Laura Lambert wrote:

Laura Lambert wrote: Laura Lambert wrote: Laura Lambert wrote:  Thursday, April 27, 2017, 14:01 Target container contains 470 discs of SiC  Target packed length = 16cm.  Mass of SiC(green)  = 52.13g Discs in target are arranged as follows: 5singles / 1pack / 65singles / 1pack / 75singles / 1pack / 75singles / 2packs / 75singles / 1pack / 75singles / 1pack / 55singles / 1pack / 5singles Container is wrapped with 1x heatshield around each side of cooling fins; no end caps are inserted yet - coated spring inserted both sides to hold discs in place. Sintering temp = 1800C Chamber is currently being pumped down.  Friday, April 28, 2017, 13:06 HS water valves turned on this morning, no leaks detected. Tapped up manually to 40A Waited ~3hrs , vacuum stable. IGP1 = 4.13e-6 Torr Initiating auto-ramp at 0.2A/min and 0.1A/min for the TGHT and TBHT respectively. TGHT max = 400A.  TBHT max at 230A.  Slope on OMEGA = 1.08 [see elog i.d. # 326 for reasoning behind OMEGA slope choice]  Tuesday, May 02, 2017, 09:24 IGP1 = 2.34e-6 Torr TBHT = 230A, 3.15V TGHT = 298A, 3.96V OMEGA = 1030C Vacuum stable, increasing ramping rate up to 0.5A/min  Tuesday, May 02, 2017, 13:20 IGP1 = 1.3e-5 Torr TGHT = 400A, 5.6V OMEGA = 1175C Increasing max setpoint to 500A     Wednesday, May 03, 2017, 13:33 TGHT had remained at 500A for 16hrs, vacuum had initially come down nicely. Vacuum was starting to creep up when i came in this morning before 8am,  IGP1 was at 1.2e-5 Torr TGHT = 500A, 7.77V OMEGA = 1440C Around 8:30 vacuum started to spike, so the TGHT was tapped down rapidly to 450A Tapping the TGHT down made no difference to the vacuum. By the time 450A was hit, it was too late and the spike in vacuum caused the evaporator to trip off. Turbo pump in epics showed on, turbo pump showed on according to TP direct controls. Everything was shut off and the venting tapped, this made it obvious the turbo pump was already off as there was no ramping down noises from the turbo pump. TP control box turned off then on again, at this point the controls showed a 'fail' message. Turns out the turbo pump control box was fried and that's what had caused the turbo pump to fail with no notice in epics causing the vacuum to spontaneously spike. Waiting on a new one from vacuum group... See photos attached of striptool screenshots.  Wednesday, May 03, 2017, 15:03 New TP control boxed installed. Turbo pump turned on, everything pumped down. Vacuum good, IGP1 = 6.92e-7 Torr. IGP2 still not working, won't turn on via epics. Tried unplugging and plugging back in...still appears red with 'fail' message...    Wednesday, May 03, 2017, 16:07 Unplugging and plugging back in seemed to work now that evap2 under vacuum IGP2 works again. Will look into replacement ion gauge...    Wednesday, May 03, 2017, 16:09 HS water valves opened, no leaks detected. Tapped up manually to 40A. Vacuum stable. IGP1 = 3.6e-7 Torr Initiated auto-ramp at 1.0A/min and 0.5A/min to 300A and 230A for the TGHT and TBHT respectively.  Thursday, May 04, 2017, 08:41 Reached 300A, 230A 10hrs ago. IGP1 = 1.5e-7 Torr OMEGA = 1070C Increasing max setpoint to 500A at a rate of 0.5A/min for TGHT  Thursday, May 04, 2017, 14:58 Back up to max setpoint that was reached before evap2 tripped off. TGHT = 500A, 7.65V IGP1 = 9.3e-7 Torr OMEGA = 1450C Increasing max setpoint to 550A, ramping up at a lower rate of 0.2A/min since this will be done overnight.  Friday, May 05, 2017, 08:53 TGHT = 550A, 8.64V IGP1 = 2.8e-7 Torr OMEGA = 1560C Increasing max setpoint to 600A at a ramping rate of 0.5A/min  Friday, May 05, 2017, 11:09 TGHT = 600A, 9.58V IGP1 = 7.3e-7 Torr OMEGA = 1670C Increasing max setpoint to 625A at a ramping rate of 0.5A/min  Friday, May 05, 2017, 12:05 TGHT = 625A, 10.05V IGP1 = 9.9e-7 Torr OMEGA = 1710C Increasing max setpoint to 650A at a ramping rate of 0.5A/min  Friday, May 05, 2017, 13:13 TGHT = 650A, 10.57V IGP1 = 1.1e-6 Torr OMEGA  = 1740C Mikron through left side windown on outside bottom left edge on container = 1750C Tapping up manually to 1800C  Friday, May 05, 2017, 13:42 Adjusted slope to 1.09 so same spot on leg using MIKRON = OMEGA TGHT = 680A, 11.08V IGP1 = 1.6e-6 Torr OMEGA = 1795C MIKRON = 1795C Plotting a temperature curve, the predicted required current to reach 1800C was 670A using a slope of 1.08 Currently sitting 10A above predicted required current. After several minutes, temperature dropped a few degrees to 1790C Window remains clear and uncoated. Tapped up to TGHT = 685A, 11.2V OMEGA = 1795C Will remain at this setpoint over the weekend.  Monday, May 08, 2017, 08:59 TGHT = 685A, 11.08V TBHT = 230A, 3.24V IGP1 = 1.98e-7 Torr OMEGA has lowered to 1342C Evap2 sat at max setpoints over the wknd. Will check window port before cooling...   *UPDATE ON TRIP-OFF* A closer look into the details using archives [see photos attached]: TP tripped off TBHT and TGHT at ~8e-5Torr Anything in the evaporator requires ~1hr to cool before turning things off. In this scenario, the target was @ ~1440C. so ~30min post TP trip, the target may still be at ~1000C. Anything above 0.02Torr could be close enough to atmopheric pressure that this would be cooling too fast and could lead to breaking the target/ cracking the Ta metal. As one can see in the screenshots attached, the vacuum lingered around 0.005Torr for ~2hrs before anything was done. This provided enough time for the target to cool before it was introduced to atmospheric pressure when the BV was closed when trying to figure out the problem. In summary, the target 'should' be OK...will inspect target further when removed from the evaporator.  Tuesday, May 09, 2017, 09:16 TGHT = 685A, 11.04V TGHT power supply = 686A, 11.31V TBHT = 230A, 3.24V TBHT power supply = 236A, 3.32V IGP1 = 1.6e-7 Torr IGP1 direct readout = 2.3e-7 mbar IGP2 = 6.8e-8 Torr IGP2 direct readout = 8.46e-8 Torr Evap2 reached max setpoint friday afternoon. Window clearly coated - see attached photo. Initiating auto cool at 2.0A/min and 1.0A/min for the TGHT and TBHT respectively.  Wednesday, May 10, 2017, 09:18 Vented in air and opened up this morning. Inspected container carefully for any cracks/ marks due to TP tripping off at 1450C Target looks good!  One sample disc removed for SEM. When removing disc for sample, the SiC came off the graphite backing and just SiC flake came out - see photo Photos attached showing inside container with no Si crystal formation/ good clear path all the way through target and sample removed for tests