Changes

===Purpose===

===Purpose===

The pulse generator built by Alex Barnes and Jon Kulakofsky produces -10V pulses of duration 1ns fwhm. These pulses are split 90:10 at the output of the pulse generator circuit, and driven out two coaxial cables. The -1V signal matches expectations for a NIM logic signal, and is fed into a discriminator to generate a trigger for the data acquisition. The coaxial cable carrying the -9V pulse is coupled directly from the coax cable conductors to the pins of a laser diode of type DL3148-025 - 635 nm, 5 mW, Ø5.6 mm. The [http://www.thorlabs.com/thorcat/11800/DL3148-025-AutoCADPDF.pdf data sheet for the laser diode] shows the following pin-out for the SOT23 package.

The pulse generator built by Alex Barnes and Jon Kulakofsky produces -10V pulses of duration 1ns fwhm. These pulses are split 90:10 at the output of the pulse generator circuit, and driven out two coaxial cables. The -1V signal matches expectations for a NIM logic signal, and is fed into a discriminator to generate a trigger for the data acquisition. The coaxial cable carrying the -9V pulse is coupled directly from the coax cable conductors to the pins of a laser diode of type DL3148-025 - 635 nm, 5 mW, Ø5.6 mm. The specs for the laser diode are shown [http://www.thorlabs.com/catalogpages/V21/1219.PDF at the bottom of this page]. The [http://www.thorlabs.com/thorcat/11800/DL3148-025-AutoCADPDF.pdf data sheet for the laser diode] shows the pin-out for the round 5.6mm package. Pin 2, which is internally shorted to the brass device enclosure, is tied to the braid on the coax, while the coax core conductor is tied to pin 1. Negative pulses provide a forward-biased signal to drive the diode laser. The third pin of the chip is connected to an internal photodiode. If the photodiode is reverse-biased, it generates a current proportional to the intensity of the light in the laser cavity. The current scale is said to be 400uA at full laser intensity, which is too small to