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Line 57: − + − *An optics design has been made for focusing the 200mJ pulses from the excimer laser onto the diamond target. We are using a fused silica lens and a CaF2 entrance window. The entrance window will be adjusted at an angle to reduce the build-up of ablated material within the chamber as well as redirecting a small percentage of the beam for real-time power measurements. The photos below show the rail and the subsequent components. − {| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto" − |- − | [[File:long_view_rail.jpg|right|thumb]] || || [[File:Brendan-optics.jpg|left|thumb]]|| ||[[File:Stage_lens_sensor.jpg|right|thumb]] − |- − |} − {| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto" − |- − | [[File:optics-laser.jpg|left|thumb]] || || [[File:optics_laser_scope.jpg|left|thumb]] || || [[File:Longview_oscilloscope.jpg|left|thumb]] − |- − |} − *These photos are taken from a TurboCAD rendering of the optics rail that I completed this week. I have also added the 0.5cm x 0.5cm x 100 micron thick diamond at the optimum focal length ([http://zeus.phys.uconn.edu/wiki/index.php/Diamond_Radiator_Thinning_Using_an_Excimer_Laser#Updates_for_April_2010 17cm]) and tilted at a 45 degree angle from the beam axis. The blue cone represents the ablation plume and its dimensions are taken from plume characteristics observed in local thin film ablation laboratories. − {| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto" − |- − | [[File:opticsE.jpg|right|thumb]] || || [[File:opticsC.jpg|left|thumb]]|| ||[[File:opticsD.jpg|right|thumb]] − |- − |} − {| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto" − |- − | [[File:optics.BlastTCW.jpg|left|thumb]] || || [[File:rail.jpg|left|thumb]] || || [[File:blastII.jpg|left|thumb]] || || [[File:diamond_blast.jpg|left|thumb]] − |- − |} − *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]] − *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. Looking at the lines we currently use, it was clear that this may be an issue as they were from Dr. Eyler's original setup used for XeCl. − *A new line has been installed and in order to remove and moisture from inside the line, I have "baked" it for over and hour at <math>110\,^\circ C</math> while under vacuum. After the system cooled to <math>60\,^{\circ}{\rm C}</math> I bled the lines and left fresh fluorine in the line for passivation. After 24 hours I will purge the system and give it a fresh fill, then test the laser output.
Diamond Radiator Thinning Using an Excimer Laser (view source)
Revision as of 02:34, 13 December 2016
, 02:34, 13 December 2016→Updates for May 2010
*Knowing <math>\mathrm\omega_{0}</math> also allows us to calculate the theoretical fluence of the beam. Assuming maximum power of 220mJ over a 1.49mm x 0.552mm area yields <math>26J/cm^2.</math> Which is above the <math>14J/cm^2</math> threshold value cited by Brookhaven National Laboratories who were conducting diamond ablation experiments with a 213nm Nd:YAG laser (213nm with the use of a 4 + 1 frequency mixing crystal). Our ArF excimer laser produces 193nm light that will be more readily absorbed by the surface of the diamond as diamond is opaque to wavelengths above the band gap. These calculations provide a level of confidence that we theoretically will be able to ablate diamond.
*Knowing <math>\mathrm\omega_{0}</math> also allows us to calculate the theoretical fluence of the beam. Assuming maximum power of 220mJ over a 1.49mm x 0.552mm area yields <math>26J/cm^2.</math> Which is above the <math>14J/cm^2</math> threshold value cited by Brookhaven National Laboratories who were conducting diamond ablation experiments with a 213nm Nd:YAG laser (213nm with the use of a 4 + 1 frequency mixing crystal). Our ArF excimer laser produces 193nm light that will be more readily absorbed by the surface of the diamond as diamond is opaque to wavelengths above the band gap. These calculations provide a level of confidence that we theoretically will be able to ablate diamond.
==Updates for May 2010==
==Ablation Chamber==
==Updates for May 2010==
==Updates for May 2010==