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– 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

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

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?

Tevatron Ring Wide Loss Plot (Dec 5)

Damage to E03 1.5m Collimator

Protons

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

December 5 quench

Abort Kicker firedFast quench could have been detected

Minimum level I Would set BLM limit.

Dipole at d4 could have pulled abort

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)

QPM Over Sample BufferDevelopment of Quench:A48U 16msecD48L 13.5msecF17L 13msecE11U 12.5 msec

Before abort

(Courtesy D. Wolff& EE Support)Quenched 5 dipoles at A48; DI/Dt = .5A/msec

Quench A48 1st Abort Fired

16msec

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

for different quenches

Other events

Separator spark before fast QPM abortsJuly 8 – B11 Vert sep spark (4 house quench)

Separator spark after fast QPM abortDec 13 – B11 Vert sep spark (E1 house only quenched)

Kicker Prefires – Nothing we can do with loopKicker 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

July 8 – B11 Hor sep sparkFast QPM abort would have stopped quenches in

4 other houses

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.

Hor orbit for F48 kick due to F4 Quench2 msec after quench

-10

-8

-6

-4

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0

2

4

6

8

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0 20 40 60 80 100 120

Ring BPM location

(mm

)

Displacement @ # msec

real orbit

diff sim-real

Hor orbit for F48 kick due to F4 Quench13 msec after quench

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 20 40 60 80 100 120

Ring BPM location

(mm

)

Displacement @ # msec

real orbit

diff sim-real

Fast QPM abort can remove beam in ~ 2msec instead of 16msec.

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