optimisation of slow extraction for sis-18 and sis-100

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


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


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 )()(



…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)



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



… ...,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


Extraction Methods

(M. Pullia)

0' QDashed line

GSI GSI

RF acceleration,Longitudinal noise,Betatron core.

Move machine tunetowards resonance.

Transverse RF excitation.

(Q‘=0)


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


RF Knock-Out Extraction

X

X‘

Intensity

Dual FM (HIMAC)

BPSK (GSI)

SeparateFunctionnot shown.


Block Functions of the SIS-18 RF Knock-Out

P. Moritz, GSIbel.gsi.de/mk/fg/ko_extr.pdf

2

)(

)()(

SC

SCS Tff

TffSinATfG


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,


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.


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.


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


Spill detection

http://www-bd.gsi.de/conf/juas/juas_script.pdf

(P. Forck)


SIS-100 Synchrotron

Doublet lattice6 super periods

RF-KO


Hardt Condition

xnn QS

DD 4

)sin()cos( 00

Dispersion zero for illustration. Hardt condition.

3 separatriceseach with a different momentum

(Á. Saá-Hernández)


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):


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


SIS-100 Extraction - Powering Scheme

Chomaticities: -0.29 (h), -2.19 (v). Normalised to tune.

Lattice version:TDR, Dec 2008 !

RF-KO Exciter


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


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


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)


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


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)


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)


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!


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)


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


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.


SIS-100 RF Knock-Out System Specification

P. Moritz, “Detailed Specification on the SIS100 RF KO”, EDMS, GSI-B-RF Systems, 31 Jan 2011


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)


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


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


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.


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


SIS-18 RF Knock-Out Simulation - Hardt Condition

Animation: Horizontal beam phase space with first extraction septum edge (left)


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.


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

optimisation of slow extraction for sis-18 and sis-100

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