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325 MHz IQ Modulator
Ding Sun and David Wildman
Fermilab Accelerator Advisory CommitteeMay 10th – 12th , 2006
2Fermilab
Outline
• IQ Modulator• Circulator (status and plan)• Fast Phase Shifter (status and plan)• Hybrid (status and plan)• Recent High Power Test Results• Conclusions
3Fermilab
325 MHz RF Distribution System
Pulse Transformer& Oil Tank
IGBT Switch & Bouncer
CAP
BANK
10 kV110 kV
Charging
Supply
300kW
MODULATOR: FNAL/TTF Reconfigurable for 1,2 or 3 msec beam pulse
SingleJPARC Klystron325MHz
3 MW
WR2300 Distribution Waveguide
TO
SH
IBA
E
3740
A
I
Q
M
I
Q
M
I
Q
M
I
Q
M
R F Q
I
Q
M
Cables inTunnel
Fast Ferrite Isolated I/Q Modulators
RF Couplers
S
I
Q
M
S
I
Q
M
R
I
Q
M
S
I
Q
M
S
I
Q
M
R
I
Q
M
600kW 40 kWmax.
D
I
Q
M
S
I
Q
M
R
I
Q
M
D
I
Q
M
S
I
Q
M
R
I
Q
M
120 kWmax.
10kV
H-
Room TemperatureCopper Cavities (16+2)
Radio FrequencyQuadrupole
Cryomodule #1-2 Single- Spoke
Resonators 1 (18)
Cryomodules#3 -4 Single - Spoke
Resonators 2 (22)
5 kW..
MEBTRT-TSR
… 60 kWmax.
110 MeV
4Fermilab
IQ Modulator (Function)
• The entire front-end linac up to 90 MeV is powered by a single 2.5 MW klystron.
• RF power is carried by a single WR 2300 waveguide alongside the beam line and partially extracted by a waveguide-coax coupler at the location of each RF structure.
• IQ modulators are used to control phase and amplitude of the input power for each RF structure.
• Circulator + hybrid + ferrite phase shifters
5Fermilab
IQ Modulator
Box size: 24” x 20”
6Fermilab
IQ Modulator (Specification)
• Peak Power– 40 kW ~ 120 kW
– 275 kW (for each drive loop of RFQ)
• Tuning Range– Phase: +/- 45 degree
– Amplitude: +/- 1.5 db
• Phase Tuner Slew Rate– 1 degree/1sec
7Fermilab
IQ Modulator (R&D Plan, 2005)
• Design and make individual circulator, hybrid and fast ferrite phase shifter.
• Power test them separately, identify problems and modify design.
• Integrate them and power test.
8Fermilab
Circulator (status)
• Stripline Y-junction Type
• Prototype (low power): RF part finished, final permanent magnet design to be completed.
• A prototype for “high” power test has been designed. 50% of mechanical drawing completed.
~ 8 inch
9Fermilab
Circulator (measured S parameters)
Isolation: -30 db
Insertion lose: -0.18 db
10Fermilab
Circulator (plan)
• Fabricate the prototype circulator (2-3 months) and measure it at low power level, modify it if necessary.
• High power test to determine:
– Power limit for this initial design
– Thermal effect
• Increase height for higher power handling capability.
• How to compensate thermal effect (cooling control).
• Finalize permanent magnet design and mech. detail.
• Time: 12 - 24 months.
• Cost: $ 20 - 30 k (cooling control not included)
11Fermilab
Phase Shifter
• Coax line is filled with ferrite material and shorted at end: power is fully reflected.
• Effective length of coax line is controlled by magnetic field applied with a solenoid.
12Fermilab
Phase Shifter (Status)
• High power tested:– 1 5/8” O.D. coax line: 85 kW
– 3 1/8” O.D. coax line: 440 kW
(2.5” long ferrite)
• Speed of phase change
(low power):
120 degree/50 sec50
A /
div
20 d
egre
e /
div
Blue: current of solenoidPurple: phase of output power
13Fermilab
Phase Shifter (plan)
• Fast phase shift during high power pulse• Measure thermal heating effects at full power • High power test up to 400 kW with 3" O.D. x
5" long garnet • Control phase and amplitude to real cavity
14Fermilab
Hybrid
• A quadrature branch line coupler made of copper sheet with thickness of 0.125”
• A matching section at end of each arm for transition of suspended striplines to 1 5/8” coaxial line ports
• No cooling• Easy fabrication – low cost• Bandwidth: ~60 MHz
Box: 20” x 20”
15Fermilab
Hybrid (measured S parameters)
phase: -89.7 degree
Amplitude: -2.99/-3.18 db
Reflection: ~ -39db
Isolation: ~ -39db
5db/div
FrequencyFrequency
5db/div
1db/div
90
degr
ee/d
iv
Port1 - Port3
Port1 – Port2
16Fermilab
Hybrid (status and plan)
• Status: high power tested: 170 kW without failure under full reflection condition
• Plan: – Add directional coupler within the box for signal
processing (cost saving).
– Further test at FNAL to see power limit using fixed coax line sections with various lengths.
– Modify design (increase height) for higher power (~ 275 kW for RFQ).
17Fermilab
Recent High Power Test Results
• A hybrid and a phase shifter together (a partial IQ Modulator) was tested up to 170 kW input power level (limit of 1 5/8” phase shifter).
• APS 1.3 MW CW Klystron configured in pulsed mode (pulse length: 4 ms, rep rate:1Hz).
• Port #2 is connected with a 1 5/8” ferrite phase shifter, port #3 is shorted.
• Amplitude and phase of output power (port #4) was controlled at all power levels by adjusting phase shifter.
18Fermilab
Recent High Power Test (setup)
19Fermilab
Recent High Power Test Results (plot)
Amplitude Modulation of Oupt Power at Various Input Power Level
0
20
40
60
80
100
120
140
160
180
-60 -40 -20 0 20 40 60
Phase difference (degree) between port #2 and #3
Am
pli
tud
e o
f O
utp
ut
po
wer
at
po
rt #
4
20 kW
30 kW
40 kW
50 kW
70 kW
80 kW
90 kW
100 kW
120 kW
140 kW
160 kW
Phase Modulation of Output Power at Various Input Power Level
0
20
40
60
80
100
120
140
160
-60 -40 -20 0 20 40 60
Phase difference (degree) between port #2 and #3
Ph
ase
of
ou
tpu
t p
ow
er a
t p
ort
#4
20 kW
30 kW
40 kW
50 kW
80 kW
100 kW
120 kW
160 kW
20Fermilab
1.3 GHz IQ Modulator
• For main linac 1.3 GHz superconducting cavities.
• Waveguide version will be delivered in July, 2006.
• Can be used for ILC.
21Fermilab
Conclusions
• IQ Modulator R&D are doing well following original plan.
• Hybrid and ferrite phase shifter together have been (1) power tested up to 170 kW which exceeds all power requirement of front linac except for RFQ and (2) functioned as IQ modulator at high power levels.
• For modest cost so far, IQ Modulator R&D is well worthwhile: enable us to have experience on how to make high power ferrite device work for HINS and possibly ILC.
• We have a plan for what to do next to get to a 325 MHz Front End Linac in Meson.