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

One MKI System: 4 PFN’s & 4 Magnets LMC: August 9, 2011M.J. Barnes2 DS Tank MS Tank TDR RG220U cables to magnet RCPS Controls PFN (~5m) Inside a PFN: 2-way electrical delay 9µsUA23 / UA87 1 of 4 Magnets at Point 2 Kicker in vacuum tank

Schematic of an MKI System M.J. Barnes3 Protons Injection from SPS Thyratron can be triggered After resonant charging During resonant charging LMC: August 9, 2011

MKI2 MS3 Erratic on 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.  Batch was 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). 4.5µs 2µs MS3 erratic MS3 erratic, after resonant charging Charging current & PFN voltageCurrent in kicker magnet M.J. Barnes4LMC: August 9, 2011

MKI2 MS3 Erratic on 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. Erratic (untriggered) turn- on of MKI2 MS3 PFNs 1 & 2 at normal voltage (~50kV) PFNs 4 at low voltage (~33kV) because of MS3 erratic ~9µs circulating beam not dumped J. Wenninger M.J. Barnes5LMC: August 9, 2011

MKI Erratic Summary MS Melton (MKI2) erratics (total: ~12):  April 2010: SoftStart - 1.7kV above nominal  August 2010: SoftStart - 3? (1 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 ~40kV; 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. Barnes6LMC: August 9, 2011

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 M.J. Barnes7LMC: August 9, 2011 Thyratron