Although thyratrons are widely used as high voltage switch devices for pulsed power supplies, their aged degradation and short lifetime has been headache for large accelerator facilities. Especially ...for X-ray free electron laser (XFEL) facilities, an instability caused by the aged thyratron and a high maintenance cost of the thyratron replacement are the serious problem. In order to overcome this problem, we have developed a solid-state high voltage switch having a long lifetime for thyratron replacement. The high-voltage switch was designed to install to the oil-filled compact modulator for XFEL facility SACLA (Spring-8 Angstrom Compact free electron LAser). It should run at a 60 pps (pulse per second) repetition rate and conducts a large current of 5 kA with a 5 us pulse width from the pulse forming network circuit charged at 50 kV in maximum. We employ a static-induction (SI) thyristor as the high-voltage switch, because it has suitable characteristics for the thyratron replacement. In total, 192 SI-thyristors (24 series, 8 parallel) are used for a 50 kV switch module. Since the modulator is filled with an insulation-oil, water cooling of the device is not suitable. Hence, we attach the SI-thyristors on aluminum heat sinks forcibly cooled by oil circulation. Performance check in high-voltage operation for the switch was carried out by connecting it to the actual klystron and modulator. The switch stably run at a 50 kV charging voltage, a 5 kA pulse current and a 60 pps repetition rate. A temperature rise of the SI-thyristor is about 7 degree, which is lower enough. Validity of employing the module for the high-voltage switching is well confirmed.
Prolactin-producing pituitary tumor (PRLoma) is the most prevalent functional pituitary tumor. If the tumor becomes large, vision can be impaired. In contrast to other pituitary tumors, cabergoline ...(CAB) is extremely effective for PRLoma and has become the first-line treatment. In this study, we examined our experience with the pharmacological and surgical management of PRLomas with visual impairment (VI) to determine whether VI could be a surgical indication. Further, we discussed the function of surgery in situations where the gold standard of PRLoma treatment was CAB administration. Of the 159 patients with PRLomas (age, 13-77 mean = 36.3 years; men, 29; women, 130) at Tokyo Women's Medical University Hospital from 2009 to 2021, 18 (age, 15-67 mean = 35.8 years; men, 12; woman, 6) had VI (subjectively, 12; objectively, 6). They started CAB treatment immediately (maximum dose: 0.5 to 6 mg/week; average: 2.17 mg/week). VI improved in 16 patients (88.9%) but did not improve in 2 (11.1%) requiring surgeries. One of the two patients had a parenchymal tumor resistant to CAB, and the other had a cystic tumor due to intratumoral bleeding. Consequently, CAB is the first-line treatment for PRLomas with VI because of its significantly high rate of improvement. However, close and rigorous surveillance is necessary for cases resistant to CAB, and the correct decision is required regarding surgical interventions at proper timing and appropriate surgical approaches considering the purpose of surgery.
