Thiosemicarbazone organocatalysis:Tetrahydropyranylation and 2-deoxygalactosylation reactions and kinetics-based mechanistic investigation

Thiosemicarbazones are introduced as a new class of highly tunable and efficient organocatalysts. We showcase this by studies of the tetrahydropyranylation reaction, where insights to the mechanism was achieved by a double Hammett analysis of both the substrate and the catalyst.</p

Heat pipes for enhanced cooldown of cyrogenic systems

In many important cryogenic applications the use of liquid cryogens for system cooling are either not feasible or are unsuitable. In such cases a cryogenic refrigeration system or multi stage cryocooler must be employed to provide the necessary cooling. To shorten cooldown time for such a system, especially if the thermal mass is large, a thermal shunt directly connecting the first stage of the cryocooler to the load during cooldown is desirable. This thermal shunt allows effective utilization of the greater cooling power available from the first stage of the cryocooler early in the cooldown. Upon reaching operating temperature, the thermal shunt must exhibit a high resistance to thermally isolate the first stage of the cryocooler from the load. Heat pipes are well suited to achieve these objectives. The Advanced Lightweight Influence Sweep System (ALISS), under development by the U.S. Navy for shallow water magnetic mine countermeasures, employs a large, conductively cooled, superconducting magnet that must be cooled from 300 to 4.2 K. Cryogenic heat pipes acting as cryocooler thermal shunts are used to shorten the cooldown time. Ethane, nitrogen and oxygen were evaluated as possible working fluids. A thermal model of the ALISS was developed to evaluate the cooldown performance of various heat pipe combinations. In conjunction with heat pipe performance tests, this model was used to select a suitable design for the heat pipe thermal shunts

Testing of the ITER CS Module #4

The ITER Central Solenoid is under fabrication by the US ITER organization and its subcontractors. US ITER will supply seven modules to ITER IO, six of which will be assembled in a stack that forms the ITER Central Solenoid (CS). All CS modules were or will be tested at 40 kA in the Final Test facility at General Atomics, Poway, CA. Testing included high voltage, as well as Paschen testing in the vacuum and global leak tests before and after the cooldown to 4.5 K and EM cycling to 40 kA. In the paper we present the results of the CS Module 4 performance, after modifications to the test facility to improve reliability and instrumentation. We measured critical temperatures in several pancakes, AC losses before and after 10 cycles to 40 kA, joints resistance and hydraulic characteristics of the coils. We also measured displacements of the coil height and vertical strain of the CSM (central solenoid module) to verify structural mechanical characteristics of the coil along with cooldown shrinkage of the coil. We studied performance of the cowound quench detectors, confirmed their effectiveness in suppression of the inductive noise, but also developed a plan to improve sensitivity of the quench detection in ITER CS. This information is necessary for verification of the stack behavior of CS in ITER operation. The test results, preliminary analyses, comparisons to the other tested modules are presented and discussed

Testing of the ITER Central Solenoid Modules

The ITER Central Solenoid is under fabrication by the U.S. ITER organization and its subcontractors. U.S. ITER will supply seven modules to ITER IO, six of which will be assembled in a stack that forms the ITER Central Solenoid. The first modules that were built by GA at their facility, went into high voltage testing, including Paschen testing in the vacuum, and then they were tested at 4.5 K and up to 40 kA to demonstrate compliance of the coil with the ITER requirements. In this article, we present the Test Plan and results of the central solenoid (CS) module's performance, especially at the full current. We measured critical temperatures in several pancakes, we measured ac losses, joint resistance, and hydraulic characteristics of the coils. We also measured displacements of the coil height and hoop strain of the CS module (CSM) to verify the structural mechanical characteristics of the coil along with the cooldown shrinkage of the coil. We studied the performance of the cowound quench detectors and confirmed their effectiveness in the suppression of inductive noise. This information is necessary for verification of the stack behavior of CS in ITER operation. The test results and preliminary analyses are presented, compared to expectations, and discussed