H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 1

GSI vacuum groupGSI vacuum group

Who we are:•5 physicists (Bellachioma, Kollmus, Krämer, Reich-Sprenger, Wilfert)

•7 engineers (Bender, Bevcic, Kaminski, Kurdal, Schäfer, Welzel, Wolff)

•23 technicans (Emmerich, de Cavaco, Gaj, Gustafson, Hammann, Herge, Heyl, Horn, Jagsch, Kischnik, Kolligs, Kredel, Leiser, Lück, Mühle, Müller, Norcia, Quador, Savino, Sigmund, Stagno, Thurau, Volz)

Responsible for:operation and service of all GSI accelerator vacuum systems,R&D on vacuum physics and techniques,Design & Layout of new accelerator vacuum systems,Installation & reconstruction of accelerator structures and experimental setups

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 2

OverviewOverview

• The existing GSI facility and its The existing GSI facility and its Future extension

• SIS18 UHV Status / Upgrade• Ion Induced Desorption

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 3

The GSI The GSI Future Accelerator Facility for Beams of Ions and Antiprotons

(FAIR)

Acceleration

I

II III

Experiments

100m

From protons to uranium In future also antiprotons

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

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

0.1 Hz to 1 Hz Repetition rate In future up to 3 Hz

Nuclear and Hadron Physics Nuclear Chemistry Atomic Physics Material Science Plasma Physics Biophysics, Medical

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 4

The GSI The GSI Future Accelerator Facility for Beams of Ions and Antiprotons

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 5

GSI International Accelerator FacilityGSI International Accelerator FacilityUHV system requirementsUHV system requirements

Due to ion beam lifetime requirements(e.g.: U28+ in SIS18):

SIS18: bakeable p≈5·10-12 mbarESR: bakeable p≈5·10-12 mbar

SIS100: cold arcs T=7-20K bakeable straight sections

T=300K p≈5·10-12 mbar

SIS300: cold arcs T=4.2K bakeable straight sections

T=300K p≈5·10-12 mbar

NESR: p≈5·10-12 mbarHESR: p≤10-10 mbarRESR: p≤10-10 mbarCR: p≤10-9 mbarHEBL: length 2.5 km, 70% cold

*all pressures: N2 equivalent

SIS100/300

HESR

NESRCR

RESR

from SIS18

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 6

The heavy ion synchrotron SIS 18 The heavy ion synchrotron SIS 18 present statuspresent status

12 sectors each: 18 m long 200 mm 4 TSP 3 Ion pumps (triode

type) 1-2 extractor gauge

2 single cryopumped collimators

7 vacuum sectors

One pumping station with turbo molecular pump (rough pumping + bake-out)

1 RGA

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 7

High Ion Beam Intensity Operation of Medium Charged High Ion Beam Intensity Operation of Medium Charged Heavy Ions Heavy Ions

influence of intensity on lifetime influence of intensity on lifetime

Desorption processes degenerate the residual gas pressure ( U28+

case )

Initiated by : Systematic beam losses on acceptance limiting devices (septa) ( 8MeV/u < E <100MeV/u ) Stripped beam ions ( 8MeV/u < E <100MeV/u ) Ionized and accelerated residual gas ( E < keV) : minor effect

at “zero ion beam current”: lifetime could be increased up to 6s (first steps of UHV upgrade in 2003) beam losses increase with number of injected ions presently the maximum accelerated U28+ ion beam intensity is limited by dynamic UHV conditions

8.75 MeV/u U28+

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 8

SIS18 residual gas composition (10/2003)RGA spectra examples

0 20 40 60 80 100

2,00E-011

4,00E-011

6,00E-011

8,00E-011

1,00E-010

1,20E-010

1,40E-010

H2 95.7%CH4 1.8%Ar 0.3%CO 0.9%CO2 --%Oil 1.3%

184W6+

184W5+

184W4+ 184W3+184W2+

ion

curr

ent [

A]

m/q

184W7+

S03VK4

0 20 40 60 80 1001E-13

1E-12

1E-11

1E-10

H2 75.2%CH4 16.2%Ar 4.7%CO 2.8%CO2 0.2%Oil 0.8%

184W6+

184W5+

184W4+

184W3+

184W2+

ion

curr

ent [

A]

m/q

184W7+

S09VK4

Ar

CxHy

S03 total pressure: 3*10-12 mbar S08 total pressure: 6.8*10-11 mbar

existing "micro-leaks"and contaminations

0 20 40 60 80 100

2,00E-011

4,00E-011

6,00E-011

8,00E-011

1,00E-010

1,20E-010

1,40E-010

H2 75.2%CH4 16.2%Ar 4.7%CO 2.8%CO2 0.2%Oil 0.8%

184W6+

184W5+

184W4+

184W3+

184W2+

ion

curr

ent [

A]

m/q

184W7+

S09VK4

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 9

Requirements + Strategy for SIS18 UHV-Requirements + Strategy for SIS18 UHV-Upgrade Upgrade

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 Desorption / ERDA Experiments,

• maximized local pumping speed at locations of ion beam loss collimation Desorption / ERDA.

optimized static conditions:• minimized outgassing rate by material and

production control, cleaning, bakeout, quality control established,

• removal of contaminations or "micro-leaks" measurements during shutdowns on TSP + SIP

• efficient and distributed pumping NEG coating.

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 10

Beam Lifetime measurements Beam Lifetime measurements 132132XeXe18+ 18+ (March 2005) SIS (March 2005) SIS /ESR/ESR

("zero" beam intensity)("zero" beam intensity)

100 200 300 400

1E-3

0,01

halflife 66 sec

Electron Cooler 0

Y A

xis

Title

X Axis Title

1305 (1) background=0.0022

132Xe18+

beam lifetime @ 7,6 MeV/u

beam lifetim

e @ 15

MeV/u

beam lifetime

@ 30 MeV/u

beam lifetim

e @ 50

MeV/u

SIS ~ 3 sec ~ 4,5 sec ~ 6 sec

ESR ~50 sec ~66 sec

ESR 6.3.2005

Main Differences of SIS18 and ESR UHV system:

Argon partial pressure concentration: ESR < 1%, SIS > 2 %

bakeout ability: ESR >200°C, SIS18 ~ 180°C

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 11

Program for Optimized Static Conditions:Program for Optimized Static Conditions:2005 2006 2007 2008

Detection and removal of micro-leaks or contaminations ( Ar !)

Rebuilt of one SIS Vacuum sector to optimized distributed pumping speed : 2 NEG coated Dipole chambers, 1 NEG coated prototype Quadrupole chamberReplacement of all 24 dipole chambers ( bakeout to 300°C, coating?) [existing new spare chambers]Replacement of all 12 quadrupole chambers ( bakeout to 300°C, coating?) [prototype and new chambers to be designed and built]Ion Pumps (TSP, SIP): optimized IP operation, if necessary: replacement by noble diodes, optimized sublimation cycles ( improved pumping speed)

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 12

Static Pressure Improvements by NEG coatingStatic Pressure Improvements by NEG coating

Remarks: calculation fitted to

measured Ptot and RGA locations in S03

H2 and CO pumping speed (H2:0.05 ls-1cm-2; CO: 0.1 ls-1cm-2) for NEG coated chambers underastimated (has to be reduced by factor of 10 for H2 and by a factor of 50 for CO in VakTrac simulation due to calculation errors),

Total pressure will be dominated by CH4 after NEG coating minimzing the number of installed SIPs, changing SIP type?,

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 13

Ion Beam Loss Induced Desorption:Ion Beam Loss Induced Desorption:UU28+28+ ion beam operation of SIS18(up to 10 ion beam operation of SIS18(up to 101010 injected ions) injected ions)

Observations: beam loss + pressure rises at all SIS sectors, pressure rises in TK9,

Scraper

SIS Injection

SIS Extraction

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 14

Desorption ProcessesDesorption Processes in in SIS18SIS18

ionincidentmoleculesemitted

desorption yield

410 101beam loss induced desorption ion induced desorption

vacuum chamber wall S: pumping speed/therm. desorption

septum or collimator

UZ+ UZ+ UZ+

XX

X

X

X

X

XX

Xq+

q e

UZ+q

los

s

los

s

X

los

s

X 50 Voltspace charge potential

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 15

Experimental Setup for Ion Beam Induced Experimental Setup for Ion Beam Induced Desorption Yield MeasurementsDesorption Yield Measurements

Experiments by:M. Bender (GSI)H. Kollmus (GSI)A. Krämer (GSI)E. Mahner (CERN)

sample holder

ion gauge

sector valve

RGA

conductance

collimator

fromaccelerator

TMP TSP

SIP

10-7mbar

10-10mbar10-8mbar

TMP

currenttransformer

ion gauge

sample holder

ion gauge

sector valve

RGA

conductance

collimator

fromaccelerator

TMP TSP

SIP

10-7mbar

10-10mbar10-8mbar

TMP

currenttransformer

ion gauge

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 16

Partial Pressure Increase due to Ion Beam Induced Partial Pressure Increase due to Ion Beam Induced DesorptionDesorption

1.4MeV/u 1.8-3.1·109 Pb27+ stainless steel 304

The measured ion current was correctedfor the ionization probabilities of the different gases:H2: x2.3CO: x0.95CO2: x0.71CH4: x0.625

Desorption dominated by H2 (87%) and CO (11%)

H. Reich-Sprenger, GSI Vacuum group, CERN, OLAV workshop (11./12.4.2005) 19

Optimized Dynamic Conditions:Optimized Dynamic Conditions:

collimators at locations of known ion beam loss: injection section / septum

extraction / septum with integrated high pumping speed:

2 cryopumps NEG coated anti-chambers?

low desorption materials:- experiments at test bench with ion beam

distributed pumping speed:- NEG ?

May/June 2003

since April 2003

March 20042006 ?

final decision depends on desorption experiment results