Pulse cables for XFELxfel.desy.de/localfsExplorer_read?currentPath=/afs/... · Pulse cables for XFEL 14.07.04. Pulse cable for XFEL Hans-Jörg Eckoldt Why Pulse cable? • Basic idea

Pulse cable for XFEL

Hans-Jörg Eckoldt

Pulse cables for XFEL

14.07.04


Hans-Jörg Eckoldt

Why Pulse cable?

• Basic idea came from the TESLA LC

– About 600 modulators have to be installed

– This large number of units should NOT be installed into the

tunnel.

• Reliability

• Maintainability

• Space would have been to small for the 800 GeV upgrade

• The modulators shall be installed in service halls at ground level

• The pulse transformer have to be installed inside the tunnel

• The energy has to be transported into the tunnel via these cables


Hans-Jörg Eckoldt

Overview TESLA


Hans-Jörg Eckoldt

View of TESLA tunnel

Pulse cables


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Tunnel Design

50 cm

520 c

m

190 c

m

440 cm

80 cm

90 c

m

30 cm

125 c

m

210 cm

Figure 2. Main LINAC, Damping Ring & Electronic Station Pulse cables


Hans-Jörg Eckoldt

View of the XFEL Tunnel


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XFEL

• Technical data of the modulator for TESLA

• max. klystron gun voltage: 120 kV

• max. klystron gun current: 140 A

• Primary Voltage 10 kV

• Primary Current 1680 A

• high voltage pulse length: 1.7 ms

• pulse repetition frequency: 10 Hz

• max. pulse power: 16,8 MW

• average power: app. 300 kW

• Number of Modulators in TESLA: 38


Hans-Jörg Eckoldt

Requirements

• No significant delay for the pulses

• No distortion of the waveform

• No “electro smog” ejected into the tunnel

• Low losses

• Radiation hardness

• Good fire resistance due to the large amount of burning material

• Very high reliability

• Good price


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Questions to be solved

• How to the terminations and splices look like?

• How to transport the cables?

• How to install the cables?


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Construction drawing


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Photo of pulse cable


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Termination


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Terminations


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General comments

• The cable is called a pulse cable due to the fact that the

modulator produces pulses

• However when looking at the time of 1,7 ms and the rise

times of more than 100 µs for the current, the cable is

working in the DC region.


Hans-Jörg Eckoldt

No significant delay for the pulses

• this would decrease efficiency

• Simulation showed that a decrease in Z0 lead to a better

pulse behavior. Too achieve this two possibilities exist. :

– Increase the diameter of the inner conductor

• The construction is not easy

• Splices in the tunnel since only short pieces can be manufactured

– Put cable in parallel

• Good solution since standard manufacturing process


Hans-Jörg Eckoldt

Low losses

• The losses are mainly determined by the resistive part of the copper

• There is no significant damping of the semiconductor layers as seen in high frequency/short pulse applications

– Semi conducting layers can be used

– Again standard manufacturing for high voltage cables can be used

• Skin effects have to be taken into account

– By paralleling the effect of the skin effect reduced since


Hans-Jörg Eckoldt

No reflections on the cables

• The pulse traveling along the cables will see the pulse

transformer at one end.

• With the stray inductance the cable is not adapted and

the pulse would be reflected.

• Therefore an adaptation network consisting of resistor

and a capacitor has to be introduced for a broad band

adaptation .

• For the four cables a value of 6.6 Ohm and 2.5µF give

good results


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RC-Adaptation-Network


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No “electro smog” into the tunnel

• For the cable a triaxial design was chosen. The fields will

stay within the cable between the inner and middle layer

• Additionally an outer shield consisting of a enclosing foil

was introduced

• Measurements for EMC are still to be performed


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Radiation hardness

• By the choice of the material there are no problems to be

expected.

• XLPE (cross linked Poly ethylene) has a radiation

hardness of 5 * 107 rad

• Additionally the cables will be beneath concrete


Hans-Jörg Eckoldt

Good fire resistance

• Due to the large number of cables and the amount of XLPE a large fire load is introduced into the tunnel

• To counteract to this the construction was carefully chosen. The cable is specified according to IEC 60332 Cat. A

– The outer shield is built as a closed foil building a barrier for the fire and the burning material

– Two layers of FRNC (Flame retardant non corrosive) materials are introduced.

• This was proven by a fire propagation test


Hans-Jörg Eckoldt

Help on construction, calculation

• M. Filtz, Institut für theoretische Elektrotechnik, TU Berlin

• Dr. Pfeiffer, Draka Multimedia Cable

• Dr. Fricke, Siemens

• W. Buchwald, Kaiser Kabel, später Nexans

• Ansoft, Supply of modells for cable simulation


Hans-Jörg Eckoldt

With these requirements the cable was

ordered

• The cable was purchased in a European wide bid for a

tender

• Several companies who are able to manufacture the

cable. The cable can be produced with standard

production procedures.

• The order was given to HVT, Germany

• Dielectric Sciences, US

• Essex, UK

• SAGEM, France


Hans-Jörg Eckoldt

Let’s come to the existing cable


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Tests with the cable in factory

• Routine tests as for any other high voltage cable

• Type test for fire propagation test IEC category A

• Smoke density test


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Preparation for fire propagation test


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Cable being firedduration 40 min


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Cable after fire propagation test

self extinguished after 20 min


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Cable after fire propagation test

Allowed propagation: 2.5 m

Reached propagation: 0.8 m


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Cable after smoke density test


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Destruction during smoke density test


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Transport of the cable

drum with 3000 m


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Installed pulse cable


Hans-Jörg Eckoldt

“tricky” parts of installation


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Electrical Test

• First tests with modulator at low voltage (max. 5kV)

• The commissioning of the test was extremely successful

• Tests on test load to check the short circuit behaviour


Hans-Jörg Eckoldt

Simulation model for modulator, cable and

klystron incl. arcs

+

V

��

D1

D2

L1 330u

R1 160C1 80u

C_Bounc700

2m

C := 1.4m

V0 := 8k

CTRL := S1

TH1

CTRL := zuenden

TFR1P2W1

VM1

LTRA1

C := 1n

R := 119u

LEN := 1.5k

G := 0

L := 50n

t_1>0.1

Dklys1 Rkurz 100m

U_brenn

100

DkS2

CT RL := S

S3

CT RL := S

+

VVM4

A

AM3

LM := 0.8

LS1 := 0.194m

LS2 := 0.1uRa 6.6

Ca 2.5u

+

V

VM2

N0040

N0015

Kl ystron

KLYSTRON17

A

AM1

A

AM2

R2

L2

40u

#

XY

Varistor

CH := XYVaris tor.VAL

XYVaristor

F ILE := resistor_ssh__XY Varistor.mdx

100m

D3R3

200m


Hans-Jörg Eckoldt

Current in modulator and transformer

A M1.I [A ] A M2.I [A ]

t [s ]

1.2k

-0.2k

0

0.2k

0.4k

0.6k

0.8k

1k

0 3.5m0.5m 1m 1.5m 2m 2.5m 3m


Hans-Jörg Eckoldt

Simulated klystron voltage at low voltage

VM4.V [V] KLYSTRON17.KLYSTR_

t [s ]

0.1Meg

-10k

0

20k

40k

60k

80k

0 3.5m0.5m 1m 1.5m 2m 2.5m 3m


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Measurement

U Klystron

I Klystron

I Modulator

U Modulator


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Test load

• Resistive value of 8.9 Ohms

• Inductance of 200 µF

• Ignitron to produce a short circuit at any

moment during the pulse

• Crowbar test with a wire to prove the allowed

amount of Joule deposited


Hans-Jörg Eckoldt

Test lead for 10 kV, Crowbar test


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Tests with test load


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Tests with Test load Short circuit


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Goal reached 128 kV

14.07.04 11.45


Hans-Jörg Eckoldt

Next Tests

• Test with klystron to full voltage

• Test with full pulse length

• High power test with 10 Hz, 128 kV, 5 MW Klystron

• Measurement of the electro magnetic radiation

• Long term tests with modulator


Hans-Jörg Eckoldt

The pulse cables behave in the way it is

foreseen.

The functionality is now proven for XFEL

Documents

Pulse cables for XFELxfel.desy.de/localfsExplorer_read?currentPath=/afs/... · Pulse cables for XFEL 14.07.04. Pulse cable for XFEL Hans-Jörg Eckoldt Why Pulse cable? • Basic idea