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MKI Erratics : Hardware and Electronics Related Aspects M.J. Barnes

MKI Erratics : Hardware and Electronics Related Aspects M.J. Barnes. Acknowledgements: Antoine, R.A. Barlow, P. Burkel, E. Carlier, N. Magnin, V. Mertens & R. Rosol. One MKI System: 4 PFN’s & 4 Magnets. Inside a PFN: 2-way electrical delay 9µs. UA23 / UA87. RG220U cables to magnet.

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MKI Erratics : Hardware and Electronics Related Aspects M.J. Barnes

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  1. MKI Erratics: Hardware and Electronics Related Aspects M.J. Barnes Acknowledgements: Antoine, R.A. Barlow, P. Burkel, E. Carlier, N. Magnin, V. Mertens & R. Rosol

  2. One MKI System: 4 PFN’s & 4 Magnets Inside a PFN: 2-way electrical delay 9µs UA23 / UA87 RG220U cables to magnet TDR DS Tank MS Tank PFN (~5m) Controls Kicker in vacuum tank RCPS 1 of 4 Magnets at Point 2 M.J. Barnes

  3. Schematic of an MKI System During resonant charging After resonant charging Thyratron can be triggered Protons Injection from SPS M.J. Barnes

  4. MKI2 MS3 Erratic on 28/7/2011 @ 16:30hrs • At 16:30:43hrs, on 28/7/2011, an erratic turn-on of MKI2 MS3 (Melton) at full PFN voltage; • Interlocks detected an MS erratic and correctly triggered MS’s and DS’s of system (within 2µs), emptying PFN via both ends. Hence all 4 kicker magnets pulsed for up to 4.5µs, emptying PFNs of energy. • Circulating beam was not in IP2 and therefore not disturbed. • Batchwas extracted from SPS but saw no kick at MKI2 and went straight into the TDI. • Note: this MS, Melton, was put in place during the last TS (July 2011) and has since made 5 erratics (only last 2 effected beam). Charging current & PFN voltage Current in kicker magnet MS3 erratic MS3 erratic, after resonant charging 4.5µs 2µs M.J. Barnes

  5. MKI2 MS3 Erratic on 28/7/2011 @ 18:03hrs • At 18:03:09hrs , on 28/7/2011 , an erratic turn-on of MKI2 MS3 (Melton) occurred during resonant charging – sending current to 1 of the 4 kickers (Note: it is unusual to have an erratic at such low voltage); • Interlocks did NOT detect erratic of MS3 (at 33kV): hence no immediate action was taken to turn-on other thyratrons. Therefore the full 9µs of PFN pulse length sent, via MS3, to kicker C. • Other 3 PFNs correctly discharged via the DS after 4ms (no further kicker magnet current); • The erratic occurred ~500µs into the charging process, and the extraction from the SPS was inhibited; • Circulating beam was swept over the aperture and protection elements (~17% of normal kick) for ~9µs. PFNs 1 & 2 at normal voltage (~50kV) PFNs 4 at low voltage (~33kV) because of MS3 erratic Erratic (untriggered) turn-on of MKI2 MS3 ~9µs circulating beam not dumped M.J. Barnes J. Wenninger

  6. MKI Erratic Summary • MS Melton (MKI2) erratics (total: ~12): • April 2010: SoftStart - 1 @ 1.7kV above nominal • August 2010: SoftStart - 3? (1 recorded) @ 1.7kV+ above nominal • Normal Op – 3? (1 recorded) • 2/9/2010: Melton replaced by Moulin • July 2011: Melton installed during TS of July 2011 (replacing Moulin) • SoftStart – 3 (1 @ ~40kV; 2 @ 2kV above nominal) • Normal Op – 2 (1 recorded) • Melton replaced by Moulin on 29/7/2011 • Other MKI2 Switch erratics since April 2010 (total: 6): • MS1 Millbrook: SoftStart - 3 • MS3 Moulin: SoftStart – 2 & Normal Op – 1 (4/7/2011). Replaced by Melton during July 2011 TS. Moulin reinstalled 29/7/2011. • DS3 Doncaster: SoftStart – 1 • MKI8 Switch erratics since April 2010 (total: 2): • MS2 Manchester: SoftStart – 1 • DS2 Dagenham: SoftStart – 1 M.J. Barnes

  7. MKI Summary of Investigations & Actions • After replacing MS Melton, and following two MS3 erratics and a further intervention (30/7/2011), the erratics have stopped (since 10 days) and the immediate danger of more erratics seems to be gone. • MS Melton brought back to lab. Current regulator on bias-board found to be damaged – supplying current corresponding to maximum of thyratron specification: this could increase rate of erratics. • Remote trending of current presently being implemented to allow possibility of remote diagnosis of this current regulator fault. • Long-term: fibre optic read-back to monitor thyratron G1 and bias-board. • Thyratron in MS Melton may be damaged – to be returned to E2V for diagnosis. • Spare MS from MKI8 now in lab for re-conditioning; can be used at Pt 2 or Pt 8. • Occasional missing G1 triggers to MS3 (5% to 10% missing) & MS4 thyratrons. This accounts for jitter noted (IQC) on MS3 & MS4. • Missing G1 accelerates wear of thyratron, hence may have contributed to quantity of erratics. • New trigger cards designed and built but not yet installed in MKI – but further investigations of cause are also required. • Long-term: detection of missing outputs of G1 power trigger unit. • Tests in UA23 have demonstrated that: • Erratic occurring after resonant charging is correctly detected; • Erratic occurring at 500µs into resonant charging was not detected. • Non-detection of MS erratics (thus no retriggering of other thyratrons) – High Priority • Inhibit/masking due to one or more modules or a noise-filter, in the erratic detection chain, may be responsible. Awaiting access, in the shadow of another intervention, to investigate further. • Low voltage fast interlock inhibition mechanism will be removed (implemented for the SoftStart) during next short TS. • May require further investigations ….. Bias-board Thyratron M.J. Barnes

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