As part of the international research program on the superconducting cavity for the International Linear Collider (ILC) R&D on the 1.3 GHz low loss superconducting cavities has been carried out at the Institute of High Energy Physics (IHEP) since 2005. A design of 1.3 GHz low loss cavity shape was proposed and six single-cell cavities of different niobium material were successfully fabricated with standard technology. In this study our priority was on large grain (LG) cavities. The two LG cavities were treated with complete procedures of surface treatments based on chemical polishing (CP) without electro polishing (EP) at IHEP. The two LG cavities and a fine grain cavity were sent to KEK for vertical testing. All the three cavities reached accelerating gradients higher than 35 MV/m and the maximum gradient of 40.27 MV/m was achieved in the LG cavity. This paper presents the process of the vertical RF tests and the comparison of the LG and fine grain cavities's performance.

We report the results of surface characterizations of niobium samples electropolished together with a single cell cavity. These witness samples were located in three regions of the cavity, namely at the equator, the iris and the beam-pipe. Auger electron spectroscopy (AES) was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive x-ray for elemental analysis (SEM/EDX) was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulphur (S) were found covering the samples non-uniformly. Niobium oxide granules with a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulphur.

For the International Linear Collider (ILC), superconducting RF cavity technology was chosen. The superconducting cavity is made of polycrystalline niobium material so far. However, the material cost is high and the cavity performance has a rather scatter now. Large grain (LG) niobium cavity has the potential of simplifying the production and reducing the cost of the superconducting RF cavities for the ILC. To investigate the feasibility of fabrication and the possibility to achieve high gradient by LG cavities, three single-cell cavities were made of China Ningxia LG niobium. A series of vertical tests has been carried out on several different surfaces treatment procedures by electro polishing. One cavity has reached the high gradient of more than 43 MV/m repeatedly. The maximum accelerating field of 47.9 MV/m has been achieved. This paper describes the features of electro polishing on China Ningxia LG niobium and presents the preliminary results of the research.

Super-conducting Radio Frequency (SRF) 9-cell cavities have been developed in Low-Loss (LL) ICHIRO shape at KEK aiming at high-gradient operation for the International Linear Collider (ILC). One of the most important issues to realize high-gradient linac with SRF cavitiest in pulsed-mode operation is the compensation of the Lorentz detuning of cavities which amounts to 3 kHz at our goal of 45 MV/m acceleration field. None of tuners to date have achieved this specification. A coaxial ball- screw tuner was designed, fabricated and proven to reach this specification in room temperature. The performance was studied also at liquid-nitrogen temperature and the needed dynamic-range for 45 MV/m operation was proven at this temperature. The microphonic vibration was measured to be 100 Hz order in a test setup. In this paper, we describe these studies and evaluate the feasibility of ball-screw tuner operation at 2 K.

KEK is constructing its superconducting RF test facility and installing 1.3 GHz superconducting accelerator structures. Learning from experience with our first 45 MV/m 9-cell accelerating structures, we have redesigned the structures to improve the characteristics and the performances. Problems found in the earlier structures are resolved in the new structures.

The status of the large grain niobium cavity R&D in Asia and the future scope are presented. Recently KEK has received CBMM and NingXia large grain niobium sheets through collaborations. KEK has fabricated 1.3 GHz single cell cavities using these materials and measured the cavity performance. Those results are presented in this paper.

We have continued the study of a series of single cell superconducting cavities at KEK. These tests are for establishing surface treatment that would reliably allow cavities to reach gradients over 45 MV/m in vertical tests. The all cavity have the low loss (LL) shape (1). They were fabricated from deep drawn niobium half shells with RRR=300 using electron beam welding. The KEK cavity preparation so called KEK recipe followed by the cavity fabrication. Early results from this series test demonstrated that reaching gradients as high as 50 MV/m was feasible, however, the yield rate was of order 50%. In this paper we will report our studies of further improvement of the surface treatment aimed at increasing the yield rate.

We are planning to construct Superconducting RF Test Facility (STF) at KEK for the R&D of ILC accelerator. In STF, four TESLA-like type 9-cell cavities and four Low- Loss (LL) type cavities will be installed into a cryomodule. We are aiming at the gradient of 51 MV/m with this LL-type cavity, and we named this cavity as ICHIRO after the back-number of famous base-ball player ICHIRO; 51. The four ICHIRO cavities were successfully fabricated and delivered to KEK. Two of them were already surface-treated and measured in vertical cryostat. In this article, the results of vertical tests by these two ICHIRO cavities would be reported.

The Balloon-borne Experiment with a Super-solenoidal Spectrometer (BESS) instrument has been flown annually from Lynn Lake Manitoba since 1993. The instrument has been upgraded several times to improve its performance. The instalment flown in 1998 was able to detect 2H clearly between 0.13 and 1.78 GeV/n as a result of improvements made on the time-of-flight (TOF) system. The BESS 98 data were analyzed to obtain the ratio and absolute fluxes of 1H and 2H over this energy range. The results were compared with different cosmic ray propagation models and their implications regarding their propagation history are discussed in this paper.

A multichannel flash ADC (analog to digital converter) system is developed for a balloon-borne experiment where flash ADCs installed in individual channels output samples of signals at the rate of 30 MHz. The system incorporates zero suppression and data compression. The samples from the converter are put to the zero suppression on a real-time basis and then submitted to the data compression. The data compression reduces the event data in a size further, so that the data of as many events as possible can be recorded on a storage device installed on the balloon-borne apparatus. A zero-suppression circuit is implemented in each channel. A data-compression module in the system begins to scan all the channels, performing compression, after the converter completes sampling. Special care is taken to keep the power consumption of the system within a moderate level.<>

A CAMAC Crate Controller is developed where three T425-25S 32-bit transputers are installed. The Crate Controller (CC) conforms to the specifications of the EUR 6500e CAMAC standard. It can be used as a stand-alone CC and also as an Auxiliary Crate Controller (ACC). The transputers on the CC are enabled to execute CAMAC dataway operations independently under the supervision of an Arbitration Logic. Each transputer is provided with an independent register set. Owing to the transputer, the CC's can be easily networked through the connection of serial links. The CC's in the network make accesses to front-end CAMAC modules in the individual crates in parallel, communicating with each other. Data are read from front-end CAMAC modules, stored into large memory, processed and then submitted to the network concurrently and autonomously.