Haiying Lin

Corrosion behavior of Ti-6Al-4V alloy welded by scanning electron beam

The corrosion behavior of Ti-6Al-4V alloy welded by SEE (scanning electron beam) is described in this paper. Solidification macrostructure of weld was transformed from 650-mu m columnar crystals to 100-mu m equiaxed crystals by SEE. Anodic polarization behavior of the weld was different following the change in solidification macrostructure. Anodic polarization curve of 150-mu m equiaxed-grain weld coincided with that of base metal, which indicated a best state of equal corrosion tendency between the base and the weld metal. Alloy element homogeneity in the equiaxed solidification structures made the weld more corrosion resistant than the columnar solidification structures. Fine microstructure and a small quantity of dislocations have a good effect on uniform corrosion resistance of the weld, but coarse microstructure, a spinodal decomposition of the metastable beta-phase and a large quantity of dislocations were related to the inferior resistance either to uniform corrosion or to local corrosion

Dealloying characterizations of Cu-Al alloy in marine environment

chinese acad sci, inst corros & protect met, state key lab corros & protect, shenyang 110015, peoples r china. shenyang polytech coll, shenyang, peoples r china.;han, z (reprint author), chinese acad sci, inst corros & protect met, state key lab corros & protect, shenyang 110015, peoples r china

Tuner control system of spoke012 SRF cavity for C-ADS injector I at IHEP

A new tuner control system for spoke superconducting radio frequency (SRF) cavities has been developed and applied to cryomodule I of the C-ADS injector I at the Institute of High Energy Physics, Chinese Academy of Sciences. We have successfully implemented the tuner controller based on Programmable Logic Controller (PLC) for the first time and achieved a cavity tuning phase error of ±0.7° (about ±4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper presents preliminary experimental results based on the PLC tuner controller under proton beam commissioning.

Some experiences with BEPCII SRF system operation

The Superconducting Radio Frequency (SRF) system of the upgrade project of the Beijing Electron Positron Collider (BEPCII) has been in operation for almost 8 years. During operation, many problems have been encountered, such as excessive heating of the power couplers, frequent beam trips during high intensity colliding, false arc interlock trigger and so on. Among them, some has been solved successfully, some have been alleviated. This paper will describe some experiences with BEPCII SRF system operation, including the symptoms, causes and solutions of problems.

Design of a 325 MHz half wave resonator prototype at IHEP

A 325 MHz β = 0.14 superconducting half-wave resonator prototype has been developed at the Institute of High Energy Physics, Beijing, which can be applied in the low energy section of continuous wave high current proton linear accelerators. The electromagnetic design, multipacting simulation, mechanical optimization and fabrication are introduced in detail. Test results at room temperature and 4.2 K, and a comparison between measured and simulated results, are analyzed in this paper.

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.

Second Sound Quench Detection on Superconducting Cavities

Second sound is an effective way to detect the quench position on superconducting cavity. A second sound quench site detection system is under developing for the PAPS. High gradient is very important for super conducting cavity, however it may be limited by quench on the cavity high field region. Quench can be caused by various reasons. To locate the position is the key to reveal the mysteries of quench. Now we are developing the quench position detection system by RTD sensors such as Cernox and OST sensors. INTRODUCTION Second sound is an effective way to detect the quench position on superconducting cavity. It was first used to detect the quench position on the SC split-ring resonators at ANL by a germanium resistor sensor [1]. Oscillating Superleak Transducers (OST) were used to locate the quench site of the 1.3 GHz 9-cell cavity at Cornell University [2]. Later after that second sound quench site detection of SC cavity by OST was widely used on the world. Second sound detection was also used in standard dressed TESLA-Shape SRF cavity at DESY [3]. Other types of sensor were also developed to detect second sound. For example, transition edge sensors was used in second sound test [4, 5]. A second sound quench site detection system is under developing for the PAPS. We chose the highly sensitive thermometers such as germanium bare chip resistor or Cernox bare chip resistor and OST as the second sound detection sensors. Tests with SC cavity and heater in liquid helium at 2K were taken.

Measurement of the transfer function for a spoke cavity of C-ADS Injector I

The spoke cavities mounted in the China Accelerator Driven sub-critical System (C-ADS) have high quality factor(Q) and very small bandwidth, making them very sensitive to mechanical perturbations whether external or self-induced. The transfer function is used to characterize the response of the cavity eigen frequency to the perturbations. This paper describes a method to measure the transfer function of a spoke cavity. The measured Lorentz transfer function shows there are 206 Hz and 311 Hz mechanical eigenmodes excited by Lorentz force in the cavity of C-ADS, and the measured piezo fast tuner transfer function shows there are 12 mechanical eigenmodes from 0 to 500 Hz. According to these results, some effective measures have been taken to weaken the influence from helium pressure fluctuation, avoid mechanical resonances and improve the reliability of RF system.

Tuner control system of Spoke012 SRF cavity for C-ADS injector I *

A new tuner control system for spoke superconducting radio frequency (SRF) cavities has been developed and applied to cryomodule I of the C-ADS injector I at the Institute of High Energy Physics, Chinese Academy of Sciences. We have successfully implemented the tuner controller based on Programmable Logic Controller (PLC) for the first time and achieved a cavity tuning phase error of ±0.7° (about ±4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper presents preliminary experimental results based on the PLC tuner controller under proton beam commissioning.

1.3 GHz SRF Technology R&D Progress of IHEP

IHEP started the 1.3 GHz SRF technology R&D in 2006 and recently enters the stage of integration and industrialization. After successfully making several single cell and 9-cell cavities of different shape and material, we designed and assembled a short cryomodule containing one large grain low-loss shape 9-cell cavity with an input coupler and a tuner etc. This module will perform horizontal test in 2016 with the newly commissioned 1.3 GHz 5 MW klystron and the 2 K cryogenic system. Beam test with a DC photocathode gun is also foreseen in the near future. We report here the problems, key findings and improvements in cavity dressing, clean room assembly, cryomodule assembly and the liquid nitrogen cool down test. A fine grain TESLA 9-cell cavity is also under fabrication in a company as the industrialization study.