NSLS-II Electrical Systems NSLS-II Stability Workshop April 18 – 20, 2007 George Ganetis

1 BROOKHAVEN SCIENCE ASSOCIATES

NSLS-II Stability Workshop April. 18-20, 2007NSLS-II Electrical Systems G. Ganetis

NSLS-II Electrical Systems

NSLS-II Stability Workshop

April 18 – 20, 2007

George 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



Global Beam Position System

BP

M D

ata

BP

M T

imin

g

PS

Data

PS

Tim

ing

BPM MagnetPS

InterfacePower

Supply

BPM MagnetPS

InterfacePower Supply

BPM MagnetPS


BPM MagnetPS


BP

M D

ata

BP

M T

imin

g

PS

Data

PS

Tim

ing

BPM MagnetPS


BPM MagnetPS

InterfacePower

Supply

BPM MagnetPS

InterfacePower

Supply

BPM MagnetPS

InterfacePower

Supply

Control NodeData Processing

and orDistribution

Control NodeData Processing

and orDistribution

Global Beam PositionProcessor

GlobalTiming System

ToControlNodes

ToControlNodes

High Speed Data

Timing Signals

Global Beam Position SystemFunctional Diagram



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.



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.




• The power supply requirements from accelerator physics are the following:- Frequency Strength - RMS- < 5 Hz 800 μrad- 20 Hz 100 μrad- 100 Hz 10 μrad - 1000 Hz 1 μrad - Resolution of last bit: 0.01 μrad- Noise Level : 0.003 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 ~ 0.003 μrad.




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.

PS(50V,20A) - 0.8 m rad offset

0.001

0.01

0.1

1

0.1 0.2 0.5 1 2 5 10 20 50 100 200 500 1000

Frequency

mra

d




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



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 0.1047 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 Imax 100 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.



Main dipole power supply

Storage & Booster Ring

Main Dipole PS Diagram



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 Imax 200 ppm- stability (10s-300 ms) – referred to Imax 200 ppm- stability (300 ms- 0 ms) – referred to Imax 100 ppm- absolute accuracy – referred to Imax 200 ppm- reproducibility long term – referred to Imax 100 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.



Multipole power supplies for quad. & sext. Magnets

Storage Ring Quad. & Sext. Unipolar Switch-Mode PS Diagram



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 unithigh accuracylow driftsbuilt-in processorGB Ethernet

• Photon BPMs will be utilized for most demanding beamlines



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

2,,,, yxyxyxyx

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 σx,y = σδ∙ηx,y , σx′,y’ = σδ∙ηx′,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 +/- 0.12 degrees and 0.005% p/p



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.

Documents

NSLS-II Electrical Systems NSLS-II Stability Workshop April 18 – 20, 2007 George Ganetis