the gsi-accelerator uhv system and its upgrade...

The GSI-Accelerator UHV System and its Upgrade Program

Hartmut Reich-Sprenger

GSI, Darmstadt, Germany

[email protected]

An overview of the existing and the proposed GSI accelerator facility will be given, focused on the heavy ion synchrotron SIS18 and the experimental storage ring ESR.

Inside the GSI future project, the SIS18 will serve as the injector for a large double ring synchrotron. Operating the SIS18 with high intensity ion-beams of low charged heavy ions (e.g. U28+), special attention has to be paid to minimum static pressure and minimized pressure rises due to ion beam related desorption processes.

The UHV systems of the SIS18 and the ESR provide presently an average pressure in the low 10-11 mbar range. In order to increase the lifetime of cruc ial ion beams (e.g. U28+ ) by one order of magnitude for all planned ion beam intensities, the aim of the UHV upgrade program is to improve the static (no ion beam) and dynamic (with ion beam) total pressures and their residual gas composition.

International workshop XHV 2003, Bad Liebenzell, 23/04/03

1H.Reich-Sprenger, UHV-Group, GSI

The GSI-accelerator UHV System and its upgrade program

The GSI-accelerator UHV System and its upgrade program

Ø The GSI accelerator complex and its future extensionØ The heavy ion synchrotron SIS18Ø U28+ ion beam lifetime:- diagnostics- measurementsØ Lifetime relevance of different gas speciesØ Vacuum Requirements for the SIS18Ø example: Cryo pumping approach, Improvement potentialØ Optimized dynamic conditions: collimator approachØ Summary



GSI future extensionGSI future extension



The GSI Accelerator Complex + extensionThe GSI Accelerator Complex + extension

100m

n From protons to uraniumn In future also antiprotons

n 1 MeV/u to 2 GeV/un In future up to 30 GeV/u

n 109 to 1011 particles/cyclen In future 1012 particles/cycle

n 0.1 Hz to 1 Hz Repetition raten In future up to 3 Hz

n Nuclear and Hadron Physicsn Nuclear Chemistryn Atomic Physicsn Material Science n Plasma Physicsn Biophysics / Medical

XHV

UHV

UHV

UHV

UHV

UHV

SIS18

ESR



The heavy ion synchrotron SIS18The heavy ion synchrotron SIS18

n 12 sectors each:n 18 m longn ∅ 200 mmn thin wall (0.5mm) dipole

and quadrupole chambers

n 4 TSPn 3 Ion pumps

n 5 (+2) vacuum sectorsn RGA network ( 7 RGAs)n 15 cal. Extractor gauges



U28+ ion beam lifetimeU28+ ion beam lifetime

Desorption Processes Degenerate the Residual Gas Pressure

Initiated by :

§ Systematic Beam Losses on

Acceptance Limiting Devices

(Septa)

§ Stripped Beam Ions

§ Ionized and Accelerated Residual

Gas

à Beam Losses Increase with Number of Injected Ions

( shorter beam life time due to stronger pressure bumps )

U28+ 8.7MeV/u



Lifetime relevance of different gas species (static vacuum)

Lifetime relevance of different gas species (static vacuum)

Ar10%

CxHy30%

CO44%

CO26%

H2O7%

H23%

Significant part from noble gases and hydro carbonic gases

Pumping speed improvement for all kinds of gas species

Ar2% CxHy

26%

CO24%

CO22%

H2O6%

H240%

Residual gas composition at 3 10-11 mbar

Contribution to ion beam lifetime

Improvement for „zero-current“ ion beam lifetime (static case)



Maschine experiments on ion-beam lifetimeMaschine experiments on ion-beam lifetime

S01MU1 dipole, location of determined ion beam

loss

Maschine experiments on ion-beam lifetime related processes

• U28+ / U73+ lifetime measurements

•detection of fast pressure rises (during determined ion beam loss)

•RGA measurements static (no ion-beam) + dynamic (with ion-beam)

RGA S01VK4

Fast pressure measurement (extractor),

3 locations



U73+ ion beam operationU73+ ion beam operation

0.00E+00

5.00E-12

1.00E-11

1.50E-11

2.00E-11

2.50E-11

3.00E-11

3.50E-11

4.00E-11

4.50E-11

5.00E-11

5.50E-11

6.00E-11

6.50E-11

7.00E-11

7.50E-11

8.00E-11

25200 25500 25800 26100 26400 26700 27000 27300 27600 27900 28200 28500 28800 29100 29400 29700 30000

time [seconds]

pre

ssu

re [

mb

ar]

S01

S02

S03

S04

S07

S08

S09

S10

S11

S12

Preparation

1E+8 ions at 1 Hz with cooler

160 micro-second chopper



Uranium 73+



U28+ ion beam operationU28+ ion beam operation

1.00E-12

1.00E-11

1.00E-10

1.00E-09

39300 39600 39900 40200 40500 40800 41100

time [seconds]

pre

ssu

re [m

bar

]

S01

S02

S03

S04

S05

S06

S07

S08

S09

S10

S11

S12

Uranium U28+ losses in S01MU1

48 microAmpere over200 microsecondseach 6.8 seconds

48 microAmpere over200 microsecondseach 1.8 seconds



Fast total pressure measurementsFast total pressure measurements

measurement principle:fast integrating current

frequency converter

Sensitivity :1pC / pulsePulse Width: 50 nsDynamic : 7 decadesLinearity : 0.1% (



U28+ / U73+ operation, RGA diagnostic [CO]U28+ / U73+ operation, RGA diagnostic [CO]

U28+, ion beam loss in S01MU1 U73+ maschine exp.,

H.Damerau, failure of dipoles at 12000

no ion beam, service ion source

U73+, H. Damerau, machine experiments no ion-beam in SIS

(4:00 to 8:00pm)

U73+, U.Blell, machine experiments.

Maschinenexperimente 5.6.2002

Ion: U73+, U28+Energien : 11,17 MeV/u (73+) ; 8,7MeV/u (28+)Messort: Prisma RGA in S01VK4Messzeit: 5.6.2002 13:00 bis 6.6.2002 12:00UhrBemerkungen:

•in der Zeitskala bis ca. 10000sec wurde U28+ mit 8,7MeV/u gezielt in S01MU1 verloren: Puls 48muA, 200mus, Zykluszeit:ca. 1,8s•in der Zeitskala von 10000 bis 85000 fanden Maschinenexperimente (Damerau,Blell) mit U73+ statt•nachfolgend sind die aufgenommen Langzeitspektren dargestellt• nur für die Masse 28 (CO, N2) ist ein signifikanter Anstieg des Partialdrucks korreliert mit dem Strahlbetrieb zu beobachten

0 20000 40000 60000 800001E-13

1E-12

1E-11

1E-10

'Total' 'N2/CO'

part

pres

sure

[mba

r]

time [sec]



U28+ / U73+ operation, RGA diagnostic [H2]U28+ / U73+ operation, RGA diagnostic [H2]

U28+, detecated ion beam loss in S01MU1

U73+ maschine exp., H.Damerau, failure of dipoles at 12000

no ion beam, service ion source

U73+, H. Damerau, machine experiments no ion-beam in SIS

(4:00 to 8:00pm)

U73+, U.Blell, machine experiments.

Maschinenexperimente 5.6.2002

Ion: U73+, U28+Energien : 11,17 MeV/u (73+) ; 8,7MeV/u (28+)Messort: Prisma RGA in S01VK4Messzeit: 5.6.2002 13:00 bis 6.6.2002 12:00UhrBemerkungen:

•in der Zeitskala bis ca. 10000sec wurde U28+ mit 8,7MeV/u gezielt in S01MU1 verloren: Puls 48muA, 200mus, Zykluszeit:ca. 1,8s•in der Zeitskala von 10000 bis 85000 fanden Maschinenexperimente (Damerau,Blell) mit U73+ statt•nachfolgend sind die aufgenommen Langzeitspektren dargestellt• nur für die Masse 28 (CO, N2) ist ein signifikanter Anstieg des Partialdrucks korreliert mit dem Strahlbetrieb zu beobachten

0 20000 40000 60000 800001E-12

1E-11

1E-10

U28+ gezielter Strahlverlust in S01MU1, RGA in S01VK4

'Total' 'H2'

part

pres

sure

[mba

r]

time [sec]



Vacuum requirements for the SIS18Vacuum requirements for the SIS18

Beam lifetime has to be significantly larger than cycling time of the SIS18(Lifetime of at least 10 seconds for all kinds of operation)

Total pressure lower 1• 10-11 mbar with a small fraction of high Z gases even for highest beam intensities

optimized dynamic conditions:• efficient ion beam loss control,• low desorption at localized ion beam

losses,• maximized local pumping speed at

locations of ion beam loss

optimized static conditions:• minimized outgassing rate through

material and production control, cleaning, bakeout

• efficient and distributed pumping



Optimized static conditions: Cryo pumps approachOptimized static conditions: Cryo pumps approach

Pumping speed improvement for chemically inert gases required

Preferred solution: seven external cryo pumps:- One per vacuum sector => larger pumping speed during

bake out- Best local pumping speed for “heavy” gases- Operational in all relevant pressure ranges- Real gas removal out of the system- Multiplication to overcome conductance limitation feasible



Improvement potential of localized cryo pumpsImprovement potential of localized cryo pumps

10

100

1000

10000

H2 H2O CO CO2 CH4 C4H8 He Ar

pu

mp

ing

sp

eed

[l/

s]

48 TSP 36 IZ 6 Turbo 6 Kryo

Nominal pumping speedsAveraging including conductance



Optimized dynamic conditions: collimator approachOptimized dynamic conditions: collimator approach

collimators in SIS18:

Ø at locations of known ion beam loss:

ü injection section / septum

üextraction / septum

Ø with integrated high pumping speed:

- cryo ?, NEG ?

Ø low desorption materials :

- experiments at test bench with ion beam

may/june 2003

since april 2003

end of 2003



Summary GSI UHV upgradeSummary GSI UHV upgrade

v upgrade of UHV diagnostics ( RGA and total pressure measurements)

vmaschine experiments on ion beam lifetime

v laboratory experiments to optimize components (pumps, bakeout,...)

v design and installation of collimators

v experiments on ion beam induced desorption (à materials)

GSI UHV group: M. Bender, M. Bevcic, P. Horn, R. Kaminski, H. Kollmus, A. Krämer, J. Kurdal, H. Reich-Sprenger, H. Rittelmeyer, G. Savino, U.

Weinrich, K. Welzel

the gsi-accelerator uhv system and its upgrade...

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