Laura Lambert wrote:

John Wong wrote: Tuesday, September 01, 2015, 17:16 Target container contains 533 discs of SiC with packed length of 17cm.  Mass of 533 discs SiC(green)  = 57.8979g Total mass SiC(green) + target container = 1455g Container is wrapped with 3 heatshields; no end caps are inserted yet. Sintering temp at 1800C - TGHT will be set accordingly.  TBHT max at 230A.  Chamber is currently being pumped down.     Wednesday, September 02, 2015, 09:11 HS water valves opened, no leaks detected. IGP1 = 1.15e-6 Torr Tapped up manually to 40A. Waited ~1hr40 for vacuum to stabilize. IGP1 = 3.6e-6 Torr. Max setpoints set to TGHT = 630A and TBHT = 230A, ~1400C Initiating auto ramp at a rate of 0.2A/min and 0.1A/min for the TGHT and TBHT respectively. Once max setpoints achieved, will tap up manually until window port becomes coated [as previously observed] Once window port becomes coated will leave at set temp for ~4hrs to continue with outgassing, then cool down, clean window and ramp back up. If LS port still clean, will continue to ramp up to final desired temperature of 1800C.  Wednesday, September 02, 2015, 14:23 IGP1 = 4.0e-5 Torr. Vacuum too high, stopped auto-ramp and tapped down manually. Dropped TGHT down from 80A to 50A Dropped TBHT down from 55A to 50A Wednesday, September 02, 2015, 15:29 Vacuum down to IGP1 = 1.2e-5 Torr. Re-initiating auto-ramp...  Tuesday, September 08, 2015, 10:04 IGP1 = 4.5e-7 Torr. TGHT = 630A, 9.6V TBHT = 230A, 3.2V DV = 0.22V OMEGA RS = 1476C OMEGA LS = 1450C see attached photo for screenshot. will tap up manually with a visual on both window ports...

 Tuesday, September 08, 2015, 15:44

TGHT has stepped up to 820A.  Coating on both windows is becoming obvious and it's interfering the temp readers; however, the left window (see attachment, which is further away from the target) is lightly coated than the right.  See attachment for The Temp (and Power) vs current plots.

Target will remained heated at the current and will be cooled down later today. 

The target will be re-conditioned up to 820A and temp and mass will be re-measured.

Plans:

The chamber will be vented tomorrow and the target will be taken out to weigh for mass change. 

The chamber windows will need to be clean.

A piece of Ta foil will be cover in front of the ionizer to trap any loss material (if any).

 Tuesday, September 08, 2015, 17:37

TGHT was at 800A for 2 hours before ramping up 820A for another 2 hours heating.  More coating on the right window is observed and temp reading came down to 1340C.  The left window remains the same and temp reads at 1646C.  

Ramping TGHT/TBHT to 0A at 2A/min and 1A/min, respectively.  

 Wednesday, September 09, 2015, 12:27

Result after the sintering process:

No yellow crystal formed (compared to previously observed SiC targets that heated up above 1900C). 

Total green mass = 57.90g 

mass of graphite foil = 0.035g x 533 discs = 18.7g 

mass of green SiC = 39.30g 

Target container with SiC before sintered = 1455g 

Target container after sintered = 1450g 

mass loss ~ 5.0g ~ 13% organic mass, as expected!  

The target will undergo the re-condition stage, and the temperature will be measured from 600A to 820A.