Mki erratics hardware and electronics related aspects m j barnes
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MKI Erratics : Hardware and Electronics Related Aspects M.J. Barnes PowerPoint PPT Presentation

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


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


DS Tank

MS Tank




Kicker in vacuum tank


1 of 4 Magnets at Point 2

M.J. Barnes

Schematic of an MKI System

During resonant charging

After resonant charging

Thyratron can be triggered

Protons Injection from SPS

M.J. Barnes

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



M.J. Barnes

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

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

    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 …..



    M.J. Barnes

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