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Diamond Radiator Thinning Using an Excimer Laser (view source)
Revision as of 20:31, 25 May 2010
, 20:31, 25 May 2010→Updates for May 2010
*A beam enclosure has been constructed to shield observers from harmful UV light. It is made from Poly(methyl methacrylate)which filters 193nm light very well as shown by the following ([http://www.gclabsite.com/files/publication/gc47_p28.pdf graph]).
*A beam enclosure has been constructed to shield observers from harmful UV light. It is made from Poly(methyl methacrylate)which filters 193nm light very well as shown by the following ([http://www.gclabsite.com/files/publication/gc47_p28.pdf graph]).
[[File:PMMA_UV.png|center|600px]]
[[File:PMMA_UV.png|center|600px]]
*Now that all components have arrived (Fluorine gas and regulator) I have begun testing the laser output. I first experienced no light except what was reflected from the pre-ionization pins. After the system was recharged with a fresh gas mixture, I began to see a light blue beam that was about 12"x6" in size (I believe this to be a fluorescence effect). It wasn't until about the 5th refill that I saw an actual laser beam. Unfortunately, the beam was very spread out, and only lasted a matter of minutes. Believing this to be an issue of passivation, I started refilling and running the laser while timing the duration of actual laser beam. The beam has hit a wall at around 5 minutes, after which it begins to mesh in with the background light until it is indistinguishable. Contacting Coherent Inc. contact Jeff Edberg lead to the proper passivation procedure. However, the red light has been only lasting a maximum of 7.5 minutes.
*I decided to re-align the optics for the laser system and replace the cracked CaF2 lens with the new one purchased from Lattice Electro Optics. After which I saw an increase in beam intensity and an increase in geometrical sharpness of the beam, but no increase in beam duration.
*I found an ([http://www.airproducts.com/NR/rdonlyres/D46880D1-71BA-4C0B-A326-6D79EF8E122F/0/467MI.pdf article]) which stresses that unclean gas handling lines can contain hydrocarbons which react with fluorine gas to produce <math>CF_4</math>, which can have a negative effect on pulse duration in ArF excimer lasers.
==Passivation for ArF==
1)Bleed all lines prior to this process.
2)Turn on HV supply (turn key to on position) and allow the thyratron to warm up for at least ten minutes.
3)Evacuate the laser cavity until the fine gauge reads in the red (zero) by turning on the vacuum pump switch located on the laser head
4)Fill the system with 150mbar fluorine and 1850 He making the total pressure 2000mbar.
5)Set the Rep. Rate to 10Hz and turn on the HV supply (push button in)
6)Turn laser on (push button in) and set High Voltage to 20kV.
7)Laser will begin to pulse a red light, allow the laser to fire until the red light's intensity is reduced to about half. For the first few runs it may be necessary to re-fill a few times. The light should last AT LEAST 10 minutes.