RF Pulse Compression system for CTF3. MDK Workshop, CERN, Geneva, April 2001 RF Pulse Compression system for CTF3. I.Syratchev, CERN MDK-2001 CERN Switzerland
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.
RF Pulse Compression system for CTF3. 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 Input phase Output 2.1 6.5 sec RF phase, degree Power gain 5.5 sec Time, ns Time, ns
RF Pulse Compression system for CTF3. 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
RF Pulse Compression system for CTF3. The flat pulse after the cavity based pulse compressor (LIPS), with modulation of the input RF phase-to-amplitude (PTA). Time LIPS LIPS+PTA 1 2 Amplitude 1 2 Comparison between PTA and PM Pros: Output pulse flat both in RF amplitude and phase. Easy RF power level control. Better stability of operation. Cons: Less efficient (~10%). Two klystrons needed.
RF Pulse Compression system for CTF3. Power gain. PM PTA Klystron pulse, sec Power gain LIPS Modified # LIPS modification is mainly the adjusting of the cavity coupling.
RF Pulse Compression system for CTF3. System operation stability. The examples of the compressed RF pulse distortion due to the klystron RF phase ripples. Because of the energy spread, the demand on the compressed pulse flatness : P/P < 2% Time Power a) RF Phase modulation. Klystron RF phase ripples 30 peak-to-peak. The main sources of instability: Klystron RF phase and amplitude jitter as result of HV supply instability. 1 Time Power b) RF Phase-to-amplitude modulation. Klystron RF phase ripples 100 peak-to-peak. PM P/P, % PTA Klystron’s RF phase amplitude of ripples, degree.
RF Pulse Compression system for CTF3. System operation stability. 2 The frequency deviation of the storage cavity, mainly because of the temperature variation. The identity of the LIPS cavities resonant frequencies. 3 F=-10 kHz -3 kHz -1 kHz Time, ns Power 2 P/P, % 3 F, kHz To keep the flatness of the compressed pulse within specified P/P, the temperature stabilization of the cavity must be < ± 0.04 0C.
RF Pulse Compression system for CTF3. System operation stability. Algorithm of the fast correction of the cavity frequency shift. Standard “SLED” Pulse RF phase modulation Flat pulse Distorted pulse -10 kHz Re-adjustment of the RF phase modulation in a fast local feedback system of the klystron. Old New Temperature control system. Flat pulse RF phase modulation
RF Pulse Compression system for CTF3. Experiments with high RF power level. R. Bossart, December 2000. Klystron output RF phase 100 1.92 ~100 Time RF power RF phase 1sec Klystron LIPS RF phase Time, ns Klystron drive phase Initial RF phase ripples correction Parameters: Q unloaded 1.6x105 Coupling 8.0 Tin 5 sec Tout 1.4 sec P out/in 34.7/18 MW P gain/teor. 1.92/2.04 P/P < 1%
RF Pulse Compression system for CTF3. Barrel Open Cavity pulse compressor. 3 GHz version. WHY? 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.
RF Pulse Compression system for CTF3. The Barrel-cavity theory. The eigen-frequency of the Barrel cavity with Emnq oscillation is the solution of the next equation: mn is a root of the Bessel function that for the big m can be approximated as: The optimal radius r0, when the external caustic has the smallest height comes from: where and are derived from: Finally the height of the external caustic and Q-factor of the cavity are: z = = r0 -d d 2h r 2a Cavity profile
RF Pulse Compression system for CTF3. The shape of the 3.0 GHz Barrel-cavity. R150 R100(L) any R50(R2) Q=1.9780*105 F=2.99855 GHz R125.113* R228(R1) 241.116* 197.75* 11.627(a) 60.150() R239.627
RF Pulse Compression system for CTF3. The modes of the 3.0 GHz Barrel-cavity. H11,1,2 E10,1,1 H9,1,4 E8,1,3 H7,1,6 2.907 GHz 3.000 GHz 2.918 GHz 3.0134 GHz 2.922 GHz E7,2,1 E6,1,5 E5,2,3 3.081 GHz 3.0215 GHz 3.097 GHz
RF Pulse Compression system for CTF3. General view and technical sketch of the 3.0 GHz BOC RF pulse compressor.
RF Pulse Compression system for CTF3. Discussion... Questions ?...