Tutorial on Design of RF system for Indus Accelerator. Maherdra Lad Head, Radio Frequency Systems Division RRCAT, Indore

Transcription

1 Tutorial on Design of RF system for Indus Accelerator Maherdra Lad Head, Radio Frequency Systems Division RRCAT, Indore

2 Basic principle of RF Acceleration RF Power Amplifier The RF source supplies power to setup oscillating electrical field in the cavity. It supplies energy to the beam Compensates for the synchrotron radiation losses. 1.5 Charged Particle Orbit / Path RF Cavity Bunch Electrical Field setup in the cavity

3 Need of RF Systems 1. To Provide Sufficient Gap Voltage for Acceleration /SR Loss 2. Power to the beam for Current build up (synchrotron Radiation loss * I beam) In the Synchrotron & Storage Ring (Electron Cyclic Accelerators) circulating electrons loose energy in the form of electromagnetic radiation. To keep them in equilibrium orbits this loss has to be compensated.the RF system provides energy for acceleration as well as compensates for this radiation loss.

4 Role of RF structure

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6 INDUS COMPLEX LAYOUT Indus Accelerator complex at RRCAT consists of two Synchrotron Radiation Sources (SRS); 450 MeV Indus-1 and 2.5 GeV Indus-2. The 550 MeV Booster Synchrotron serves as common injector for these storage rings. Three major RF Systems, Booster RF system & Indus-1 Storage ring RF System at MHz and Indus-2 RF system at MHz have been developed, commissioned and deployed successfully. workshop on RF Systmes For Acclereators, IUAC New Delhi

7 Selection of RF frequency

8 Selection of RF frequency : Indus-2 a case study # Properties of required SR : like emittance, bunch length, brightness # Circumference of the ring # Frequency of the RF system of Injector # Availability of the high power RF source for required power level Circumference of Indus-2 ring = m Revolution Frequency (f r ) = 3*10^8 /172.6 = MHz RF Frequency Should be Integer harmonic of the Injector ( Booster synchrotron) RF frequency = MHz and also multiple of Revolution Frequency (f r ) RF Frequency = N* f r = MHz 16 th harmonic = *16 = MHz No. of Bunches (N) = 291

9 Accelerating voltage for Indus-2 Indus-2 Particle Energy Bending Radius = 2.5 GeV = 5.5 m Synchrotron Loss per turn = 628 kev per turn Hence to compensate for energy loss due to SR minimum 628 kv accelerating voltage is required However for sufficient beam life time over voltage factor (more than 2) is required. We provide 1500kV in Indus-2 through four RF cavities

10 RF Power Requirement To Generate Accelerating Voltage 1500 kv is generated through four RF Cavities Each operating at V = 1500/4 = 375 kv RF Cavity power P = V 2 / R sh ( R sh = 6.6 MΩ) = 21.3 kw ( each cavity) Why? To Compensate for Synchrotron Loss Synchrotron Loss Power = Stored Current x SR Loss per turn = 200 ma x 622 kev = 124 kw for 200 ma at 2.5 GeV Total power required for 200mA, 2.5 GeV operation P Total = 21.3* = kw RF

11 Indus-2 RF System Taking into account design margin, four RF stations with 60kW RF power each were installed initially. These have been upgraded to 80kW.

12 Resonant Frequency Shunt Impedance Quality Factor RF Cavities used in Indus

13 T h a n k s

14 RF (LLRF) Instrumentation The RF instrumentation includes RF instruments : Spectrum analyzer, VNA RF Parameter monitoring (power, phase ) a)directional couplers b)rf-dc detectors c)phase detectors d)rf splitters/dividers e)protection workshop equipments on RF :isolators,

15 Optimization of Indus-2 RF System For Higher energy and Current RF Cavity Coupling Coefficient (β) Adjustment For 250mA, 2.5Gev β is adjusted to 2.8 (Over Coupled ) Baking and RF conditioning of Indus-2 RF cavity. B 30 Rflected Power (in %) In put Impedance at coupler side Phase Synchronization of Indus-2 RF Cavities Four RF Cavity signals are synchronized For proper Injection For ramping to High energy Loaded quality factor characterization using VNA Beam Energy (in MeV) With increase in Beam power decrease in reflected power is an indication over coupled β 18 Stn 1 Stn 2 Stn 3 Stn 4 Net Power(kW) Beam Current (ma) proper synchronization phase of four RF cavity Tuner Movement showing the same beam loading in two RF stations Graph showing equal power sharing from each station With optimized RF System parameters, Indus-2 is utilised by users regularly at 150mA, 2.5GeV Recently successful operation for 181mA stored current at full deigned energy of 2.5GeV has also been achieved.

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17 6 1/8 Coaxial Directional Coupler Coupling Factor: db Directivity : 30 db workshop on RF

18 RF-DC detectors & Phase detectors workshop on RF

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23 workshop on RF

24 workshop on RF

25 workshop on RF

26 workshop on RF

27 workshop on RF

28 workshop on RF

29 workshop on RF

30 Synchrotron Radiation Spectrum workshop on RF