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Installing the 40m Lab Pre-stabilized Laser

Installing the 40m Lab Pre-stabilized Laser

- Contributed by Peter King

Hot on the heels of the LIGO Livingston Pre-stabilized Laser (PSL) installation, Rich Abbott and I were approached by Alan Weinstein and asked about the possibility of building a LIGO-type PSL for the 40m Lab. At the time, we thought it would be a breeze, merely a case of cranking the handle one more turn, since we knew where to order the parts and we were already gearing up for installation of the Hanford 4k PSL. A piece of cake, no problem at all...

Oh how wrong could one be?

In order to glean as much as possible from the experience of the PSLs at the observatories, ordering of the opto-mechanical components was held back as late as possible. Eighteen months and approximately $350k later, the PSL is currently being installed at the 40m Lab.

Installation commenced with the laser safety enclosure being put in place. In a departure from other laser safety enclosures, the 40m Lab enclosure has laser safe viewing windows installed in the doors. The material selection was performed by Lee Cardenas, who tested its suitability. Surprisingly, the quarter-inch thick material withstood the full blast of the 10-W laser for a day without the laser beam breaking through!

About a fortnight ago, the reference cavity and vacuum chamber was assembled by Lee in the laser safety enclosure. The reference cavity is identical to the ones deployed at the observatories but the vacuum chamber is shorter, as is the vibration isolation stack. Driven over in the CDS Goggomobil by part-time gladiator Ben Abbott, the laser was thus delivered to the 40m Lab.

After placing the laser on the table, the various cables were pulled and dressed in the cable trays. The water chiller was installed and the laser power supply firmly bolted to the PSL rack. We performed the laser safety walk through to check that no one was hiding down the arms of the interferometer. Gathered round the laser power supply were Alan, Dennis Ugolini, Lee, Steve Vass and your narrator. The big moment was nigh. Safety glasses were donned and I called upon Alan to throw the switch. This was it! Alan turned the key...

Nothing.

The power supply displayed "LWE MOPA SYS". The power supply then checked for the presence of the water chiller and displayed "CHK CHLLR" and after an agonizing wait, displayed "CHLLR FLT". Okay, no problem, as we probably forgot to set the RS232 button on the chiller. After checking that, Alan was again asked to do the honors. Here we go!

Again, nothing.

The same message displayed. After swapping the two RS232 cables around, Alan turned the key, toggled the switches, and this time a little piece of history was made. On May 23rd, 2001, a little after 6pm, 1064 nm light was turned on in the 40m Lab.

In the following few days, the MEDM operator screens and EPICS slow loop sequencer were copied over. Dennis was able to get these running in almost no time.

Then it was time to haul over the optics, optical mounts and electronics. The PSL electronics were being assembled by Rick Karwoski and Paul Russell (aka PR) after some testing in the lab. Meanwhile Lee and I were installing the optics, first the optical train towards the pre-modecleaner, and then the one towards the reference cavity. Most of the installation should be complete by mid-June, with testing and performance tuning to take place during the following months.

At Work in the 40 meter

40m Lab PSL Laser Enclosure.

Above: Guillaume Michel says "peek-a-boo" through the 40m Lab PSL laser enclosure. "Where did all this stuff come from?"

Paul and Rick make adjustments.

Paul Russell and Rick Karwoski search for that missing 2-56 screw from the RF photodetector. "I know it fell in here somewhere!" In the foreground is the pump station used for evacuating the reference cavity vacuum chamber. The laser is the beige colored box on the lower right hand side.

Dennis adjusts beam going into reference cavity.

Dennis Ugolini finds the missing 2-56 screw and adjusts the beam going into the reference cavity at the same time.

A view of the 40m Lab PSL.

A view of the 40m Lab PSL looking over the reference cavity vacuum chamber in the lower left. Yet to be installed are the beam tubes and the input optics train.