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Advanced Optics Control, CERN, Masamitsu Aiba, PSI Swiss Light Source Swiss Light Source: – 3 rd generation light source – 18(+2) beamlines – 2.4 GeV, 400 mA (top-up) – 12 TBA cells – x = nm – C~288 m SLS
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Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Recent optics measurements at SLS
M. Aiba, M. Böge, Á. Saá Hernández, D. Mayilyan and A. Streun
Paul Scherrer Institut
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Contents
• SLS• “Local” LOCO• Emittance monitor status• Energy spread measurement using TBT data• Summary
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Swiss Light Source
Swiss Light Source: – 3rd generation light source– 18(+2) beamlines– 2.4 GeV, 400 mA (top-up)– 12 TBA cells– ex= 5.5-7.5 nm– C~288 m
SLS
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
“Local” LOCO (1)• Motivation
– LOCO* optics correction did not converge for bV-beat<~2% at SLS**
0 1 2 3 40.00
0.05
0.10
0.15
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0.35
Number of iterations
Ver. o
rbitr
espo
nse d
eviat
ion,rm
s (m/
rad)
0
1
2
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5
Ver. beta-beat,rms (%)
0 1 2 3 40.00
0.02
0.04
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0.160 1 2 3 4
Number of iterations
Hor. o
rbitr
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nse d
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ion,rm
s (m/
rad)
0
2
4
6
8
10
Hor. beta-beat,rms (%)
|ORM_meas – ORM_fit|After partial LOCO fit (BPMs & Correctors)
|Meas. ORM – Model ORM|After full LOCO fit (BPMs, Correctors & Quads)
b-beat from fit model
ORM difference after BPM&corrector fit/calibration (black plots) - Should be comparable to the measurement noise level (0.01 m/rad) after iteration - Should fluctuate within the measurement noise level after a couple of iterations - Should be close to ORM difference with full LOCO fit (red plot) There is something wrong especially in the vertical plane…?
Method to probe the ring optics “locally” may give a better insight. * J. Safranek, NIM-A, 388, p.27 (1997)** M. Aiba et al., PRST-AB, 16, 012806 (2013)
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
“Local” LOCO (2)• Local orbit response matrix
measurement– Keep orbit feedback running except for
the section under measurement – Measure orbit response as in LOCO for
the correctors in the measurement section
– Statistical measurement error ~0.02 m/rad in the vertical plane (cf. full ORM ~0.01 m/rad)
– Larger error in the horizontal (dispersive) plane, not fully understood
Local orbit response matrix example(V correctors #19-#31 out of #1-#73)
- Local response matrix measurement is established- Quadrupole errors outside the measurement section are transparent
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
“Local” LOCO (3)• First results (using only vertical data):
Sect. 4-5, ORM meas. vs ORM fit model (unsuccessful case)
Sect.2-3 Sect.3-4 Sect.4-5 Sect.6-7RMS residual before/after LOCO fit|ORM_meas - ORM_fit| (m/rad) 0.0207/0.0099 0.0312/0.0267 0.0494/0.0439 0.0264/0.0145Average quad change, <|dK|> (m^-2) 0.0020 0.0066 0.0071 0.0044
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
“Local” LOCO (4)
• Comparison – LOCO and Local LOCO
It seems that there is something wrong around Sector 4-5!
Quad corrections from fit
0 50 100 150 200 250-0.03
-0.02
-0.01
0.00
0.01
0.02
Full LOCO Sect. 2-3 Sect. 3-4 Sect. 4-5 Sect. 6-7
dK (m
^-2)
s (m)
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
“Local” LOCO (5)
Straight section 5 accommodates Femto beamline…– With wiggler, chicane, additional quads…– With additional p phase advance and irregular optics
SLS optics
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Emittance monitor status (1)• Vertical emittance monitors at SLS
– Synchrotron radiation -> Vertical beam size -> ey
– Monitor #1* used for achieving ey =0.9 pm** (sy ~3.6 mm) reaching the resolution limit
* A. Andersson et al., NIM-A 591, p.437 (2008)** M. Aiba et al., NIM-A 694, p.133 (2012)
Hill-Valley ratio → Beam size
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Emittance monitor status (2)– Monitor #2 development*
• Longer arm to improve the resolution (+ optical table accessible even during operation)• Plan A: Toroidal mirror optics → l independent Plan B: Lens optics (as in Monitor #1)• Interferometric method is also implemented
- Plan A: small image aberrations from toroid misalignment- Plan B: clean images, so far ey =1.3 pm** (sy ~4.3 mm) measured - Another vertical emittance tuning campaign is foreseen with Plan B
* Work supported by TIARA WP6 TIARA-REP-WP6-2012-015** Á. Saá Hernández et al., ICFA Newsletter 62 (2013)
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Energy spread measurement (1)• Energy spread measurement using TBT data*
– Procedure• Merge TBT data from all BPMs• Fit (locally) sine function to data to find the envelope of the betatron oscillation• Fit theoretical formula** to the envelope
→ Energy spread corresponds to one of fitting parameters * D. Mayilyan, Master thesis, ETH Zurich (2014)** A. Sargsyan, NIM-A, 638, p.15 (2011)
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Energy spread measurement (2)
Sine fit,single BPM
Sine fit,all BPMs
Envelop fit (a good example)
Fixed parameters(measured separately):- 1st order chromaticity, x1 Fitting parameters:- Energy spread- Amp. dependent tune shift(s) - 2nd order chromaticity- Synchrotron tune- Kick amplitude
Energy spread…?
x1 =3,5,7Pinger= 100, 300, 700 A
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Summary• “Local” LOCO
– Method to probe the ring optics locally under development– First results indicate that Sector 4-5 could be a source that
prevents LOCO from converging • Vertical emittance monitor #2 R&D is on-going
– Difficulties with Toroidal mirror…– Another ey tuning campaign is foreseen with Monitor #2 (Plan
B)• Energy spread measurement attempted
– Using TBT data– Measured values depend on chromaticity and kick amplitude…
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Back up slides
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Local orbit response matrix analysis (1)
• Procedure– BPM calibrations from normal LOCO– Momentum deviation found from non-
measurement section BPMs (not important for vertical plane)
– Corrector calibrations found from Local response matrix
– Find best quadrupole setting (corrections) by fitting (SVD)
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
• BPM and corrector calibration for Sector 2-3
Local orbit response matrix analysis (2)
Advanced Optics Control, CERN, 05-06.02.2015 Masamitsu Aiba, PSI
Local orbit response matrix analysis (3)
• Momentum deviation– Momentum is slightly
varied when the measurement corrector is in a dispersive section
– Momentum correction (1 Hz) is independent, and there can be residual momentum deviation at the time of measurement
– Local orbit response data is corrected by finding momentum deviation using the non-measurement BPMs
0 10 20 30 40 50 60 70-0.05
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Horizontal LORM Dispersion term fit
LOR
M (m
/rad)
BPM ID
Momentum deviation fir forSector 2-3 (BPM 7-18)