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R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 Beam Stability and StabilizationR. Hettel
NSLS-II Stability Workshop
April 18-20, 2007
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
AcknowledgmentsPrimary developers:
T. Straumann: real-time processing, system architecture and communication
A. Terebilo: accelerator physics, system operation development
J. Sebek: turn-turn BPM processing
D. Martin: BPM systems
F. Rafael, G. Leyh: corrector power supply development
Main contributors:S. Allison
J. Corbett
R. Hettel
E. Medvedko
G. Portmann
T. Rabedeau
J. Safranek
C. Wermelskirchen
E. Daly, N. Kurita, J Langton, A. Ringwall, J. Tanabe (SPEAR 3 mech des)
EDM electrical support group
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
Stability Requirements
experiment parameters
E/E(coher) < 10-4t < 0.1% ttiming, bunch length
E/E(coher) < 5 x 10-5
E/E(rms) < 10-4
(und n = 7)
x < ~5 rad
y < ~1 rad(undulator)
< 10-4 photon energy resolution
E/E(coher) < 10-4
E/E(rms) < 10-4
x,y < 0.1% x,y
x,y < 0.1% x,y
x,y < 5% x,y
x,y < 5% x,y
< 0.1% intensity
steering to small samples
beam energy/
energy spreadbeam sizebeam orbit
experiment parameters
E/E(coher) < 10-4t < 0.1% ttiming, bunch length
E/E(coher) < 5 x 10-5
E/E(rms) < 10-4
(und n = 7)
x < ~5 rad
y < ~1 rad(undulator)
< 10-4 photon energy resolution
E/E(coher) < 10-4
E/E(rms) < 10-4
x,y < 0.1% x,y
x,y < 0.1% x,y
x,y < 5% x,y
x,y < 5% x,y
< 0.1% intensity
steering to small samples
beam energy/
energy spreadbeam sizebeam orbit
• Stability requirements for small beams may be relaxed if beam size at experiment is limited by beam line optics (e.g. mirror slope error, point-spread function, etc.)
• Stability requirements depend on time interval
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
• Disturbance time scale << experiment integration time: Orbit disturbances blow up effective beam and , reduce intensity at
experiment, but do not add noise
For / = cm/o < ~10%: ycm(rms) < ~0.3 y ycm(rms) < ~0.3 y'
Note: can have frequency aliasing if don't obey Nyquist….
• Disturbance periods experiment integration time:Orbit disturbances add noise to experiment
For / = ~2 cm/o <~10%: ycm(rms) < 0.05 y ycm(rms) < 0.05 y'
• Disturbance periods >> experiment time (day(s) or more):
Realigning experiment apparatus is a possibility
• Sudden beam jumps or spikes can be bad even if rms remains low
Peak amplitudes can be > x5 rms level
• Most demanding stability requirements:
Orbit disturbance frequencies approximately bounded at high end by data sampling rate and a low end by data integration and scan times
noise not filtered out
Stability Time Scales
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
• Short stiff girders and magnet supports (>20 Hz)
• Chamber constrained vertically and horizontally at BPMs
• Invar supports for key BPMs (~3 m/oC)
• 18”-24” concrete floor
• Tunnel temp stable to ± ~1oC/day
SPEAR 3 Mechanical Design
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 Electrical Design – Power SuppliesDipole:
stability: 50ppm (or better); 3 ppm/OC diurnalripple: 0.2% pk-pk of full output voltage ripple (DC-1 MHz)chopper freq: 20 kHz
Quadrupole and Sextupole:stability: 100 ppm; 6 ppm/OC diurnal ripple: 0.2% pk-pk of full output voltage ripple (DC-1 MHz)
chopper freq: 40 kHz
Correctors:stability: 500ppm; 30ppm/OC diurnalnoise: 17 ENOB, 0.001 Hz – 4 kHz chopper freq: 40-60 kHzDAC resolution/update rate: 24-bit (>18 bit for ± 1 mrad corrector) / 4 kHzbandwidth: ~1 kHz
RF HVPS (90 kV)stability: < 0.1% FSripple: < 1% pk-pk (<0.2% rms) above 60 kV
Power supply stability requirements depend on ring design
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 BPMs and ProcessorsBergoz MX-BPM (modified)• mux'd button processing (16 kHz)
• ADCs sample baseband button signals (before internal analog position calc circuit)
• SPEAR 3 version has:o 5 dB more input attenuation than standard
module for 500 mAo wider IF filter to sample turn-turn orbit (2.2
MHz vs. 0.4 MHz)o ~2 mm res for injected beam (0.03 mA)
Echotek Digital Receivers • parallel I/Q processing of down-converted
button signals (8 chan/module = 2 BPMs)
IF = 16.65 MHz (13 frev)
sample freq = 64.02 MHz (50 frev)
• provision for simultaneous processing of test tone calibration signal
• ~0.3-mm res for injected beam (0.03 mA)
• 2-µm turn-turn resolution at >~10 mA
• nanometer resolution in 100 Hz BW
84 mm44
.2
mm 34
m
m
24 mm13 mm18.8 mm
12-mm diam buttons
BPM processor temperature regulated to < ± 0.4oC pk
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 BPM Processing and Fast Orbit Feedback
Corrector Power Supplies - Bldg. 118 rev. 4/12/07
Central BPM/Orbit Feedback
StationBldg. 117
EPICSnetwork
Injecttrig
6 Hcorrs
6 Vcorrs
spare/misc.
IOC
/ctr
lIO
C/c
trl
IOC
/ctr
l
IOC
(PP
C)
MC
OR
Com
m(1
00 M
b E
’net
no T
CP
/IP)
BP
M/F
dbk
CP
U/IO
C(P
PC
)
T-S
tam
p/S
ync
out
BP
M C
omm
(2ea
100
Mb
E'n
etno
TC
P/IP
)
West Pit (quadrants 1 & 4) East Pit (quadrants 2 & 3)
8 Hcorrs
8 Vcorrs
8 Hcorrs
IOC
/ctr
lIO
C/c
trl
IOC
/ctr
l
8 Hcorrs
8 Vcorrs
8 Hcorrs
IOC
/ctr
lIO
C/c
trl
IOC
/ctr
l
8 Vcorrs
8 Vcorrs
8 Vcorrs
IOC
/ctr
lIO
C/c
trl
IOC
/ctr
l
8 Vcorrs
8 Vcorrs
8 Vcorrs
IOC
/ctr
lIO
C/c
trl
IOC
/ctr
l
frev =1.28 MHz
sync/4 kHz T-stamp
BPM74
BPM 46 BPM 73 BPM92
BPM27
BPM 1 BPM 28 BPM45
4 kHz sync
LO LO
IF C
lk
4 kH
z sy
nc
LO LO
IF C
lk
4 kHz / T-stamp
MCOR comm
EPICS network
fRF = 476.300 MHz
frevout
RF/ClockSig Gen
LOout
IF Clkout
syncsync
IOC
/A
DC
s
error
sumphotonBPMs
29-BPMMUX'd Button Processing
baseband buttondetect ADCs
18-BPMParallel Button
Processing(in progress)
digital IF detect(1st turn, turn-turn,
closed orbit)
T-Stmp/Sync
IOC(PPC)
ctrl
Ene
t
BP
M E
net
sync
out
frev
syn
c/T
-stm
p
27-BPMMUX'd Button Processing
baseband buttondetect ADCs
18-BPMParallel Button
Processing(in progress)
digital IF detect(1st turn, turn-turn,
closed orbit)
T-Stmp/Sync
IOC(PPC)
ctrl
Ene
t
BP
M E
net
sync
out
frev
syn
c/T
-stm
p
Note:
SPEAR 3 was commissioned and operated until recently using slow orbit feedback running on MATLAB
(Corbett, Portmann)
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 Fast Orbit Feedback
Rx TUSVR
x T1)( UVS
Static orbit correction Dynamic orbit correction
nxK̂n PI T1)( USV
naKmnaKnaK̂ P0m
IPI
· 4 kHz update · latency (pipeline delay + deadtime) = 0.7-1 ms· RTEMS realtime OS · EPICS control and monitoring
x
xref
S-1UTx KPI V
2 ea remote IOCs (+ phBPM IOC)
Central CPU(1 GHz powerPC+altivec)
18 ea remote IOCs (8 correctors/IOC)
100 Mb/s E’net broadcastno TCP/IP
2 ea 100 Mb/s E’netno TCP/IP
+
-
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
Distributed weak perturbations:
• Uncorrelated small (~1μm) vibrations of individual magnets and supports cause orbit motion is concentrated in the modes with large singular values and frequency range 1-200Hz.
SPEAR 3 Orbit Motion
Localized strong perturbations:• Gap or phase changes in undulators occur
on a ~1s time scale. Local feed-forward correction was implemented using ID trim coils, adjacent quads (tune) and skew quads (coupling). Cause global orbit distortions of a few m rms without FOFB.
• Vehicle traffic on the overpass bridge causes slow (~1s) motion of the floor and microns of orbit instability.
• RF power supply ripple inducing synchrotron oscillations
08:00 08:30 09:00 09:30 10:000
0.5
1
1.5
2
2.5
3x 10
-3
time
r.m.s
. orb
it 0.
5s a
vera
ge [
m]
Horizontal
Vertical
SOFB FOFB
FOFB correction of ID gap changes and bridge traffic effects. Based on 2 hours of averaged (0.5s)
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 Phase Oscillations and RF HVPS Ripple
• Phase oscillations measured with turn-turn BPM:
3.6 mrad rms = ~1.2 ps rms
bunch length = 17 ps rms
• Working to implement mode-0 feedback
• RF HVPS ripple induces 0-mode longitudinal phase oscillations
• Problem with RF HVPS causes extra oscillation amplitude @ 60 Hz nominal ripple: 0.4% rms of 70 kV
100 ms
4 ms
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
FOFB effect on distributed weak wide bandwidth perturbations. Based on 1s of 4kHz BPM data
Fast orbit feedback in operation since June, 2006. Integrator loop gains set conservatively for start of operations. Studies ongoing to find optimal tuning.
SPEAR 3 Fast Orbit Feedback – Bandwidth
100
101
102
103
10-4
10-2
100
102
Frequency [Hz]
Inte
gra
ted
R.M
.S.
Po
we
r S
pe
ctr
um
[ m
2 ]
FOFB Off
FOFB OnFOFB On, more gain
100
101
102
103
10-4
10-3
10-2
10-1
100
Frequency [Hz]
R.M
.S.
Po
we
r S
pe
ctr
al
De
ns
ity
[ m
2 /Hz
]
FOFB Off
FOFB OnFOFB On, more gain
-10
-8
-6
-4
-2
0
2From: u1 To: y1
Mag
nitu
de (
dB)
102
103
-135
-90
-45
0
Pha
se (
deg)
Bode Diagram
Frequency (rad/sec)
Data
3zero-3pole model
Limiting factors:
• Corrector field penetration in vac chamber (copper with CuNi inlays for bandwidth to ~200 Hz)
• Time delay - 3 clock cycles
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
0 20 40 60 80 100 12010
-5
10-4
10-3
10-2
10-1
100
101
102
Singular Values
SPEAR 3 Fast Orbit Feedback - Eigenmodes
1. Uncorrected orbit error from ‘real’ sources
2. ‘Spilling’ from other modes accumulating in corrector magnets
050
100150
200
0
20
40
60-4
-2
0
2
4
x 10-3
Time [min]
Orbit Error in BPM space
BPM #
y [
mm
]
050
100150
200
0
20
40
60-2
0
2
4
6
8
10
x 10-3
Time [min]
Orbit Error in eigenmode space
Eigenmode #
y U
[m
m]
Eigenmode spectrum
Ignoring even a single eigenmode results in gradual buildup of error:
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
0 50 100 150 200 250 300 350 400 450 5000
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
PS
D [
m2 ]
/Hz
BL11 pBPM PSD
No FOFB
Currrent Ki only
Reduced Gain
0 50 100 150 200 250 300 350 400 450 5000
5
10
15
20
25
30
35
40
Frequency [Hz]
IPS
[m
2 ]
BL11 pBPM Integrated PS
No FOFB
Currrent Ki only
Reduced Gain
3. When modal Ki and Kp gains are tuned to reduce motion seen by in-loop electron BPMs, out-of-loop photon BPMs suffer
10 20 30 40 5010
-1
100
101
102
Vertical eigenmode #
Inte
gra
tor
frquency [
Hz]
Ki values for different eigenmodes
integrator bandwidths for different eigenmodes
SPEAR 3 Fast Orbit Feedback – Eigenmodes – cont.
4. Feedback gain/BW is reduced for higher eigenmodes to reduce orbit noise but to still allow modal “mop-up”
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
• Vertical motion at photon BPMs (~15-20 m from source) not included in feedback can be 10s of microns even though stability shown by electron BPMs is <1 m
• “Beam Line Dynamic Steering” (BLDS) has been introduced:
• Response of photon BPMs to a local angle bump in 2 electron BPMs is measured offline
• Photon BPM data averaged for 1 min for each beamline
• Once a minute apply calculated correction to the electron BPM FOFB target.
• BLDS is not perfect: 1 degree of freedom does not exactly correct source motion; combination of position and angle could be tuned to maximize performance
• FOFB architecture allows to bring in pBPM data at 4 kHz rate and response matrix can be extended to include pBPMs
• Practical issue for including pBPMs in response matrix: need to reconfigure matrix (add/remove rows) on the fly when beam lines open and close
-0.45 -0.4 -0.35 -0.3 -0.25 -0.2-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
eBPM [mm]
pB
PM
[m
m]
pBPM/eBPM measured off-line
Measured
linear
SPEAR 3 Photon Monitor Feedback
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
Beam Line Mirror FeedbackT. Rabedeau, SSRL
• error signal obtained from position sensitive detector near beam focus
• error signal used to control piezo high voltage
• piezo provides mirror fine pitch control with typical full range of motion +/- 30 rad or +/- 0.6mm or more focus motion.
focus 1.4 m rms
source 17.3 m rms
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 Fast Orbit Feedback – Operator Interface
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
2oC
RF frequency (green) changes by 1 kHz (C/C = ~0.5 mm/234 m) for a 2oC tunnel temperature variation (red) over 1 month period
RF Frequency Feedback
RF frequency (green) changes ~30 Hz twice daily from lunar tide
(9oC pk-pk outside diurnal temperature over 4 days shown in violet)
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR Floor Motion
-0.00040
-0.00030
-0.00020
-0.00010
0.00000
0.00010
0.00020
0.00030
0.00040
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
June 2003 - July 2003 Nov 2003 - July 2003 Sep 2004 - July 2003
400 µm
-0.00040
-0.00030
-0.00020
-0.00010
0.00000
0.00010
0.00020
0.00030
0.00040
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38
June 2003 - July 2003 Nov 2003 - July 2003 Sep 2004 - July 2003
400 µm
Floor monument changes in first year of operation
HLS (Georg Gassner)
• Data correlation analysis over 1 year suggests external temperature is the main factor for short term floor movement, not the internal temperature of the tunnel.
• More HLS sensors to be added
R. Hettel SPEAR 3 Orbit Stability and Stabilization NSLS-II Stability Workshop April 18-20, 2007
SPEAR 3 Orbit Stability and Feedback – Future Development
• Plan to characterize diurnal instability of floor, ring and beam line components using high resolution sensors (HLS, etc). This information might be included in feedback/feedforward
• Studying to potential improvement gained by adding a roof over SPEAR (and possibly subsequent air conditioning)
• Beam line dynamic steering to be integrated into FOFB
• Better photon monitors are being developed
• More parallel BPM processors will be added (will pay attention to new SLS/DESY design)
• Plan to continue developing feedback to incorporate ring and beam line sensors and actuators