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A reassessment of the basic equation governing calorimetry shows the crucial importance of temperature stability in the calorimeter environment. Following the principles derived, we have developed a new temperature control method and demonstrated it in a prototype calorimeter over a wide dynamic range (5 μW-2 W). Temperature control is achieved by using a metal block of high thermal inertia, surrounded by heat flow sensing thermopile arrays, which is embedded in an isothermal environment. Any temperature fluctuations in this environment are detected by the heat flow sensors and can be corrected by conventional feedback control. The advantage of this method is its high sensitivity to temperature changes: whereas conventional thermometers typically provide signals in the order of 1×10[sup -3] V/K[sup -1], a correctly selected combination of inertial mass and thermopile arrays can provide signals in the order of 1 V K[sup -1], thus permitting an improvement of temperature control by three orders of magnitude. A commercially available thermoelectric calorimeter in an isothermal environment controlled by the new method permitted measurement of sample powers with ±10 μW accuracy (long-term, shor-term noise ∼ ±1 μW), whereas in a conventional thermostatic bath (temperature stability ±0.02 K h[sup -1]) its resolution was limited to ± 3 mW. [ABSTRACT FROM AUTHOR]

Abstract: A time-dependent thermo-hydraulic simulation for an ITER toroidal field (TF) coil gradual cool-down to 80K has been performed using a new FORTRAN code. The code is based on a 1D helium flow and 1D multi-region solid heat conduction model. The whole TF coil is simulated taking into account thermal conduction between winding pack and case, which are cooled down separately. To limit coil mechanical stresses and coolant pressure drop in the cooling channels, an improved cool-down mode has been developed based on the analysis. Typical and gradual cool-down temperature distributions of TF coil and case are presented. The results indicate that gradual cool-down to 80K can be achieved in 3 weeks. [Copyright &y& Elsevier]

Mainstreams in research on measurement systems for cryogenic process monitoring are reviewed with the aim of defining key current trends and possible future evolutions. At this aim, research mainstreams are classified according to the measurand: liquid level, flow rate, and pressure. In these fields, research on innovative measurement systems is surveyed, by highlighting main basic ideas, original design solutions, main results, and positioning in the innovation landscape. Then, current and future research trends are outlined in order to draw evolution scenarios of measurement systems for cryogenics monitoring. [ABSTRACT FROM AUTHOR]

Active mitigation of pulsed heat load is foreseen for the ITER superconducting magnets during cyclic plasma scenarios to ensure stable operation of the cryoplant. The paper addresses a promising feedback control to smooth heat pulses in the primary cryogenic circuits of the ITER magnets. A feedback control signal is proposed that can be derived from direct measurements of helium parameters in a low pressure return cryoline to the cryoplant. Configurations with two or more LHe baths were investigated at the Auxiliary Cold Box (ACB) level. Efficiency of the proposed control approach was evaluated in thermohydraulic simulations. A possibility to control several cryogenic loops using a common regulator is demonstrated. [ABSTRACT FROM AUTHOR]

A transducer based on a virtual low meter is proposed for monitoring helium distribution and consumption in cryogenic systems for particle accelerators. The virtual low meter allows technical and economical constraints, preventing installation of physical instruments in all the needed measurement points, to be overcome. Virtual low meter performance for the alternative models of Samson [http://www.samson.de (2015)] and Sereg-Schlumberger [http://www.slb.com/ (2015)] is compared with the standard IEC 60534-2-1 [Industrial-process control valves--Part 2-1: Flow capacity--sizing equations for fluid low under installed conditions (2011), https://webstore.iec.ch/publication/2461], for a large temperature range, for both gaseous and liquid helium phases, and for different pressure drops. Then, the calibration function of the transducer is derived. Finally, the experimental validation for the helium gaseous state on the test station for superconducting magnets in the laboratory SM18 [Pirotte et al., AIP Conf. Proc. 1573, 187 (2014)] at CERN is reported. [ABSTRACT FROM AUTHOR]

Process studies for Toroidal Field Structure (TF ST) system with a dedicated Auxiliary Cold Box (ACB-ST) have been conducted under 15 MA baseline, including plasma disruptions. ACB-ST consists of two heat exchangers immersed in the Liquid Helium (LHe) subcooler, which are placed at the inlet/outlet of a Supercritical Helium (SHe) cold circulator (centrifugal pump). Robustness of ACB-ST is a key to achieve the stability of TF coil operation since it provides the thermal barrier at the interface of the TF Winding Pack (WP) with ST. The paper discusses the control logic for the nominal plasma operating scenario and for Mitigation to regulate the dynamic heat loads on ST. In addition, the operation field of a cold circulator is described in the case of plasma disruptions. The required performance of heat exchangers in the ACB-ST is assessed based on the expected operating conditions. [ABSTRACT FROM AUTHOR]

The pressure head necessary for the forced convection of supercritical helium (SHe) across the ITER superconducting (SC) magnet system is generated by centrifugal-compressor type cold circulators. From the viewpoint of the cryogenic system, simulation results indicate that the main challenge of the ITER Central Solenoid (CS) operation is the peaking pressure head of SHe across the cold circulator induced during the rapid ramping of electrical current on the coils. Excess variation in pressure head will push the operation point of the rotating machine beyond the surge line in the compressor map which can trip the circulator and in the worst case result in damages. Therefore, in order to avoid the occurrence of a surge, it has been proposed to open adaptively a cryogenic valve, installed in parallel with the CS cooling channels, during the high pressure head instances. Such an action creates an additional flow channel which consequently suppresses the pressure head peak. The proposed strategy has been numerically benchmarked and tests have been performed in existing cryogenic facilities. In this paper, we will present the test results of pressure head mitigation across the cold circulator dedicated to the KSTAR CS and Poloidal Field (PF) coil cooling circuit with the main purpose of demonstrating the safe operation of the ITER CS circulator as well as cooling circuit during plasma shots. The tests were performed by progressively increasing the coil by-pass valve opening during identical PF/CS current shots and monitoring the tendency of the maximum pressure head variation across the cold circulator. Also, preliminary results of pressure head mitigation during real plasma experiments will be introduced. [ABSTRACT FROM PUBLISHER]

The dynamic simulation of a sub-scale ITER Central Solenoid (CS)/STRucture (STR) cooling loop has been performed to investigate the cryogenic control strategies against pulsating heat loads. HELIOS facility has been modified for this particular study, which consists of a Liquid Helium (LHe) reservoir with two immersed heat exchangers, a circulation pump and an approximately 130 m long piping with three evenly distributed heated sections. The setup provides the equivalent thermo-hydraulic configuration of the ITER CS/STR, cooled by the forced-flow Supercritical Helium (SHe). The dynamic simulator, C-PREST, has been utilized to model the HELIOS test loop and to compare the results with the experimental data sets. This paper presents the dynamic simulation results and discusses the control strategy to minimize the cooling power requirements, to have high reliability. [ABSTRACT FROM PUBLISHER]

One of the main challenges of the ITER cryogenic system is to manage the large pulsed heat load variation generated by the superconducting magnet system during the fusion experiments. A solution proposed to smooth such pulses and verified by numerical simulations is to use the ITER magnet structure (ST) system as a thermal buffer by taking advantage of its large mass of about 5,000 tons and consequent thermal inertia. In order to validate the simulated predictions, tests have been executed on existing cryogenic facilities. [ABSTRACT FROM PUBLISHER]

In some alcohol-related pathologies of chronic alcoholism women are more vulnerable than men. A consecutive sample of 62 chronic alcoholics was studied, 18 females and 44 males, aged between 28 and 69 years to assess the incidence and distribution of peripheral neuropathy with regard to gender. All patients underwent clinical and neurological observations, laboratory tests, and electroneurography. Total lifetime dose of ethanol (TLDE) and other risk factors for neuropathy (disease duration, age, nutritional status) were calculated and correlated to sural nerve sensory-evoked potential (SEP) amplitude. In 42 patients (67.7%), we observed the presence of clinical and/or infraclinical neuropathy, mostly axonal, in 29 males (65.9%) and 13 females (72.2%). In women, compared to men, TLDE and disease duration were significantly inversely correlated to sural nerve SEP amplitude, i.e. in women, SEP amplitude is significantly reduced in relation to TLDE and disease duration increase. These data indicate a higher sensitivity of females towards the toxic effects of ethanol, other than malnutrition, on peripheral nerve fibres. [ABSTRACT FROM PUBLISHER]