Update on MKI Performance: TS3 to 02/10/2012 M.J. Barnes Acknowledgements: P. Adraktas, V. Baglin, A. Bertarelli, G. Bregliozzi, S. Calatroni, F. Caspers, H. Day, L. Ducimetière, M. Garlasche, A. Gérardin, B. Goddard, J.M. Jimenez, V. Mertens, E. Métral, B. Salvant, M. Taborelli, B. Teissandier, J. Uythoven, W. Vollenberg, W. Weterings 02/10/20121M.J. Barnes

Motivation for exchanging MKI8D Motivation for changing MKI8D during TS3 was to gain valuable experience of the improved MKI beam screen, installed in the LHC, prior to LS1 (in view of a bulk upgrade of all MKIs during LS1), – especially reduced beam induced power deposition (MKI8D was limiting the availability of the LHC – see LMC 27/06/2012), while maintaining the HV performance. 4 MKIs in RA87 MKI8D MKI8C MKI8B MKI8A Injected Beam 02/10/20122M.J. Barnes

MKI8D Exchange (TS3) New ceramic tube & 19 (c.f. 15) beam screen conductors, each with stretched spheres. MKI#5 has an expected power deposition of one-half to one- third of installed MKIs. New NEG coated bypass tubes Removal of “old” MKI8D (no jacket) Transport of “new” MKI8D (with jacket) MKI8D exchange completed in 4.5 days, teams working around the clock, and MKI8 handed back to the CCC several hours in advance of the ambitious planning. Sincere thanks to all teams for excellent preparation and extraordinary efforts throughout TS3 which made this operation possible. Plus: measures to ensure that emissivity of inside of MKI5 tank was ≥ 0.1. Exchange envisaged, at Chamonix 2012, during Preparation very tight for improvements: worked with available components, e.g. ceramic tube. 02/10/20123M.J. Barnes

MKI2 and MKI8 Temperatures: 29/09-01/10 The “old” MKI8D had the highest measured temperature of all the MKIs, prior to TS3. Since TS3, the “new” MKI8D has the lowest measured temperature (it is estimated that the “old” MKI8D would have been at ~60˚C, at 02:00hrs on 01/10/2012). Note: measurements are not absolute, because of thermal contacts, etc. 02/10/20124M.J. Barnes 01/10/2012: MKI8D measured temperatures lowest of all MKI8s!

Breakdown ~23:20hrs): No precursor to breakdown of MKI8D: occurred at Q5 end (beam screen suspected). Possibly related to transport and relatively short HV re-conditioning (magnet was OK in lab). Vacuum Activity: B1: 4e13 max charge. Anti-ecloud solenoids initially at 3A. Relatively high pressure close to MKI8s when B1 injected. When solenoid current was increased from 3A to 5A large reduction in pressure in C-D interconnect and thus in MKI8C and MKI8D: SIS interlock level increased for MKI8 solenoids. Significant vacuum activity on VGPB.192.5R8.R during subsequent MKI8 SoftStart. MKI8. 24/09/ /10/20125M.J. Barnes B1 intensity VGPB.192.5R8.R (Q5 side of MKI8D) VGPB.192.5R8.R (SoftStart): B1 circulating Solenoid: 3A Solenoid: 5A C-D interconnect Spark MKI8C MKI8D NO BEAM 4E13 Pressure FS: 1E-9

Anti-Ecloud solenoids on MKI interconnects did not effect pressure near MKI8s (unlike 24/09 evening). Also B1 does not effect pressure near MKI8s. Good part of pressure rise originates in ceramic tube - strong surface conditioning occurred. MKI8. Initial Intensity Ramp-up, 26/09/ /10/20126M.J. Barnes e-8mbar (Q5 side of 8D) 6+2*36 6e-8mbar (C-D interconnect) 2e-8mbar (MKI8D) 2e-8mbar (Q5 side of 8D) 3e-8mbar (Q5 side of 8D) 6+36 Pressure FS: 9E-8 1.4E13

Definite surface conditioning effect – which would be even more dramatic if normalized to charge. Note: a time delay of 1-3 mins between injection of B2 and onset of pressure rise. MKI8. Initial Intensity Ramp-up, 26-27/09/ /10/20127M.J. Barnes B2: 6+2* * * * * e-8mbar (Q5 side of MKI8d) 2.5e-8mbar 5e-9mbar (MKI8D) 1.2E14Pressure FS: 6E-8 1hour/div ~2mins B2 ~2mins 1.2E13

Vacuum Pressure Oscillations 07:30h improved beam screen temperature tuning Courtesy: B. Holzer, J. Wenninger 02/10/20128M.J. Barnes Vacuum pressure oscillations in phase with Q5 beam screen temperature.

Spent 13 hrs “scrubbing only”, without going to stable beams: this was very efficient, with high vacuum levels. Then spent further 25 hrs scrubbing while providing in parallel physics to the experiments, from the first fill with 452 bunches up to the fill with 1374 bunches with reduced bunch intensity. The vacuum during this period was roughly a factor of 2 to 3 better than during the “scrubbing only”. MKI8. 50ns, 26/09/2012 – 01/10/ b, 1.4e11p/b (FBCT prob.) 1E-82E-8 2.2E14 6+2* b, 1.5e11p/b 7e33 cm-2s-1. Q5 side of MKI8D ~5e-9 (Q5 side of 8D) e-9 (MKI8D) 02/10/20129M.J. Barnes

Effect of MKI Pressure High pressure in both the kicker magnet tank and near to the capacitively coupled end of the beam screen, when pulsing the kickers, increases the probability of an electrical breakdown. Tank pressure SIS vacuum threshold for injection is 2e-9 mbar (temporarily increased to 2.5e- 9 mbar, for 25 ns beam, during October 2011). “Ceramic tube” SIS vacuum interlock threshold for injection is 5e-9 mbar (NEW interlock). Pressure is measured on interconnects, just outside the kicker tanks. On the new MKI8D, in the lab, the probability of sparking increased with increasing pressure (>~5e-9mbar). A risk of sparking is deposition of metal on a ceramic surface – further increasing risk of sparking, even with lower pressure, and possibly requiring the exchange of an MKI (interruption of normal program – most likely more than 5 days). Occasional sparks at end of screen conductors, at bottom LHS (lab). 02/10/201210M.J. Barnes

Recall: MKI8, UFO MD – 50ns. 22/06/2012 After switching off interconnect solenoids, pressure in C-D interconnect increased by a factor of ~70 !! Solenoids of Q4 & Q5 also effect MKI8D (and MKI8C) pressure. Spark in MKI8C (probably at end of beam screen) after 11 pulses – [MD: pulsing MKIs in beam gap]. To minimize probability of beam screen spark, recently interlocked injection (SIS) on pressure of (kicked beam) interconnects: threshold of 5e-9 mbar. 02/10/201211M.J. Barnes Q5 side of MKI8D Solenoids on interconnects Solenoids by Q4 & Q5 Pressure rise in MKI8C-D interconnect MKI8C MKI8D MKI8C spark Q4 & Q5 solenoids OFF Interconnect solenoids OFF Pressure rise on Q5 side of MKI8D 1 2 Pressure FS: 1E-8 ~6.5e-9

MKI Sparks Reason for vacuum integrals - “Old” MKI8-D sparked on:  April 17, and 7800ns – following a period of “high” pressure (50ns beam);  Oct. 25, and 1200ns (SS) – following a period of pressure of ~9e-9 mbar (25 ns beam, Anti-ecloud solenoids off). 02/10/201212M.J. Barnes 8 Feb 2011 to 18 Apr 2011 (Spark on 17/04) Pressure.Time Integral: MKI8D: 4.7*10^-7 mbar.hours March April 8 Feb 2011 to 18 Apr 2011 (Spark on 17/04) Pressure.Time Integral: C-D interconnect: 1.1*10^-6 mbar.hours 1 Sept 2011 to 26 Oct 2011 (Spark on 25/10) Pressure.Time Integral: MKI8D: 2.9*10^-7 mbar.hours Oct. 1 Sept 2011 to 26 Oct 2011 (Spark on 25/10) Pressure.Time Integral: C-D interconnect: 7*10^-7 mbar.hours 5x x x x x x x10 -8

MKI Sparks “Old” MKI8-D also sparked on:  April 9, and 7800ns – following a period of “high” pressure (50ns beam);  Apr. 15, and 7800ns (SS). Vacuum Integral threshold for new MKI8D set to same value as previous MKI8D. As of 08:00hrs on 01/10/2012 MKI8C/D at 10%/70% of thresholds – these magnets were sublimated in the shadow of another intervention, and integrals subsequently reset to zero. 02/10/201213M.J. Barnes MKI8D: 13/03/2012 to 15/04/2012 8x x10 -9

Preliminary UFO Observations for new MKI8D magnet 02/10/201214M.J. Barnes 53 In total 53 candidate MKI UFOs in Pt.8 since TS#3. Low statsistics but reduced UFO activity in new MKI.D5R8 so far. 44 MKI UFOs in Pt.8 since TS#3. Signal RS04 > 2∙10 -4 Gy/s. No correction for new BLM positioning. 502 MKI UFOs in Pt.8 from April 2012 until TS#3. Signal RS04 > 5∙10 -4 Gy/s. since TS#3 until TS#3 Courtesy: T. Baer

3mm gap between ceramic tube and conducting cylinder 1mm gap between ceramic tube and conducting cylinder Screen conductors On-going R&D Working closely with VSC to devise a method to apply Cr 2 O 3 to inside of (~3m long) ceramic tube: literature shows that ceramic insulators treated with Cr 2 O 3 had a voltage hold-off of the surface of the alumina increased by ~50%. In addition the peak measured SEY of 95% alumina of ~6.4 was reduced to ~1 after treatment. Author of paper located and contacted…. VSC also looking at other coatings (e.g. Carbon). Studying means of reducing electric field gradient on surface of ceramic tube to permit 24 screen conductors to be used without HV breakdown! Intention is to bring as many of these improvements to fruition, as possible, during LS1 (for all MKIs). 02/10/201215M.J. Barnes

Remarks  Significant surface conditioning of new MKI8D ceramic tube has taken place (required 13 hrs scrubbing without going to stable beams. 25 hrs scrubbing while providing physics to the experiments).  High pressure in the kicker magnet tank, and near the capacitively coupled end of the beam screen, when pulsing the kickers, increases the probability of an electrical breakdown.  SIS interlocks prevents injection with pressure >2e-9 mbar in an MKI tank;  SIS interlock now implemented for pressure in the beam-pipes immediately around the MKIs >5e-9 mbar. Pressure threshold will be adjusted based on experience: it is presently considered to be safe but not unduly conservative.  The pressure in the MKI tanks is presently integrated w.r.t. time and SIS interlock thresholds are defined for each integral.  If the integral exceeds the SIS threshold a sublimation should be carried out on MKI8D, and possibly MKI8C: last carried out 01/10/2012. To minimize HV de-conditioning of the MKIs, and the need for a sublimation, it is recommended that the MKI anti-ecloud solenoids are kept on throughout both normal operation and, in general, during MDs.  Anti-ecloud solenoids:  SIS interlock prevents injection if current of solenoids, around MKIs, < threshold.  Have MKI anti-ecloud solenoids (and maybe those next to Q4 & Q5) ON during the 25ns scrubbing run: ‘probe’ the effect of changing the coil current. 02/10/201216M.J. Barnes

Conclusions  Significant scrubbing and surface conditioning of new MKI8D has taken place, total scrubbing time hours.  Initial analysis of “new” MKI8D measured temperatures indicates that beam induced power deposition is significantly reduced in comparison with the “old” MKI8D, as per design – further operational data with high beam intensities required for more quantitative conclusions.  Preliminary data indicates that new cleaning procedures have significantly reduced the number of UFOs at the replaced magnet.  The present SIS vacuum interlocks in the kicker tank and interconnects are based on experience in the lab and the machine following magnet breakdowns after being exposed to bad vacuum.  Working towards a bulk upgrade of MKIs during LS1. 02/10/201217M.J. Barnes

Spare Slides …. 25/09/201218M.J. Barnes

Note: Anti-Ecloud Solenoids installation as follows: TS : Q4 & Q5 sides of both MKI2 and MKI8 06-Jul-11: MKI8 B-C & C-D Interconnects (B1 & B2) TS : MKI2 All Interconnects 02/10/201219M.J. Barnes Pressure FS: 4E-8 1.4E14 MKI2 Interconnects Following Exchange of MKI2B (Dec. 2010)

POINT 8 (Anticlockwise Inj.): Vacuum & BLM Systems Capacitive Coupling (Double foot)TMR (Single foot) BEAM 2 VGPB.176.5R8.R VGP.158.5R8.C VGPB.138.5R8.R VGP.118.5R8.C VGPB.98.5R8.R VGP.78.5R8.C VGPB.59.5R8.R VGP.39.5R8.C VGPB.4.5R8.R VGPB.14.5R8.R BLM m BLMQI.04R8.B1I30_MQY BLM m BLMEI.05R8.B2E20_MKI.C5R8.B2 BLM m BLMEI.05R8.B2E10_MKI.D5R8.B m m m m m m to m VVGST.I5R8.R Distance: m BLMI.5R8.B m BLMQI.C5R8 B MKI.B5R8.B2 C MKI.C5R8.B2 D MKI.D5R8.B2 A MKI.A5R8.B2 BLM m to m VVGST.A5R8.R m BLMQI.F4R m VGPB.D5R8.R m VGPB.E5R8.R m VGPB.F5R8.R m VGPB.G5R8.R m VGPB.H5R8.R m VGP.A5R8.C m VGP.B5R8.C m VGP.C5R8.C m VGP.D5R8.C m VGPB.C5R8.R VGPB.4.5R8.B VGPB.60.5R8.BVGPB.99.5R8.B VGPB.139.5R8.BVGPB.192.5R8.BVGPB.195.5R8.B VGPB.2.6R8.BVGPB.2.5R8.B VGPB.2.5R8.R VGPB.195.5R8.R VGPB.2.6R8.R Q4R8 side VGI.36.5R8.CVGI.75.5R8.C VGI.115.5R8.CVGI.155.5R8.C VIESA.193.5R8.C PS: VRPMB.21.5R m. Cct 12 VIESA.3.5R8.C PS: VRPMB.21.5R m. Cct 12 Q5R8 side Interaction Point BLM m BLMQI.05R8.B2E30_MQY m BTVSI.C5R8.B2 (BTVSI084) Anti-Ecloud solenoids installed: on Q4 side and Q5 side during TS 2010/2011; B-C and C-D interconnects 6/07/2011 A-B interconnects?? (after 22/09/2011) 25/09/201220M.J. Barnes

Ecloud solenoid layout Courtesy of V. Baglin Q5 Q4 MKI8DMKI8CMKI8BMKI8A Anti-Ecloud Solenoids at MKI, LSS8 25/09/201221M.J. Barnes

MKI8. 25ns, 24/10/2011 B2: 9e13 max charge. Anti-elcoud solenoids switched between 0A and 5A. Max pressure on B2 close to MKI8s: 6e-8mbar on VGPB.192.5R8.R (Q5 side of MKI8D). Pressure on VGPB.192.5R8.R not sensitive to Ecloud solenoid current (in this case)….. Pressure in C-D interconnect, and thus magnet, is sensitive to Ecloud solenoid being on or off. Max. C-D interconnect pressure during injection ~6e-9, with several injections > 4e-9 mbar. VGPB.192.5R8.R MKI8D C-D interconnect Switching solenoids off results in an increase in pressure, on C-D interconnect, and thus MKI8D by factor of ~3. 25/09/201222M.J. Barnes

During MKI8 SoftStart, following breakdown of MKI8D, considerable vacuum activity seen on VGPB.192.5R8.R: vacuum activity reduces for subsequent SoftStarts….. 25/09/201223M.J. Barnes MKI8. 50ns, 24/09/2012 B1 intensity VGPB.192.5R8.R (SoftStart): B1 circulating Solenoid: 3A Solenoid: 5A C-D interconnect VGPB.192.5R8.R (SoftStart) B2 intensity VGPB.192.5R8.R (SoftStart) Spark

LHC Injection Kicker: Maximum Temperatures During Oct  Magnet PT100’s are mounted on ground plates: these plates contact the ground busbar and magnet capacitors;  Ground busbar does not contact ferrites – hence heat conduction to magnet PT100’s is mainly via magnet capacitors. Hence Mag_Up would be expected to measure a higher temperature than Mag_Dn, but ….  Tube_Up temperature > Tube_Dn temperature, maybe because of more cooling at “Dn” end (due to SS tube and “cage” around ferrites??).  The Power (W/m) shown is derived from impedance measurements – measured magnet temperature does not correlate with the power…. Kicked Beam TMR connection entrance box connection capacitor ferrite yoke ground plate ground plate HV plate PT100 Tube_Dn Beam impedance reduction ferrite (lossy + low-loss) Beam impedance reduction ferrites (lossy + low-loss) PT100 Mag_Dn PT100 Tube_Up PT100 Mag_Up Screen conductors soldered to “ground” (Ferrites mounted on SS tube) Screen conductors capacitively coupled to “ground” (metallization on ceramic tube) NO Capacitor here 18/04/201224M.J. Barnes: LMC

Planning for TS3 The exchange of MKI8D will take ~4.5 days with shifts, requiring full commitment from all teams involved to achieve this optimized intervention time. 25M.J. Barnes: LMC27/06/2012 Courtesy: G. Bregliozzi & V. Baglin