Integrated cryogenic fluid flow distribution and cooling scheme with helium liquefier/refrigerator for SST1 magnet system (original) (raw)

Adopted Methodology for Cool-Down of SST1 Superconducting Magnet System: Operational Experience with the Helium Refrigerator

2008

Liquid 3He-4He mixture phase diagram in restricted geometry Low Temp. Phys. 38, 16 (2012) Negative ions at an interface between liquid helium mixtures Low Temp. Phys. 37, 803 (2011) Spectroscopic investigation of OCS (p-H2)n (n = 1-16) complexes inside helium droplets: Evidence for superfluid behavior J. Chem. Phys. 132, 064501 (2010) Bubble nucleation in a superfluid 3He-4He mixture induced by acoustic wave Low Temp. Phys. 34, 308 Nonlinear excitation of temperature waves in 3He-4He superfluid solutions due to absorption of light waves Low Temp. Phys. 33, 811 (2007) Additional information on AIP Conf. Proc.

Cryogenic system of steady state superconducting Tokamak SST1: Operational experience and controls

Fusion Engineering and Design, 2006

The cryogenic system of SST-1 consists of the helium cryogenic system and the nitrogen cryogenic system. The main components of the helium cryogenic system are (a) 1.3 kW helium refrigerator/liquefier (HRL) and (b) warm gas management system (WGM), where as, the nitrogen cryogenic system called as liquid nitrogen (LN 2 ) management system consists of storage tanks and a distribution system. The helium flow distribution and control to different sub-systems is achieved by the integrated flow distribution and control (IFDC) system. The HRL has been commissioned and operated for performing a single toroidal field coil test as well as for the first commissioning of SST-1 superconducting-magnets up to 68 K. Analysis of the results shows that the compressor and turbine parameters of the HRL, namely, the speed and pressure are very stable during operation of the HRL, confirming to the reliability in control of thermo-dynamic parameters of the system. The thermal shield of the SST-1 cryostat consists of ten different types of panels, which have been cooled down to the minimum temperature of 80 K and maintained during the first commissioning of SST-1. The operation and controls of the LN2 management system have been found to be as per the design consideration.

Process optimization of helium cryo plant operation for SST-1 superconducting magnet system

IOP Conference Series: Materials Science and Engineering, 2017

Several plasma discharge campaigns have been carried out in steady state superconducting tokamak (SST-1). SST-1 has toroidal field (TF) and poloidal field (PF) superconducting magnet system (SCMS). The TF coils system is cooled to 4.5-4.8 K at 1.5-1.7 bar(a) under two phase flow condition using 1.3 kW helium cryo plant. Experience revealed that the PF coils demand higher pressure heads even at lower temperatures in comparison to TF coils because of its longer hydraulic path lengths. Thermal run away are observed within PF coils because of single common control valve for all PF coils in distribution system having non-uniform lengths. Thus it is routine practice to stop the cooling of PF path and continue only TF cooling at SCMS inlet temperature of ~ 14 K. In order to achieve uniform cool down, different control logic is adopted to make cryo stable system. In adopted control logic, the SCMS are cooled down to 80 K at constant inlet pressure of 9 bar(a). After authorization of turbine A/B, the SCMS inlet pressure is gradually controlled by refrigeration J-T valve to achieve stable operation window for cryo system. This paper presents process optimization for cryo plant operation for SST-1 SCMS. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Cool Down Experiences with the SST-1 Helium Cryogenics System before and after Current Feeders System Modification

Physics Procedia, 2015

The SST-1 machine comprises a superconducting magnet system (SCMS), which includes TF and PF magnets. In order to charge the SCMS, we need superconducting current feeders consisting of SC feeders and vapor cooled current leads (VCCLs). We have installed all 10 (+/-) pairs of VCCLs for the TF and PF systems. While conducting initial engineering validation of the SST-1 machine, our prime objective was to produce circular plasma using only the TF system. During the SST-1 campaign I to VI, we have to stop the PF magnets cooling in order to get the cryostable conditions for current charging of the TF magnets system. In that case, the cooling of the PF current leads is not essential. It has been also observed that after aborting the PF system cooling, there was a limited experimental window of TF operation. Therefore, in the recent SST-1 campaign-VII, we removed the PF current leads (9 pairs) and kept only single (+/-) pair of the 10,000 A rated VCCLs to realize the charging of the TF system for the extended window of operation. We have observed a better cryogenic stability in the TF magnets after modifications in the CFS. In this paper, we report the comparison of the cool down performance for the SST-1 machine operation before and after modifications of the current feeders system.

Prediction of Helium Vapor Quality in Steady-State Two-Phase Operation of SST-1 Superconducting Toroidal Field Magnets

IEEE Transactions on Applied Superconductivity

Steady State Superconducting Tokamak (SST-1) at the Institute for Plasma Research (IPR) is the first superconducting Tokamak in India and is an `operational device'. Superconducting Magnets System (SCMS) in SST-1 comprises of sixteen Toroidal field (TF) magnets and nine Poloidal Field (PF) magnets employing cable-in-conduit-conductor (CICC) of multi-filamentary high current carrying high field compatible multiply stabilized NbTi/Cu superconducting strands. SST-1 superconducting TF magnets are successfully and regularly operated in a cryo-stable manner being cooled with two-phase (TP) flow helium. The typical operating pressure of the TP helium is1.6 bar (a) and the operating temperature is the corresponding saturation temperature. The SCMS cold mass is nearly thirty two tons and has a typical cool-down time of about 14 days from 300 K down to 4.5 K using helium refrigerator/liquefier (HRL) system of equivalent cooling capacity of 1350 W at 4.5 K. Using the available experimental data from the HRL, we have estimated the vapor quality during the cryo-stable operation of the TF magnets using the well-known correlation of two-phase flow. In this paper, we report the detailed characteristics of two-phase flow for given thermo-hydraulic conditions during long steady state operation of the SST-1 TF magnets as observed in the SST-1 experimental campaigns.

Cooldown Experiences with The SST-1 Helium Cryo System Before and After Current Feeders System Modifications

The SST-1 machine comprises of superconducting magnets system (SCMS) which includes TF and PF magnets. In order to charge the SCMS, we need superconducting current feeders system consisting of SC feeders and vapor cooled current leads (VCCLs). We have installed all 10 (+/-) pairs of VCCLs for the TF and PF systems. While conducting initial engineering validation of SST-1 machine, our prime objective was to produce circular plasma using only the TF system. During the SST-1 campaign I to VI, We have to stop the PF magnets cooling in order to get the cryo stable conditions for current charging of the TF magnets system. In that case, the cooling of the PF current leads is not essential. It has been also observed that after aborting PF system cooling, there was a limited experimental window of TF operation. Therefore, in the recent SST-1 campaign-VII, we removed the PF current leads (9 pairs) and kept only single (+/-) pair of the 10,000 A rated VCCLs to realize the charging of the TF system for extended window of operation. We have observed better cryogenic stability in the TF magnets after modifications in CFS. In this paper, we report the comparison of the cooldown performance for the SST-1 machine operation before and after modifications of the current feeders system.

Cryogenic process optimization for simultaneous cool down of the TF and PF superconducting coils of SST-1 Tokamak

IOP Conference Series: Materials Science and Engineering, 2019

Recent experiments of SST-1 have shown that cryogenic heat loads are more than installed cold capacity. Due to this fact, the system cool down goes into the status-quo in temperatures at ~12K and further cool down is not possible. This issue can be resolved in three folds i.e. by grouping and distribution of the PF coils, optimization of the cryogenic plant process and heat loads reduction. First, we replaced common PF coils distribution to three groups having equal path lengths. Secondly, providing the best possible pressure heads to each PF groups during cool down and using turbine-C to get cold capacity with active cooling of all paths. Third is the heat loads reduction at some parts of SST-1. While adopting the same, it has been shown that the simultaneous cool down of the TF and PF coils are possible while achieving superconducting transition in all the coils except PF-5(lower).

Refrigerator-recirculator systems for large forced-cooled superconducting magnets

Cryogenics, 1977

Forced-cooled superconductors are viewed as a promising alternative in the development of high field superconducting magnets for future fusion devices. The high current density cabled superconductor is protected against thermal instabilities by forcing (single phase) supercritical helium through the cable. The cryogenic cooling system for a forced-cooled superconducting magnet works as a refrigerator and a recirculator at the same time. The paper discusses the conceptual design of the cooling systems for forced-cooled superconducting magnets with the overall objective of reducing the refrigeration costs. The general conclusion of this article is that economic cooling systems must employ efficient cold pump recirculators in which the large flow demanded by the forced-cooled superconducting magnet is confined to the cold end of the refrigerating column. If the liquid helium pump efficiency is less than 40°/o, systems employing elevated temperature compressors are more economic.

Superconducting current feeder system with associated test results for SST1 Tokamak

IEEE Transactions on Applied Superconductivity, 2004

The current feeder system (CFS) consists of 20 numbers 10 kA current leads assembled inside a specially designed cryostat, superconducting bus bars assembled in a vacuum duct with bends and the joint box interface in cryogenic environment at 4.5 K. Support structure between room temperature and 4.5 K surfaces with an intercept at 80 K has been designed specially to minimize the conduction heat load as well as to take care of the electromagnetic forces. The hydraulics design of the CFS has been optimized in order to be able to interface with the liquid helium refrigerator/liquefier. A sophisticated instrumentation and control system has been designed and developed as well as tested. The paper describe the design concepts, mechanical and hydraulic analysis, instrumentation & control system as well as some test results of the current feeder system.