Selective mono-fluorination of diols via a cyclic acetal of N,N-diethyl-4-methoxybenzamide

Selective mono-fluorination of 1,2- and 1,3- diols was achieved using N,N-diethyl-4-methoxybenzamide diethyl acetal and Et3N-3HF. The reaction proceeds through a cyclic acetal of the benzamide, and only one hydroxy group was fluorinated and another one was acylated

First simultaneous detection of electron and positron bunches at the positron capture section of the SuperKEKB factory

Abstract The direct simultaneous detection of electron and positron bunch signals was successfully performed for the first time with wideband pickups and a detection system at the positron capture section of the SuperKEKB factory. The time interval between the electron and positron bunches, their bunch lengths, and bunch intensities depending on the phase of accelerating structures were measured to investigate their capture process and to maximally optimize the positron intensity. The results show that the time intervals were measured in the range of 135–265 ps, and the line-order switch of the electron and positron bunches in the axial direction was clearly observed as a function of the phase. The positron (electron) intensity was maximized at the optimal phase (180 $$^{\circ }$$ ∘ shifted from the optimum). These series of measurements have never been experimentally conducted so far. It is demonstrated that the positron intensity can be systematically optimized with this system as functions of beam parameters in multidimensional spaces for any positron capture section

DEVELOPMENT OF FPGA-BASED TDC WITH WIDE DYNAMIC RANGE FOR MONITORING THE TRIGGER TIMING DISTRIBUTION SYSTEM AT THE KEKB INJECTOR LINAC

Abstract A new field-programmable gate array (FPGA)-based time-to-digital converter (TDC) with a wide dynamic range greater than 20 ms has been developed to monitor the timing of various pulsed devices in the trigger timing distribution system of the KEKB injector linac. The pulsed devices are driven by feeding regular as well as any irregular (or event-based) timing pulses. For monitoring the timing as precisely as possible, a 16-ch FPGA-based TDC has been developed on a Xilinx Spartan-6 FPGA equipped on VME board with a time resolution of 1 ns. The resolution was achieved by applying a multisampling technique, and the accuracies were 2.6 ns (rms) and less than 1 ns (rms) within the dynamic ranges of 20 ms and 7.5 ms, respectively. The various nonlinear effects were improved by implementing a high-precision external clock with a built-in temperaturecompensated crystal oscillator