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Development of Solid State Long Pulse Klystron Modulators. Carlos DE ALMEIDA MARTINS (CERN - AB/PO). Collector (GND). On the electrical “side”, behaves like a transistor. ~ hundreds kV. -15 V. +. +. Emitter. -. -. V. Anode mod (grid). (or DC). Base. Collector. Filament - PowerPoint PPT Presentation
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CERN
28 March 2008
Development of solid state long pulse klystron modulators 1
Development of Solid State Long Pulse Klystron Modulators
Carlos DE ALMEIDA MARTINS(CERN - AB/PO)
CERN
28 March 2008
Development of solid state long pulse klystron modulators 2
What is a Klystron?
It’s an Electrical to RF power converter !!!Collector(GND)
Cathode(-)
Filament(source)
~ hundreds kV+
-
On the electrical “side”,behaves like a transistor
-15 V
Base
Collector
Emitter V
GND
(or DC)
(or DC)
Anode mod(grid)
+
-
CERN
28 March 2008
Development of solid state long pulse klystron modulators 3
Klystron as an electrical load
Icathode
Vcathode
1/RA resistor … variable
CollectorCathode
Klystron arcing and protection
Arc: Behaves like a short circuit (arc voltage ~ 50V);
Maximum allowed energy in the arc: ~20 J
(Power supply has to be quiclky switched off or bypassed)
Normal operation
CERN
28 March 2008
Development of solid state long pulse klystron modulators 4
A - Anode;C - Collector;K - Cathode;F - Filament
C
K
C
K
F
A
Klystron100 kV crowbar (Thyratron)
RFPO
Past experience in klystron supply from Power Converters group at CERN.
Thyratron CROWBAR
100 kV, 40A, DC (CW) power converter for LHC klystrons
CERN
28 March 2008
Development of solid state long pulse klystron modulators 5
Methods for klystron powering in pulsed mode
Two main approaches, depending on the klystron type:
Klystrons with Anode Mod terminal Klystrons without Anode Mod terminal
C
KLYSTRON
K
PULSER
AC
DC
C
KLYSTRON
K
A
PULSER
AC
Limitations:
• Klystrons are more expensive and less reliable;
• Cathode voltage permanently applied - > insulation stress
Challange:
• Development of the “pulser” power supply;
• Power supply (converter) = klystron modulator
CERN
28 March 2008
Development of solid state long pulse klystron modulators 6
Klystron supply in pulsed mode.J-PARC, GSI topologies
With Anode mode terminal
Ex: at GSI, GermanyEx: at J-PARC, Japan
CERN
28 March 2008
Development of solid state long pulse klystron modulators 7
Klystron supply in pulsed mode.Traditional topologies
Without Anode Mod terminal (Thyratron + PFN based topology)
Limitations:
• Use of cathodic tubes (thyratrons, ignitrons);
Limited lifetime with increased maintenance;
• Bulky and expensive system (PFN’s with increasing number of cells for large pulse widths;
• Possible periodic PFN tuning required to compensate for ageing effects;
DC
C
K
Thyratron
PFN
Pulsetransformer
Ex: Linac 2, CTF3 at CERN
CERN
28 March 2008
Development of solid state long pulse klystron modulators 8
Klystron supply in pulsed mode.Some recent solid state topologies
The TESLA type modulator, H. Pfeffer, D. Wolff, and Al., FERMILAB
(Without pulse transformer)
Simplified electrical schematic, with pulse transformer
120 kV, 140A, 1.6ms, 5 Hz
CERN
28 March 2008
Development of solid state long pulse klystron modulators 9
Klystron supply in pulsed mode.Some recent solid state topologies
The Oak Ridge Nat Lab (SNS) type modulator, Bill Reass and Al. Los Alamos Lab
140 kV, 70A, 1.6ms, 60 Hz
CERN
28 March 2008
Development of solid state long pulse klystron modulators 10
Klystron supply in pulsed mode.Some recent solid state topologies
The SLAC type modulator, G. Leyh, R. Cassel and Al, SLAC
115 kV, 135A, 1.5 ms, 5 Hz
CERN
28 March 2008
Development of solid state long pulse klystron modulators 11
3 MeV Test Stand project
3 MeV Test Stand – Phase I (2007, 2008)
45
3 MeV Test Stand ( end 2007)
1 klystron modulator
Due to the pulsed nature of the Linac,a pulsed solution was chosen for the klystron modulator
CERN
28 March 2008
Development of solid state long pulse klystron modulators 12
Klystron modulator parameters for the 3 MeV Test Stand (LEP CW klystron)
Cathodes power supply- Pulse width: 0.8 ms- Flat-top duration 0.6 ms- Precision at flat-top: < 1%- HF ripple at flat-top: < 0.1%- Repetition rate: 2 Hz- Nominal voltage: 100kV- Nominal current: 20A- Rise/fall times: 150µs- Cooling: Air (natural and forced)- Maximum energy in case of arc: < 20 J
Anode Mode polarization power supplies- Stability at flat-top: < 1%- HF ripple at flat-top: < 0.1%- Nominal voltage to cathode : 40..60 kV- Nominal current: 5 mA
Filament heater power supplies- Stability and ripple: < 1%- Nominal voltage: 30V- Nominal current: 35A- Floating withstand voltage to ground: 180kVdc for 1 min.
Pulse width
Rise time fall time
timeFlat-top
CERN
28 March 2008
Development of solid state long pulse klystron modulators 13
CERN prototype of solid state pulsed klystron modulator.
Proposed topology
(to be used in the 3 MeV Test Stand and Linac 4)Description• Capacitor bank charged via a
standard commercial power converter, PS1;
• Pulses formed by solid state medium-voltage switches;
• Step-up pulse transformer with oil insulation;
• Droop compensation system, PS2;
• Commercial anode and filament power converters, PS3 and PS4, possibly with dry insulation;
• No CROWBAR needed in the HV line for klystron protection
Simplified schematics
PULSETRANSFORMER
(OIL TANK)
Main solid stateswitches
A1
C
KF
1:10
Ca
pa
cit
or
ba
nk
ch
arg
er
po
we
r c
on
ve
rte
r, P
S1
Anode powerconverter, PS3
A - Anode;C - Collector;K - Cathode;F - Filament
Filament powerconverter, PS4
Vout
Droop compensation powerconverter or “bouncer”, PS2
0.1mF
Capacitordischarge
system
VPS1
VPS2
12 kV max-1
20
kV
ma
x
KLYSTRON(OIL TANK)
DC
Hign FrequencyISOLATION
TRANSFORMER
DC
K1
PS1, PS3, PS4 - CommercialPS2 - CERN made
120 kV High voltage cables
120 kV High voltage connectors
DIODERECTIFIER
A
DRIVER DRIVER
CERN
28 March 2008
Development of solid state long pulse klystron modulators 14
PULSETRANSFORMER
(OIL TANK)
Main solid stateswitches
A1
C
KF
1:10
Ca
pa
cit
or
ba
nk
ch
arg
er
po
we
r c
on
ve
rte
r, P
S1
Anode powerconverter, PS3
A - Anode;C - Collector;K - Cathode;F - Filament
Filament powerconverter, PS4
Vout
Droop compensation powerconverter or “bouncer”, PS2
0.1mF
Capacitordischarge
system
VPS1
VPS2
12 kV max
-12
0 k
Vm
ax
KLYSTRON(OIL TANK)
DC
Hign FrequencyISOLATION
TRANSFORMER
DC
K1
PS1, PS3, PS4 - CommercialPS2 - CERN made
120 kV High voltage cables
120 kV High voltage connectors
DIODERECTIFIER
A
DRIVER DRIVER
CERN prototype of solid state pulsed klystron modulator.
Some new technological improvements
Droop compensation power converter, PS2• Switch mode type;• Standard semi-conductor components;• Air insulation;• Fast closed loop feedback control
DC~540 V
+
-
PULSETRANSFORMER
(OIL TANK)
Main solid stateswitches
A1
C
KF
1:10
Ca
pa
cit
or
ba
nk
ch
arg
er
po
we
r c
on
ve
rte
r, P
S1
Anode powerconverter, PS3
A - Anode;C - Collector;K - Cathode;F - Filament
Filament powerconverter, PS4
Vout
Droop compensation powerconverter or “bouncer”, PS2
0.1mF
Capacitordischarge
system
VPS1
VPS2
12 kV max
-12
0 k
Vm
ax
KLYSTRON(OIL TANK)
DC
Hign FrequencyISOLATION
TRANSFORMER
DC
K1
PS1, PS3, PS4 - CommercialPS2 - CERN made
120 kV High voltage cables
120 kV High voltage connectors
DIODERECTIFIER
A
DRIVER DRIVER
Switch mode filament power converter, PS4
CERN
28 March 2008
Development of solid state long pulse klystron modulators 15
Cathode ratings: 100 kV, 20A, pulsed 2 Hz, flat-top: 600 s
A global klystron supply solution:(Cathode, Anode, Filament) in one system
CERN prototype of solid state pulsed klystron modulator.
CERN
28 March 2008
Development of solid state long pulse klystron modulators 1616
Load Voltage
-20
0
20
40
60
80
100
120
0.E+00 2.E-04 4.E-04 6.E-04 8.E-04 1.E-03 1.E-03
time (s)
Vk
(k
V)
Cathode voltage
Thyratron Firing
Cathode Voltage(20kV/div)
Cathode Current (4A/div)
Earc (65kV)=0.44JEarc (100kV)~1J200µs
Normal Operation Arc protection(short circuit with Thyratron)
Load Voltage (Zoom)
95
97
99
101
103
105
107
-2.E-04 0.E+00 2.E-04 4.E-04 6.E-04 8.E-04
time (s)
Vk
(k
V)
With bouncer
Without bouncer
< 1%
Cathode voltage (zoom at flat-top)
Test of the prototype in a dummy load
Cathode ratings: 100 kV, 20A, pulsed 2 Hz, flat-top: 600 s
CERN
28 March 2008
Development of solid state long pulse klystron modulators 1717
Normal Operation at nominal
Test of the prototype with the LEP klystron
Cathode ratings: 100 kV, 20A, pulsed 2 Hz, flat-top: 600 s
Ch4:Anode Voltage to ground(10 kV/div)
Ch3:Cathode Current(4A/div)
Ch2: Cathode Voltage to ground(20 kV/div)
Ch4:Anode Voltage to ground(1 kV/div)
Ch3:Cathode Current(0.8A/div)
Ch2: Cathode Voltage to ground(2 kV/div)
1.2%
1%
< 1%
Zoom at flat-tops
CERN
28 March 2008
Development of solid state long pulse klystron modulators 18
Surface building for klystrons and modulators
LINAC 4 Tunnel
~ 100m
The Linac 4 project
Linac 4 – Phase II (~ end 2012)
Linac 4
16 klystron modulators
1st stage: Linac4 injects into the old PSB increased brightness for LHC
2nd stage: Linac4 into SPL (and PS2) renewed and improved LHC injection
PS2 (2016 ?) Low-duty SPL (2016 ?)
Linac4(2013)
CERN
28 March 2008
Development of solid state long pulse klystron modulators 19
Klystron modulator parameters for Linac 4 (LEP CW klystrons + new pulsed klystrons)
Cathodes power supply- Pulse width: 1.5ms- Flat-top duration 1.2 ms- Precision at flat-top: < 1%- HF ripple at flat-top: < 0.1%- Repetition rate: 2 Hz- Nominal voltage: 120kV (*)- Nominal current: 2x20A (*)- Rise/fall times: 150µs- Cooling: Air (natural or forced)- Maximum energy in case of arc: < 20 J
Anode Mode polarization power supplies- Stability at flat-top: < 1%- HF ripple at flat-top: < 0.1%- Nominal voltage to cathode : 60 kV (*)- Nominal current: 5 mA (*)
Filament heater power supplies- Stability and ripple: < 1%- Nominal voltage: 30V (*)- Nominal current: 35A (*)- Floating withstand voltage to ground: 180kVdc for 1 min.
Pulse width
Rise time fall time
timeFlat-top
(*) to be confirmed, taking the new klystrons design into consideration
CERN
28 March 2008
Development of solid state long pulse klystron modulators 20
A possible klystron modulator topology for large average power (Full SPL at 50 Hz).
The dual topology of the LHC switch-mode converters (QF, QD):
LHC magnets : High current / Low voltage -> several modules in parallel
SPL klystrons: High voltage / Low current -> several modules in series
DC-link
CR
Linear HFtransformer
LR Lf
Cf
+
HVOutput
CR
Linear HFtransformer
LR Lf
Cf
CR
Linear HFtransformer
LR Lf
Cf
-
1
2
n
Pulse former: In the tunnelCapacitor charger: In surface building
AC
DC
+
-
140 kV, 70A, 0.6ms?, 50 Hz