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.