test-particle calculations of pressure profiles …
TRANSCRIPT
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TEST-PARTICLE CALCULATIONS OF PRESSURE PROFILES
AND PUMPING EFFICIENCIES: APPLICATION TO SOME
VACUUM DEVICES OF ITER
R. KersevanVacuum Pumping Group, ITER International Organization,
Route de Vinon, 13165 St. Paul lez Durance, France
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 2
Abstract:- This paper describes the application of the Molflow+ code to the analysis and optimization of some vacuum components envisaged for installation on ITER. Molflow+ is a code written in C/C++ which runs on Windows-based PCs and laptops. It implements the Test-Particle Monte Carlo (TPMC) method [1]. It allows file import from the popular CAD export "STL" file format, allowing the analysis of complex geometries.
- The vacuum system of ITER is composed of a multitude of sub-components, ranging in size and vacuum level, going from the >1000 m3
volume toroidal vacuum chamber in transition flow down to few liters volume components such as RF heating lines under ultra-high vacuum conditions.
- Pumps and pumping manifolds and geometries must be optimized also in view of cost-containment measures.
- Within the Vacuum Pumping Group of the Fuel Cycle Division, the optimization of the design of the ultra-high vacuum system of some subsystems and components has been undertaken.
- The paper will briefly highlight the main features of Molflow+ and then move on to show some applications to ITER.
REFERENCES: [1] R. Kersevan, J-L. Pons, J. Vac. Sci. Technol. A, 27, 1017 (2009).
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 3
AGENDA:
1) ITER on the fly
2) Case Study: ITER’s Pumping Ports
3) Results and Discussion
4) Conclusions
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 4
ITER: a complex vacuum system
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 5
ITER Vacuum Systems
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 6
ITER’s Pumping Ports
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 7
ITER Divertor Geometry
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 8
ITER: tokamak pumping
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- A reduction of the number of TCPs has been
recently proposed in the framework of simplification
and cost-containment of the project.
- Before proceeding to the implementation of such
action a formal “Project Change Request” (PCR) has
been issued.
- A PCR consists of a rather detailed study of the
pros and cons of the proposed change and its overall
impact on the project, and requires formal approval
of all parties before its implementation.
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- The PCR consists of the elimination of the 3 branched
TCPs
- Vacuum-wise, the main impact is a possible reduction of
the pumping speed at divertor level
- In this study, the comparison of the pumping speeds in
molecular flow at the divertor level and inside the vacuum
vessel have been performed using Molflow+
- Prior to that, a modelisation of the latest version
of the TCP has been carried out, and the obtained
results have been compared to previous calculations
made by FZK on a older design
(FZK, EFDA Task, 2007).
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2) Modelization and analysis of the TCP alone:
Drawings for
2007 design
vs
2011 design
- 800 mm ID inlet flange
- 28x 1000 mm x 200 mm charcoal-coated
cryopanels, cooled by 4.5 K SC He
- 11x coaxial 80K thermal shields
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2) Modellisation and analysis of the TCP alone:
TPMC Model for
2007 design
vs
2011 design
(not to same scale!)
Integrated valve: 50 cm stroke
Integrated valve: 47 cm stroke
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 13
Modellisation and analysis of the TCP alone: 2007 results
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STICKING
0.7
0.95
0.95
0.2
1.0
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 14
Modelisation and analysis of the TCP alone: 2011 results
SPEED
m3/s
97.79
70.13
62.39
63.26
35.12
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Modellisation and analysis of the TCP alone: 2011 results
Valve Stroke S(He) m3/s
5 cm 14.6410 cm 30.18
20 cm 49.11
30 cm 57.73
40 cm 61.73
47 cm 63.26
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 16
Modellisation and analysis of the Pumping Port with TCP
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 17
Modelisation and analysis of the Pumping Port with TCP
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 18
Modellisation and analysis of the Pumping Port with TCP
He pumping speed at Vacuum Vessel:
with 2 TCPs = 37.18 m3/s
with 1 TCP = 30.28 m3/s
Net Loss ~7 m3/s (18.6%)
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R. Kersevan – Test-Particle Calculations and… - Sect.6 “ITER” Wed 18/5/2011 19
Conclusions
1) The pumping speed of the ITER Torus Cryopump has been
recalculated and compared to previous calculations, and found higher
than for the 2007 version, probably due to a favorable change in the
geometry in front of the pump’s inlet flange
2) The effective pumping speed in the vacuum vessel and at the
divertor level has been calculated for the direct+branched version
and the PCR-direct-only version of the Lower Port Cryo Pump (LPCP)
3) A substantial reduction of the effective pumping speed has been
obtained for the direct-only version, with a loss of ~19% with
respect to the original direct+branched LPCP version
4) More refined simulations will be run shortly
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Acknowledgments:
Many thanks to M. Dremel, A. Antipenkov and C. Gliss for
helpful discussions and help with CAD drawings, details,
and more.
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