MAX II RF system 100 MHz technology Lars Malmgren 10th ESLS RF Meeting Dortmund September 27-28, 2006

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1 MAX II RF system 1 MHz technology Lars Malmgren 1th ESLS RF Meeting Dortmund September 27-28, 26

2 Facts and figures MAX-II Frequency [MHz] Harmonic number No of cavity cells No of transmitters Cell radius [m] Tot length of cavities [m] Tot R shunt ( V*V/P) [MΩ] Q-value Tot Voltage [kv] Cu losses [kw] Beam 25mA [kw] Available power [kw] Net power [kw] Bucket height [%] Synchrotron frequency [khz] Rms bunch length [cm] (53) 21 (29) 35 (5) 9 93(135)

3 Simple circuit model of the RFsystem with beam Z c =cavity impedance Z Z c L coup L C R s I beam n λ/2 L coup << L β = R Z S L coup L Z R = βs L coup L N 2 N=transformer ratio

4 RF-system with beamloading Z = 2 I + U c R β Z sinφ + s i Q DC s 1 ξ 2 I U DC c R s cosφ s Φ s is the phase angle between the synchronous electron and the zero crossing of the cavity voltage. A. Matched condition of resistive part: ReZ=Z 2 IDC RS β = 1+ sinφs UC 2 I U R 2 R P β = 1+ sinφ = 1+ P = 1+ DC C S S beam 2 S 2 beam UC UC PC B. Matched condition of reactive part: ImZ= 2 f 2 I DC Rs Q ξ = Q = cosφs f U c C A. Defines the coupling factor of the cavity B. Defines the necessary detuning of the cavity

5 Cavity A. The main cavities are of the capacity-loaded type. B. The tuning is made by squeezing the cavity side.

$1 MHz cavity 1 MHz Capacity-loaded Cavity for MAX-II and -III, F = 1.8323 MHz 4 4 35 35 3 3 25 25 2 2 15 15 1 1 5 5 5 1 15 2 25 3 35 4 45 5 55 C:\LANL\EXAMPLES\RADIOFREQUENCY\PILLBOXCAVITIES\1MHZ.$

6 1 MHz cavity 1 MHz Capacity-loaded Cavity for MAX-II and -III, F = MHz C:\LANL\EXAMPLES\RADIOFREQUENCY\PILLBOXCAVITIES\1MHZ.AF :3:5 1 MHz cavity profile with fundamental mode E-field lines 1 MHz Capacity-loaded Cavity for MAX-II and -III, F = MHz Q-value 19 Tot. R shunt 3.2 MΩ C:\LANL\EXAMPLES\RADIOFREQUENCY\PILLBOXCAVITIES\1MHZ.AF :16:42 E-field lines of the high order mode at 456 MHz 5 The high order modes are damped by antennas in the endplate. This endplate is convenient to use since the fundamental mode is not affected.

7 Landau cavity The Landau cavities are of simple pill-box type. Tuning is done both by plunger and temperature.

RF amplifier and feeder line The generator system consists of three 3 kw FM transmitters (Itelco T254T) feeding one cavity each The power stages are tetrode amplifiers Class C

8 RF amplifier and feeder line The generator system consists of three 3 kw FM transmitters (Itelco T254T) feeding one cavity each The power stages are tetrode amplifiers Class C operation for high efficiency An integer λ/2 long coaxial 3 1/8 transmission line is feeding the cavity input coupler. The reflected wave will add in phase with the wave at the generator

RF path φ φ Power amplifier Phase control loop 1 MHz master oscillator Main cavity Power control loop Single stub tuner Frequency tuning loop The power

9 RF path φ φ Power amplifier Phase control loop 1 MHz master oscillator Main cavity Power control loop Single stub tuner Frequency tuning loop The power control makes the cavity to see a matched condition at the generator. A phase control system is used to control the phase difference between the cavities.

10 Stub matching network A stub matching network is installed to keep an optimal match of transmitter and cavity for every beam current.

11 An alternative to a circulator λ/4 +n λ S 3 db hybrid Dummy load Dummy load Switchless combiner Tetrode amplifiers

12 BPM system Band pass filter 3 MHz Low pass filter ADC Multiplexer Demultiplexer ADC From buttons Analog Signal Processing ADC ADC The BPM receivers are working at the third harmonic. This minimizes the risk of 1 MHz leakage from the transmitters. Resolution << 1µm

13 CONCLUSION The 1 MHz 9 kw RF system has been in operation since September 24. The system is now running at 24 ma with two wigglers at 15 and 2A. Beam lifetime I*t=6mAh with Landau cavity in operation. BPM system resolution <<1 µm. The transmitter tubes must have high anode loss capability when working without circulator. This is an disadvantage but a solution is presented.

Detailed Design Report

Detailed Design Report Chapter 2 MAX IV 3 GeV Storage Ring 2.6. The Radio Frequency System MAX IV Facility CHAPTER 2.6. THE RADIO FREQUENCY SYSTEM 1(15) 2.6. The Radio Frequency System 2.6. The Radio Frequency