High-power conditioning of a damped-cavity for high brilliant synchrotron radiation source

Abstract

A new type of damped-structure Radio Frequency (RF) cavity was developed for the Vacuum Ultra Violet (VUV) and Soft X-ray (SX) synchrotron radiation source. The high power conditioning started with an input power of a few hundreds watt and the power level was slowly increased in order to keep the vacuum pressure below 5 x 10(exp -6) Torr. The tuning plunger was adjusted to compensate for a thermal detuning of the cavity. After 20 hours conditioning, the input power reached up to 60 kW. The vacuum pressure became 5 x 10(exp -8) Torr without RF (Radio Frequency) power. In order to try higher power conditioning under the lower vacuum pressure, the cavity was baked at 150 C for 24 hours. After the baking, the pressure was down to 3 x 10(exp -9) Torr, and then pulse conditioning at 100 kW with 10 percent duty was carried out for 12 hours. After that, Continuous Wave (CW) conditioning was restarted. Total conditioning time was 60 hours. The input power of more than 150 kW was obtained without any severe problems. Small glowing points and occasional arcing grew with increasing input power. However, as high power conditioning progressed, the number of these glowing points decreased.

真空紫外光および軟X線シンクロトロン放射源(VSX光源)用の、新型減衰構造の高周波(RF)空洞を開発した。高電力状態調節は数100Wの入力から始め、真空度を5×10(exp -6)Torr台に保つため電力は徐々に上げた。同調プランジャは空洞の熱的離調を補正するように調節した。20時間の状態調節の後、入力電力は60kWに達し、RF(高周波)電力をかけない時の真空度は5×10(exp -8)Torrになった。さらに良い真空下でさらに高電力での状態調節を試みるため、空洞を150度Cで24時間ベーキングした。ベーキング後、圧力は3×10(exp -9)Torrに下がり、続いて10％の負荷で100kW、12時間のパルス状態調節を行った。その後、連続波で状態調節を再開し、合計60時間状態調節した。150kW以上の入力電力を重大な問題なく得ることが出来た。入力電力の増大とともに小さなグローやアークが増加したが、高電力状態調節が進むにつれグローを起こす点の数は減少した。