cable fire at the ler tfb kicker stan ecklund for investigation committee and other helpers

Cable Fire at the LER TFB Kicker

Stan Ecklund for investigation committee and other helpers

25-27 Oct. 2006 PEP-II MAC Review 2

Investigation Committee

• Ron Akre• Stan Ecklund (Chair)• Keith Jobe• Joseph Olszewski • Bob Reek• Ponciano Rodriguez• Mike Stanek • Uli Wienands• Andrew Young


Charge

1. Research the sequence of events leading to the fire. Determine the cause of the fire, if possible, or determine probable causes.

2. Identify damage and recommend a course of action to repair or replace damaged equipment.

3. Based on determined cause, recommend changes to this and similar systems that will prevent future incidents.

4. Coordinate with the ORPS investigation (do not duplicate)


Location in PEP-II Region 4


LER Horizontal Kicker 3040


Transverse Kicker Pickup Structure

This picture shows the kicker as a pickup. The picture below is the time domain response of a by4 fill pattern. If it was a by2 fill pattern, the signal in the red circle would move to the blue circle thus, the leading edge of the next bunch cancels the trail edge of the previous bunch.

The round trip time(4.2ns) = 2L/c where L = 63cm


Kicker

• 1.755” radius (44.577 mm) • 120 deg. • 24.62” long


Photo by David Kharakh on 11 Oct. 2005


Photo by Mike Zurawel on Aug. 17 2006


Wall Side


Breach in Cable


Melted center conductor


Cable Trays


Investigation Activities

• Observe and document situation• Many Photos at:

– V:\AD\AreaManagers\MZurawel\LER X Kicker 8-17

• Roped off Site to keep undisturbed during investigation • Calculated beam power to cables (Steve Smith, Andrew Young,

Anatoly Krasnykh, John Fox)• Tested another fan, stalled• Looked at cable/tray damage• Mined history data


Event Sequence (Uli Wienands)

• 2000 mA, 861 bunches, by-4 (0:3442:4)• 17:42 arc T3040Ki2 sees temp. rise• 17:46 arc T3040K14, K15 see temp. rise• 17:48 elog LER Abort with LR42 Latched• 17:50 elog Fire Alarm 3114 IR-4 Building

– Starts in tunnel, then B645 (rf), then B640 (dnstairs)(no time line, just recollection)

• 17:51:32 errlog PR03 174 trips on gnd fault17:51:52 errlog PR08 5162 trips mag. Intlk #2

• 17:53:12 errlog P2HZDSOFF started


Current and Temps

Normal Run At time of fire

LER Current

T3040KI2X- LoadConnector

HOM

T3040K14Body

T3040K15 Bellows


TFB Drive Connections

• Note A: Damage found in the output section of the amplifier, the output transistor not connected to circuit

• Note B: Cable center pin was found not mating contact with filter. This causes the beam reflected signal to see an open at the amplifier

• Note F: Fire damage. X- drive cable damage is present up to 5 m from the kicker


TFB Load Connections

• Note C: A cable breach was discovered, the center conductor copper clad was melted and showed signs of arching on the opposite side of the conductor.

• Note D: The short pigtail that went from the long haul cable to the attenuator showed signs of melting and had an impedence of 25 ohms at the min.

• Note E: The beam was misaligned by 1 cm to the –x side• Note G: x+ load cable damage is present up to 5 m from the kicker


Power to Cable

• Strip-line kicker, like directional coupler• Upstream connector has beam induced signal• No bunch-to-bunch cancellation in by 4 bucket spacing. • Power calculated for centered beam (S. Smith, A. Young)

– 774 to 1200 Watts to cable– Loss 4.7 W/ft

• Observed 1 cm beam offset doubles power– Loss 9.4 W/ft

• Insulation Melts at 7 W/ft• LDF4 (1/2 in heliax) spec is 5 W/ft• Conclude cable should have failed as it did.


Observations and Conclusions

• Hottest part of fire inside ring, near fan• Two Candidates for Ignition source.

– Fan due to malfunction– RF cable from kicker

• Tested identical fan with stall – did not ignite, circuit opened• Autopsy of fan consistent with it being victim, not cause• Calculation of Beam induced Power into load cable exceeded cable

rating– Beam in a by 4 pattern. No Cancellation as in by 2 pattern.– Beam offset by 1 cm. Doubles power from centered beam.– Bad Cable connection at x- drive could also increased reflected power.– Cable to load measured low Z=25 would also reflect power.

• Conclusion:– Cause of ignition is exceeding power capacity of Load cable – Fan provided fuel, accelerating fire.


Repairs

• Clean Area – done• Build platform for cable repairs – done• Cable repairs -

– EWP, LOTO - done– Start DC cables – Complete DC cables– RF cables

• Checkout


Corrective Actions

• Additional Measures– Higher power rating on RF Load cables (7/8 inch vs. ½ inch)– Replace RF cables with those with Fire retardant jacket.– Add monitoring (Machine Protection) to TFB systems

• Thermocouple on cable• Forward and reverse power couplers/diodes

– Operational Limit on current, specific to pattern (by 4)– Understand and correct orbit offset


End

Extra Slides


Ref orbit During MD 17 Aug 2006 13:43


Orbit Consistently off x= -9 mm


XCOR making bump


Field at wall for 1 cm offset of beam


Power to –x electrode doubles at -1 cm offset

PEP-IITransverse Kicker

Beam Power Estimate

Steve Smith

Sept. 19, 2006


Procedure

• Foam Coax Rated for 5 Watt/ft loss– Independent of size– Size affects loss, not max loss

• Estimate beam power from idealized stripline kicker model• Compare prediction to observed waveforms


The Andrew's Cable average power handling specs. for this cable are 1.91KW @ 300MHz and 532W @3GHz. Using these numbers the limiting power density of the cable = ~5W/ft with inner conductor of 100oC. The melting temperature of the foam dielectric is 120 -130oC


Andrew LDF4 CableLDF4 Cable SpecsFrom Andrew data sheet

Freq Loss Max Power Loss Const Max loss/ft(MHz) dB/100' (kW) dB/100ft/sqrt(GHz) (Watt)

100 0.684 3.39 2.2 5.3200 0.983 2.36 2.2 5.3300 1.22 1.91 2.2 5.4400 1.42 1.64 2.2 5.4500 1.6 1.45 2.3 5.3700 1.92 1.21 2.3 5.3

1000 2.34 0.994 2.3 5.32000 3.45 0.673 2.4 5.33000 4.38 0.532 2.5 5.34000 5.18 0.448 2.6 5.35000 5.93 0.392 2.7 5.36000 6.64 0.351 2.7 5.38000 7.94 0.293 2.8 5.3

Estimate “Loss Constant” = 2.2 dB/100’/GHz

Limiting power loss per length = 5.3 W/ft


Andrew FSJ1 (1/4”) Cable

Andrew FSJ1 Data sheetFreq Loss Max Power Loss Const Max loss

(MHz) dB/100' (kW) dB/100ft (Watt/ft)/sqrt(GHz)

100 1.81 1.23 5.7 5.1200 2.58 0.865 5.8 5.1300 3.19 0.701 5.8 5.1400 3.7 0.603 5.9 5.1500 4.16 0.537 5.9 5.1700 4.97 0.45 5.9 5.1

1000 6 0.372 6.0 5.12000 8.73 0.256 6.2 5.13000 10.9 0.204 6.3 5.14000 12.8 0.174 6.4 5.15000 14.6 0.153 6.5 5.16000 16.2 0.138 6.6 5.18000 19.1 0.117 6.8 5.0

Estimate “Loss Constant” = 6 dB/100’/GHz

Limiting power loss per length = 5.1 W/ft


Kicker Model• Parameters– Length– Width– Impedance– Shunt capacitance– Beam charge– (Bunch length)


• For zero bunch length, the beam current spectrum is a series of delta functions at harmonics of the bunch spacing frequency.

• For the by-4 fill pattern the frequencies are

• The current in in each line is given by

• For finite bunch length the spectrum gets rolled off at high frequencies.

• Assuming Gaussian bunch shape with t = 38 ps

• The beam-induced power is down by about 3 dB at f.

Beam Spectrum

GHzt

f 42

1

02

0

nI

nII

b

bnMHzn

MHznFnF bn 119

4

476


• Assuming – weak coupling between striplines and – matched impedances at both ends

• (Modify later for shunting capacitance)

• impulse response:– two impulses of opposite polarity separated by

• Impulse:

• Frequency response:

Stripline Kicker

c

Lt2

bQZ

qZVdta22

)(2 nbn ffsQZV

|)4

sin(|)(L

fcffs


Paddle Capacitance• Paddle area A~ 2.8 in2 • Paddle gap d = 0.25 in• Paddle capacitance C = A/d ~2.6 pF

• Fc ~ 2.25 GHz


Power Disspation in LDF4

• Assumes:• Weakly-coupled striplines of

Z=50 Ohms– underestimates power

– Odd –mode is 50 Ohm

– Even mode is 64 Ohm??

• Directionality– Divide by 2 for even split

• No waveguide modes– Reduces power

• No HOM power from other sources– Increases power

• Centered beam

Beam Current I 2 AmpsKicker Coverage fraction phi/ 2pi 0.333Bunch Length SigT 38 psStripline Impedance Strip Z 50 OhmsGaussian width of bunch in frequency unitsSigma F 4188.3 MHzPaddle Capacitance Cp 2.6 pF 2.6

LDF4 LossBunch Stripline Paddle Integral Integral

Bunch HarmonicFreq(MHz) Current Form Factor FormFactor Rolloff Power Loss/ft Power Loss/ft0 0 2 1.00 0 1.00 0 0 0 01 119 4 1.00 1 1.00 88 0.2 88 0.22 238 4 1.00 0 0.99 0 0.0 88 0.23 357 4 1.00 1 0.99 86 0.3 174 0.44 476 4 0.99 0 0.98 0 0.0 174 0.45 595 4 0.99 1 0.97 81 0.3 256 0.86 714 4 0.99 0 0.95 0 0.0 256 0.87 833 4 0.98 1 0.94 75 0.4 331 1.18 952 4 0.97 0 0.92 0 0.0 331 1.19 1071 4 0.97 1 0.90 68 0.4 399 1.5

10 1190 4 0.96 0 0.89 0 0.0 399 1.511 1309 4 0.95 1 0.87 60 0.4 459 1.912 1428 4 0.94 0 0.85 0 0.0 459 1.913 1547 4 0.93 1 0.83 53 0.4 512 2.214 1666 4 0.92 0 0.81 0 0.0 512 2.215 1785 4 0.91 1 0.79 46 0.3 558 2.616 1904 4 0.90 0 0.77 0 0.0 558 2.617 2023 4 0.89 1 0.75 39 0.3 597 2.918 2142 4 0.88 0 0.73 0 0.0 597 2.919 2261 4 0.86 1 0.71 33 0.3 630 3.120 2380 4 0.85 0 0.69 0 0.0 630 3.121 2499 4 0.84 1 0.67 28 0.2 658 3.422 2618 4 0.82 0 0.65 0 0.0 658 3.423 2737 4 0.81 1 0.64 24 0.2 682 3.624 2856 4 0.79 0 0.62 0 0.0 682 3.625 2975 4 0.78 1 0.61 20 0.2 701 3.826 3094 4 0.76 0 0.59 0 0.0 701 3.827 3213 4 0.75 1 0.58 16 0.2 718 3.928 3332 4 0.73 0 0.56 0 0.0 718 3.929 3451 4 0.71 1 0.55 14 0.1 731 4.130 3570 4 0.70 0 0.54 0 0.0 731 4.131 3689 4 0.68 1 0.52 11 0.1 742 4.232 3808 4 0.66 0 0.51 0 0.0 742 4.233 3927 4 0.64 1 0.50 9 0.1 752 4.334 4046 4 0.63 0 0.49 0 0.0 752 4.335 4165 4 0.61 1 0.48 8 0.1 759 4.436 4284 4 0.59 0 0.47 0 0.0 759 4.437 4403 4 0.58 1 0.46 6 0.1 765 4.438 4522 4 0.56 0 0.45 0 0.0 765 4.439 4641 4 0.54 1 0.44 5 0.1 770 4.540 4760 4 0.52 0 0.43 0 0.0 770 4.541 4879 4 0.51 1 0.42 4 0.0 774 4.542 4998 4 0.49 0 0.41 0 0.0 774 4.543 5117 4 0.47 1 0.41 3 0.0 778 4.644 5236 4 0.46 0 0.40 0 0.0 778 4.645 5355 4 0.44 1 0.39 3 0.0 780 4.646 5474 4 0.43 0 0.38 0 0.0 780 4.647 5593 4 0.41 1 0.38 2 0.0 782 4.648 5712 4 0.39 0 0.37 0 0.0 782 4.649 5831 4 0.38 1 0.36 2 0.0 784 4.750 5950 4 0.36 0 0.36 0 0.0 784 4.7

Total Power = 774Power Dissipation per foot 4.7Est Melting Threshold 7.0


Power Disspation in FSJ1

• Assumes:• Weakly-coupled striplines of

Z=50 Ohms– underestimates power

– Odd –mode is 50 Ohm

– Even mode is 64 Ohm??

• Directionality– Divide by 2 for even split

• No waveguide modes– Reduces power

• No HOM power from other sources– Increases power

• Centered beam

Kicker Coverage fraction phi/ 2pi 0.333Bunch Length SigT 38 psStripline Impedance Strip Z 50 OhmsGaussian width of bunch in frequency unitsSigma F 4188.3 MHzPaddle Capacitance Cp 2.6 pF 2.6

FSJ1 LossBunch Stripline Paddle Integral

Bunch HarmonicFreq(MHz) Current Form Factor FormFactor Rolloff Power Loss/ft Loss/ft0 0 2 1.00 0 1.00 0 0.0 0.01 119 4 1.00 1 1.00 88 0.4 0.42 238 4 1.00 0 0.99 0 0.0 0.43 357 4 1.00 1 0.99 86 0.7 1.14 476 4 0.99 0 0.98 0 0.0 1.15 595 4 0.99 1 0.97 81 0.9 2.06 714 4 0.99 0 0.95 0 0.0 2.07 833 4 0.98 1 0.94 75 0.9 2.98 952 4 0.97 0 0.92 0 0.0 2.99 1071 4 0.97 1 0.90 68 1.0 3.9

10 1190 4 0.96 0 0.89 0 0.0 3.911 1309 4 0.95 1 0.87 60 0.9 4.812 1428 4 0.94 0 0.85 0 0.0 4.813 1547 4 0.93 1 0.83 53 0.9 5.714 1666 4 0.92 0 0.81 0 0.0 5.715 1785 4 0.91 1 0.79 46 0.8 6.616 1904 4 0.90 0 0.77 0 0.0 6.617 2023 4 0.89 1 0.75 39 0.8 7.318 2142 4 0.88 0 0.73 0 0.0 7.319 2261 4 0.86 1 0.71 33 0.7 8.020 2380 4 0.85 0 0.69 0 0.0 8.021 2499 4 0.84 1 0.67 28 0.6 8.622 2618 4 0.82 0 0.65 0 0.0 8.623 2737 4 0.81 1 0.64 24 0.5 9.224 2856 4 0.79 0 0.62 0 0.0 9.225 2975 4 0.78 1 0.61 20 0.5 9.626 3094 4 0.76 0 0.59 0 0.0 9.627 3213 4 0.75 1 0.58 16 0.4 10.028 3332 4 0.73 0 0.56 0 0.0 10.029 3451 4 0.71 1 0.55 14 0.3 10.430 3570 4 0.70 0 0.54 0 0.0 10.431 3689 4 0.68 1 0.52 11 0.3 10.732 3808 4 0.66 0 0.51 0 0.0 10.733 3927 4 0.64 1 0.50 9 0.2 10.934 4046 4 0.63 0 0.49 0 0.0 10.935 4165 4 0.61 1 0.48 8 0.2 11.136 4284 4 0.59 0 0.47 0 0.0 11.137 4403 4 0.58 1 0.46 6 0.2 11.338 4522 4 0.56 0 0.45 0 0.0 11.339 4641 4 0.54 1 0.44 5 0.1 11.440 4760 4 0.52 0 0.43 0 0.0 11.441 4879 4 0.51 1 0.42 4 0.1 11.642 4998 4 0.49 0 0.41 0 0.0 11.643 5117 4 0.47 1 0.41 3 0.1 11.744 5236 4 0.46 0 0.40 0 0.0 11.745 5355 4 0.44 1 0.39 3 0.1 11.746 5474 4 0.43 0 0.38 0 0.0 11.747 5593 4 0.41 1 0.38 2 0.1 11.848 5712 4 0.39 0 0.37 0 0.0 11.849 5831 4 0.38 1 0.36 2 0.1 11.950 5950 4 0.36 0 0.36 0 0.0 11.9


Predicted vs Measured Beam signals


Tentative Conclusions• Observed bandwidth about half of calculated

– Limitations of model– Directionality vs frequency

• Calculate marginally enough power loss in LDF4 to melt dielectric– Only requires 7 W/ft loss

• Losses in FSJ1 much higher!• FSJ1 failure may have increased losses in LDF4• Did not include position sensitivity

cable fire at the ler tfb kicker stan ecklund for investigation committee and other helpers

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