Pulse cable for XFEL
Hans-Jörg Eckoldt
Pulse cables for XFEL
14.07.04
Pulse cable for XFEL
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
Overview TESLA
Pulse cable for XFEL
Hans-Jörg Eckoldt
View of TESLA tunnel
Pulse cables
Pulse cable for XFEL
Hans-Jörg Eckoldt
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
View of the XFEL Tunnel
Pulse cable for XFEL
Hans-Jörg Eckoldt
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
Pulse cable for XFEL
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
Questions to be solved
• How to the terminations and splices look like?
• How to transport the cables?
• How to install the cables?
Pulse cable for XFEL
Hans-Jörg Eckoldt
Construction drawing
Pulse cable for XFEL
Hans-Jörg Eckoldt
Photo of pulse cable
Pulse cable for XFEL
Hans-Jörg Eckoldt
Termination
Pulse cable for XFEL
Hans-Jörg Eckoldt
Terminations
Pulse cable for XFEL
Hans-Jörg Eckoldt
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.
Pulse cable for XFEL
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
Pulse cable for XFEL
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
Pulse cable for XFEL
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
RC-Adaptation-Network
Pulse cable for XFEL
Hans-Jörg Eckoldt
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
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
Pulse cable for XFEL
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
Pulse cable for XFEL
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
Pulse cable for XFEL
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
Let’s come to the existing cable
Pulse cable for XFEL
Hans-Jörg Eckoldt
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
Preparation for fire propagation test
Pulse cable for XFEL
Hans-Jörg Eckoldt
Cable being firedduration 40 min
Pulse cable for XFEL
Hans-Jörg Eckoldt
Cable after fire propagation test
self extinguished after 20 min
Pulse cable for XFEL
Hans-Jörg Eckoldt
Cable after fire propagation test
Allowed propagation: 2.5 m
Reached propagation: 0.8 m
Pulse cable for XFEL
Hans-Jörg Eckoldt
Cable after smoke density test
Pulse cable for XFEL
Hans-Jörg Eckoldt
Destruction during smoke density test
Pulse cable for XFEL
Hans-Jörg Eckoldt
Transport of the cable
drum with 3000 m
Pulse cable for XFEL
Hans-Jörg Eckoldt
Installed pulse cable
Pulse cable for XFEL
Hans-Jörg Eckoldt
“tricky” parts of installation
Pulse cable for XFEL
Hans-Jörg Eckoldt
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
Pulse cable for XFEL
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
Pulse cable for XFEL
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
Pulse cable for XFEL
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
Measurement
U Klystron
I Klystron
I Modulator
U Modulator
Pulse cable for XFEL
Hans-Jörg Eckoldt
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
Test lead for 10 kV, Crowbar test
Pulse cable for XFEL
Hans-Jörg Eckoldt
Tests with test load
Pulse cable for XFEL
Hans-Jörg Eckoldt
Tests with Test load Short circuit
Pulse cable for XFEL
Hans-Jörg Eckoldt
Goal reached 128 kV
14.07.04 11.45
Pulse cable for XFEL
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
Pulse cable for XFEL
Hans-Jörg Eckoldt
The pulse cables behave in the way it is
foreseen.
The functionality is now proven for XFEL