ALBERT

Notes: The 10-T wiggler is an iron-cored superconducting wiggler destined for Electrotechnical Laboratory's 800-MeV electron storage ring to enhance the available radiation. The design and manufacturing contract for this magnet was started in April 1990 and was preceded by a feasibility study. The major features of the magnet are described in the article. Also, the effect of the superconducting wiggler with high magnetic field on the stored electron beam has been simulated. © 1995 American Institute of Physics.

Notes: Calculations of the radiation from a four-period polarizing undulator by use of the general radiation equation and numerical integration including the effects of electron-beam emittance, energy spread, and finite observation distance are presented. Accurate electron-beam profiles have been experimentally determined and modeled by the Monte Carlo method. Good agreement is found in spectral intensity between the measured and calculated spectra. © 1995 American Institute of Physics.

Notes: The system of single bunch injection (SBI) for the storage ring NIJI-IV was completed. The system was used for the injection of the short pulse beams from an electron gun into only one of the 16 rf buckets in the ring. On a compact storage ring, the multipulse beams in one pulse train can be stored into only one of many bunches by one injection. The optimum number of the grid pulse in one pulse train was determined to improve the storage efficiency and the storage current by one injection. The keeping time of the bump orbit was calculated by using the transfer matrices. The optimum pulse number obtained by the calculation is 2. In the SBI system, the number of grid pulses in one pulse train can be selected by the gate circuit. A snap off diode and a clip line are used to generate 2 ns grid pulses. The measured grid pulse was shorter than the longitudinal space 5.5 ns of the rf bucket with voltage of −80 V. The EIMAC Y-646B cathode-grid assembly is used as the electron source. It is expected that the injection system provides a higher peak current and easier free electron laser use operation in comparison with the rf-knockout system. © 1995 American Institute of Physics.

Notes: Canopy structure, productivity and their relationships were examined in 2-year-old swards of fourteen tall fescue (Festuca arundinacea Schreb.) strains during the vegetative and reproductive growth stages. During the vegetative growth stage morphological characters, particularly tiller size, were closely associated with productivity. Swards with large tillers showed an effective distribution of the incoming light energy within the canopy and hence low extinction coefficient (K) value and high productivity at complete light interception. On the other hand, although there was no apparent correlation between K and the productivity or the whole crop during the reproductive growth stage, the productivities of the reproductive and vegetative tillers were positively and negatively related to K respectively. Leaf area index of the reproductive tillers and their position in the canopy had marked effects on the distribution of the incoming light energy within the canopy and on the productivity of both types of tillers. The productivity of the vegetative and the reproductive tillers is discussed in terms of the effect of the competition for incoming light energy between both types of tillers.

Notes: Nowadays contact recording has become one of the most important mechanisms for high-density recording of HDD. The contact recording head is always subject to friction when sliding. If the friction causes vibration on the sliding head, the swaying of the head is likely to lead to some undesirable bit shifts. The authors previously measured the head movement in sliding with a Watrous-type suspension where it was verified that the front edge of the head fell down to the disk surface because the rotational center of the pitching motion of the head was located above the sliding surface, inducing a heavy sticking. In order to prevent the sticking from occurring, we have already proposed RCC (remote centered compliance) suspension (15 mm in thickness) which consists of a pair of inclined plates. With this suspension, the front edge of the head is raised up because of the enhanced location of the rotational center which is now below the sliding surface. In this article we present a newly designed micro-RCC suspension (125 μm in thickness) for an acutal small MR head (1×1×0.5 mm) of the contact recording. It has two pairs of the inclined plates structure for two-axis frictions which are caused by seeking and tracking motions of the head, respectively.This suspension is fabricated from a 125 μm thick sheet of polyimide using the ultraviolet laser beam. We evaluate its movement in sliding at low speed (50 μm/s) and at high speed (2 m/s) under a 10 mN load on a sputtered disk, respectively. The normal and frictional forces are measured by a micro two-axis force sensor (0.01 mN resolution) with parallel-plate structure and the pitching motion of the head is measured by an inclination sensor by means of laser reflection angle measurement (10 μrad resolution). From the experiment at low speed, we have clarified that the head yields a stable friction (0.15±0.02 mN) and has the nose-up attitude (0 to + 100 μrad). In addition, from the evaluation at high speed, we have observed the stable read-back signal (±7% modulation) because of the stable motion without any sticking. As a reference suspension, we prepare a micro-Winchester-type suspension. From the similar evaluation, we have identified that the reference head shows unstable friction (0.25±0.1 mN) with the nose-down attitude (0 to −500 μrad) and an unstable signal (±50% modulation). We have confirmed through these observations that the micro-RCC suspension will be an indispensable tool for contact recording in order to realize a stable recording against the friction. © 1996 American Institute of Physics.

Notes: We have studied light-induced degradation in hydrogenated and deuterated amorphous silicon alloy solar cells. Replacing hydrogen with deuterium in the intrinsic layer of the cell improves stability against light exposure. Possible explanations for the improved stability are discussed. © 1997 American Institute of Physics.

Notes: The bunch length was measured by using a highly sensitive streak camera with a time resolution of 2 ps. It was found that fine structures appeared in the electron bunch shape and that the shapes of electron bunches were described by a Gaussian distribution on the average. The dependence of bunch length on beam current was measured for an electron beam of 607 MeV. The bunch length was well represented by a power function of beam current with an exponent of 0.197 at currents lower than 35 mA or 0.30 at high currents. The experimental results suggest that the longitudinal coupled-bunch beam instability takes place at low beam currents and the turbulent instability dominates at high currents. It was also found from the three-dimensional bunch shape measurements that the bunch shape tended to blow up at high currents.