Progress on the construction of the 100 MeV/100 kW electron linac for the NSC KIPT neutron source

IHEP, China is constructing a 100 MeV/100 kW electron Linac for NSC KIPT, Ukraine. This linac will be used as the driver of a neutron source based on a subcritical assembly. In 2012, the injector part of the accelerator was pre-installed as a testing facility in the experimental hall ≠2 of IHEP. The injector beam and key hardware testing results met the design goal. Recently, the injector testing facility was disassembled and all of the components for the whole accelerator have been shipped to Ukraine from China by the ocean shipping. The installation of the whole machine in KIPT will be started in June, 2013. The construction progress, the design and testing results of the injector beam and key hardware are presented.     

Error and jitter e ect studies on the SLED for the BEPCⅡ-linac

An RF pulse compressor is a device used to convert a long RF pulse to a short one with a much higher peak RF magnitude. SLED can be regarded as the earliest RF pulse compressor to be used in large-scale linear accelerators. It has been widely studied around the world and applied in the BEPC and BEPCⅡ linac for many years. During routine operation, error and jitter effects will deteriorate the performance of SLED, either on the output electromagnetic wave amplitude or phase. The error effects mainly include the frequency drift induced by cooling water temperature variation and the frequency/Q₀/β unbalances between the two energy storage cavities caused by mechanical fabrication or microwave tuning. The jitter effects refer to the PSK switching phase and time jitters. In this paper, we re-derive the generalized formulae for the conventional SLED used in the BEPCⅡ linac, and the error and jitter effects on SLED performance are also investigated.     

RF thermal and new cold part design studies on a TTF-Ⅲ input coupler for Project-X

An RF power coupler is one of the key components in a superconducting (SC) linac. It provides RF power to the SC cavity and interconnects different temperature layers (1.8 K, 4.2 K, 70 K and 300 K). The TTF-Ⅲ coupler is one of the most promising candidates for the High Energy (HE) linac of Project X, but it cannot meet the average power requirements because of the relatively high temperature rise on the warm inner conductor, so some design modifications will be required. In this paper, we describe our simulation studies on the copper coating thickness on the warm inner conductor with RRR values of 10 and 100. Our purpose is to rebalance the dynamic and static loads, and finally lower the temperature rise along the warm inner conductor. In addition, to get stronger coupling, better power handling and less multipacting probability, one new cold part design was proposed using a 60 mm coaxial line; the corresponding multipacting simulation studies have also been investigated.     

Beam dynamics studies on the 100 MeV/100 kW electron linear accelerator for NSC KIPT neutron source

We designed a 100 MeV/100 kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the basis of subcritical assembly. Beam dynamics studies have been conducted to reach the design requirements (E=100 MeV, P=100 kW, dE/E<1% for 99% particles). In this paper, we will present the progress of the design and the dynamic simulation results. For high intensity and long beam pulse linear accelerators, the BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at a low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced downstream of the 1st accelerating section; the unwanted particles will be collimated there.     

Error and jitter effect studies on the SLED for the BEPC Ⅱ-linac

An RF pulse compressor is a device used to convert a long RF pulse to a short one with a much higher peak RF magnitude. SLED can be regarded as the earliest RF pulse compressor to be used in large-scale linear accelerators. It has been widely studied around the world and applied in the BEPC and BEPC linac for many years. During routine operation, error and jitter effects will deteriorate the performance of SLED, either on the output electromagnetic wave amplitude or phase. The error effects mainly include the frequency drift induced by cooling water temperature variation and the frequency/Q 0 /β unbalances between the two energy storage cavities caused by mechanical fabrication or microwave tuning. The jitter effects refer to the PSK switching phase and time jitters. In this paper, we re-derive the generalized formulae for the conventional SLED used in the BEPC linac, and the error and jitter effects on SLED performance are also investigated.     

多条形电极束流能散度探测器的张角优化

 采用Surperfish对北京正负电子对撞机的多条形电极束流能散度探测器进行了电磁场模拟计算。在带模拟束流的情况下,计算分析了探测器对束流位置和能散度的分辨能力与电极张角之间的关系,首次计算了条形电极间的电容耦合综合强度。电极张角优化结果表明：在不考虑噪声水平的情况下,电极张角为20°时,探测器的灵敏度和分辨率达到最优。而当噪声影响很大时,可以适当增加电极张角,同时考虑减小噪声的措施。     

571.2MHz次谐波聚束腔的高频电磁场效应

高频谐振腔中的电磁场通常以两种方式影响谐振腔的特性. 一种方式是通过作用在谐振腔内壁上的高频热, 这主要 由高频功率的欧姆损耗导致; 另一种方式是通过作用在谐振腔内壁上的洛仑兹力, 这主要由谐振腔内壁上的面电流 和面电荷导致. 联合使用有限差分软件Superfish和有限元软件ANSYS，本文对571.2MHz次谐波聚束腔中的高频电磁场 效应进行了研究. 此外, 本文还对BEPCⅡ未来预注入器第1个次谐波聚束腔中的高频热效应进行了讨论.     

等梯度加速结构中的尾场计算研究

带电粒子束在穿过加速结构时激起的尾场, 会导致束流能散和发射度的增大. 准确计算尾场对正确估计尾场效应对束流性能的影响具有重要意义. 本文对等梯度加速结构中短程尾场、中长程尾场和超长程尾场的计算方法进行了较系统的研究, 并首次给出了超长程尾场的计算公式. 此外, 本文还给出了BEPCⅡ直线加速器等梯度加速结构中短程尾场、中长程尾场以及超长程尾场的计算结果, 并对多种方法计算结果的一致性和在某些范围内的差别做了分析说明.     

Accelerating structure design and fabrication for KIPT and PAL XFEL

ANL (Argonne National Laboratory) and the National Science Center “Kharkov Institute of Physics Technology” (NSC KIPT, Kharkov, Ukraine) jointly propose to design and build a 100 MeV/100 kW linear accelerator which will be used to drive the neutron source subcritical assembly. The linac has almost finished assembly in KIPT by a team from the Institute of High Energy Physics (IHEP, Beijing, China). The design and measurement result of the accelerating system of the linac will be described in this paper.     

3 dB桥误差对能量倍增器性能的影响

根据能量倍增器的工作原理,对3 dB桥误差引起的能量倍增器性能变化进行了理论分析,并对BEPC和BEPCⅡ直线加速器所使用能量倍增器的3 dB桥误差进行了讨论,为判断焊接后3 dB桥桥臂波导变形提供了理论参考。结果表明:无论是功率分配不平衡,还是相位关系偏离,都会使部分功率反射回速调管。功率分配不平衡和微波相位关系偏离值越大,则功率倍增因子下降得越多。