Coupling and Girder Re-alignment of the Diamond Storage RingM. Apollonio – Diamond Light Source Ltd

ESLS – XXI Workshop, ANKA Karlsruhe, November 21st 2013

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

M1 M2

1/17

- Motivations

- Coupling & Feedback

- Alignment

- Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe 2/17

Outline

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Why aligning the machine?

- a perfectly aligned machine ensures nominal performance - first requirement to get nominal photon beam properties

- misalignments are minimized via orbit corrections

- CMs (dipoles) correct the orbit but introduce dispersion in both planes

- CMs correct the orbit at BPMs- Orbit can be ≠ 0 everywhere else

Motivations Coupling&Feedback Alignment Conclusions

3/17

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Effect of orbit leaks

off axis orbit at quadrupolesdipole kicks more corrector strength more dispersionH dispersion errors H emittance errorsV dispersion V emittance (> quantum limit ~0.6 pm)

off axis orbit at sextupolesdipole kicks more corrector strength more dispersiontune shift (H offset at sextupoles makes a normal quad)-beatingbetatron coupling (V offset at sextupoles makes a skew quad)dynamic aperture reductionlifetime reductionincrease loss and change in loss distribution

strong correction impliesdecapole when H corrector is excitedoctupole when skew quad is excited

others (polarisation, etc)

These distortions can become relevant especially at low coupling ... 4/17

Motivations Coupling&Feedback Alignment Conclusions

x (mm)

y (m

m)

-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

x (mm)

y (m

m)

-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

In response to request from Science Division, vertical emittance has been reduced from 27 pm.rad to 8 pm.rad for user operation (1% to 0.3% coupling)

Initially confined to machine development periods

Two week period from 17th October to 1st November 2012

Standard operational mode since 6th March 2013

Benefits include increased brightness / transverse coherence, smaller spot size

1% coupling 0.3% coupling

Reduced Vertical Emittance

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Motivations Coupling&Feedback Alignment Conclusions

5/17

(courtesy of I. Martin DLS)

coupling lifetime current

Coupling feedback started

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Reduced Vertical Emittance

6/17

Motivations Coupling&Feedback Alignment Conclusions

Setting the vertical emittance:• LOCO correction during start‐up  (~2h to complete)• Apply correction to all skews  • Add offset to set desired εy value• Use feedback to stabilise during user time

Issues:• Coupling correction only optimal for a particular 

configuration of ID gaps• Quality of correction drifts over days / weeks Investigating whether we can speed up LOCO 

measurement and fit Begun girder re‐alignment campaign to increase 

margin between minimum and desired εy values

-0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.20

5

10

15

20

skew offset (A)

y (p

m.ra

d)

operating point

0 50 100 150

8

10

12

time (s)

y (p

m.ra

d) Feedback off

10

20

30

ID g

ap (m

m)

0 50 100 150

8

10

12

time (s)

y (p

m.ra

d) Feedback on

10

20

30

ID g

ap (m

m)

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Reduced Vertical Emittance

7/17

Motivations Coupling&Feedback Alignment Conclusions

(courtesy of I. Martin DLS)

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

dR

S

Survey Data August 2013

> 1mm sway

dZ

S

H-plane

V-plane

Motivations Coupling&Feedback Alignment Conclusions

8/17

- middlelayer/AT model - MATLAB functions change magnet positions according to survey- girder (sway,yaw, heave,pitch)- quadrupoles/sextupoles magnetic centres moved w.r.t. to girder according to data

- residuals <50um- 8/74 girders were swapped

- BPM positions in the model defined accordingly- primary fixed to floor- secondary anchored to girder

DX

YAW

QUAD

SEXT

BM

Girder moves – model

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

primaryBPM secondary

BPM

9/17

Motivations Coupling&Feedback Alignment Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Girder Moves explain 2/3 of the H-orbit. In V-orbit there is phase agreement, amplitude is not reproduced.

Girder moves – effect on orbit

10/17

Motivations Coupling&Feedback Alignment Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Girder moves – tests- 5-cam axis motor system (u,v,) - preliminary to possible program for complete machine re-alignment

- assess validity of predictions- reinforce confidence in model

- gain confidence in control system (*)

11/17

Motivations Coupling&Feedback Alignment Conclusions

Girder Heave/Sway (um) Yaw/Pitch (urad) Date

HC3G2 +324 0 04122012

VC20G1 +94.2 -53.5 19022013

VC8G2 +197 0 30042013

VC2G2 -162.5 0 02072013

VC13G2 +194 -8.6 24092013

VC3G1 -245.2 -21.4 22102013

(*) - at present operated via rack inside the tunnel - 1 girder at a time- protection system to limit excessive strain on bellows

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Girder moves – tests- model highly predictive when describing changes

- orbit variationcorrectly reproduced

- CM variation correctly reproduced

- local reduction in total CM kick angle reasonably reproduced

original position

new positionC03

G1 G2 G3HC3G2sway=+324um

12/17

Motivations Coupling&Feedback Alignment Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Girder moves – tests- model highly predictive when describing changes

- CM variation correctly reproduced when BBA corrections are introduced in the model (as done in the machine)

- local reduction in total CM kick angle reasonably reproduced

VC8G2heave=+197um

original position

new position

13/17

Motivations Coupling&Feedback Alignment Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Girder moves – testscorrector strength reduction in vertical girder moves

VC3G1VC13G2

VC2G2VC8G2

VC20G1

integrated |VCM| strength

172

1ii

14/17

Motivations Coupling&Feedback Alignment Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Girder moves – transparent re-alignment- leading idea: re-align the machine with minimal impact on operating beamlines- orbit variations compensated by introducing Golden Offsets at primary BPMs

15/17

Motivations Coupling&Feedback Alignment Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Test of transparent re-alignment at BL03: BBA (1) and orbit restoration via Golden Offset (2)

(1) (2)

VC3G1heave = -245 umpitch = -21.4 urad

model

measured

BBA iterations

16/17

Motivations Coupling&Feedback Alignment Conclusions

21/11/2013 M. Apollonio – ESLS XXI - Karlsruhe

Conclusions

- aligning the Diamond Storage Ring would represent a benefit in terms of reduced vertical emittance

- increase stability on feedback for present low coupling system

- model of girder moves available (AT)- still inaccurate in predicting global effects (orbits, correctors)- very precise when determining local effects (girder moves)

- a campaign of survey-based girder moves has started- using the present 5-cam control system- 1-H and 5-V vertical moves actuated so far- gained great knowledge both of the control system and of the model

- in future : progress to multi-girder moves, possibly distributed on the entire machine

17/17

Motivations Coupling&Feedback Alignment Conclusions