Outline Stability Requirements Feedback Implementation 1 Slow Orbit - - PDF document

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

Orbit Control at the SLS Storage Ring

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop

• n

Nanometre-Size Colliding Beams (September 2-6, 2002, Lausanne)

Outline

• Stability Requirements
• Feedback Implementation

1 Slow Orbit Feedback

• Results of Slow Orbit Feedback
• Upgrade to Fast Orbit Feedback

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

SLS Parameters Stability Requirements

! ! !

Energy: 2.4 GeV RF frequency: 500 MHz Circumference: 288 m Emittance (horizontal): 5.0 nm·rad Vertical Beamsize @ ID (short straights): X10 µm (1% coupling) Beta functions @ short straights: horizontal: 1.4 m vertical: 0.9 m Source fluctuations < one order of magnitude below resolution of experimental stations angular stability: position stability: ∆Θ < 1 µrad

beam

1/10th of vertical beam size at location of insertion devices 1 suppress oscillations up to 100 Hz by factor of 10 1 µm in vertical plane

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

72x72

A =

• 1

1 72 1 72 bpm corr.

Feedback Strategy

! using all 72 BPMs and all 72 corrector magnets in each plane ! ! RF frequency as independent control parameter global orbit feedback based on SVD algorithm

Slow Orbit Feedback Fast Orbit Feedback

100 Mbit/s Ethernet

SLS Storage Ring beam dynamics server

central processing unit:

!

calculate inverted response matrix (SVD)

!

all BPM values

!

calculate correction

!

new corrector settings

!

use control system network read set

! !

processing and in the 12 BPM stations (6 BPMs and 6 corrector magnets per station) decentralized integrated

100 Mbit/s Ethernet

SLS Storage Ring beam dynamics server

40 Mbyte/s point-to-point fibre optic links

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

Slow Orbit Feedback: Properties

! ! ! ! ! ! ! stroboscopic position readings with a rate of (BPM resolution < 0.5 µm) BPM server sends data to feedback client with a rate of sliding average of BPM data over a predefined no. of successive samples (default: 3) correction calculated on TRACY server toggle correction between x & y plane full correction cycle < 3 s ( ) running since Aug. 2001 3 Hz 2 Hz X0.4 Hz

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

177 179 178 181 180

Results of Slow Orbit Feedback

beam current:

Example: 3 days run, 13 Aug 2002 - 16 Aug 2002

70 14 28 42 56 84

time [h] current [mA] 180 mA top-up

−3

∆I / I = 3.3E10

! top-up operation 1 thermal equilibrium of machine 1 nearly no drifts 1 no beam current dependencies of BPMs 1 constant heat load on experiments ! correct orbit to “golden orbit”

• minimum coupling (beam based

alignment)

• requested local bumps at ID

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

Global Orbit Stability

70 14 28 42 56 84

time [h]

5 10 15 20 25 30 35

x (rms) [µm]

70 14 28 42 56 84

time [h]

5 10 15 20 25

y (rms) [µm]

1 2 3 4 y (rms) [µm]

1 orbit globally stabilzed to micron level

1 2 3 4

x (rms) [µm]

number of samples @ 0.4 Hz

RF freq. corrections

Global RMS Values:

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

Global Horizontal Mean Position:

70 14 28 42 56 84 time [h] x mean [µm]

5

• 5
• 50
• 10
• 45
• 15
• 20
• 25
• 30
• 40
• 35

RF frequency corrections

RF frequency corrections: if path length changes correspond to > 5 Hz frequency changes

• number of samples @ 0.4 Hz
• 3e-05

3e-05

• 2e-05

2e-05

• 1e-05

1e-05

• 4e-05

4e-05

dp / p

• 5

Energy Stability: G2E10

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

RF Frequency Change:

1 day 1 day 70 14 28 42 56 84 time [h]

• utside temperatures [deg C]

10 30 12 14 16 18 20 22 24 26 28

Outside Temperatures:

1 day 1 day 70 14 28 42 56 84 time [h]

∆f [Hz] ∆f = 5 Hz 1 ∆U Z 3 µm (circumference)

• 1630
• 1540
• 1550
• 1560
• 1570
• 1580
• 1590
• 1600
• 1610
• 1620

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

x position:

RF BPM @ Insertion device 6S (protein crystallography beamline):

upstream BPM x position [µm]

5

• 5

10

• 10

15

• 15
• 20

70 14 28 42 56 84

time [h] y position [µm]

5

• 5

10

• 10

15

• 15
• 20

70 14 28 42 56 84

time [h] upstream BPM

y position [µm]

number of samples @ 0.4 Hz

• 2

2

• 4

4

σ = 0.65 µm

y

downstream BPM horizontal:

σ = 0.98 µm

x

vertical:

σ = 0.64 µm

y

y position:

x position [µm]

number of samples @ 0.4 Hz

• 2

2

• 4

4

σ = 1.04 µm

x

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

Angular Stability @ ID

horizontal angle: vertical angle:

σ = 0.29 µrad

∆Θ

number of samples @ 0.4 Hz horizontal angle [µrad]

• 1.5
• 1
• 0.5

0.5 1 1.5

σ = 0.19 µrad

∆Θ

number of samples @ 0.4 Hz vertical angle [µrad]

• 1.5
• 1
• 0.5

0.5 1 1.5

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002 8.6 17.2 25.8 34.4

time [h]

• 80
• 75
• 70
• 65
• 60
• 85
• 90
• 95
• 100

y position [µm]

X-BPM Results

! X-BPM @ ! start of X-BPM commissioning: middle of Aug. 2002 ! data from 3 days run: 9 Aug - 12 Aug 2002 Protein Crystallography Beamline

• 10
• 5

5 10

number of samples @ 0.4 Hz x position [µm]

σ = 2.7 µm

x

• 10
• 5

5 10

number of samples @ 0.4 Hz y position [µm]

σ = 1.5 µm

y

! drift: X1.7 µm per day ! subtracting the drift

1

1

horizontal: vertical:

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

Fast Orbit Feedback

Properties: ! ! ! ! !

!

update rate: BPM

• nly between
• ver point-to-point fibre optic links

(40 Mbytes/s) (1reflecting the localized structure of the inverted response matrix)

• f magnet power supplies

(by-passing control system) global BPM data exchange < 8 µs implementing communication between beam dynamics server and individual BPM/feedback stations planned start of commissioning: Dec. 2002 (priority to multibunch feedback system) 4 kHz data exchange adjacent sectors direct control Status: Important Prerequisite: reliable BPM data 1 “intelligent” BPM software which detects faulty data and disables BPM 1already implemented for slow orbit feedback

• T. Schilcher

26th Advanced ICFA Beam Dynamics Workshop ,Sep. 2 - 6, 2002

Conclusion !

stabilized to in both planes with a rate of 0.4 Hz

!

to compensate path length changes

!

beam stability @ low beta insertion devices to (sub)micron level: position angle horizontal vertical

!

thermally stable machine only needs feedback when

• moving IDs
• changing RF frequency

!

fast feedback required in order to

• compensate ID movements
• suppress beam oscillations in the low

frequency band (<40 Hz) - if necessary global orbit 1 µm RF frequency control X 1.0 µm X 0.3 µrad X 0.7 µm X 0.2 µrad