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78 Kr 34+ 600 MeV/u. 12 C 6+ 430 MeV/u. Spill intensity. Optimisation of Slow Extraction for SIS-18 and SIS-100. M. Kirk Synchrotrons Group, GSI. Available at http://www-linux.gsi.de/~kirk. Overview. Principles of resonant extraction Extraction schemes SIS-18 Spill-ripple feedback - PowerPoint PPT Presentation
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M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Optimisation of Slow Extraction for SIS-18 and SIS-100
M. KirkSynchrotrons Group, GSI
Spi
ll in
ten
sity
78Kr34+ 600 MeV/u12C6+ 430 MeV/u
Available at http://www-linux.gsi.de/~kirk
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Overview
• Principles of resonant extraction
• Extraction schemes
SIS-18
• Spill-ripple feedback
• Spill intensity control
• Spill measurement and analysis
• Hardt condition
SIS-100
• “Not so Hardt” condition
• Power converter ripple (main quadrupoles)
• RF Knock-Out specification
• Conclusion & Outlook
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Resonance Theory – Sextupole Perturbation
Change variables …
22'
2
1yxgB y
B-field of a sextupole
221
2
2
)()( xsKxsKds
xdsextsquads
# over circumference: „Tune“
BxsB
sK ysexts
22 )()(
Equation of motion
BxsB
sK yquads
22 )()(
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Resonance Theory – Sextupole Perturbation
…to normalized coordinates (u, p) as function of
xxu
)(1
0
sQQ
dsx
s
x
ds
dxx
d
du
Qp x
x
x
1
)cos(222
2
nQuAuQd
udn
0
25 )cos()(n
nnsextsx nAsKQ
s = point of interest
Close to just oneresonance (n)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Resonance Theory – Sextupole Perturbation
Change variables (u,p) (r,) to find unstable fixed points (A,B,C)
)/(tan3/ 1
22
upn
pur
eventually obtaining
3cos83
3sin82
rAQndd
rAddr
n
n
at the unstable fixed points A,B,C0 ddddr
Which yield the conditions on r and …
= Separatrix
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Resonance Theory – Sextupole Perturbation
… ...,34,32,03
nAQnr 83
x
un xxA
d
dx
8
22
ddxx 6
> effective septum width!
22
348resQQ
SA
LKS sx23
2
1
Area of separatrix
Spiral step along the extraction arm
3
nQres
„Third order/integer“ resonance
Normalised sextupole strength
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Extraction Methods
(M. Pullia)
0' QDashed line
GSI GSI
RF acceleration,Longitudinal noise,Betatron core.
Move machine tunetowards resonance.
Transverse RF excitation.
(Q‘=0)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
RF Knock-Out Extraction
Power density
Frequencymf0
Qf*f0 Qf*f0
Transverse Schottky Spectrum
PAM spectrum
~5 MHz ~300MHz
Pick-Up BW
…
KO Exc.(m=0, USB)
(m+1/3)f0
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
RF Knock-Out Extraction
X
X‘
Intensity
Dual FM (HIMAC)
BPSK (GSI)
SeparateFunctionnot shown.
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Block Functions of the SIS-18 RF Knock-Out
P. Moritz, GSIbel.gsi.de/mk/fg/ko_extr.pdf
2
)(
)()(
SC
SCS Tff
TffSinATfG
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Theory
tfQtfp
pQtQ rippleripples 2sin2sin)( 0
Time variation in tune of a bunched beam subject to ripple from the power supplies to the quadrupoles
Therefore area of separatrix will also oscillate:
dt
dQQQ
Sdt
dAres 2
3482
Thus, to minimize sensitivity to ripple in the quadrupoles, extract with as high S as possible without distortion to the separatrix.
dsssK )()(4
11
where,
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Effect of tune ripple on separatrix
(a) Beam before powering resonance
(b) First Extraction Septum Edge
(a)
(b)
Septum change due to tune ripple
Unstable resonant particle at Nth turn
14
7
10
N
'X
X
…Spill intensity is modulated.
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Ripple Injection
Active ripple excitation (Moritz 2003)
…spill ripple reduced.
Analyzer + generatorreplaced with feedback amplifier…
Extraction delay determined.Sets limit for spill intensity control.
F/B off
F/B on
300 Hz
Traces offset.
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Spill Analysis DAQ Systems at GSI
ABLASS / ABLAX• Pulse Counting• NIM modules (discriminator: analogdigital pulse)• 4 x 32-bit Multi-Scalers (time slice: bin size)• Multi purpose VME module (event decoder)• Particles counted: primary beam or secondaries• Detectors: Numerous types• Detectors at: SIS, HEBT, CAVES• Spill intensity versus time• Countrate histogram
TRigger LOgic• Pulse Counting• Detector: Scintillator• Pile-up 50-100 ns• CFDFirmware (counting etc.)• Particles counted: products• Detectors at: LAND, FRS• ~103..5 particles per Prim. (FRS)• Time interval (pulse-pulse) hist.
ABLASS/X Detectors
• Plastic Scintillator• Pulse (ELR) ~20 ns• Pulse Counting • 1 Pulse per Prim.• Mean 106 Prim./s• Bin size min. 10 s
• Ionisation Chamber• Pulse (Gas-ions) ~10 s• Current-to-Frequency fmax=1 MHz• Pulse per Prim. depend on beam• Mean 104..9 Prim./s• Bin size >10 s
• Secondary e- Monitor• Pulse (sec. e-) < 10 ns• Current-to-Frequency• depend on beam• Mean >108 Prim./s• Bin size >> 10 s
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Spill detection
http://www-bd.gsi.de/conf/juas/juas_script.pdf
(P. Forck)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-100 Synchrotron
Doublet lattice6 super periods
RF-KO
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Hardt Condition
xnn QS
DD 4
)sin()cos( 00
Dispersion zero for illustration. Hardt condition.
3 separatriceseach with a different momentum
(Á. Saá-Hernández)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Several Sextupoles Virtual Sextupole
Normalised strength:
Betatron phase:
2
,,
2
,, )3sin()3cos(
nSextsnxn
nSextsnxnvirt SSS
nSextsnxn
nSextsnxn
virtx S
S
Tan
,,
,,
1, )3cos(
)3sin(
3
1
virt
1st Extr. Sept.
Virtual Sextupole
C
isextsx dsesKs x
0
323 )()( Driving term (Guignard 1978):
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Chromaticity Correction
Chromaticity correctionin SIS-18:
CxCyCyCxCx
natxxCynatyyCx
CeffC D
QQQQ
NLK
3,1,3,1,1,
,3,,3,
1,1,2
4
0
,p
p
d
dQQ
Adjusted chromaticity (sextupoles on):
Natural chromaticity (sextupoles off):natQ
CxCxCeff
CeffCCxCxnatxxC NDL
LKNDQQK
3,3,3,
1,1,21,1,,3,2
4
dssDssKQ xx
C
sextsx )()()(4
1
0
' dssDssKQ xy
C
sextsy )()()(4
1
0
'
N = # 1C-Sextupoles = # 3C-Sextupoles
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-100 Extraction - Powering Scheme
Chomaticities: -0.29 (h), -2.19 (v). Normalised to tune.
Lattice version:TDR, Dec 2008 !
RF-KO Exciter
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Momentum Sensitivity of Separatrix
Qx = 17.3132, Qy = 17.8Phase parameter P2 = 3*15 deg
K2L: Amplitude = -0.159 m^-2, SH=SV= -0.39 m^-2
-0,010
-0,008
-0,006
-0,004
-0,002
0,000
0,002
0,004
0,006
0,008
0,010
-0,07 -0,06 -0,05 -0,04 -0,03 -0,02 -0,01 0 0,01 0,02 0,03 0,04 0,05 0,06 0,07
x [m]
x' [
m]
dp/p = 0%
dp/p = +0.05%
dp/p = -0.05%
Septum
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Optimising the RF Knock-Out Bandwidth
0
1
2
3
4
5
0,020 0,025 0,030 0,035 0,040 0,045 0,050 0,055 0,060 0,065 0,070
Excitation bandwidth (2fclock/f0)
Po
rtio
n o
f in
itia
l in
ten
sity
in r
ing
aft
er 5
00 m
s [%
]
SIS-100:238U28+
B=100Tm
0
0,2
0,4
0,6
0,8
1
1,2
-2 -1,5 -1 -0,5 0 0,5 1 1,5 2
Frequency (f-fcarrier)/fMLS clock
No
rmal
ized
Po
wer
Den
sity
Power density
Working point
Resonance
BW 2
)(
)()(
SC
SCS Tff
TffSinATfG
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-18 Quadrupoles - Power Converters
0°120°240°
0°120°240°
Active filter(50-70 kHz)
R (magnets + cable)
L (magnets)
(-15)
(+15)
12 pulse SCR power converter
(50 Hz in)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-18 Quadrupoles - Power Converters
12-pulse SCR supply.Grid 50 Hz, 3-phase.Main component 600 Hz.Smaller 300 Hz also present.
-15
+15
120°
120°
30°
Active filter reduces U/U0 to <2%
%20
U
U
dtdILRIU maxmax
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-18 Power Converter Ripple
Measurements taken on the flattop of three machine cycles.
Circuit Rigidity B [Tm]
6 10 18
In
[A]
Freq.[Hz]
I[mA]
In
[A]
Freq.[Hz]
I[mA]
In
[A]
Freq.[Hz]
I[mA]
S01QS1F 420 300 0.2 700 300 0.2 1270 300 0.2
600 0.2 600 0.7 600 0.5
S12QS1F 420 300 0.2 700 300 0.2 1270 300 0.2
600 0.1 600 0.5 600 0.2
S01QS2D 400 300 0.3 665 300 0.2 1203 300 0.2
600 0.6 600 0.1 600 0.5
S12QS2D 400 300 0.4 665 300 0.4 1203 300 0.2
600 1 600 0.8 600 0.4
S01QS3T 81 300 0.2 137 300 0.2 248 300 0.1
600 0.1 600 0.3 600 0.5
S11MU2 1092 600 2 1820 600 4 3340 600 2
1050 8 900 8 900 6Dipoles
F-Quadrupoles2 Series Circuits
D-Quadrupoles2 Series Circuits
T-Quadrupoles1 Series Circuit
(H. Welker, H. Ramakers, M. Kirk)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-18 Power Converter Ripple
Measurements taken at constant maximum current in the main quadrupoles.
Circuit In [A] I at 300 Hz [mA] I at 600 Hz [mA]
S01QS1F 1764 0.5 0.8
S12QS1F 1760 0.2 0.4
S01QS2D 1750 0.2 0.4
S12QS2D 1750 0.2 0.4
S01QS3T[1]
S01QS3T[2]
807820
0.30.4
0.40.4
[1] Measured in „computer“ mode.[2] Measured by „hand“.
(H. Welker, H. Ramakers, M. Kirk)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-100 Quadrupoles - Power Converter
600 Hz also in SIS-100 quadrupole power converters:
•12 pulse line commutated converter (SCR.)• Switching Mode (SM) structure: Hard switching.• Supplies current to the main quadrupoles.• All main quadrupoles but 2 are superconducting.• Umax = 640 V at 100 Tm• U/Umax = 1%• Strongest ripple at f = 600 Hz• L = 29 mH (series load)• R from connecting cable only.• Z 2fL• I=U/Z = 59 mA• Imax = 7.8 kA (100 Tm)• I/I = 7.5x10-6
• Closed-loop control has N=18-bit ADC for current measurement.• 2N-1 levels from zero to Imax (Unipolar current, Bipolar voltage.)• Therefore, minimum possible accuracy is 30 mA300 Hz component: U/Umax = 0.5% would yield same I
During flattop: Magnets are not ramped!
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Main Quadrupoles – Power Converter Ripple
0
2
4
6
8
10
12
14
16
0 1 2 3
Amplitude (peak) in magnet current ripple I/In [x10-4]
Sp
ill q
ual
ity
fact
or
I max
/I mea
n
MIN
MAX
MEAN
Spi
ll Q
ualit
y F
acto
r (I
max
/Im
ean)
SIS-100: 100Tm 238U28+ ions
0.26 (B=22-100 Tm)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Bunched Beam Extraction
WP2 - Ions, slow extraction (Qx=17.3132,Qy=17.8)
0
100
200
300
400
500
600
0 2 4 6 8 10 12 14
Time [ms]
Co
un
ts Vrf=0
Vrf=400kVp
F and D quadrupoles: I/I=±10-4
SIS-100: 238U28+ at 100 Tm
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Spill Quality - Sensitivity to Momentum Spread
0
1
2
3
4
5
6
7
0 0,05 0,1 0,15 0,2 0,25
Initial RMS longitudinal momentum Gauss-spread p/p in ring [%]
Sp
ill q
ua
lity
fa
cto
r I
max/I
mean
MIN
MAX
MEAN
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
0 0,05 0,1 0,15 0,2 0,25
Initial RMS longitudinal momentum Gauss-spread p/p in ring [%]
RM
S e
xtr
ac
ted
em
itta
nc
e [
mm
.mra
d]
1
1,1
1,2
1,3
1,4
1,5
1,6
1,7
Ion
s lo
st
at
se
ptu
m (
no
rma
lize
d)
Emittance
Losses (normalized)
Sp
ill
Qu
ali
ty F
ac
tor
(Im
ax/
I me
an)
RM
S E
xtra
cted
Em
itta
nce
[m
m.m
rad
]
SIS-100:U (A=238, q=28+) at 100TmDC beam.
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-100 RF Knock-Out System Specification
P. Moritz, “Detailed Specification on the SIS100 RF KO”, EDMS, GSI-B-RF Systems, 31 Jan 2011
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Beam Intensity Control
Open-Loop control. SIS-100 238U28+ 100Tm:
0
10
20
30
40
50
60
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5
Time [s]
KO
-Am
pli
tud
e [
kV
pp
]
0
20
40
60
80
100
120
140
160
Sp
ill
Cu
rre
nt
[arb
. U
nit
s]
KO-AmplitudeSpill Currents
)()( 42
3222
121 ttHbtttHate
e
Ue
e
UUV
tt
KO
Heavyside
b=0
b>0
t4
:43 tt
(a=0)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
0
1
2
3
4
5
6
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
Time [s]
RF
-KO
am
plit
ud
e [k
V]
(pea
k)
0
0,2
0,4
0,6
0,8
1
1,2
Inte
nsi
ty in
rin
g (
no
rmal
ized
)
RF-KO amplitude
Intensity: Actual
Intensity: Set-point
SIS-100: U28+ at 100Tm(VP = 0)
SimulationProportional plus Integral (PI) control:
Beam Intensity Control - Spill Feedback
1
0
1
tI
NIT
PKO IdtT
NtVVV
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-18 Synchrotron
SX1,FQ,DQ,SX2,QT
Doublet latticeSuper periodicity 12Sextupoles in odd periods• SX1 = Res. + Hor. Chro.• SX2 = Ver. Chro.• FQ = Foc. Quad.• DQ = Defoc. Quad.• QT = Triplet Quad.• ES = Electrostatic Extr. Sept.• MS1 = First Extr. Mag. Sept.• MS2 = Second Extr Mag. Sept.• RF-K.O. = RF Knock-Out ExciterInjection
ES
MS1,MS2
RF-K.O.Reinjection
FQ,DQ,QT
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Beam Intensity Control – Feedforward
SIS-18:29 July 2011
0
0,5
1
1,5
2
2,5
3
0 1000 2000 3000 4000 5000 6000 7000
Time [ms]
Spi
ll C
ount
rate
(de
tect
or H
TM
DIA
I)
0
50
100
150
200
250
300
350
400
450
Cur
rent
in S
IS18
(S
09D
T_M
L) [
arb.
un
its]
& R
F-K
O p
eak-
ampl
itude
[V
]
HTMDIAI
S09DT_ML
KO amplitude
MeasurementBeam: 12C6+
Energy: ~300 MeV/u
C. Bert, A. Constantinescu, D. Ondreka, M. Kirk et al.
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-18 RF Knock-Out Simulation - Hardt Condition
DC beam: p/p () = 7.7x10-5
RF Knock-Out:Amplitude (peak) = 2 kVBandwidth = 6.2 mQ (FW)
Bin size 10 s
~1% of ions lost at extr. septum
MAX/AVG: ~14RMS/AVG: ~230%
181Ta61+ at 300 MeV/u (B=7.97 Tm)
Tunes: 4.3296(h), 3.27(v)Resonance (1C) + Chromaticity Sextupoles (1C):Amplitude K2L=0.1 m-2
Phase = -161Offset K2L = 0.211 m-2
Remaining Chrom (3C) Sextupoles:K2L = -0.381 m-2
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
SIS-18 RF Knock-Out Simulation - Hardt Condition
Animation: Horizontal beam phase space with first extraction septum edge (left)
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Conclusion
No real success so far in uniting a good:
• Extraction efficiency,• Beamsize,• Transmission to target,• AND microstructure!
Macrostructure at least could be a success story, even for SIS-100.
M. Kirk, Beschleuniger Palaver, GSI, 19th Jan 2012
Preliminary Outlook
• Code benchmarking• Other dynamical effects• Other extraction techniques, e.g. stochastic extraction
P. Spiller, N. Pyka, P. Moritz, U. Scheeler, G. Franchetti, D. Ondreka,P. Forck, T. Hoffmann, H. Reeg, H. Klingbeil, S. Sorge, E. Feldmeier,A. Dolinskii, H. Eickhoff, T. Furukawa (NIRS), H. Ramakers,H. Welker, Á. Saá Hernández, S. Pietri (FRS), C. Bert, A. Constantinescu,HKR operations crew.
Acknowledgements