Feedback systems and Low Level RF Alessandro Drago X SuperB General Meeting SLAC 6-9 October 2009

Main topics Tests of 500 W power amplifiers for transverse bunch-by-bunch feedback systems Low Level RF collaboration proposal from CNRS Grenoble team

AR 500 W power amplifiers On the rear panel analog i/o, RS232, GPIB and USB Flat screen power Gain knob Menu keys key

Very compact, heavy but still portable

TFB power amplifiers For transverse and longitudinal bunch-by-bunch feedback system in general (DAFNE, PEPII, other circular accelerators) 250 W power amplifiers are used, typically one for each kicker port In DAFNE, due to the need of more power on the horizontal e+ feedback system for the presence of a very fast instability (of the order of 5 microsec. grow rate) two ways are under study: double the horizontal e+ feedback system double the horizontal final stage amplifier power To do b) two new 500W amplifiers have been bought; the laboratory tests are just finished and they are presented in the following talk

Case a) double feedback systems Implemented in november 2008 Presented in April’09 MiniMAC

Case b) analysis Note to the following measurements The nominal gain of the amplifier is 57 dB On the amplifier output, in cascade, there are 3 stage of 20dB attenuators, the first working up to 1500W, the second up to 100W, the third 20 W All the measurements in the following slides are done by this setup, so the effective nominal gain -3 dB and, if we consider also the cables, -3.3 dB

Network analyzer HP 8753B Magnitude (dB) Phase (degree)

Network analyzer HP 8753B Magnitude (dB) Phase (degree)

RF signal generator HP 8664A Spectrum Analyzer Tektronix RSA3303A Amplifier Research AR 500A250AM1

In input: 0dBm sinusoid at 100MHz

we can observe a spurious signal at 200MHz, -21 dB

Pulse response Oscilloscope LeCroy WaveSurfer 64Xs Pulse/Function generator HP 8116A

Pulse (8ns) response: input to amplifier Trigger

Pulse (8ns) response: output from amplifier Trigger

Input Pulse(2ns) to AR amplifier

Output Pulse(2ns) from AR amplifier

Results on 500W amplifiers Very compact: about the same size that the 250W model, only the weight is higher It asks 2500 Watts from the mains at 220V Roughly the cost is ~linear with power: ~25keuro+VAT, for a 250 W amplifier, ~50keuro+VAT, for a 500 W model Good technical performances within specs Perfect response to the pulse Good flatness versus magnitude (< 3dB) Good linearity in phase - apart for freq > 240Mhz

Critical Aspects on 500W amplifiers First harmonic at -21 dB, it is a trouble or not? As the first also the other harmonics with f<250 MHz are in the output signal Gain knob must be adjusted to the right value that is different for each individual amplifier: it can be set from 0% to 100% but it is not easy to choose the value that gives the maximum gain without reproduce distortion or saturation in the output In fact the presented tests are done with gain values from 50% to 70% in base to the chosen input signal

Conclusion on power strategy 250W amplifier gives 54 dBm that is 115V output for 0dBm input signal 500W amplifier gives 57 dBm that is 160V output for 0dBm input signal, this means a 1.4 factor The amplifier cost is linear with the power but of course the bunch to be deflected obeys to the Lorentz law and this means to the applied voltage As consequence using 500W amplifier has the advantage to be very compact but it does not optimize cost versus effect Installing more feedback system is more effective solution if the space (for kickers) is not a problem and if the cost of the feedback processing unit is not expensive

How much space ? In PEPII, the installation of 6 bunch-by-bunch feedback systems asks for >10 racks, for power amplifiers, electronics and instrumentation. There is also some other space for the operators with computers and desks. In DAFNE, there is a similar situation with 13 racks for seven bunch-by-bunch feedback systems – the space for the operators is in the main control room. In both cases the power amplifiers are not very far (<20m) from the kickers to avoid power reductions on long cables

Low Level RF collaboration with LPSC -Grenoble

LPSC Electronics Group Who are we : LPSC : Laboratory of Subatomic Physics and Cosmology. IN2P3/CNRS laboratory in Grenoble/France (ex. ISN) Electronics Technical Group of 21 people devoted to the conception and installation of electronics systems for the physics experiments of the LPSC. Activities of the electronics group : Systems Electronics Microelectronics (ASIC and data conversion) Integration and tests PCB CAD team Possible manpower for SuperB (TDR phase)  1 engineer FTE O. Bourrion, C. Vescovi, D. Tourres 23

Previous work The electronics group is involved in most of the LPSC projects. Some examples : Astro/Cosmo : AMS : RICH front-end electronics CREAM : CHERCAM sub-detector + HVPSU Planck : Control electronics for the Sorption Cooler (JPL/NASA) and Dilution Cooler (Air Liquide-DTA) LHC experiments ATLAS : pre-sampler calorimeter Alice : EmCal, Jet trigger and super-modules Integration and Tests Electronics for Accelerators CNAO : LLRF GENEPI/GUINEVERE : Control/Command of the neutron generator 24

CNAO Synchrotron for hadrontherapy installed in Pavia (Italia) Development of a purely digital LLRF control system Wideband (300kHz-4MHz) single cavity Cavity (amplitude and tuning) and Beam (oscillations and position) controls Design at LPSC, tests at CERN/PSB in cooperation with CERN LEAR team More Info on EPAC08 papers : http://accelconf.web.cern.ch/AccelConf/e08/papers/tupc139.pdf http://accelconf.web.cern.ch/AccelConf/e08/papers/tupc154.pdf 25

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