Laser Monitoring System Hardware

In order to monitor the response of the calorimeter, a fairly simple system has been installed. It's components are as follows:

A Laser-Photonics LN-300 Nitrogen laser
A piece of plastic scintillator which serves as a wave shifter
A bundle of plastic fibers
Plastic prisms
Three sheets of MIL spec plexiglas (MIL spec in order to get a long attenuation length)

Here's how it works:

The laser, upon recieving a TTL level signal, fires. The UV light is absorbed by the plastic scintillator mounted inside the laser cavity. (This is desirable for safety, since it destroys the coherence of the light.) The scintillator then emits incoherent blue light. This light goes into a bundle of plastic fibers. These fibers transport the blue light to the tops and bottoms of the plexiglas sheets. Connecting the fibers to the plexiglass are several (approx. 6 per sheet) prisms. The prisms serve two functions: 1) they help the increase uniformity in the plexiglas, and 2) they provide a means of turning the light 90 degrees.

A Few Words of Warning

Nitrogen lasers dump most of their energy in the ultra-violet part of the spectrum. Thus, they can permanently damage your eyes. Under no circumstances should ANYONE (not you, not your mother, and not your father) oprate the laser without all of the covers in place and the scintillator installed.

The aluminum box which is attached to the laser holds the end of the fiber bundle. If you open this box with the high voltage on you WILL DAMAGE the calorimeter's photomultiplier tubes. Also before opening this box make sure the high voltage supplies to the monitoring system normalization PMT and photodiodes are off. (The PMT should be powered from the LeCroy 4032A power supply in the LGD HUT, and the diodes are powered by a supply mounted on top of the transporter.)