[en] Since the SLAC/KEK joint meeting was first held at SLAC in March 1987, we have had such a meeting annually with the present one the 6th. This meeting is planned to discuss the damping ring issue in particular. We have ever stressed the importance of study of damping rings and considered construction of a test damping ring as key issue for the ATF project, since we started construction of the ATF in 1987. In 1991 we had large-scale reconstruction of a building to make a shielded area where a 1.54 GeV injector linac for the ring is to be installed. (J.P.N.)

[en] The purpose of the ATF is to develop beams with very small transverse and longitudinal emittances. A 1.37 nm horizontal emittance was confirmed by emittance measurements using wire scanners in the extraction line and a measurement of the horizontal spacial coherence using an SR interferometer. This paper reports on the transverse emittance ratio and gives a discussion on an extreme intra-beam scattering effect. It also describes some problems which should be overcome

[en] The ability to generate highly precise timing signals is essential for the operation of particle accelerators, particularly so in future linear colliders. As a tool to generate precise fixed delays, a module called TD-2.1 has been developed for use at the ATF (Accelerator Test Facility). TD-2.1 is an improved version of a previous module called TD-2, developed for the TRISTAN accelerator. The new version can be used at clock frequencies of up to 1.5 GHz, almost three times the bandwidth of the previous version. Since TD-2.1 is applied in many places to synchronize the ATF accelerator operation, high reliability and stability (low jitter) are essential. The long-term stability and timing jitter of the module were evaluated. The jitter was found to be around 5 ps within the operating range. Stable operation of the module was verified in long-term tests. (author)

[en] We want to accurately know the energy spread and bunch length dependence on current in the ATF damping ring. One reason is to know the strength of the impedance: From the energy spread measurements we know whether or not we are above the threshold to the microwave instability, and from the energy spread and bunch length measurements we find out the extent of potential-well bunch lengthening (PWBL). Another reason for these measurements is to help in our understanding of the intra-beam scattering (IBS) effect in the ATF. The ATF as it is now, running below design energy and with the wigglers turned off, is strongly affected by IBS. To check for consistency with IBS theory of, for example, the measured vertical beam size, we need to know all dimensions of the beam, including the longitudinal one. But beyond this practical reason for studying IBS, IBS is currently a hot research topic at many accelerators around the world (see e.g. Ref. [1]), and the effect in actual machines is not well understood. Typically, when comparing theory with measurements fudge factors are needed to get agreement (see e.g. Ref. [1]). With its strong IBS effect, the ATF is an ideal machine for studying IBS, and an indispensable ingredient for this study is a knowledge of the longitudinal phase space of the beam. The results of earlier bunch lengthening measurements in the ATF can be found in Refs. [2]-[4]. Measurements of current dependent effects, especially bunch length measurements using a streak camera, can be difficult to perform accurately. For example, space charge in the camera itself can lead to systematic errors in the measurement results. It is important the results be accurate and reproducible. In the measurements of both December 1998[3] and December 1999[4], by using light filters, the authors first checked that space charge in the streak camera was not significant. And then the Dec 99 authors show that their results agree with those Dec 98, i.e. on the dates of the two measurements the results were reproducible. Since IBS is so strong in the ATF, in the Dec 99 measurements an attempt was made to estimate the impedance effect using the following method: First, from the form of the energy spread vs. current measurements it was concluded that the threshold to the microwave instability was beyond 2 mA. Then, by dividing the bunch length vs. current curve by the energy spread vs. current curve the effect of IBS was divided out, and PWBL was approximated. The assumption is that PWBL can be treated as a perturbation on top of IBS. The result was that this component of bunch lengthening was found to grow by 7-15% (depending on the rf voltage) between the currents of .5 mA and 2 mA, about a factor of 3 less than the total bunch length growth. The conclusion was that the inductive component of the impedance was small, in fact much smaller than had been concluded earlier in Ref. [2]. Electron machines generally run in a parameter regime where IBS is an insignificant effect, and impedance measurements and calculations have also normally been performed for machines where IBS is unimportant. To simplify the interpretation of the impedance from bunch length measurements, in April 2000 the energy spread and bunch length measurements of Dec 99 were repeated, but now with the beam on a linear (difference) coupling resonance, where the horizontal and vertical emittances were approximately equal. For this case the effect of IBS was expected to be very small. An energy spread vs. current measurement under such conditions will also allow us to more clearly see whether we reach the threshold to the microwave instability. As part of the April data taking we, in addition, repeated the earlier off-coupling measurements, in order to check the reproducibility of the earlier results. In this report we present and analyze this recent set of data, and compare it with the results of the earlier measurements, particularly those of Dec 99. The measurements and analysis of data in this report follow essentially the same procedure as was used in Ref. [4]. In the present report we will try to be relatively brief. The comparison of our results with IBS theory will be given in a following report. For more details about the measurement and analysis techniques presented in this report, the reader should consult Ref. [4]

[en] In TRISTAN accumulation ring (AR), electrons and positrons are acceralated up to 8 GeV, then extracted, transported and injected to main ring (MR). Slow bump and fast bump magnets are used to generate a closed bump orbit for the extraction and injection. A BRG CAMAC module was developed in order to control the power supply for the slow bump magnet. The fall time ( = rise time) and the flat-top time of the ramp pulse can be changed in the range of 0.1 to 150 sec and of 0.1 to 1500 sec by CAMAC command (F(17)), respectively. The outputs of the ramp pulse generator are bipolar (-10.240 V ∼ +10.235 V) and have accuracy of ± 2.5 mV. One can use either CAMAC command (F(25)) or a external timing pulse for the trigger of this ramp pulse. The timing jitter on the start trigger is less than 150 nsec. (author)

[en] A compact MW peak power THz source is of high interest and possible to construct in a small accelerator facility (∼2 m) by using pre-bunched FEL scheme. High gradient photo-cathode RF gun and few tens of femto-second laser system can directly generate a pre-bunched electron beam of a few hundred femto-seconds. Furthermore, small undulator can coherently generate MW THz photons in a few hundred femto-seconds. We are considering the reflection of the THz photons to make a collision with the pre-bunched electron beam and to generate a few hundred femto-second soft X-ray. A multi-bunch photo-cathode RF gun to generate ∼10 MeV electron beam is under development. The design for the soft X-ray source is presented.

[en] The TRISTAN timing system is divided into fast and slow timing systems. In the fast timing system, the 50Ω coaxial cables for the timing signal transmission were replaced with special single-mode optical fiber cables. New fast timing signal transmission system achieved the timing accuracy within 11psec over the temperature range from 10 to 35C. In the slow timing system, a dedicated microprocessor (LSI-11) for the generation of slow timing signals was ejected and the software was rewritten and installed into one minicomputer in the computer network for the TRISTAN accelerator control. This modification gives more reliability and more flexibility. In this paper the authors describe the improvement of the TRISTAN timing system

[en] Electron beam lifetimes in the Accelerator Test Facility (ATF) damping ring are limited by elastic and inelastic beam-gas scattering as well as the Touschek effect, which, due to intrabeam scattering, transfers transverse into longitudinal momentum exceeding the momentum acceptance of the machine, thus leading to particle loss. Since the Touschek effect depends strongly on the vertical beam size, it can be utilized to determine the vertical beam emittance, thus providing a cross-check for data obtained by different methods, e.g. using the synchrotron radiation monitor. First results of beam lifetime studies and estimates of the vertical emittance are presented. (author)

No abstract available

[en] We almost achieved the design horizontal and vertical emittance with single bunch beam of low intensity. However, emittance growth rate with beam intensity is greater than the expected growth by the estimation of intra-beam scattering. The multibunch operation is now facing the problem of the weak radiation shielding and the leakage of neutron. Even with the single bunch operation only, many instrumentation developments and beam experiments are now under way. We report it briefly such developments and also discuss the emittance problems and radiation problems. (author)