The tentative experiment for producing low-photon-energy quasi-x-ray laser using a capillary is described. This flash x-ray generator was improved in order to increase the x-ray intensity and to produce high-intensity characteristic x-rays by forming the linear plasma x-ray source. The generator consists of a high-voltage power supply, a polarity-inversion ignitron pulse generator, a turbo-molecular pump, and a radiation tube with a capillary. A high-voltage condenser of 0.2 (mu) F in the pulse generator is charged up to 20 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing the ignitron. In the present work, the chamber is evacuated by the pump with a pressure of about 1 mPa, and the carbon anode and cathode electrodes are employed to produce K(alpha) characteristic x-rays. The diameter and the length of the ferrite capillary are 2.0 and 29 mm, respectively, and both the cathode voltage and the discharge current displayed damped oscillations. The peak values of the voltage and current increased when the charging voltage was increased, and their maximum values were -9.9 kV and 4.4 kA, respectively. The pulse durations of the x-rays were nearly equivalent to those of the damped oscillations in the voltage and current, and their values were less than 20 microseconds. In the spectrum measurement, we observed the carbon K(alpha) line.