Cathode Power Supply Cable

I fixed the used spark gap and put it into the trigger generator this morning. In the afternoon, I tested the trigger generator, it worked very well. It's better to buy a new spark gap as a backup, I contacted Chip Yang from General Atomics, because they did not produce this part, he transferred my email to another company(Dave Drury at L-3 Titan PSD, Email: ddrury@titan.com).

The X-ray cathode pulse was not good yet, Mike asked me to cut the cathode power supply cable reducing the pre-discharging. I did cut the end of x-ray cathode power supply cable, the cathode spark gap trigger became better than before. However it could not be moved forward to x-ray anode pulse peak. It's very hard to cut that power cable, it took me whole afternoon, I did not have more time to check the PCB board. I will ask Mike to help me check the circuit board tomorrow.

Spark gap fixed

I asked Kevin to remove the broken piece from the spark gap holes. He told me that the broken part is not very serious, we can use this spark gap. I also send email to General Atomics company, but I have not received the reply yet. So I tried to use the old one, better than nothing.

I received the tube fittings from McMaster-Carr at 4:00pm this afternoon, I found the ordered connectors not match our part well. I changed the broken one, the other connector was not replaced. After assmebly, I did not put it into the oil tank but test the gas leakage. Firstly there was a big leak from the connector. After using new O ring and more teflon tape, tightening the tube connector, I did not find the leak more. I will put the spark gap into the oil tank tomorrow.

The spark gap switch leaking

When I turned on the trigger generator this morning, I found the gas pressure could not be applied to 60 psi. I heard gas leak sound in the generator oil tank, it must be a big leakage in the spark gap switch. So I moved out the switch and found oil totally filled into the spark gap. The spark gap was determinate by the oil. The leakage may be caused by the spark gap holes and the gas pipe connectors, the connect holes were very crispy, one was broken when I tried to remove it, the edge of the other was lightly cracked. The connectors and O-ring looked very bad, I wanted to replace them, however I could not find the same connectors in the lab, I will order them from Swagelok tomorrow. I also will ask Kiven to remove the debris from the spark gap hole, otherwise I could not put new connector. In case this spark gap does not work, I contacted the General Atomics (formerly Maxwell Lab. Inc.) to order a new spark gap.

Trigger enerator for Rail Gap

We guessed the rail gap trigger may effect the x-ray gun trigger, so I wanted to check the rail gap trigger generator. I pulled out the Rail Gap trigger enerator 40151-B and disassembled it this morning. I did not find any disconnect inside the oil tank, please look at the right picture. Then Sankar and I cleaned the spark gap switch, using Scoth-Brite to polish the electrodes. The irradiation electrode was also polished carefully.
In the afternoon we adjusted the distance between the irradiation electrode and the middle electrode. The breakdown voltage of the irradiation electrode gap is about 1.2 kV, which is the value in the mannul. Then we put back the spark gap switch into the oil tank. I did not find any leak from the spark gap switch. I will try to test this trigger generator tomorrow.

Thyratron CX1585

We closed the Prometheus chamber and filled oil on Wednesday, the oil became stable after one day. So I ran the system this morning, unfortunately the x-ray cathode pulse could not be synchronized with x-ray anode pulse. Keith and Bill suggested I should check the cathode thyratron CX1585, I replaced the thyratron and found the situation became wrose. I had to put the thyratron back. The picture shows the bottom of the Thyratron CX1585 in the x-ray cathode trigger box.This wave forms show (1) the x-ray anode signal without cathode pulse, the railgap were trigger randomly, I don't know what caused the x-ray cathode noise; (2) the cathode pulse without anode signal, the negtive cathode pulse looked well; (3) anode and cathode trigger pulses were applied to the x-ray gun, the cathode signal became worse, the noise followed the anode pulse, and the cathode pulse peak could not move forward to match the anode peak.

Maintenance of Rail gap switch 402000

Disassembled and cleaned the rail gap switch. The right picture shows how dirty of the rail gap switch. Because the SF6 gas flowed into the switch everyday, it might conterminated the box. The front window should be clear, however from here nothing could be seen inside. There are 4 pieces of this kind of spark gap used in our large aperture KrF Excimer Amplifier system. The 40 kV high voltages are applied to this spark gap in order to trigger the main high voltage pulses.

This is the cleaned rail gap switch. The front window looks pretty clear. The brass electrodes are shiny, the trigger rail is set in the middle of the electrodes.

We already cleaned and reassembled one spark gap, 3 pieces has been cleaned. Now I am testing the leakage of the finished one.

We installed 2 spark gaps in the North Bank, and one spark gap in the South Bank. The front windows of South Bank also were replaced with brand new windows. Below, the left picture shows the North Bank and the right picture shows South Bank.

X Ray Gun 检测

今天终于还是把X RAY GUN取出进行检测。发现阳极头碳化很严重，左图为X RAY GUN的阳极绝缘头。每根阴极棒的电阻约为28K，经过初步清洗后，一边的电阻为7M，另一边为1M。基本上可以认为最近的问题差不多都是因为阴极棒的污染造成的。

另外在往外接X RAY GUN的时候，因为没有注意到CHAMBER里有一支架，所以拉的方位有点不对，下次时一定要注意。从右图中可以看到那个支架有两个小缺口，只有当X RAY GUN的两排螺丝与这两个缺口相对应时，X RAY GUN才容易拉出来。

准分子激光器X光预电离

上午基本上解决了阴极触发的问题，主要原因是250欧姆的充电电阻漏电，以及放电电极的接触不太好。更换电阻并拧紧电极接头后，阴极的触发变得比昨天稳定许多。但是后来发现X光的阳极触发变得十分不稳定，经检查发现是电压输入接头松动。

UV短脉冲激光在毛细管中的传输特性研究的初步实验

今天上午把一束UV飞秒激光输入到以前的空间滤波器，可能是因为焦距太短的缘故，出射光的光束质量非常差。下一步考虑是否用长焦距的透镜，目前手头有的最长的焦距为2米，准备更换以后再对光束进行测量。

下午，新订的DRY AIR到货，检测了X RAY GUN的阴极与阳极脉冲，发现两个脉冲还是不能重合，阴极脉冲总是晚于阳极脉冲。测量阴极与地之间的电阴为14 k Ohm，怀疑是否阴极板有问题？和KEITH商量后，他说可能还是控制电路部分的问题。

光物理与量子电子学网站

相当不错，
Optical Physics and Quantum Electronics

作者单位：
Division of Engineering and Applied Sciences , Harvard University