Transcript No Slide Title

MDK Workshop, CERN, Geneva, April 2001
CLIC
RF Pulse Compression
system for CTF3.
I.Syratchev, CERN
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
1
CLIC
 RF Pulse Compression is the only way to
increase RF power level from the number
of klystrons available for CTF#3.
 RF phase/amplitude modulation is the tool
to control the RF pulse shape in a system klystron plus “SLED”-like RF pulse compressor.
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
2
RF Pulse Compression system for CTF3.
CLIC
The flat pulse after the cavity based pulse compressor (LIPS), with
modulation of the input RF phase (PM).
The linear part of the phase slop will be
compensated with the frequency shift:
Tout = 
LIPS cavity Q0 =1.8x105, =8
2 .3 8 1 4 6
2 .5
2.3
6
260
2.1
250
5000
6500
2
Power gain
200
a
i
b
1 .5
6.5 sec
5.5 sec
i
a1
i
b1
i
180
ph 
j 
Output
phase
180

150
ph1
i
100
1
Input
phase
50
0 .5
0
0
0
0
0
0
0
0
1000
2000
3000
4000
Time, ns
t
i
I. Syratchev, MDK Workshop, Geneva, CERN
5000
6000
7000
3
7 1 0
April 2001
1000
2000
3000
4000
t1  t
j i
5000
Time, ns
6000
7000
3
7 10
3
RF Pulse Compression system for CTF3.
CLIC
The effect of residual RF phase sage and energy spread. R. Corsini
Energy spread
The residual phase
envelops after two
RF stations
1=60 2=80
1=80 2=60
1
minimized
2
Single bunches profiles after re-combination.
No energy spread
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
4
RF Pulse Compression system for CTF3.
CLIC
The flat pulse after the cavity based pulse compressor (LIPS), with
modulation of the input RF phase-to-amplitude (PTA).
RF phase modulation
3
2.283
1
1
LIPS
1
Pl
Kl#2
Kl#1
PL
40 MW
6.5 sec
40 MW
6.5 sec
Amplitude
2
0.5
PL
k1
k1
LIPS+PTA
1
k1
Pl
0
0
k1
0.5
2
1
0.995
1
0
0
1
2
3
4
td
k1
Time,1000ns
2
80 MW Amplitude
modulated RF pulse
5
6
7
7
1 1
4500
4500
Time
 Output pulse flat both in
LIPS#2  2
RF amplitude and phase.
80 MW flat RF
1.6 sec
S1
S2
S3
I. Syratchev, MDK Workshop, Geneva, CERN
5500
td
k1
6000
6500
6500
Comparison between PTA and PM
Pros:
LIPS#1  2
5000
S4
2
 Easy RF power level control.
 Better stability of operation.
April 2001
Cons:
 Less efficient (~10%).
 Two klystrons needed.
5
RF Pulse Compression system for CTF3.
CLIC
Power gain.
2.525
2.6
po
p8
Pgg
Pgv
PM
Modified
LIPS
2.4
2 2.2
PTA
mk
2
mk
2
mk
mk
LIPS
1.8
1.6
1.43427
1.4
4.5
4.5
5
5.5
6
t
6.5
Klystron pulse, sec
mk
7
7.5
7.5
# LIPS modification is mainly the adjusting of the cavity coupling.
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
6
RF Pulse Compression system for CTF3.
CLIC
System operation stability.
Because of the energy spread, the
demand on the compressed pulse
flatness :
P/P < 2%
The examples of the compressed RF pulse
distortion due to the klystron RF phase ripples.
a) RF Phase modulation. Klystron
RF phase ripples 30 peak-to-peak.
2.5
2.128
The main sources of instability:
2
Klystron RF phase and amplitude
1 jitter as result of HV supply
instability.
1.5
A
j3
A
j4
1
0.5
0
50
0
100
0
0
1000
Time
2000
3000
A
j0
4000
5000
6000
3
6 10
b) RF Phase-to-amplitude modulation.
Klystron RF phase ripples 100 peak-to-peak.
PM
10
p
i
2.004
2.5
P/P, %
p1
i1
p2
i2
2
1
PTA
1.5
PL
k1
1
0.17 0.1
0.1
0.2
1
ph 2  ph1 2  ph2
i
i1
i2
10
100
50
0.5
Klystron’s RF phase amplitude
of ripples, degree.
0
0
0
0
1
2
3
4
Time
td
k1
5
6
7
7
1000
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
7
RF Pulse Compression system for CTF3.
CLIC
The frequency deviation of the
storage cavity, mainly because
of the temperature variation.
2
2.6
System operation stability.
3
20
2.6
The identity of the LIPS
cavities resonant frequencies.
100
F=-10 kHz
2
2.45
-3 kHz
a2
i
d 1 0 0
k
C1
i  1 2.3
3
100
d 
k 2
-1 kHz
C2
i1
10
1
2.15
2
2
4000
4000
0.686957 0.1
4750
5500
C
i0
Time, ns
6250
0
1
7000
7000
2
4
6
F, kHz
f01
k
8
10
10
To keep the flatness of the compressed pulse within specified P/P, the
temperature stabilization of the cavity must be < ± 0.04 0C.
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
8
RF Pulse Compression system for CTF3.
CLIC
System operation stability.
Algorithm of the fast correction of the cavity frequency shift.
Standard “SLED”
Pulse
5.27181
6
RF phase
modulation
Flat pulse
200
179.999848
2.32804
4
C
3
2 .5 7 9 6 1
C
 180
i1 
100
C
2
C
i1
2
i1
1
0
0
0
0
2000
4000
C
i0
6000
8000
 03
6.944441
2.37117
0
0
5000
4500
C
C
i1
0
0
0
0
6500
1 8 0
i1 
2000
4000
C
i0
6000
8000
 03
6.944441
0
0
0
2000
4000
C
i0
6000
8000
 03
6 .9 4 4 4 41
0
0
0
0
2000
4000
C
i0
6000
8000
 03
6.944441
Flat pulse
I. Syratchev, MDK Workshop, Geneva, CERN
Re-adjustment of the
RF phase modulation in
a fast local feedback
system of the klystron.
Old
180
C1 
i1 
1
0
i0
1
200
179.99984 8
3
2
C
6000
3
-10 kHz
2
i1
0
Distorted pulse
New
100
0
5000
4500
C
6000
i0
phase
RF
modulation
April 2001
6500
Temperature control
system.
9
RF Pulse Compression system for CTF3.
CLIC
Experiments with high RF power level. R. Bossart, December 2000.
Klystron
RF phase
RF power
Klystron drive phase
LIPS
Klystron output
RF phase
Initial
RF phase ripples
correction
Time, ns
~100
Time
I. Syratchev, MDK Workshop, Geneva, CERN
Parameters:
Q unloaded
Coupling
Tin
Tout
P out/in
P gain/teor.
P/P
1sec
April 2001
1.6x105
8.0
5 sec
1.4 sec
34.7/18 MW
1.92/2.04
< 1%
10
RF Pulse Compression system for CTF3.
CLIC
Barrel Open Cavity pulse compressor.
3 GHz version.
1. We need at least four more RF pulse compressors.
2. The BOC has one cavity, operating in a travelling wave
regime - solves the problem of the cavity’s pair identity.
3. Easy to manufacture than LIPS. We can do it in CERN.
4. The test prototype is preparing for the high RF power test.
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
11
RF Pulse Compression system for CTF3.
CLIC
The Barrel-cavity theory.
The eigen-frequency of the Barrel cavity with
Emnq oscillation is the solution of the next equation:
z
=
ka   mn 
=
2h
r0
-d
mn is a root of the Bessel function that for the
big m can be approximated as:
 omn  m  t n0
d
r
2a
Cavity profile
2

 r 

z  ar0 1    

 a 

I. Syratchev, MDK Workshop, Geneva, CERN
(q  1 2)
sin 
t n0
( n  12
, ,...),
 [( n  0.25)15
. ] ,
23
 m
 
 2
13
.
The optimal radius r0, when the external caustic
has the smallest height comes from: r0  2a sin 2 
where  and  are derived from:
m
a
cos 
sin  
sin 
 mn
r0
Finally the height of the external caustic and Q-factor
of the cavity are:
z q 1
asin 
 2 ( q  1 2)
k sin 2
April 2001
QE 
a
s
12
RF Pulse Compression system for CTF3.
CLIC
The shape of the 3.0 GHz Barrel-cavity.
R150
any
R100(L)
R50(R2)
Q=1.9780*105
F=2.99855 GHz
197.75*
60.150(
)
241.116*
R125.113*
R228(R1)
11.627(a)
R239.627
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
13
RF Pulse Compression system for CTF3.
CLIC
The modes of the 3.0 GHz Barrel-cavity.
H11,1,2
2.907 GHz
E7,2,1
3.081 GHz
E10,1,1
3.000 GHz
E6,1,5
3.0215 GHz
I. Syratchev, MDK Workshop, Geneva, CERN
H9,1,4
2.918 GHz
E8,1,3
3.0134 GHz
H7,1,6
2.922 GHz
E5,2,3
3.097 GHz
April 2001
14
RF Pulse Compression system for CTF3.
CLIC
General view and technical sketch of the 3.0 GHz BOC
RF pulse compressor.
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
15
RF Pulse Compression system for CTF3.
CLIC
Discussion...
Questions ?...
I. Syratchev, MDK Workshop, Geneva, CERN
April 2001
16