Shigeru Takeda

A separation method of 0ν- and 2ν-events in double beta decay experiments with DCBA

Abstract A detector called Drift Chamber Beta-ray Analyzer (DCBA) will provide momentum information of each β-ray in double beta decay. The DCBA is expected to have good capabilities for particle identification, detection efficiency, background elimination and decay-source integration. Under the assumption of mass mechanism dominance in neutrinoless double beta decay, a simulation study shows that a combination method using both sum and single-energy distributions of double beta decay events can separate 0 ν - and 2 ν -events down to 0.05 eV of the effective neutrino mass with the help of a calculated nuclear matrix element, even though the DCBA has relatively poor energy resolution.

The TRISTAN control system

The 8 GeV accumulation ring and the 30 GeV main ring of TRISTAN, an accelerator-storage ring complex at KEK, are controlled by a highly computerized control system. Twenty-four minicomputers are linked by optical fiber cables to form an N-to-N token ring network. The transmission speed on the cables is 10 Mbps. From each minicomputer, a CAMAC serial highway extends to the controlled equipment. At present, twenty minicomputers are connected to the network and are used to control the accumulation ring. The software system is based on the NODAL language devised at the CERN SPS. The KEK NODAL system retains main features of the original NODAL: the interpretive scheme, the multi-computer programming facility, and the data-module concept. In addition, it has the following features: (1) fast execution due to the compiler-interpreter method, (2) a multi-computer file system (3), a full-screen editing facility, and (4) a dynamic linkage scheme for data modules and NODAL functions. The accelerators are operated through five operator consoles, each of which is managed by one minicomputer in the network. An operator console contains two 20-inch high-resolution color graphic displays, a pair of touch-panels, and ten small TV monitors. One touch-panel is used to select a program and a piece of equipment to be controlled; the other is used mainly to perform the console actions.

KEKB accelerator control system

The KEKB accelerator control system including a control computer system, a timing distribution system, and a safety control system are described. KEKB accelerators were installed in the same tunnel where the TRISTAN accelerator was. There were some constraints due to the reused equipment. The control system is based on Experimental Physics and Industrial Control System (EPICS). In order to reduce the cost and labor for constructing the KEKB control system, as many CAMAC modules as possible are used again. The guiding principles of the KEKB control computer system are as follows: use EPICS as the controls environment, provide a two-language system for developing application programs, use VMEbus as frontend computers as a consequence of EPICS, use standard buses, such as CAMAC, GPIB, VXIbus, ARCNET, RS-232 as field buses and use ergonomic equipment for operators and scientists. On the software side, interpretive Python and SAD languages are used for coding application programs. The purpose of the radiation safety system is to protect personnel from radiation hazards. It consists of an access control system and a beam interlock system. The access control system protects people from strong radiation inside the accelerator tunnel due to an intense beam, by controlling access to the beamline area. On the other hand, the beam interlock system prevents people from radiation exposure by interlocking the beam operation. For the convenience of accelerator operation and access control, the region covered by the safety system is divided into three major access control areas: the KEKB area, the PF-AR area, and the beam-transport (BT) area. The KEKB control system required a new timing system to match a low longitudinal acceptance due to a low-alpha machine. This timing system is based on a frequency divider/multiply technique and a digital delay technique. The RF frequency of the KEKB rings and that of the injector Linac are locked with a common divisor frequency. The common divisor frequency determines the injection timing. The RF bucket selection system is also described. r 2002 Elsevier Science B.V. All rights reserved.

Ground motion studies for large future linear colliders

A future large accelerator, such as a TeV linear collider, should have an extremely small emittance to give the required luminosity. Precise alignment of machine components is essential to prevent emittance dilution. The ground motion spoils alignment of the accelerator elements and results in emittance growth. This paper discusses ground motion and its effect on the main linac. The ground motion in the frequency range of seismic vibration is mostly coherent in the related accelerator. However the incoherent diffusive or Brownian like motion may become dominant for a frequency region less than seismic vibration. This paper starts from the power spectrum of the ATL model then shows typical parameters of main linacs and considers measured data including excavated effects.

The DCBA experiment for studying neutrinoless double beta-decay

In order to search for neutrinoless double beta-decay, the DCBA (Drift Chamber Beta-ray Analyzer) experiment uses a momentum analyzer, which mainly consists of drift chamber and a uniform magnetic field. A beta ray from a source plate make helical trajectory in the drift chamber owing to the magnetic field. Momentum of each beta ray is obtained by three-dimensional track reconstruction. A test prototype called DCBA-T2 has been constructed and operated at KEK. Another prototype DCBA-T3 is also under construction to improve the energy resolution. The results of DCBA-T2 engineering run are described together with the status of DCBA-T3.

ELECTRICAL MEASUREMENT OF WIRE TENSION IN A MULTI-WIRE DRIFT CHAMBER

Abstract A new and simple technique has been developed to measure the wire tension of a multi-wire drift chamber, which is the prototype chamber of DCBA (Drift Chamber Beta-ray Analyzer) for double beta decay experiments. The present method uses two wires adjacent to each other in the chamber for applying AC and DC electric fields, and can easily detect a weak current signal at the resonance frequency corresponding to the wire tension. The wire tension has been measured with an accuracy of about 1%.

Man-Machine Interface of Tristan

This report describes a console system which is the essence of man-machine interface used to operate TRISTAN. Ergonomic design and its implementation has been done in construction of the TRISTAN Central Control Room (TCCR) and Operators Console (OPC). The environment of the console is designed to minimize fatigue, eyestrain and discomfort by optimizing light fixtures, minimizing noises made by fans or footsteps and harmonizing colors and brightness throughout the control room. The OPC is composed of a special supervisory console at the center and five identical standard consoles. The difference between the two types is that hard-wired switches which manipulate beam gates and related equipments to assure the safety of personnel are mounted only on the former console. The safety system is based on the hardware techniques similar to those have been accepted for the control of critical industrial installations. Each of the consoles contains ten color TV monitors, two high resolution graphic display monitors and two touch-panels with color character display monitors. Each console is managed by a minicomputer of the TRISTAN control computer network. The graphic displays are connected directly to the computer. The touchpanels and the corresponding character video RAM modules are through CAMAC serial highway.

The rejuvenation status of TRISTAN accelerator control system

Abstract Ten years have passed since the current control system started the operation of the TRISTAN accelerator. The system uses CAMAC as a front-end electronics, and they are controlled by 25 Hitachi process computers linked by a N to N token ring network. In order to have the ability to perform complicated accelerator operations, there is a strong request to renew these 25 process computers. Firstly, we review how we will rejuvenate the current control system under some constraints, such as the lack of man-power, limited time and financing. This is followed by proposals for the next step of rejuvenation.

Design of the Control System of TRISTAN

We summarize here the outline of our system. (1) Distributed computer control scheme is adopted. (2) Twenty-five 16-bit mini-computers are connected by 10 Mbps optical fiber cables to form an N-to-N ring network. (3) NODAL interpreter and compiler are used throughout the program development of the system. (4) CAMAC serial highways are used as the means of communication between the mini-computers and the devices. (5) TRISTAN system is controlled from a single control center.

RF Acceleration in KEK Booster

The KEK booster synchrotron is a rapid-cycling machine with a repetition rate of 20 Hz. The rf system was designed for accelerating the proton beam injected at 20 MeV up to its final energy of 500 MeV. The booster succeeded in accelerating 8 x 10/sup 10/ protons/pulse to the designed energy on Dec. 12, 1974. Since then the beam intensity was steadily increased to 5.7 x 10/sup 11/ protons/pulse with adjustments and improvements of the machine components, especially of the rf system. An outline of the rf system and the present status of its operation are presented. Main parameters characterizing the rf system are listed, and accelerating parameters and the estimated beam characteristics are shown.