排序方式: 共有53条查询结果,搜索用时 281 毫秒
1.
2.
Dr. Roberta Pievo Brigitta Angerstein Dr. Alistair J. Fielding Dr. Christian Koch Prof. Dr. Ivo Feussner Prof. Dr. Marina Bennati 《Chemphyschem》2013,14(18):4094-4101
Electron paramagnetic resonance (EPR) spectroscopy in combination with the rapid freeze‐quench (RFQ) technique is a well‐established method to trap and characterize intermediates in chemical or enzymatic reactions at the millisecond or even shorter time scales. The method is particularly powerful for mechanistic studies of enzymatic reactions when combined with high‐frequency EPR (ν≥90 GHz), which permits the identification of substrate or protein radical intermediates by their electronic g values. In this work, we describe a new custom‐designed micro‐mix rapid freeze‐quench apparatus, for which reagent volumes for biological samples as small as 20 μL are required. The apparatus was implemented with homemade sample collectors appropriate for 9, 34, and 94 GHz EPR capillaries (4, 2, and 0.87 mm outer diameter, respectively) and the performance was evaluated. We demonstrate the application potential of the RFQ apparatus by following the enzymatic reaction of PpoA, a fungal dioxygenase producing hydro(pero)xylated fatty acids. The larger spectral resolution at 94 GHz allows the discernment of structural changes in the EPR spectra, which are not detectable in the same samples at the standard 9 GHz frequency. 相似文献
3.
As part of the design and machining of the RFQ accelerator in the Compact Pulsed Hadron Source (CPHS) project at Tsinghua University, the design process of the undercuts and dipole stabilizer rods is presented in this paper. In particular, the relationship between the inter-vane voltage slope and the local frequency of the undercut section is described quantitatively. With the identification of modes existing in the cavity, the specific parameters are optimized by the SUPERFISH and MAFIA codes. In addition, the water-cooling requirement of the dipole stabilizer rods is briefly discussed. 相似文献
4.
LIU Ge LU YuanRong YIN XueJun ZHANG XiaoHu DU Heng JIANG PeiYong LI ZhongShan LI XiaoNi HE Yuan WANG Zhi GAO ShuLi YANG YaQing ZHU Kun YAN XueQing CHEN JiaEr YUAN YouJin XIA JiaWen ZHAO HongWei 《中国科学:物理学 力学 天文学(英文版)》2014,57(7):1311-1317
The 53.667 MHz continuous-wave heavy ion RFQ has been designed and manufactured for the SSC-LINAC project.This four-rod RFQ accelerates ions with maximum mass to charge ratio of 7 from 3.728 keV/u to 143 keV/u.Measurements have been carried out to check the RF performance of the cavity and the quality of the electric field.The S11 of the power coupler is adjusted to better than-44 dB,and the Q0 of the cavity is 6440.The quality of the electric field is evaluated by the perturbation method.The measurement procedure and data analysis will be discussed in detail.The error due to gravity of the perturbation bead has been corrected by averaging the fields in different quadrants.As a result,the unflatness of the electric field is±2.5%,and the dipole field component distributes from 0%to 20%in different longitudinal positions,which indicates the asymmetry of the quadrupole field.The unflatness of the quadrupole field distribution represents a good agreement with the simulation results.High power RF test and beam commissioning of the RFQ are on schedule in early 2014. 相似文献
5.
G. Marx D. Ackermann J. Dilling F.P. Hessberger S. Hoffmann H.-J. Kluge R. Mann G. Münzenberg Z. Qamhieh W. Quint D. Rodriguez M. Schädel J. Schönfelder G. Sikler C. Toader C. Weber O. Engels D. Habs P. Thirolf H. Backe A. Dretzke W. Lauth W. Ludolphs M. Sewtz 《Hyperfine Interactions》2001,132(1-4):459-464
The ion trap facility SHIPTRAP is being set up to deliver very clean and cool beams of singly-charged recoil ions produced
at the SHIP velocity filter at GSI Darmstadt. SHIPTRAP consists of a gas cell for stopping and thermalizing high-energy recoil
ions from SHIP, an rf ion guide for extraction of the ions from the gas cell, a linear rf trap for accumulation and bunching
of the ions, and a Penning trap for isobaric purification. The progress in testing the rf ion guide is reported. A transmission
of about 93(5)% was achieved.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
7.
在以时间为自变量的PARMTEQ程序的基础上,添加了另一带相反电荷的束流进行动力学计算,同时考虑了正、负离子束加速的空间电荷效应和束团间的作用.并针对特定结构参数的RFQ加速器,给出了双束加速的动力学模拟过程和结果.模拟计算的目的在于研究正、负离子束在RFQ加速结构中同时加速所引起的动力学问题.结果表明,正、负离子束同时加速有助于克服径向空间电荷效应,但在流强较大时,双束加速时,将会在纵向出现明显的异性电荷之间的“捕捉”(trap)现象,从而导致纵向粒子损失数目的增加.因此,为实现双束加速,必须专门重新设计RFQ加速器,使其传输效率高于单束,才能体现出双束加速的优越性 相似文献
8.
P N Ostroumov 《Pramana》2002,59(6):895-913
The Nuclear Science Community in the Unites States has unanimously concluded that developments in both nuclear science and
its supporting technologies make building a world-leading Rare-Isotope Accelerator (RIA) facility for production of radioactive
beams the top priority. The RIA development effort involves several US Laboratories (ANL, JLAB, LBNL, MSU, ORNL). The RIA
facility includes a CW 1.4 GeV driver LINAC and a 100 MV post-accelerator both based on superconducting (SC) cavities operating
at frequencies from 48 MHz to 805 MHz. An initial acceleration in both LINACs is provided by room temperature RFQs. The driver
LINAC is designed for acceleration of any ion species; from protons up to 900 MeV to uranium up to 400 MeV/u. The novel feature
of the driver LINAC is an acceleration of multiple charge-state heavy-ion beams in order to achieve 400 kW beam power. Basic
design concepts of the driver LINAC are given. Several new conceptual solutions in beam dynamics, room temperature and SC
accelerating structures for heavy ion accelerator applications are discussed. 相似文献
9.
10.
It is proposed to construct a spallation neutron source (SNS) at Centre for Advanced Technology (CAT) based on a 1 GeV proton
synchrotron with 100 MeV H− LINAC as injector. Additionally, the LINAC can form the first 100 MeV part of a 1 GeV proton LINAC to be built in future
for accelerator driven system (ADS) applications. We are exploring a configuration of the 100 MeV LINAC which will consist
of an H− ion source, a 4–6 MeV RFQ followed either by a 20 MeV drift tube LINAC (DTL) and 100 MeV separated function drift tube LINAC
(SDTL) or a coupled cavity drift tube LINAC (CCDTL) structure. In this paper, we present the results of our preliminary physics
design studies of the RFQ-SDTL, RFQ-CCDTL and RFQ-DTL-SDTL configurations. The design of the 4.5 MeV RFQ is discussed along
with the matching sections between the RFQ-SDTL/DTL and RFQ-CCDTL. The choice of the accelerator configuration and that of
various parameters of the individual accelerator structures under consideration are discussed. The design objectives are to
arrive at a configuration which eases heat removal for CW operation and which is less prone to halo formation in order to
reduce the beam loss at higher energies. 相似文献