NICA Collider: status and further steps
O.S. Kozlov
LHEP, JINR, Dubna
for the NICA team
Machine Advisory Committee, JINR, Dubna, October 19-20, 2015
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Contents
1. Collider optics and parameters
2. Instabilities in collider
3. Correction systems of the rings
4. Dynamic Aperture estimation
5. Multipole corrector parameters
6. Collider optics: further steps
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1. Collider general parameters
Circumference, m
Number of bunches
Rms bunch length, m
Beta-function at IP, m
Betatron tunes, Qx / Qy
Chromaticity, Q’x / Q’y
Ring acceptance, mmmrad
Long. acceptance, p/p
Gamma-transition, tr
Ion energy, GeV/u
Ion number per bunch
Rms p/p, 10-3
Rms beam emittance, hor/vert,
(unnormalized), mmmrad
Luminosity, cm2s1
IBS growth time, sec
Tune shift, Qtotal =QSC +2
503.04
22
0.6
0.35
9.44 / 9.44
-33 / -28
40
0.010
7.088
1.0
3.0
4.5
2.0∙108 2.4∙109 2.3∙109
0.55
1.15
1.5
1.1/
1.1/
1.1/
0.95
0.85
0.75
0.6∙1025 1.0∙1027 1.0∙1027
160
460
1800
-0.050
-0.037 -0.011
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1. Collider Optics
Periodic Cell
Lcell=11.96m
Ldip=1.94m Bmax=1.8T
Lquad=0.46m Gmax=23T/m
Lcorr=0.30m (dipole,
quadrole, sextupole,
octupole windings)
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1. Collider Optics
Optics for both beams (Half of the Ring). L(Triplet-IP)=5.25m
Dy not compensated
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1.2. Collider Ring scheme & Layout, Ion Mode
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1.2. Collider Ring scheme & Layout, Ion Mode
Stochastic cooling systems layout in collider
SC system parameters:
W=24 GHz, P= up to 500 W amplifier,
L_pickup=2m
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2. Specification of the instabilities in NICA collider
Sidorin,Zenkevich
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2. Specification of the instabilities in NICA collider
Sidorin,Zenkevich
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3.1. Dipole correction: Closed Orbit Correction
Magnet alignment tolerances realized by geodetic system and
relative dipole guiding field tolerance
Error Type
Dipole magnets:
Quadrupole magnets:
Relative field error, (BL)/(BL)
R.m.s. value
0.0005
Longitudinal displacement, S
0.5 mm
Transverse displacement, Y
0.5 mm
Roll error,
0.5 mrad
Transverse displacement, X/ Y
0.10/0.10 mm
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2.1. Closed Orbit Correction
C.O. Distortion Statistics for N=100 random orbits
Horizontal orbit [mm]: Xmin
Vertical orbit [mm]:
Ymin
Xmax
Ymax
<X>
<Y>
-17.4
18.1
5.7
-19.1
14.6
5.6
Maximal/minimal horizontal/vertical pickup readings before/after correction
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2.1. Closed Orbit Correction
C.O. Correction Algorithm - MICADO
C.O. Correction Statistics for required r.m.s residual orbit=0.1 mm
Horizontal orbit [mm]: Xmin
Xmax
<X>
-0.55
0.49
0.12
Vertical orbit [mm]:
Ymax
<Y>
-0.53
0.62
0.13
Ymin
Maximal corrector strenght:
max X/Y [mr]
0.30 / 0.30
Max. number of used correctors
25
Correction Quality X/Y
33/30
Required maximal values of
horizontal/vertical corrector strength.
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3.2. Quadrupole correction of tune
 Nominal Betatron Tunes Qx/Qy=9.44 9.46
require for effective Stochastic Cooling in
Energy range 3 4.5 GeV/u;
 Qx/Qy=9.10 – second possible working point:
Ecool up to 3GeV/u, larger DA;
 Collider correction range: Qx/Qy=9.109.46 ;
 Main collider quadrupoles: Imax=11kA
 Trim quadrupoles families in long straights
used for tune correction together with another
Tune diagram up to 7th
matching conditions: Imax=1kA
resonance order
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3.2. Quadrupole correction of tune
Tuning of the ring with trim
quadrupoles (an example
for 1 half of the straight
section).
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3.3. Skew quadrupole corrections: Coupling
Sources of X/Y coupling in collider:
 Solenoids: MPD: Bs=0.5T, Leff=5.8m; ECool: Bs=0.2T, Leff=6.0m
 Quadrupoles random roll: =0.1mrad expected
Solenoid effects:
 Tune Shifts
 X/Y Coupling, but x  y
Correction @ Ek=1GeV/u :
 Tune Shifts: min +/-0.01, max +/- 0.03
 Coupling: correction of 2 nearest resonances Qx-Qy=0, Qx+Qy=19
by skew quads (or solenoids).
MPD[ + ], ECool [ - ]
4 Skew Quadrupole Families K1[m-2]: -0.0209, +0.0048, +0.0068, +0.0176
Gmax=0.3[T/m] LSQ =0.3m
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3.3. Skew quadrupole corrections: Coupling
Correction of 2 nearest coupling
resonances with harmonics p=0, 19:
Qx ± Qy = p
p = (4 )-1  KL( x  y )1/2 exp[i(  x ± y - (Q x ± Qy - p) ]
Betatron tunes and tune Splits:
QX/ QY
Unpertubed tunes
Qx-Qy=0
Qx+Qy=19
Difference
resonance modes
before correction
Difference
resonance modes
after correction
QX/ QY
9.4352/ 9.4374
9.4257/ 9.4477
9.4356/ 9.4378
-0.0100/+0.0100
+0.0004/+0.0004
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3.3. Skew quadrupole corrections: Dy
Dispersion functions:
horizontal Dx,
vertical Dy (before/after correction)
Correction of the vertical dispersion Dy could be provided by at least
2 additional skew quadrupole families located in arcs near maxima of
Dx-dispersion (8 correctors, Gmax= 1 T/m)
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3.4. Sextupole correction, Chromaticity of tune
 Cancellation of sextupole nonlinearity influence on DA : =1800 between
correctors of one family (F/D)
 Sextupoles adjusted to minimaze tune variation: 4 families of sextupole
correctors for second order chromaticity correction,
Tune spread over the momentum
acceptance ±4
p
before (1) and
after (2) correction
 Natural chromaticities: Q’x=-33, Q’y=-28 ( Q’x,y~20 from 2 IPs)
 Corrected chromaticities: Q’x=-1.5, Q’y=-1.5
 Ncorr=24, G’max=150T/m^2
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3.5. System of Octupole correctors
1. Compensation Amplitude dependent Tune Spread from Sextupoles:
2 families of Octupole correctors in arcs (Nf=Nd=10), Gmax=400T/m3.
2. Introduction Amplitude dependent Tune Spread to compensate head-tail
instability:
 Corrected (low) chromaticity could decrease higher order modes of beam instability
and improve DA consequently beam lifetime;
 Too low chromaticity can make the beam unstable due to weak head-tail instability ;

One way to compansate this effect is to introduce octupoles to create large amplitude
dependent tune spread;

If the shifted coherent tunes due to wake fields is within incoherent betatron tune
spread or synchrotron tunes all unstable higher mode can be damped by Landau
damping;
 Problems from octupoles: additional 2nd order chromaticity, reduction of DA
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4. Dynamic Aperture
No space charge
X/Y DAs @ IP for Chrom. Correction Q’x,y=0: DAx=150pi,
Day=180pi
(B/B)3,dip=4E-4 (EK = 1GeV/u) DAx = 140pi, DAy = 140pi
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4. Dynamic Aperture
DA simulation with MAD-X code methods:
1. Thin lenses approximation – Symplectic integration of particle motion;
2. PTC - Polymorphic Tracking Code – Symplecticity + Space Charge .
Conditions for calculations:
RF cavities, Chromaticity sextupoles, Dipole nonlinearities (odd harmonics) ON
Npart=105 – max.number of particles: Nturn=103105 – number of turns.
The long-term DA is evaluated by the Giovannozzi approach:
where D- asymptotic DA, b and k parameters are defined from dependency D(N).
Results:
Asymptotical DA for Qx,y =9.44/9.44 working point:
D=100  mmmrad (PTC), 60 mmmrad (tnin lens) > Ax,y=40  mmmrad
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4. Dynamic Aperture
Zenkevich, Bolshakov
Dynamic Aperture (PTC),
“survival plot”
Dynamic aperture,
envelope (PTC).
Npart=105 – number of particles
Nturn=103 – number of turns
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4. Dynamic Aperture
Dynamic aperture (PTC, thin-lens methods and approximations) vs
number of turns Nturn.
Npart=105 – max.number of particles
Nturn=105 – max.number of turns
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5. Multipole corrector
Set of multipole correcting elements for 1 ring
Multipole
Component
Dipole
Quadrupole
“Skew
quadrupole
Sextupole
Octupole
Function
Closed orbit
correction and
control
Betatron tune
correction
Coupling
compensation
and vert. disp.
correction
Chromaticity of
tune control
Second order
corrections
Max.
Max. parameter
parameter of
of magnetic
power supply
field
[kA-turns]
Number
0.15 Т
8.0
40
2.2 Т/m
3.8
12
1.0 Т/m
1.7
4; 8
150 Т/m2
5.7
48
400 Т/m3
3.8
20
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6. Optimization of Collider optics and beam dynamics
 Main quadrupoles (max 11kA) + Trim-Quadrupoles families (max 1kA) :
betatron tunes correction in range Qx/Qy=9.19.46;
 Introduction of additional skew quads families for Dy-correction near IP;
Further considerations for optics and dynamics:
 * variation at IP, *=[0.351.0] m;
 Resonances correction (various multipoles) ;
 Systems of (scraper-collimator) for localization of particle losses with large
amplitudes;
 Further simulation of long term Dynamic Aperture with space charge, also
taking into account fringe fields of the magnetic elements;
 Checking of beam dynamics at working point Qx/Qy~9.1, and QxQy.
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6. * variation
Characteristic IBS growth times (sec), tX tY  tL
(MAD-X, beam parameters – Table p.3)
EK=1.0 GeV/u
EK=3.0 GeV/u
EK=4.5 GeV/u
*=0.35 m
max=190 m
220
600
2000
*=1.0 m
max =65 m
300
900
2500
 s    * 
s2
*
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6. Fringe fields effect
Zenkevich,Bolshakov
preliminary results
Dynamic Aperture (PTC tracking),
Npart=105, Nturn=103 ,
taking into account Final Focus
Quadrupoles Fringe fields:
(6th, 10th, 14th order resonances
excitation)  small DA
Dynamic Aperture (PTC tracking)
with Fringe field and MPD Solenoid
Working point: Qx=9.34, Qy=9.32
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Thank you for your attention !
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1.2. Collider Ring scheme & Layout, Polarized Mode
MPD
Polarization
Control
1-st Solenoid
SS
2-nd Solenoid
SS
Polarization
Control
SPD
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