start of Pb run, i.e. 31/10/2016);
Vacuum acceptance of spare tank is critical: will be decided with VSC;
MKP-L will be exchanged, during EYETS, provided spare is ready and that static-pressure of upgraded MKP-L is OK;
start-up planning of SPS must allow for conditioning of new magnet;
need to coordinate the exchange with the TIDVG exchange happening right nearby.
4/10/2016
Update on MKP Strategy

12. Questions ?
4/10/2016
Update on MKP Strategy

13. Outgassing due to Heating
MKP-L installed during LS1 showed significant temperature related outgassing. However:
For a given measured temperature, there has been a reduction in pressure by a factor of 4-5 between Mar-Apr and Feb-Apr 2016 (4 at 30˚C; 4.5 at 45˚C).
Vacuum team outgassing tests on Peraluman plates, as a function of temperature, do NOT explain high pressure rise of the installed plates.
4/10/2016
Update on MKP Strategy

14. Fast Pressure Rise Corrected for Temp.
19/06/15 to 20/06/15 (25ns scrubbing run):
25/03/16 to 28/03/16 (25ns scrubbing run):
Normalized pressure, corrected to 30˚C measured, is ~1x10-20 mbar/proton.
Operation at an elevated temperature seems to have reduced subsequent outgassing.
Normalized pressure, corrected to 30˚C measured, is ~4x10-21 mbar/proton. Hence some limited conditioning over the last 9 months.
In general the corrected pressure and beam intensity curves have the same shape, indicating that the fast pressure rise is attributable to multipacting;
Studies of multipacting by A. Romano et al confirm it would be expected for MKP-L & MKP-S.
Methods of reducing SEY are being considered (e.g. LESS and Cr2O3) – but would need extensive testing (HV, UFOs, etc.), and it may not be possible to use Cr2O3 on ferrite, but OK on alumina.
Cr2O3 applied by magnetron sputtering (Polyteknik) on alumina: good results for reducing SEY;
Present plans are to install a Cr2O3 coated anodized aluminium in the SPS, during the EYETS, for tests.
Spiegarla meglio
4/10/2016
Update on MKP Strategy