A PCS7-based control and safety system for operation of the W7-X Multi-Purpose Manipulator facility

doi:10.1016/j.fusengdes.2017.05.125

Fusion Engineering and Design

Volume 123, November 2017, Pages 699-702

https://doi.org/10.1016/j.fusengdes.2017.05.125 Get rights and content

Highlights

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Multi Purpose Manipulator as user facility at W7-X.
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Process Control System based on Siemens PCS7.
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Full controlled movement by Siemens Sinamic drive unit.
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Safety Integrity Level 3 (SIL3).

Abstract

The Multi-Purpose Manipulator (MPM) for Wendelstein 7-X, at the Max-Planck-Institute for Plasma Physics in Greifswald (MPIPP), is used to transport electrical probes and targets to the edge of the inner vessel. It is a lock system, which is attached to the outer port in the equatorial plane of the cryostat vessel. At the parking position, the tip of the probe coincides with the inner vessel wall; a fully controlled movement into the edge plasma for all magnetic field configurations is feasible. The whole functionality of the MPM system is maintained by a distributed control system (DCS) based on Siemens PCS7, which is the recommended standard for machine and diagnostic control at W7-X. Beside standard scenarios like target exchange and generation of ultra-high vacuum conditions a high variety of parameter selections for stroke depth, velocity or acceleration is selectable in the sequence control system within safety limits. A sophisticated error handling facilitates a reliable remotely controlled operation without manual access over longer periods.

Introduction

The W7-X stellarator [1], [2], [3] started operation in December 2015. The optimised magnetic field structure is produced by superconducting coils positioned in a cryostat, which surrounds the inner plasma vessel. For investigation of the plasma and plasma-surface interaction near the wall of the inner vessel electrical probes and material targets must be transported through the cryostat [4], [5]. The Multi-Purpose Manipulator system is situated at the AEK40 cryostat port on W7-X. It is intended to be a user facilityfor loading and unloading of electrical probes and targets for measurement of edge plasma parameter and plasma-material surface interaction, respectively. A general description of the MPM is given in reference [5]. The principal setup for the MPM control is shown in Fig. 2.

Two stage fast reciprocating probes are used in other fusion devices, e.g. [6]. Beside the complete control of the probe heads motion concerning speed and acceleration a large variety of control features are integrated to operate many different probe heads. Exchangeable probes within a volume of 120 mm diameter and 150 mm length can be connected to 32 electrical pins. The probe head is electrically isolated and can be set floating or to any potential between 0 and 1000 V. Also gas pulses through the inserted probe are feasible and controlled by the PCS7 control system.

The main features for the Programmable Logic Controller (PLC) system at the MPM are maintaining and control of UHV (UltraHighVacuum) conditions in the target, exchange and intermediate chamber, the operation of the separate linear motion units for slow and fast motion, respectively, the temperature monitoring of the probe head and custom target interface, the application of biasing voltage and gas injection. The PCS7 controls (Fig. 2) all functions of MPM operation and communicates with the W7-X central PLC. Inside the torus hall the operational status is visualized on a touch panel, where also predefined sequences, e.g. probe exchange, can be started. The whole function control for remote operation with plasma can be given to a virtual PC in the central diagnostic room. The parameters for stroke depth, velocity profile, biasing, and gas injection are freely selectable within margins. Even several strokes can be initiated from the central timing of W7-X, during one discharge with a single trigger. Due to the limited access to the torus hall a high standard failure management is applied to avoid or minimize damage of the MPM and W7-X.

Section snippets

PLC/PCS7

The SIMATIC process control system from Siemens (PCS7) [7] is a development system for the S7-PLC and the WinCC visualization from Siemens (Fig. 2).

It is frequently used in the process automation like the chemical industry but up to now seldom used for scientific experiments. Nevertheless the demands on automation systems for complex scientific experiments are certainly comparable to those on the process automation as accuracy, reliability, easy service and extensibility. Since PCS7 is

Requirements for movement

Although the probe head carrier is equipped with water-cooling at the interface, the probe is not able to withstand prolonged exposure to the plasma at the edge or the head loads occurring excessive stroke depths. In order to minimize the exposition to the plasma and for getting strong signals from the coils measuring the magnetic field, a velocity profile of a triangle was chosen for the fast axle. After the trigger is recognized by the SINAMICS, the probe head and the support system of 30 kg

User interface

The HMI (Human Machine Interface) is realized with WinCC as a client-server system. Only the server sends data to and receives data from the PLC. The clients, which are the operator stations, transfer inputs from the user to the server and display the status information of the PLC by demanding the appropriate information from the server. Since the clients are derived from the server, the HMI is developed only once − for the server. The structure of the HMI of the MPM is due to the structure of

Inner tube potential

The potential of the probe head is the same as that of the inner tube, which is moved by the fast axle. To get information about the plasma like the density of electrons and ions, Langmuir probes are used, which are mounted on the probe head [4]. In order to measure electrons or ions the probe head must be biased to different potentials. So the inner tube by relay switches can be connected to ground, to biasing source or it is floating. In order to be decoupled from protection earth the power

Acknowledgments

We would like to thank the W7-X-team for their continuous support during installation, commissioning and validation.

References (9)

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EV.001
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Diagnostics for first operation of the wendelstein 7-X stellarator
Submitted to This Conference
(2017)
R. König
Rev. Sci. Instrum.
(2014)
P. Drews
P4.025

There are more references available in the full text version of this article.

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Therefore, these designs are considered carefully for the DIMS at W7-X in the current design and following prototyping stage. Furthermore, short time material exposures in W7-X are made available by the Multi-Purpose Manipulator (MPM) [10,11], which is usually equipped with various smaller measurement units, but serves as important design input for the drive system, exchange chamber and safety. The exposure of retractable/exchangeable material and component samples to divertor plasma conditions has been realized in different ways.
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^☆: This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and trainingprogramme 2014–2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

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A PCS7-based control and safety system for operation of the W7-X Multi-Purpose Manipulator facility☆

Highlights

Abstract

Introduction

Section snippets

PLC/PCS7

Requirements for movement

User interface

Inner tube potential

Acknowledgments

EV.001

Diagnostics for first operation of the wendelstein 7-X stellarator

Submitted to This Conference

Rev. Sci. Instrum.

P4.025