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Peter Spiller,
Heavy Ion Fusion Symposium
Princeton
June 7-11, 2004
Accelerator Plans at GSI for Plasma Physics Applications
Plasma Physics Requirements
1 . Maximum number of particles
: 1-2 x 1012 /cycle)
2. Beam energy
: 400 – 2715 MeV/u
3 . Short, single bunch on target
: 25 - 90 ns
4. Focal Spot
: 1 mm ?
The Future Accelerator Facility - FAIR
UNILAC
SIS18
SIS 100/300
HESR
Super FRS
NESR
CR
Gain Factors
Primary beam intensiy : x 100 – 1000 Secondary beam intensiy : x 10000 Ion energy : x 15 New: cooled pbar beams (15 GeV) Special : intense cooled RIBs Parallel operation and time sharing
Uranium Beam Intensity – Status SIS18
Limit untill mid of 2002 by low UNILAC beam currents
Significant progress with source und UNILAC developments
Status of the uranium currents in TK9 (SIS Injection) :
U73+ 1 mA
U28+ 2.7 mA
Expected number of particles in SIS :
U73+ 6 x 109 (MIT x15)
U28+ 4 x 1010 (MIT x15)
Highest accelerated U73+ - beam intensity : 4.5 x 109
(Dec. 2003 MEVVA ion source and MTI)
Two Stage Synchrotron Concept
High Intensity- and Compressor Stage
SIS100 with fast-ramped superconducting magnets and a strong bunch compression system.
BR = 100 Tm - Bmax = 2 T - dB/dt = 4 T/s Intermediate charge state ions e.g. U28+-ions up to 2715 MeV/u Protons up to 30 GeV
High Energy- and Stretcher Stage
SIS300 with superconducting high-field magnets and stretcher function.
BR = 300 Tm - Bmax = 6 T - dB/dt = 1 T/s
Highly charges ions e.g. U92+-ions up to 34 GeV/u Intermediate charge state ions U28+- ions at 400 to 2715 MeV/u with 100% duty cycle
SIS100/300 Design Parameters
First Stage Second Stage
Acceleration + Acceleration +
Compression Stretcher
Reference Ions
U28+
p
U28+
U92+
Rigidity [Tm] 100 300
Circumf. [m] 1083 1083
Intensity 1-2 · 1012
2.5 · 1013
1 · 1012 /s
1 · 109 /s
Energy [GeV/u]
2.7
29
2.7
34
Pulse length
[ns]
25 – 90
< 50
d.c.
slow ext.
Flux Density [T]
2 6
Ramp Rate [T/s]
4 1
Main Magnets s.c. wf s.c. cos
SIS300SIS100
SIS100/300 Underground Tunnel
5 m
-24 m
SIS100 Magnet R&D
Nuclotron Cable Nuclotron Dipole
Significant R&D progress achieved on dynamic losses and field quality
Bmax = 2 T – B’ = 4T/s Window frame magnet with s.c. coil
Main task : Reduction of AC losses during ramping by improved iron yoke design (40 W/m > 13 W/m)
> Talk G. Moritz
Power Net Connection
Today : GSI in series connection with Darmstadt
Step 1 : (summer 2005) : Separate 110kV connection to Urberach - upgrade Leonhardstanne
Contracts prepare
Step 2 : upgrade Leonhardstanne by an additional 63 MVA Transformer
Spitzen-
leistung
Feld-
rate
SIS 12 +26 MW
-17 MW
10 T/s
SIS100 ±18 MW 4 T/s
SIS300 ±30 MW 1 T/s
Power Oscillations
Torsion resonance nucl. power plant Biblis B
(monitoring and forced disconnection)
RF Systems in SIS100
Dual Harmonic Acceleration Systems SIS100 21 ferrite loaded Cavities - Va,tot 400 kV Frequency Range : 1.15 – 2.67 MHz (h=10)
Compression Systems SIS100 25 MA-loaded Cavities - Vc,tot = 1 MV Frequency Range : 465 kHz (±70) (h= 2)
Barrier Bucket Systems SIS100 (precompression and stacking) Broad band MA-loaded Cavities - Vb = 2x 15 kV
Frequency = 2.4 MHz
Total Length of RF-Systems ~ 150 m ( 14 % of circumference )
Bunch Compression in SIS100
Short pulses for optimum target matching PP and Super-FRS and fast cooling in CR
SIS100 RF V 0,a[kV] V0,c [kV] Na,c La,c [m] Pc [MW]
Separate
Systems
16 40 21+25 57+21 20
Combined Systems
3 10 115 90 10
50 ns
2.5 %
0.5 %
0.75 %
bunch rotation
adiabatic debunching
on Target
Phase space tomography of compression experiments in SIS18
Bunch Compression Studies
0
50
100
150
200
250
300
350
400
10 30 50 70 90
Pre-bunching RF voltage [kV]
Pu
lse
len
gth
FW
HM
[ns]
0
0,5
1
1,5
2
2,5
3
Pe
ak
po
we
r [T
W]
Pulse length (no space charge)
Pulse length (Space charge)
Peak power (no space charge)
Peak power (space charge)
Amorphous, cobalt based MA core
Nanocrystalline, iron based MA core
Magnetic alloy R&D
Prototype cavity for SIS18
Samples of magnetic alloy tape wound cores, measured f or the SI Sbunch compressor project. The ring to the lef t is a FineMet core, produced by Hitachi in J apan. The right one is a VitroVac core, produced by Vacuumschmelze in Hanau.
Samples of magnetic alloy tape wound cores, measured f or the SI Sbunch compressor project. The ring to the lef t is a FineMet core, produced by Hitachi in J apan. The right one is a VitroVac core, produced by Vacuumschmelze in Hanau.
In order to optimize shunt impedance and inductivity a large variety of scaled (1:5) nanocristaline (Fe based) and amorphous (Co based) core materials were investigated
In order to minimize the visible impedance, semi conductor high power switched must shorten the gap
40 KV per gap
MA-material Properties
Space limitation enforce high voltage per meter length
high power requirements
high performance MA-cores
R&D with : Honeywell, Vakuumschmelze, Hitachi and Radiotechnical Institute
Improved ribbon thickness, filling factor and manufacturing techniques
20 amorphous (Vakuumschmelze VITROVAC 6030F) and
20 nanocrystalline (Hitachi FT-3L) cores ordered
Significant improvement of quality factor Qf from 3.6 to 5.5 GHz !
Lattice Structure of SIS100
Maximum beam acceptance („small“ aperture magnets for fast ramping)
Dispersion free straight sections (no transv. Longit. coupling in rf systems)
Low dispersion in the arcs (momentum spread during compression) Dx = 2.5 m
Six superperiods (space for large tune shift and long storage time)
General optimization criteria for high current, U28+-operation and compression
Life Time of U28+- ions
Life Time of U28+ is significantly shorter
than of U73+
Life Time of U28+ depends strongly on the
residual gas pressure and gas components
High intensity, heavy ion beams require intermediate charge states ( U73+ > U28+ )
Desorption Processes degenerate
the residual gas pressure
Beam losses increase with
number of injected ions
(vacuum instability)
Pressure Dynamics
Fast variations (time scale s) Slow variations (time scale sec.)
New Design Concepts
Principal GOAL : No additional load for the UHV system during beam operation.
1. From all loss mechanisms, only particles which are further stripped by
collisions with the residual gas atoms are able to reach the beam pipe
within one lattice cell !
2. Each lattice cell must be designed as a charge separator. The „stripped“
beam (U29+) must be well separated from the reference beam. The low dispersion
function in the SIS100 arcs comlicate this issue.
3. The main lattice structure optimization criteria is the collimation efficiency
for U29+-ions.
4. The collimation efficiency for U29+ - ions must be 100%.
5. Mainly single (no multiple) ionized ions are generated.
6. The 100% collimation efficiency must be achieved with collimators at maximum distance from the beam edge. No significant acceptance reduction shall be caused by the collimators.
7. No ionization beam losses shall occure on cold and NEG coated surfaces.
8. By a dedicated design, the effective desorption rate of the collimators shall be almost zero.
New Design Concepts
Multiple Ionisation
1 10 1001
2
3
4
5
U28+
H
N
Ar
a
vera
ge
nu
mb
er
of p
roj l
oss
ele
ctro
ns
E (MeV/u)
Ref. : R. Olsen et.al.
SIS100 injection energy
SIS18 injection energy
Lattice Optimization
CDR triplet lattice (Acceptance : 100 x 55 mm mrad)
Doublet lattice with 3 dipoles per cell (Acceptance : 170 x 50 mm mrad )
Collimation Efficiency
80%
82%
84%
86%
88%
90%
92%
94%
96%
98%
100%
1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2,0
Distance from Beam Axis [ n*Rbeam]
Col
limat
ion
Effi
cien
cy
Acceptance CDR
CDR-lattice
Acceptance 3 Dipole DF
3 Dipole DF
The collimation concept is suitable for uranium operation.
The collimation efficiency for other ions species is lower.
The vacuum pressure is effected by uncontrolled losses and gas desorption.
Therefore beam tubes of the magnets shall be cold and act as cryopumps.
Without active cooling, the dipole tube temperature is about 50K.
Additinal cooling channels must be foreseen at least in the drift- and
quadrupole chambers.
NEG coating of SIS100/300 magnet chambers is not possible since baking
would be required.
about 700 m of the chambers will be cold an act as cryo pumps
(Present ) Limits of the Concept
Collimation Concept
wedge collimator at 80 K
cold, pumping sec. chamber at 4,5 K
Wedge collimator, Secondary chamber + cryo pump
The collimations system must controle the desorption gases (eff = 0)
Prototype Desorption Collimator
Vacuum Stabilization
Short cycle time and short sequences
SIS12 :10 T/s - SIS100 : 4 T/s
(new network connection in preparation)
Enhanced pumping power
(Actively cooled magnet
chambers 4.5 K (750m), NEG coating (250m)
(local and distributed)
Localization of losses and controle
of desorption gases
Prototype desorption collimator installed in S12
Low-desorption rate materials
Desorption rate test stand in operation
wedge collimator
increased pressure
ion beam
cryo pump
Summary of UHV issues
1. A promising concept for the high current U28+ operation exists.
2. The situation of the SIS12 booster operation is more critical since the lattice
is not optimized for collimation and multiple ionization is more probable.
3. No consistent concept for the operation with other heavy (e.g. Au, Pb) ions
is worked out. Collimation efficiency is lower and fractions of the beam may
get lost uncontrolled. Ionisation cross section drop for lighter ions.