Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 1

Measurement of Gas Retention in ASDEX Upgrade

- A Technical View -

Thomas Härtl,ASDEX Upgrade Team

Max-Planck-Institut für Plasmaphysik, EURATOM Association

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 2

Outline

• Methods of Measurement • Reasons for Retention • Gas Sources - Sinks• Ideal Gas Law• Options of Measurement• Status of Gas-Balance Measurement• Torus Pumping System (TPS)• Concepts of Measurement• Summary

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 3

Methods of Measurement

Measurement retention: 2 options

Direct => Post-Mortem-Analyses• Analyses of components• Average of long time period with many

different events• Single events may change whole campaign

Indirect => Gas-balance• Measurement of inflow• Measurement of outflow Small difference of big numbers

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 4

Reasons for Retention

Reasons for retention

• Adsorption • Absorption• Deep implantation• Trapping• Co-deposition

• In vessel cryo-pumpLiquid Nitrogen and liquid Helium panelHigh capacityHigh pumping speed (100,000 l/s)Dependent on gas species No pumping speed for Helium and HydrogenDifferent conductance

Consideration of black box is not sufficient

Metal wallTungsten coated

tilesCables …

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 5

Gas Sources - Sinks

Many different sources and sinkshas been investigated

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 6

Ideal Gas Law

Ideal Gas Law

• n - Amount of Substance [mole]• P - Pressure [Pa]• V - Volume [m3]• T - Temperature [K]• R - Gas constant

Measurement error

• V - Vessel volume 1m3

(1m ±1mm) ± 0.3%• P - Accuracy 0.1% F.S.

(use at 10% F.S.) ± 1%• T - Accuracy 1K

(Room temp. 300K) ± 0.3%homogenous in volume

TRnVp m

V

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 8

Status of Gas-Balance Measurement

Calculate RetentionDetermine overall inlet is necessary in all cases

Cryo-pumpPumping speed (PS) * pressure- PS not constant, dependent of speciesConductance dependent of plasma scenario

Applied standard

Mass of cryo sorbate- Dependent of gas composition- Marginal compared to cryo-pump

Not applicable

Regeneration of cryo sorbate,no pumping to outside,Pressure, volume (Alcator C-Mod)- Temperature not homogeneous

Measurement system outside

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 9

Torus Pumping System (TPS)

Gas transfer pumping system

• In vessel base pressure ≈ 10-7 mbar• Compression ≈ 1010

3 stage pumping system

Gate valve

Turbo molecular pump (TMP) (14)• Operational range: 10-7 mbar … 10-2 mbar• Compression

(depending of gas species and pressure): >105

• Pumping speed ≈ 2000 l/s (28.000 l/s)Roots pump (1)

• Operational range: 10-4 mbar … 3 mbar• Compression: (depending of pressure): <101

• Pumping speed ≈ 7500 m3/h (2.000 l/s)Rotary vane pump (2)

• Operational range: 10-3 mbar … 10+3 mbar• Compression: 106

• Pumping speed ≈ 250 m3/h (140 l/s)

Torus 10E-7

Gate valve

TMP

Roots pump

Rotary vane pump

Atmosphere

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 10

Concepts of MeasurementPumping speed (PS)

Requirement on PS• constant over wide range• Independent of gas

Requirement on pressuremeasurement

• Precise• Independent on gas

Requirement on T measurement

• Fast• Little feedback

Very little modificationNo influence on operationNo restriction on gas amount

Flow rate

Requirement on device• Wide measuring range• Independent on gas Volume counter

CharacteristicNeed pressure difference

up to 5 mbarCounts n-times a definite

volume

Few modificationLittle influence on operationLittle restriction on

gas amount

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 11

Concepts of Measurement

Typical amount of gas in AUG shots

Shot: ca. 1.5 bar l 50 bar l /d, 150 bar l /w

GDC: ca. 5 barl /each, 10 / d 50 bar l /d

Ver.1/2: Store at p ≈ 1E-1 mbar

not possible pAUG > pStrorage

Ver.3: Store at p ≈ 10 mbar

VStorage ≈ 5,000lVer.3: Store at p ≈ 100 mbar

VStorage ≈ 500l

Ver.4: Store at p ≈ 1000 mbar

VStorage ≈ 50l

Storage in volume

Requirements:Volume not to large,

max. 1…2 m3

“static” compressionindependentof gas combination

Modification is necessaryInfluence on operationGas amount is design criteria

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 12

Details: Storage in VolumeStorage in volumeStandard operations

End pressure, PTorus < 1E-7 mbar

KFV > 10E4

GDC, PTorus 3E-3 mbar S >1500 l/s at 2E-2 mbar

Regenerate cryo-pumpPV TMP < 3E-1 mbar

Volume of fore vacuum line buffers

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 13

Details: Storage in VolumeStorage in volumeStandard operations

End pressure, PTorus < 1E-7 mbar

KFV > 10E4

GDC, PTorus 3E-3 mbar S >1500 l/s at 2E-2 mbar

Regenerate cryo-pumpPV TMP < 3E-1 mbar

Volume of fore vacuum line buffers

Regenerate cryo-pump afterlong operations (>50 bar l)

Bypass TMPs Bypass first (second) stage

All scenarios could be handledNew fore vacuum system necessary

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 14

Concepts of MeasurementStorage at constant pressure

Requirements:

Constant ambient pressure

Δp 5 mbar

VStorage ≈ 50 l (for 1 day operation)

Independent to pumping system

No feed back to system

Established reference standard

also for H2

Thomas Härtl, IPP, Measurement of Gas Retention in AUG, WP10-PWI-01-01-07/II/BS, 19. July 2010 15

Summery

Pumping speed• Good accuracy at higher pressure• Difficult at low pressure, long time measurement• Temperature measurement imprecise

Flow rate• Very precise at operational range (0.3 %)• Uncertain at high and very low flow rate• Temperature may vary at very high flow rate

Storage in volume• Precise pressure measurement • Continues compression may influence temperature• Modification of pumping system necessary

Storage at constant pressure• Very precise (< 0.3 %)• Constant conditions for P, T• Independent of nature of pumping system