1 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis NSLS-II Electrical Systems NSLS-II Stability Workshop April 18 – 20, 2007 George Ganetis

2 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Outline Global Beam Position System ( Hardware Configuration ) Corrector magnets & power supplies Main dipole power supply Multipole power supplies for quad. & sext. Magnets Instrumentation ( Igor Pinayev ) RF systems ( Jim Rose ) Summary

3 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Global Beam Position System

4 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Global Beam Position System BPM data transferred to a single processor. The processor will calculate the corrector strengths. Corrector strengths transferred to individual ps interfaces. This processor will calculate both Slow/alignment and fast corrections. A global timing system will supply synchronized triggers. Expected throughput is ~ 5 kHz Detailed design needs to be done & need to investigate the following: - The methods of data transfer between the various elements of the system. - The number of bpm and ps interfaces that are connected to a control node. - The data throughput of the overall system. - The choice of the process platform that meets calculation speed requirements.

5 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Corrector magnets & power supplies The system will use 120 corrector magnets with separate horizontal and vertical coils. The magnets will be deigned for fast correction of ~ 100 Hz. The dc transfer function of the magnet is 1000 μrad per 19.2 Amps. The magnets will be located over stainless steel bellows and or flanges. The magnets are placed at the ends of each main dipole magnet. There will be 120 horizontal and 120 vertical power supplies. These corrector magnets and power supplies will be also used in slow and alignment corrections. The power supplies will have a high current requirement for slow/alignment corrections and high voltage requirements for fast corrections.

6 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Corrector magnets & power supplies The power supply requirements from accelerator physics are the following: - Frequency Strength - RMS - < 5 Hz 800 μrad - 20 Hz 100 μrad Hz 10 μrad Hz 1 μrad - Resolution of last bit: 0.01 μrad - Noise Level : urad ( ~ 4 ppm of 800 μrad ) (These rating are for vertical correction and the horizontal correction is less stringent and they need to be quantified.) Power Supply Description: - Four quadrant switch-mode class D amplifier to be incorporated into a bipolar current regulated power supply. - Small signal bandwidth of the power supply will be ~ 2 kHz - Amplifier has a switching frequency of 81 Hz. which gives a ripple current of ~ 2 ppm. - Resolution of 0.01 μrad is planed. Two 16 bit DACs will be used. One will be used for the slow large strength correction and the other for the fast smaller strength correction. - Two DACs will have an affective resolution of 18 bits or ~ μrad.

7 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Corrector magnets & power supplies Peak corrector strength as a function of frequency for a corrector at a fixed offset of 800 μrad for a bipolar power supply with a rating of 50 volts and 20 amps.

8 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Corrector magnets & power supplies The following is the planed R&D for corrector power supplies and magnets: Measure the magnet field of a proto-type corrector magnet as a function frequency. These measurements will include transfer function and multi-poles. Design and build a proto-type corrector power supply measure the frequency response of the current regulator. Measure the current ripple of the power supply and overall current noise. Horizontal Coils Vertical Coils Horizontal & Vertical Corrector Magnet

9 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Main dipole power supply The power supply is a unipolar, 2-quadrant, current-regulated supply. It will use two 12- pulse SCR converters in series with the center point connected to ground. Each converter will have a two-stage LCRL passive filter and a series pass active filter. Each main dipole magnet bending angle of rad. The CDR has the current ripple spec. ( referred to Imax) of 5 ppm for freq. 60 Hz and greater. This gives a ~ 524 nrad noise in the horizontal direction. CDR has the following power supply parameters: - resolution of reference current 18 bit + 1LSB - stability (8 h-10 s) – referred to Imax 40 ppm - stability (10s-300 ms) – referred to Imax 20 ppm - stability (300 ms- 0 ms) – referred to Imax 10 ppm - absolute accuracy – referred to Imax100 ppm - reproducibility long term – referred to Imax 50 ppm To ensure long-term stability and reproducibility - high-precision DMMs will be used to monitor the power supply current, a redundant current sensor, and the analog current set point. R&D for the main dipole ps is to develop a more thorough electrical circuit model of the system, that will include transmission line effects of the overall circuit.

10 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Main dipole power supply Storage & Booster Ring Main Dipole PS Diagram

11 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Multipole power supplies for quad. & sext. Magnets There is one power supply for each magnet. The power supply is a unipolar, single-quadrant, current-regulated switch-mode design. The power supply will use a DCCT as the current feedback device. To minimize current ripple, an additional output filter will be used. The CDR has the current ripple spec. ( referred to Imax ) of 15 ppm for freq. 60 Hz and greater. CDR has the following: - resolution of reference current 16 bit + 1LSB - stability (8 h-10 s) – referred to Imax200 ppm - stability (10s-300 ms) – referred to Imax200 ppm - stability (300 ms- 0 ms) – referred to Imax100 ppm - absolute accuracy – referred to Imax200 ppm - reproducibility long term – referred to Imax100 ppm To ensure long-term stability and reproducibility - high-precision DMMs will be used to monitor the power supply current, a redundant current sensor, and the analog current set point. The R&D for the multipole power supplies is to build a proto-type and confirm the accuracy, stability, and current ripple of the power supply.

12 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Multipole power supplies for quad. & sext. Magnets Storage Ring Quad. & Sext. Unipolar Switch-Mode PS Diagram

13 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Instrumentation for Orbit Stability ( Igor Pinayev ) BPM buttons with 5 mm radius (design similar adopted at RHIC) 210 regular BPMs 2 ultrastable BPMs per insertion device Libera Electron is considered for processing unit  high accuracy  low drifts  built-in processor  GB Ethernet Photon BPMs will be utilized for most demanding beamlines

14 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis RF systems ( Jim Rose ) Effect of RF jitter on the beam: Amplitude modulation of the RF fields leads to momentum deviations of the beam, Likewise phase modulations translate into amplitude modulations again leading to momentum deviations. The momentum errors affect beam size and orbit jitter as follows: The beam size in the center of the 5 m straight is given by Since the dispersion is near zero (~1mm) and the natural energy spread is <0.001 the second term is negligible and the beam size becomes σ x,y = 40μm, 2.4 μm Orbit jitter is given as σ x,y = σ δ ∙η x,y, σ x′,y’ = σ δ ∙η x′,y’ Because of the near zero dispersion in the ID straights, this is not the limiting factor in determining the RF tolerances Timing experiments in IR beamlines impose limit of phase variations to be <5% of bunch length: Phase error limit of +/ degrees and 0.005%  p/p

15 BROOKHAVEN SCIENCE ASSOCIATES NSLS-II Stability Workshop April , 2007 NSLS-II Electrical Systems G. Ganetis Summary Detailed designs are needed for the data transfer & processing hardware for the global beam position system. Magnet prototype needs to have it field characterized as a function frequency. Power supplies R&D program should be sufficient to confirm that the ps meet the storage ring stability requirements. Instrumentation will be discussed in more detail by Igor Pinayev. RF systems will be discussed in more detail by Jim Rose.