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Tevatron Abort Overview

Tevatron Abort Overview. Jerry Annala 1/27/05 Slides from Dean Still and Dan Wolff with input from many others. Philosophy over time. Initial Days of the Tevatron Protect against any possible quench Unnecessary abort wastes a single beam pulse Early days of Collider

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Tevatron Abort Overview

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  1. Tevatron Abort Overview Jerry Annala 1/27/05 Slides from Dean Still and Dan Wolff with input from many others

  2. Philosophy over time • Initial Days of the Tevatron • Protect against any possible quench • Unnecessary abort wastes a single beam pulse • Early days of Collider • Tevatron can survive a quench • An abort turns off collider for ~ 1 Day • A quench is no worse than an abort • Run II intensities • There is enough beam to damage Tevatron again • Improve protection of Tevatron components • Do not cause unnecessary down time

  3. Abort loop basics • Abort inputs • QPM • Beam Loss monitors (masked during stores) • Power supplies (etc.) • Abort Loop • Hardware Fail safe loop • Can abort beam within a couple revolutions • Aborts synchronized to single beam abort gap

  4. Wake up Call • December 5, 2003 • Tokyo Pots move into beam • Beam loss causes damage to 2 collimators and a spool piece (3 correction elements) • Could we have protected ourselves from this damage? • Are there other events for which we need to better protect ourselves?

  5. Tevatron Ring Wide Loss Plot (Dec 5)

  6. Damage to E03 1.5m Collimator Protons

  7. Sequence of Events (Dec 5) • Pot #3 moves into beam quickly • Losses generated quickly quench A48U • Field in 5 dipoles start decaying (500 A/sec) • Orbit moves everywhere • Beam moves through D49 target, E11 spool piece, and E03 Collimator. • Protons are extinguished in E03 collimator in about several turns • QPM detects quench in A48 upper • Abort kickers fire

  8. December 5 quench Minimum level I Would set BLM limit. Fast quench could have been detected Abort Kicker fired Dipole at d4 could have pulled abort

  9. Abort mechanisms at that time • QPM abort • 60 Hz interrupt rate -> 16 msec reaction time • Necessary to detect 100 mV signals in the presence of 1000 Volt common mode voltages and 200 Volt differential voltages • 3 Line cycle averaging used to reduce noise even at 60 Hz update rate. • BLM abort (upgrade coming) • Masked • Set at 2msec interupt rate on Dec 5 (too fast?) • Dipole Regulators – (Masked from loop)

  10. 16msec Quench A48 1st Abort Fired QPM Over Sample Buffer Development of Quench: A48U 16msec D48L 13.5msec F17L 13msec E11U 12.5 msec Before abort (Courtesy D. Wolff & EE Support) Quenched 5 dipoles at A48; DI/Dt = .5A/msec

  11. Other fast quenches previous to installing fast abortShows how fast quench detection falls within the 60 Hz interrupt cycle for different quenches

  12. Other events Separator spark before fast QPM aborts July 8 – B11 Vert sep spark (4 house quench) Separator spark after fast QPM abort Dec 13 – B11 Vert sep spark (E1 house only quenched) Kicker Prefires – Nothing we can do with loop Kicker building loss of power (installed UPS) Vacuum valve move into beam (upgraded vacuum abort + fast QPM abort) May 15 – Unknown cause – Damaged E03 collimator again

  13. July 8 – B11 Hor sep sparkFast QPM abort would have stopped quenches in 4 other houses

  14. B11 sep spark causes F48U to fast quench. This shows the actual and predicted orbit distortion resulting from the field collapsing in the F48 cell. The Magenta trace shows the actual orbit change measured, and the blue trace shows the predicted orbit at two different times. Fast QPM abort can remove beam in ~ 2msec instead of 16msec.

  15. What to Do? • Fast QPM abort – Done • Upgrade BLMs – In progress • Don’t let Kickers pre-fire ? • UPS A0 Kicker hardware – done • Use dipole regulator aborts ? • Stop devices from moving into the beam • Vacuum abort upgrade done. • Pot motion upgrade done. • Better record keeping – In progress

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